Seafarers: Four Islands and Through the Desert maps

Add two map-only scenarios. A scenario now says where the starting
settlements may go (SeaStart); SeaState.starts holds the starting
islands, and the first-landing bonus skips all of them. Saves without
starts fall back to the home island.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01TWwLCrXa9aFVg8dZsCdLBZ

.github/scripts/stage-pages-site.sh

@@ -0,0 +1,66 @@
+#!/usr/bin/env bash
+# Assembles the Cloudflare Pages site for plg.wallacenet.ca into ./pages-out.
+#
+# Usage: stage-pages-site.sh <prod|dev> <tag> <apk-path>
+#
+# A Pages deploy replaces the whole site, and both channels live in one site,
+# so this stages the channel being published and then re-fetches the *other*
+# channel's current files from the live site so the deploy does not erase them.
+set -euo pipefail
+
+channel="$1"; tag="$2"; apk="$3"
+base="${PAGES_BASE_URL:-https://plg.wallacenet.ca}"
+out="pages-out"
+limit=$((25 * 1024 * 1024)) # Cloudflare Pages: 25 MiB per file
+
+case "$channel" in prod) other=dev ;; dev) other=prod ;; *) echo "bad channel: $channel" >&2; exit 2 ;; esac
+
+rm -rf "$out"
+mkdir -p "$out/$channel" "$out/$other"
+cp site/index.html site/404.html site/_headers "$out/"
+
+name="$(basename "$apk")"
+cp "$apk" "$out/$channel/$name"
+cp "$apk" "$out/$channel/ProLibertateGames.apk"
+# node rather than jq: the Gitea runner's image has node but not jq.
+node -e 'console.log(JSON.stringify({tag: process.argv[1], apkName: process.argv[2], apkUrl: process.argv[3], channel: process.argv[4]}, null, 2))' \
+  "$tag" "$name" "$base/$channel/$name" "$channel" > "$out/$channel/latest.json"
+
+# PLG_SKIP_OTHER=1 is for the very first deploy, when the site does not exist
+# yet and the domain answers 403 (Cloudflare error 1014) instead of 404.
+if [ -n "${PLG_SKIP_OTHER:-}" ]; then
+  echo "PLG_SKIP_OTHER set; not carrying over $other."
+  rm -rf "$out/$other"
+  find "$out" -type f | sort
+  exit 0
+fi
+
+# Carry the other channel over. 404 means it was never published; any other
+# failure must stop the deploy rather than silently dropping that channel.
+code="$(curl -sS -o "$out/$other/latest.json" -w '%{http_code}' "$base/$other/latest.json" || true)"
+: "${code:=000}"
+# Cloudflare error 1014 (403 + "error code: 1014") means the domain's CNAME
+# points at a Pages project that does not exist yet, so there is nothing to
+# preserve — the same as a 404, and what a push-triggered first deploy sees.
+if [ "$code" = 403 ] && grep -q 'error code: 1014' "$out/$other/latest.json" 2>/dev/null; then
+  code=404
+fi
+if [ "$code" = 404 ]; then
+  echo "No $other channel published yet; skipping."
+  rm -rf "$out/$other"
+elif [ "$code" = 200 ] && ! other_name="$(node -p 'const j = JSON.parse(require("fs").readFileSync(process.argv[1], "utf8")); if (!j.apkName) process.exit(1); j.apkName' "$out/$other/latest.json" 2>/dev/null)"; then
+  # A 200 that is not our JSON: Pages without a 404.html answers unknown paths
+  # with index.html. Nothing is published on that channel.
+  echo "No $other channel published yet (200 but no latest.json); skipping."
+  rm -rf "$out/$other"
+elif [ "$code" = 200 ]; then
+  curl -fsS -o "$out/$other/$other_name" "$base/$other/$other_name"
+  cp "$out/$other/$other_name" "$out/$other/ProLibertateGames.apk"
+else
+  echo "Fetching $other/latest.json returned HTTP $code; refusing to deploy." >&2
+  exit 1
+fi
+
+find "$out" -name '*.apk' -size +"${limit}c" -print | grep . >&2 && {
+  echo "APK exceeds Cloudflare Pages' 25 MiB per-file limit." >&2; exit 1; } || true
+find "$out" -type f | sort

.github/workflows/ci.yml

@@ -1,27 +1,28 @@
 name: CI
 
 # Pre-merge checks. Runs on the dev branch and on every pull request aimed at
-# dev or main, so breakage is caught before it reaches main.
+# dev or main, so breakage is caught before it reaches main and triggers a
+# release.
 #
-# On a push to dev it also publishes the build as a dev-channel prerelease on
-# this Gitea instance, so the in-app updater can offer it to anyone on the dev
-# channel. Prereleases are used deliberately: the "latest release" endpoint
-# skips them, so a production-channel user never sees a dev build. Pull
-# requests only build and check — they never publish, which keeps a PR from a
-# fork from shipping anything.
-#
-# These files live in .github/workflows/ on purpose: Gitea Actions reads that
-# path as well as .gitea/workflows/, so one file serves both. Publishing goes
-# through Gitea's REST API (the same routes the app's updater reads) rather
-# than the `gh` CLI, which a runner image need not carry.
+# On a push to dev it also publishes the build as a dev-channel prerelease, so
+# the in-app updater can offer it to anyone who has switched to that channel.
+# Prereleases are used deliberately: GitHub's "latest release" endpoint skips
+# them, so a production-channel user never sees a dev build. Pull requests only
+# build and check — they never publish, which keeps a PR from a fork from
+# shipping anything.
 on:
   push:
     branches: [ dev ]
   pull_request:
     branches: [ main, dev ]
   workflow_dispatch:
+    inputs:
+      first_deploy:
+        description: "First Cloudflare deploy: skip carrying over the other channel (the site does not exist yet)"
+        type: boolean
+        default: false
 
-# Needed by the job token to create the release and attach the APK.
+# Needed to publish the dev-channel prerelease below.
 permissions:
   contents: write
 
@@ -34,6 +35,8 @@ jobs:
   build:
     name: Build and check
     runs-on: ubuntu-latest
+    outputs:
+      version: ${{ steps.stage.outputs.version }}
     env:
       # Stamp the APK as a dev-channel build exactly when it is a build of the
       # dev branch, which is exactly when it can be published below. Pull
@@ -41,7 +44,10 @@ jobs:
       # <series>.0-dev: they are never published and must not claim a channel
       # version.
       #
-      # This condition has to stay in step with the publish steps' own.
+      # This condition has to stay in step with the publish steps' own. Stamping
+      # a build the publish steps would ship, or shipping one this left
+      # unstamped, both end the same way — an APK claiming versionCode 1, which
+      # the updater can never see as an upgrade over anything.
       PLG_CHANNEL: ${{ github.ref == 'refs/heads/dev' && 'dev' || '' }}
     steps:
       - name: Checkout
@@ -74,6 +80,19 @@ jobs:
           if-no-files-found: error
           retention-days: 14
 
+      - name: Upload JVM crash logs
+        # A JVM crash writes hs_err_pid*.log into the workspace, which dies
+        # with the job container; keep it so the failing frame can be read.
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: ProLibertateGames-jvm-crash
+          path: |
+            hs_err_pid*.log
+            replay_pid*.log
+          if-no-files-found: ignore
+          retention-days: 14
+
       - name: Upload lint and test reports
         # Reports are most useful precisely when a step above failed.
         if: always()
@@ -89,39 +108,74 @@ jobs:
       # branch itself, after it has built, tested and linted clean above.
       #
       # Gated on the branch alone rather than on the event, which is how
-      # release.yml gates main. A pull request is still excluded without
-      # needing to name it: a PR build runs against refs/pull/N/merge, never
-      # refs/heads/dev, so a fork still cannot ship anything.
+      # release.yml has always gated main. A pull request is still excluded
+      # without needing to name it: a PR build runs against refs/pull/N/merge,
+      # never refs/heads/dev, so a fork still cannot ship anything.
       - name: Stage dev APK
         id: stage
         if: github.ref == 'refs/heads/dev'
         run: |
           set -euo pipefail
-          # The series and the offset come from gradle.properties, which is
-          # the same file the build read when it stamped the APK — so the tag
-          # and what is inside it cannot name different versions. The number
-          # is run number + offset, exactly the arithmetic build.gradle.kts
-          # did for versionCode.
+          # The series comes from gradle.properties, which is the same file the
+          # build read when it stamped the APK — so the tag and what is inside
+          # it cannot name different versions.
           series="$(sed -n 's/^plgVersionSeries=//p' gradle.properties)"
-          offset="$(sed -n 's/^plgVersionRunOffset=//p' gradle.properties)"
           test -n "$series"
+          offset="$(sed -n 's/^plgVersionRunOffset=//p' gradle.properties)"
           test -n "$offset"
-          stamp="$(( ${{ github.run_number }} + offset ))"
-          version="v${series}.${stamp}-dev"
+          # Same arithmetic as build.gradle.kts, so the tag names the APK's own number.
+          version="v${series}.$(( ${{ github.run_number }} + offset ))-dev"
           src="app/build/outputs/apk/debug/app-debug.apk"
           dest="ProLibertateGames-${version}.apk"
           cp "$src" "$dest"
           echo "version=$version" >> "$GITHUB_OUTPUT"
           echo "apk=$dest" >> "$GITHUB_OUTPUT"
 
-      - name: Publish dev channel prerelease
+      - name: Upload staged dev APK for the Pages deploy
         if: github.ref == 'refs/heads/dev'
+        uses: actions/upload-artifact@v4
+        with:
+          name: plg-dev-staged
+          path: ${{ steps.stage.outputs.apk }}
+          if-no-files-found: error
+          retention-days: 1
+
+  # Publishes the build to https://plg.wallacenet.ca (Cloudflare Pages), which is
+  # the only release channel: the in-app updater reads latest.json from there.
+  #
+  # Both workflows deploy into one Pages site, and a deploy replaces the whole
+  # site, so they share a concurrency group and never run at the same time.
+  deploy-pages:
+    name: Deploy to Cloudflare Pages
+    needs: build
+    if: github.ref == 'refs/heads/dev'
+    runs-on: ubuntu-latest
+    concurrency:
+      group: plg-pages-deploy
+      cancel-in-progress: false
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Download staged APK
+        uses: actions/download-artifact@v4
+        with:
+          name: plg-dev-staged
+          path: staged
+
+      - name: Assemble site
         env:
-          # The job's built-in token: contents: write is declared above.
-          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
-          RELEASE_TAG: ${{ steps.stage.outputs.version }}
-          RELEASE_APK: ${{ steps.stage.outputs.apk }}
-          RELEASE_KIND: prerelease
-          RELEASE_TARGET: ${{ github.sha }}
-        # One script, also runnable by hand — see docs/CI.md.
-        run: ./scripts/publish-release.sh
+          PLG_SKIP_OTHER: ${{ inputs.first_deploy && '1' || '' }}
+        run: .github/scripts/stage-pages-site.sh dev "${{ needs.build.outputs.version }}" "staged/ProLibertateGames-${{ needs.build.outputs.version }}.apk"
+
+      - name: Deploy
+        env:
+          CLOUDFLARE_API_TOKEN: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+          CLOUDFLARE_ACCOUNT_ID: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
+        run: |
+          set -euo pipefail
+          # Creates the project on first run; fails harmlessly if it exists.
+          npx --yes wrangler@3 pages project create plg --production-branch main || true
+          # --branch main makes this the production deployment, which is what
+          # plg.wallacenet.ca serves, whichever branch the workflow ran on.
+          npx --yes wrangler@3 pages deploy pages-out --project-name plg --branch main --commit-dirty=true

.github/workflows/release.yml

@@ -1,17 +1,18 @@
 name: Build and Release APK
 
-# Production-channel build. Runs on a push to main, or by hand
-# (workflow_dispatch), and publishes to this Gitea instance's releases — which
-# is the channel the in-app updater reads. See docs/CI.md.
-#
-# Publishing goes through Gitea's REST API rather than the `gh` CLI, which a
-# runner image need not carry.
+# Build an APK and publish it as a GitHub Release whenever commits land on main
+# (for example when a pull request is merged). Can also be run manually.
 on:
   push:
     branches: [ main ]
   workflow_dispatch:
+    inputs:
+      first_deploy:
+        description: "First Cloudflare deploy: skip carrying over the other channel (the site does not exist yet)"
+        type: boolean
+        default: false
 
-# Needed by the job token to create the release and attach the APK.
+# Allow the built-in token to create releases and upload the APK.
 permissions:
   contents: write
 
@@ -23,13 +24,16 @@ concurrency:
 jobs:
   build:
     name: Build APK and publish release
-    # workflow_dispatch can be aimed at any branch from the Actions UI. The
-    # production stamp belongs to main alone — anything else is a no-op rather
-    # than shipping unreviewed code to everybody.
+    # workflow_dispatch can be aimed at any branch from the Actions UI. Releases
+    # are what the in-app updater installs, so only main may produce one —
+    # anything else is a no-op rather than shipping unreviewed code to everyone.
     if: github.ref == 'refs/heads/main'
     runs-on: ubuntu-latest
+    outputs:
+      version: ${{ steps.stage.outputs.version }}
     env:
-      # Stamps the APK as a production-channel build.
+      # Stamps the APK as a production-channel build, versioned with the run
+      # number that matches the tag published below.
       PLG_CHANNEL: production
     steps:
       - name: Checkout
@@ -45,44 +49,76 @@ jobs:
       - name: Set up Android SDK
         uses: android-actions/setup-android@v4
 
-      - name: Build production APK
-        run: ./gradlew assembleDebug --no-daemon --stacktrace
+      - name: Build release APK
+        run: ./gradlew assembleRelease --no-daemon --stacktrace
 
-      - name: Stage APK
+      - name: Stage APK for release
         id: stage
         run: |
           set -euo pipefail
-          # The series and the offset come from gradle.properties, which is
-          # the same file the build read when it stamped the APK — so the tag
-          # and what is inside it cannot name different versions. The number
-          # is run number + offset, exactly the arithmetic build.gradle.kts
-          # did for versionCode.
+          # The series comes from gradle.properties, which is the same file the
+          # build read when it stamped the APK — so the tag and what is inside
+          # it cannot name different versions.
           series="$(sed -n 's/^plgVersionSeries=//p' gradle.properties)"
-          offset="$(sed -n 's/^plgVersionRunOffset=//p' gradle.properties)"
           test -n "$series"
+          offset="$(sed -n 's/^plgVersionRunOffset=//p' gradle.properties)"
           test -n "$offset"
-          stamp="$(( ${{ github.run_number }} + offset ))"
-          version="v${series}.${stamp}"
-          src="app/build/outputs/apk/debug/app-debug.apk"
+          # Same arithmetic as build.gradle.kts, so the tag names the APK's own number.
+          version="v${series}.$(( ${{ github.run_number }} + offset ))"
+          src="app/build/outputs/apk/release/app-release.apk"
           dest="ProLibertateGames-${version}.apk"
           cp "$src" "$dest"
+          # The same build again under a name that never changes. GitHub's
+          # /releases/latest/download/<name> redirect needs a constant file
+          # name, so this second copy is what makes a permanent download link
+          # possible — the versioned copy stays as the traceable one.
+          cp "$src" "ProLibertateGames.apk"
           echo "version=$version" >> "$GITHUB_OUTPUT"
           echo "apk=$dest" >> "$GITHUB_OUTPUT"
 
       - name: Upload APK as workflow artifact
         uses: actions/upload-artifact@v4
         with:
-          name: ProLibertateGames-apk
+          name: plg-prod-staged
           path: ${{ steps.stage.outputs.apk }}
           if-no-files-found: error
 
-      - name: Publish production release
+  # Publishes the build to https://plg.wallacenet.ca (Cloudflare Pages), which is
+  # the only release channel: the in-app updater reads latest.json from there.
+  #
+  # Both workflows deploy into one Pages site, and a deploy replaces the whole
+  # site, so they share a concurrency group and never run at the same time.
+  deploy-pages:
+    name: Deploy to Cloudflare Pages
+    needs: build
+    if: github.ref == 'refs/heads/main'
+    runs-on: ubuntu-latest
+    concurrency:
+      group: plg-pages-deploy
+      cancel-in-progress: false
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Download staged APK
+        uses: actions/download-artifact@v4
+        with:
+          name: plg-prod-staged
+          path: staged
+
+      - name: Assemble site
         env:
-          # The job's built-in token: contents: write is declared above.
-          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
-          RELEASE_TAG: ${{ steps.stage.outputs.version }}
-          RELEASE_APK: ${{ steps.stage.outputs.apk }}
-          RELEASE_KIND: release
-          RELEASE_TARGET: ${{ github.sha }}
-        # One script, also runnable by hand — see docs/CI.md.
-        run: ./scripts/publish-release.sh
+          PLG_SKIP_OTHER: ${{ inputs.first_deploy && '1' || '' }}
+        run: .github/scripts/stage-pages-site.sh prod "${{ needs.build.outputs.version }}" "staged/ProLibertateGames-${{ needs.build.outputs.version }}.apk"
+
+      - name: Deploy
+        env:
+          CLOUDFLARE_API_TOKEN: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+          CLOUDFLARE_ACCOUNT_ID: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
+        run: |
+          set -euo pipefail
+          # Creates the project on first run; fails harmlessly if it exists.
+          npx --yes wrangler@3 pages project create plg --production-branch main || true
+          # --branch main makes this the production deployment, which is what
+          # plg.wallacenet.ca serves, whichever branch the workflow ran on.
+          npx --yes wrangler@3 pages deploy pages-out --project-name plg --branch main --commit-dirty=true

CLAUDE.md

@@ -1,95 +1,109 @@
-# Working on this repo (agent notes)
+# Working on this repo with Claude
 
-ProLibertateGames — Wallacenet's build of an Android collection of card and
-board games, playable against AI or over Wi-Fi (LAN). Upstream:
-[adrianoftyriel/ProLibertateGames](https://github.com/adrianoftyriel/ProLibertateGames)
-(GPL-3.0, kept as the `upstream` remote). Canonical repo:
-<https://git.wallacenet.ca/devadmin/ProLibertateGames>.
+CI runs on **Gitea Actions** at `git.wallacenet.ca/devadmin/ProLibertateGames`
+(workflows in `.github/workflows/`), publishing to Cloudflare Pages
+(`plg.wallacenet.ca`). The workflow below was measured on the dev machine
+(`~/ProLibertateGames`); it replaces the earlier GitHub-sandbox notes, which no
+longer apply.
 
-## Ground rules
+## Build, test and lint locally
 
-- **Licences travel.** `LICENSE` is GPL-3.0 and must stay. The Uncial Antiqua
-  font ships with its OFL licence at `docs/licenses/UncialAntiqua-OFL.txt`;
-  never delete or edit either. Attribution to the upstream lives in the README.
-- **No Catan trademarks or brand assets** — the one hard line. The app's own
-  branding is the upstream's, restored (see README → Branding): tartan launcher
-  icon and splash, Wallace clan red on production and hunting green on dev,
-  launcher names *Pro Libertate Games* / *Pro Libertate Games DEV*. The
-  installed identity is `ca.wallacenet.prolibertategames` (+ `.dev`).
-- **The existing catalogue is the regression safety net.** Keep every game
-  green; new games (Katan) arrive as separate tasks, not edits to old ones.
-  The 22 reference games are `available = true`; Katan is listed with
-  `available = false` (*Coming soon*) until its game task lands.
-- **Docs conventions**: every game gets `docs/RULES-<id>.md` (index and gaps in
-  `docs/README.md`); build/CI/release decisions go in `docs/CI.md`. Update the
-  docs when behaviour changes — they are the check against the rules code.
+Gradle works on the dev machine. Two environment variables are required: the
+default JDK is 25, which Gradle 8.14 cannot use, and the Android SDK lives in the
+home directory.
 
-## Build
-
-```sh
-export JAVA_HOME=...   # JDK 17
-export ANDROID_HOME=...  # SDK with platform 34, build-tools 34
-./gradlew assembleDebug            # dev-channel APK (default)
-PLG_CHANNEL=production ./gradlew assembleDebug   # production APK
-./gradlew testDebugUnitTest        # JVM unit tests (rules/AI/net/score)
-./gradlew lintDebug                # Android lint (CI runs it)
+```
+export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64
+export ANDROID_HOME=$HOME/android-sdk      # platform 34, build-tools 34.0.0
+./gradlew testDebugUnitTest lintDebug assembleDebug
 ```
 
-On the Wallacenet project workspace a ready toolchain sits at
-`../.toolchain/` (`jdk17/`, `android-sdk/`) — export `JAVA_HOME` and
-`ANDROID_HOME` to it rather than installing again. Both variants must build:
-they install side by side (different applicationId, launcher name, colour).
+The Katan tests run in seconds; a clean build takes a few minutes. Run the full
+suite, lint and `assembleDebug` before pushing: they are what CI runs. There is
+no KVM, so no emulator; the engine and the UI logic are covered by unit tests
+(see `docs/UI-catan.md`).
 
-## Channels and OTA
+## Shipping: branch, PR, CI, merge
 
-One flag — `isDevBuild` in `app/build.gradle.kts` — drives applicationId,
-launcher name and brand colour together. Never set them individually.
+1. Branch from `dev`; before pushing, merge `origin/dev` in (it moves between
+   sessions).
+2. Plain `git push` has no credentials. Use the Gitea token as a one-off header:
+   `git -c "http.extraheader=Authorization: token $(cat ~/.config/gitea/token)" push -u origin <branch>`.
+3. Open the PR with `POST /api/v1/repos/devadmin/ProLibertateGames/pulls`
+   (same token, `Authorization: token ...`). CI (`ci.yml`) runs on the PR: build,
+   unit tests and Android lint; it publishes nothing. Poll
+   `/actions/runs` until it completes (about 7 minutes).
+4. Merge with `POST .../pulls/N/merge {"Do":"merge"}`. The push to `dev` runs
+   `ci.yml` again and publishes the build (about 9 minutes).
 
-In-app OTA points at this repo's own Gitea releases
-(`/api/v1/repos/devadmin/ProLibertateGames/releases…`) and is **on**:
-`BuildConfig.OTA_ENABLED` is `true`. The channel is a decision already made and
-recorded — `docs/CI.md` documents the endpoints, the build-number scheme, and
-what publishing requires. Setting the flag to `false` is the kill switch.
+## Merging is a shipping action
 
-## CI
+Both long-lived branches publish, so a merge is a release, not just an
+integration:
 
-`.github/workflows/` — Actions-compatible so the Gitea instance runs them.
-`ci.yml`: build + test + lint + artifact, and a dev prerelease from `dev`.
-`release.yml`: production release from `main`. Both publish through
-`scripts/publish-release.sh` (Gitea REST API), which is also runnable by hand.
+- **`dev`** publishes a `v<series>.N-dev` build to
+  `https://plg.wallacenet.ca/dev/latest.json`, offered by the in-app updater to
+  anyone on the Dev channel.
+- **`main`** runs `release.yml` and publishes a **production** release for
+  everyone on the Production channel. Confirm before merging to `main`.
+  `release.yml` runs `assembleDebug` only (no tests, no lint), so a `main`
+  release is only as verified as the `dev` build it replays.
 
-**No Actions runner is registered on the instance yet**, so the workflows are
-idle until one is — the local gradle commands above are the source of truth,
-and CI green means those plus lint. Do not treat a workflow that has never run
-as evidence.
+## Katan
 
-## Code map
+The island game is catalogue id `catan`, shown as **Katan**. It has two expansions
+(toggles, `CatanOptions.expansions`; none on is the base game): the base game (`docs/RULES-catan.md`), Cities & Knights
+(`docs/RULES-catan-ck.md`, code in `game/catan/CatanCk*.kt`, state behind
+`CatanState.ck`, which is null in the base game) and Seafarers
+(`docs/RULES-catan-seafarers.md`, code in `game/catan/CatanSea*.kt`, state behind
+`CatanState.sea`). The base and Seafarers rules read the board from `state.topo`, not from
+`CatanBoard` directly, because a Seafarers map is not the 19-hex island
+(Cities & Knights is always the standard island and still uses `CatanBoard`). The
+Catan Universe reverse engineering that shaped the landscape HUD and trade board
+is in `docs/RE-catan-universe.md`. The screen is layered; see
+`docs/UI-catan.md` before changing it.
 
-- `game/` — rules engines and AI, **pure Kotlin, no Android types**, unit
-  tested. `Catalog.kt` is the registry (id, title, blurb, options, `available`).
-- `net/` — wire protocol, LAN transport (mDNS + TCP), lobby, host-authoritative
-  match driver; `score/` the scorekeeper sheet, also pure.
-- `ui/` — Compose screens; `ui/theme/Theme.kt` holds the brand palette
-  (`BrandField`/`BrandDeep`/`BrandAccent`) and table accents.
-- `update/` — OTA policy (`UpdatePolicy.kt`, pure and tested) and the gated
-  fetch (`Updater.kt`).
-- `settings/` — DataStore preferences.
+## Bash output is filtered before it reaches the model
 
-Host is authoritative over the wire; clients send intents, host re-validates
-against the rules. Keep `game/` free of Android imports — the JVM tests depend
-on it.
+`.claude/settings.json` registers a `PreToolUse` hook on `Bash` that rewrites
+each command through [rtk](https://github.com/rtk-ai/rtk): `git status` runs as
+`rtk git status`, and rtk compresses the output. Write commands normally — the
+rewrite is transparent and costs nothing to invoke.
 
-## Git
+Measured on this repo rather than quoted from rtk's README:
 
-- Branches: `main` (production), `dev` (integration). Feature branches → PR
-  into `dev`.
-- Commits by Paperclip agents end with
-  `Co-Authored-By: Paperclip <[email protected]>`.
-- Pull upstream fixes with `git pull upstream` (the GitHub source); do not
-  point `origin` anywhere but this repo's Gitea URL.
+| Command | Raw | Filtered | Saved |
+| --- | --- | --- | --- |
+| `git diff HEAD~3` | 521 KB | 28 KB | 95% |
+| `grep -rn "fun " app/src/main` | 117 KB | 19 KB | 84% |
+| `find . -name "*.kt"` | 7.7 KB | 1.7 KB | 79% |
+| `git log -20` | 20 KB | 5.3 KB | 74% |
+| `git diff --stat` | 4.0 KB | 4.0 KB | 1% |
+| `ls` of a single package | 50 B | 62 B | −24% |
 
-## Legacy files
+The saving is all in the large outputs, which is the point — a full diff of a
+few commits is otherwise most of a context window. Already-compact output grows
+slightly, because rtk adds a header; at those sizes it does not matter. `rtk
+gain` reports what the current session has actually saved.
 
-`.claude/` and `.rtk/` are the upstream author's assistant tooling, harmless
-and left as inherited. This file supersedes the upstream's CLAUDE.md (which
-documented their GitHub sandbox; that history is still in git).
+Two limits are worth knowing. The `Read`, `Grep` and `Glob` tools are not
+`Bash`, so they never reach the hook and are unaffected; a deliberate `rg` or
+`find` in a shell *is* filtered. And filtering never truncates a file: `cat`
+becomes `rtk read`, which was checked byte-for-byte against this repo's longest
+Kotlin source (`GameSetupScreen.kt`, 946 lines) and came back identical. Commit
+messages survive the rewrite intact, quotes and colons included. To bypass
+filtering for one command, run `rtk proxy <cmd>`.
+
+## rtk is reinstalled at the start of every session
+
+The container starts empty, so `.claude/hooks/session-start.sh` installs rtk
+before the session does anything. It pins `RTK_VERSION`, because the installer
+otherwise asks `api.github.com` for the latest tag and the proxy answers 403 for
+every repository except this one — the lookup fails and takes the install with
+it. Bump that variable by hand.
+
+The hook is written not to matter when it fails. Outside the sandbox it installs
+nothing and just prints the command to run, since dropping a binary into
+someone's `~/.local/bin` uninvited is not its business; if the download fails it
+says so and exits clean. With rtk absent the rewrite hook no-ops, and the only
+consequence is verbose output.

README.md

@@ -1,32 +1,24 @@
-# ProLibertateGames
+# Pro Libertate Games
 
 A collection of card and board games for Android, playable against the computer
 or against other people over Wi-Fi (LAN).
 
-Wallacenet's build of [ProLibertateGames](https://github.com/adrianoftyriel/ProLibertateGames)
-by adrianoftyriel (GNU GPL v3 — see [LICENSE](LICENSE)), hosted at
-<https://git.wallacenet.ca/devadmin/ProLibertateGames>. Game rules documentation
-lives under [docs/](docs/README.md); build, CI and release decisions live in
-[docs/CI.md](docs/CI.md). Katan itself arrives in later work — it is listed under
-Board Games as *Coming soon* — and this app ships the reference catalogue
-unchanged as the regression safety net.
-
 ## What works today
 
 The app shell is complete and every game in the catalogue is playable end to end:
 
 | | |
 | --- | --- |
-| **Cards** | Euchre, Kaiser, President, Golf, Wizard, Crazy 8s, Cribbage, Hearts, Klondike, FreeCell, Spider, Pyramid |
-| **Table** | Sequence, Chess, Checkers, Backgammon, Mastermind, Nine Men's Morris, Peg Solitaire, Yahtzee, Pirates and Bulgars, Ta Yü, Katan *(coming soon)* |
+| **Cards** | Euchre, Kaiser, President, Golf, Wizard, Crazy 8s, Cribbage |
+| **Board** | Sequence, Chess, Checkers, Backgammon, Mastermind, Nine Men's Morris, Pirates and Bulgars, Ta Yü |
 
-One entry is marked *Coming soon*: Katan, the island game, whose engine and
-screen land with their own task. The machinery is still there and still tested:
-a game listed in `GameCatalog` with `available = false` appears in the menu
-marked *Coming soon* **on dev builds only**, so a production release lists just
-what can actually be played and nobody installs it and taps into a dead end. The
-menu decides this from the installed APK's own version name — the same source
-the updater uses to know which channel it is on.
+Nothing is marked *Coming soon* at the moment, because nothing is waiting. The
+machinery for it is still there and still tested: a game listed in `GameCatalog`
+with `available = false` appears in the menu marked *Coming soon* **on dev builds
+only**, so a production release lists just what can actually be played and nobody
+installs it and taps into a dead end. The menu decides this from the installed
+APK's own version name — the same source the updater uses to know which channel
+it is on.
 
 Adding a game means writing a `GameRules` implementation, a `GameAi` and a
 screen, then flipping `available` — the menu, lobby, networking, settings and OTA
@@ -119,53 +111,55 @@ it: every rule above is a pure function and unit-tested on the JVM.
 - **Sound** on/off.
 - **Animation speed**, 0.5×–2×. One multiplier drives card movement and how long
   the computer appears to think.
-- **Updates** — check on launch, or check on demand. The channel is this
-  project's own Gitea releases ([docs/CI.md](docs/CI.md)), and **there is no
-  channel to choose**: a build updates from its own channel and no other. The
-  settings screen states which one is running rather than offering a switch.
-  `BuildConfig.OTA_ENABLED` is the kill switch, not a preference.
+- **Updates** — check on launch, or check on demand. **There is no channel to
+  choose**: a build updates from its own channel and no other. A production
+  install is offered production builds from `main`; a dev install is offered dev
+  builds from `dev`. The settings screen states which one is running rather than
+  offering a switch.
 
   The check on launch **only ever speaks when there is a build to install**. It
   runs behind the splash and waits for it to clear, and an app that is already
-  current — or a phone that cannot reach the release server — says nothing,
-  because opening the app was not a question. The button in Settings is a
-  question, so it answers every time, including "you're on the latest" and
-  whatever went wrong.
+  current — or a phone that cannot reach GitHub — says nothing, because opening
+  the app was not a question. The button in Settings is a question, so it
+  answers every time, including "you're on the latest" and whatever went wrong.
 
   Wanting both means installing both — they are separate apps and each updates
   itself, see [Both channels on one device](#both-channels-on-one-device).
 
 ## Branding
 
-The app wears the upstream's own branding, restored (WALA-118 review): the
-Wallace tartan is the launcher icon and the splash, drawn as vector drawables and
-Compose code so it stays sharp at every density and needs no PNGs. The app opens
-on the tartan held under the name, set in a Celtic uncial hand for two seconds
-before it fades into the menu.
+The launcher icon is a single square of the Wallace tartan set on the bias, and
+the app opens on the same cloth carrying the name in a Celtic uncial hand for two
+seconds before fading into the menu.
 
-A dev build wears the **hunting green** sett where production wears the **clan
-red**, and installs as *Pro Libertate Games DEV*. That is what tells the two
-copies apart when both are on the phone; see
-[Both channels on one device](#both-channels-on-one-device). The tartan is drawn
-by `ui/theme/Tartan.kt` (`TartanBackground`, `threadWidthFor`) off
-`BuildConfig.DEV_BUILD`; the matching vector colours are generated per build by
-`resValue` in `app/build.gradle.kts` — the icon vectors reference
-`@color/tartan_field` rather than a literal, which is how one set of vectors
-serves both colourways.
+A dev build wears **Wallace Hunting** instead — the same threadcount with green
+where the clan sett has red — and installs as *Pro Libertate Games DEV*. That is
+what tells the two copies apart when both are on the phone; see
+[Both channels on one device](#both-channels-on-one-device).
+
+The tartan is drawn, not an image: `ui/theme/Tartan.kt` lays the sett down as
+warp and then as weft at half opacity, which is what produces the blended
+squares instead of a flat grid. The icon is the same construction as a vector
+drawable, so it stays sharp at every density and needs no PNGs.
 
 Two honest caveats:
 
+- **The sett is the published threadcount: `K/4 R32 K32 Y/4`.** The slashes are
+  pivots, so `WallaceSett` holds the half-sett and reflects it out to
+  `K4 R32 K32 Y4 K32 R32` — 136 threads, about half black, half red, with a
+  yellow line worth 3%. Two details define the pattern and are easy to get
+  backwards: the yellow overstripe runs down the *centre of a wide black band*,
+  and the narrow black guard sits *between two red blocks*. The icon is
+  generated from the same numbers, so the icon and the splash cannot drift.
+  Weave scale is derived from the sett rather than fixed, so changing the
+  threadcount rescales both instead of silently zooming in. The hunting
+  colourway is the same threadcount passed a different field colour, not a
+  second copy of the numbers, so it cannot fall out of step either.
 - **The typeface is bundled under a licence.** Uncial Antiqua, © 2011 Brian J.
   Bonislawsky DBA Astigmatic, Reserved Font Name "Uncial Antiqua", used under
   the SIL Open Font License 1.1. The full licence is at
   [docs/licenses/UncialAntiqua-OFL.txt](docs/licenses/UncialAntiqua-OFL.txt) and
   must stay with the font — the OFL requires it to be distributed alongside.
-- **Katan is the one place this app deliberately diverges.** No Catan
-  trademarks or brand assets ship anywhere in it; the island game is listed
-  under its own name with original art only. The GPL-licensed history that
-  produced this app remains in git, and the source stays at
-  [adrianoftyriel/ProLibertateGames](https://github.com/adrianoftyriel/ProLibertateGames)
-  as the `upstream` remote.
 
 ## Screen sizes
 
@@ -189,70 +183,122 @@ smaller than a fingertip.
 
 Requires JDK 17 and the Android SDK (compileSdk 34).
 
-A local build is a dev build: it installs as
-`ca.wallacenet.prolibertategames.dev` under the name *Pro Libertate Games DEV* on
-the hunting-green sett, so it goes on beside a production copy rather than over
-it. Set `PLG_CHANNEL=production` to build the production package
-(`ca.wallacenet.prolibertategames`, clan red).
+A local build is a dev build: it installs as `org.prolibertate.games.dev` under
+the name *Pro Libertate Games DEV* in the hunting sett, so it goes on beside an
+installed release rather than over it. Set `PLG_CHANNEL=production` to build the
+production package instead.
 
 ## CI
 
-Full decision record: [docs/CI.md](docs/CI.md).
-
 - `.github/workflows/ci.yml` — builds, tests and lints on `dev` and on pull
-  requests into `dev` or `main`, and publishes a dev prerelease from `dev`.
-- `.github/workflows/release.yml` — builds and publishes the production release
-  on push to `main`, or by hand (`workflow_dispatch`).
-- Both publish through [scripts/publish-release.sh](scripts/publish-release.sh)
-  against Gitea's REST API, which is also runnable by hand. **No Actions runner
-  is registered on the instance yet**, so until one is, the local build is the
-  guaranteed path (`./gradlew assembleDebug && ./gradlew testDebugUnitTest`)
-  and releases go out via the script.
+  requests into `dev` or `main`. Its APK artifact is a dev build, versioned
+  `<series>.0-dev` — the series being whatever `plgVersionSeries` says in
+  `gradle.properties`, currently **1.3**.
+- `.github/workflows/release.yml` — on push to `main`, builds the APK and
+  publishes it as a GitHub Release tagged `v<series>.<run-number>`. The in-app updater
+  reads that tag, which is why the APK's `versionCode` is the same run number.
+
+### Hosting: plg.wallacenet.ca
+
+Both channels are also deployed to one Cloudflare Pages project (`plg`), served at
+`https://plg.wallacenet.ca`:
+
+```
+/                        landing page (reads both latest.json files)
+/prod/latest.json        {tag, apkName, apkUrl, channel} — what the updater reads
+/prod/ProLibertateGames.apk, /prod/ProLibertateGames-v<series>.<n>.apk
+/dev/...                 same, for the dev channel
+```
+
+Each workflow's `deploy-pages` job runs `.github/scripts/stage-pages-site.sh`,
+which stages its own channel and re-fetches the other channel from the live site,
+because a Pages deploy replaces everything. The two share a concurrency group so
+they cannot race. Needs repo secrets `CLOUDFLARE_API_TOKEN` (Account → Cloudflare
+Pages → Edit) and `CLOUDFLARE_ACCOUNT_ID`. Pages caps files at 25 MiB.
+
+**First deploy:** the site does not exist yet, so the domain answers 403 (Cloudflare error 1014) and the carry-over fetch would abort. Dispatch the workflow once with `first_deploy` ticked, then attach `plg.wallacenet.ca` as a custom domain on the new `plg` Pages project. Later runs need no input.
+
+The in-app updater reads these `latest.json` files, and this is the only release
+channel: the workflows no longer create GitHub or Gitea releases. They run on
+Gitea Actions (`https://git.wallacenet.ca/devadmin/ProLibertateGames`); the GitHub
+repository is frozen and should stay public with its last releases, because
+installs that predate the Cloudflare updater still read them to reach it.
+
+Build numbers are `run number + plgVersionRunOffset` (1000, in `gradle.properties`),
+so moving CI hosts, which restarts run numbers, can never publish a `versionCode`
+lower than one already installed.
+
+### Installing without the app
+
+The newest production build is always at **https://plg.wallacenet.ca/prod/ProLibertateGames.apk** (dev: `/dev/ProLibertateGames.apk`). The GitHub link below is the frozen pre-migration release:
+
+**https://github.com/adrianoftyriel/ProLibertateGames/releases/latest/download/ProLibertateGames.apk**
+
+Every release carries the same APK twice — once named for its version, and once
+as plain `ProLibertateGames.apk`, because GitHub's `/releases/latest/download/`
+redirect needs a file name that stays put. The in-app updater deliberately picks
+the versioned copy, so an installed build can always be traced back to its tag.
+
+There is no equivalent link for the dev channel: `/releases/latest` skips
+prereleases by design, and that is exactly what keeps a production install from
+being handed a dev build. A dev build is reached by the in-app updater of a dev
+install — which looks at the prerelease list rather than that endpoint — or from
+the releases page.
 
 ### The version series
 
-A version is **`<series>.<build number>`**. Both values are set by hand, once,
-in `gradle.properties`:
+A version is **`<series>.<run number>`**. The series is set by hand, once, in
+`gradle.properties`:
 
 ```properties
-plgVersionSeries=1.4
-plgVersionRunOffset=1000
+plgVersionSeries=1.3
 ```
 
-Both workflows read those same properties when they name a release tag, and the
-build reads them when it stamps the APK, so the tag and what is inside it cannot
-name different versions. Changing either is a one-line change to that file and
-nothing else — but they are not equivalent:
+Both workflows read that same property when they name a release tag, and the
+build reads it when it stamps the APK, so the tag and what is inside it cannot
+name different versions. Bumping a series is a one-line change to that file and
+nothing else.
 
-- The **series** is a name for people. Bumping it changes nothing about
-  ordering.
-- The **build number** is what the machines compare: `versionCode`, the tag's
-  trailing number, and the number in `versionName`, all the same figure —
-  `CI run number + plgVersionRunOffset`. Because the offset never changes and
-  the run number only climbs, going from 1.4 to 1.5 never looks like a downgrade
-  to Android and never interrupts an OTA update.
-
-The offset exists because Gitea Actions restarts run numbers at 1 for each
-workflow: without a floor, the first release of a fresh instance would collide
-with the `versionCode 1` every unstamped local build carries, and a counter
-reset would make Android refuse the next build outright. Full reasoning in
-[docs/CI.md](docs/CI.md).
+The number after it is the CI run number and keeps climbing on its own, which is
+what makes a series bump safe: `versionCode` is the run number *alone*, so
+going from 1.0 to 1.1 never looks like a downgrade to Android and never
+interrupts an OTA update. The series is a name for people; the run number is
+what the machines compare.
 
 ### Update channels
 
-`ci.yml` stamps builds of `dev` as dev-channel, `release.yml` stamps `main` as
-production, so an APK's identity is decided where it is built. Publishing goes
-to this project's Gitea releases, and the rules it keeps:
+Both pipelines publish, to two separate channels:
 
-- production comes only from `main` (`release.yml` refuses any other branch);
-- dev prereleases are marked so the "latest release" endpoint can never hand one
-  to a production install;
-- pull requests build and check but never publish.
+| Channel | Published by | Tag | Marked |
+| --- | --- | --- | --- |
+| Production | `release.yml`, push to `main` | `v<series>.<n>` | release |
+| Dev | `ci.yml`, any build of `dev` | `v<series>.<n>-dev` | prerelease |
+
+Dev builds are published as **prereleases** deliberately: GitHub's "latest
+release" endpoint skips prereleases, so a production-channel install can never
+be handed a dev build even by accident. Pull requests build and check but never
+publish, so a PR from a fork cannot ship anything.
+
+**Both pipelines gate publishing on the branch rather than on what triggered
+the build**, so a manual run from the Actions tab publishes exactly as a push
+does — useful when a push cannot fire the workflow itself, which is the case
+for anything pushed by an automation token. The safety property is unchanged,
+because publishing still happens only after that same job has built, tested and
+linted clean. A pull request is still excluded without having to be named: a PR
+build runs against `refs/pull/<n>/merge`, never `refs/heads/dev`.
+
+In `ci.yml` the `PLG_CHANNEL` stamp is gated on the same condition as the
+publish steps, and the two have to stay in step. Stamping a build that then
+ships, or shipping one that was left unstamped, both end with an APK claiming
+`versionCode` 1 — which the updater can never see as an upgrade over anything.
+
+`release.yml` refuses to run off any branch but `main`, so a manual dispatch
+aimed elsewhere does nothing rather than shipping unreviewed code.
 
 **The two channels have independent version sequences** — a build's `versionCode`
-is the build number of the workflow that produced it (run number + offset), and
-the two workflows count separately, so the numbers say nothing across the
-divide.
+is the run number of the workflow that produced it, and the two workflows count
+separately. Dev is on 69 while production is on 40, so the numbers say nothing
+across the divide.
 
 That is why **an install only ever updates within its own channel**, and why
 there is no setting for it. The app reads the `-dev` suffix in its own
@@ -264,18 +310,18 @@ unit-tested on the JVM like the rules engines are.
 
 ### Both channels on one device
 
-A dev build installs under its own `applicationId`,
-`ca.wallacenet.prolibertategames.dev`, so it is a separate app as far as Android
-is concerned and can sit beside the production copy rather than replacing it. Each channel still updates itself
+A dev build installs under its own `applicationId`, `org.prolibertate.games.dev`,
+so it is a separate app as far as Android is concerned and can sit beside the
+production copy rather than replacing it. Each channel still updates itself
 normally, because an update within a channel keeps the same package.
 
 Three things move together, all off `isDevBuild` in `app/build.gradle.kts`:
 
 | | Production | Dev |
 | --- | --- | --- |
-| `applicationId` | `ca.wallacenet.prolibertategames` | `ca.wallacenet.prolibertategames.dev` |
+| `applicationId` | `org.prolibertate.games` | `org.prolibertate.games.dev` |
 | Launcher name | Pro Libertate Games | Pro Libertate Games DEV |
-| Tartan sett | clan red | hunting green |
+| Sett | Wallace (red) | Wallace Hunting (green) |
 
 Anything that is not an explicit `PLG_CHANNEL=production` build is a dev build,
 so a local `assembleDebug` is a dev build too and installs alongside a release
@@ -285,11 +331,11 @@ They have to move together. A dev package wearing the production name and
 colours is precisely the mix-up that having both installed is meant to prevent,
 which is why one flag drives all three rather than each being set by hand. The
 name and the colours reach the resources through `resValue`, so `app_name`,
-`brand_field` and `splash_background` are generated by the build and are
-deliberately *not* in `res/values/` — the icon vectors reference
-`@color/brand_field` rather than a literal, which is how one set of vectors
-serves both colourways. `BuildConfig.DEV_BUILD` carries the same flag into
-Kotlin, where `BrandField` picks the matching Compose colour for the splash.
+`tartan_field`, `splash_background` and `ic_launcher_background` are generated
+by the build and are deliberately *not* in `res/values/` — the icon vectors
+reference `@color/tartan_field` rather than a literal, which is how one set of
+vectors serves both colourways. `BuildConfig.DEV_BUILD` carries the same flag
+into Kotlin, where `AppSett` picks the matching Compose sett for the splash.
 
 Because they are separate apps, having both is a matter of installing both, and
 each then updates itself down its own line. Nothing in the app moves a phone
@@ -303,7 +349,7 @@ for a signature mismatch.
 ## Rules
 
 The exact rules implemented, and the options that vary them, are documented per
-game (index: [docs/README.md](docs/README.md)):
+game:
 
 - [Euchre](docs/RULES-euchre.md)
 - [Sequence](docs/RULES-sequence.md) — **note the caveat about the board layout**
@@ -326,6 +372,10 @@ game (index: [docs/README.md](docs/README.md)):
 - [Ta Yü](docs/RULES-tayu.md) — **note the caveats about the reconstruction**:
   the game is out of print and the rulebook could not be obtained, so the
   document says which parts are attested and which were derived
+- [Katan](docs/RULES-catan.md) — the island game (catalogue id `catan`); the
+  rules engine, AI and screen are in place
+- [Katan: Cities & Knights](docs/RULES-catan-ck.md) — the expansion rule set, chosen on
+  the setup screen: commodities, knights, barbarians, city improvements and progress cards
 
 ## Layout
 
@@ -348,11 +398,11 @@ game/          rules engines and AI — pure Kotlin, no Android, unit-tested
   mastermind/  Mastermind codes, scoring, and a code breaker
   pirates/     Pirates and Bulgars — the cross board, the hunt, search
   tayu/        Ta Yü tile geometry, river rules, scoring, AI
+  catan/       Katan island geometry, production, trade, dev cards, Cities & Knights, heuristic AI
 net/           wire protocol, LAN transport, lobby, match driver
 score/         scorekeeper sheet — pure Kotlin, unit-tested — and its store
 settings/      DataStore-backed preferences
-update/        OTA updater against this repo's Gitea releases, and the
-              channel rule — pure, tested
+update/        Cloudflare Pages OTA updater, and the channel rule — pure, tested
 ui/            Compose screens
 ```
 

app/build.gradle.kts

@@ -16,18 +16,10 @@ val buildChannel = System.getenv("PLG_CHANNEL").orEmpty()
 val runNumber = (System.getenv("GITHUB_RUN_NUMBER") ?: "").toIntOrNull() ?: 0
 val stampVersion = buildChannel.isNotEmpty() && runNumber > 0
 
-// The fixed floor every stamped build number is measured from, in
-// gradle.properties. Gitea Actions restarts its run numbers at 1 for each
-// workflow, so an unstamped build (versionCode 1) and the first release of a
-// fresh instance would otherwise collide — and once a phone has installed
-// versionCode N, Android refuses anything smaller as a downgrade. Adding a
-// permanent offset is what makes "the counter never resets" true by
-// construction: it is read from one place, it never changes, and the tag,
-// versionName and versionCode all get the same number (see docs/CI.md).
+// See plgVersionRunOffset in gradle.properties: the stamped build number is the
+// CI run number plus a permanent floor, so a counter that restarts on a new CI
+// host can never produce a lower versionCode than one already installed.
 val runOffset = (project.findProperty("plgVersionRunOffset") as String?)?.toIntOrNull() ?: 0
-
-// The stamped build number: what the release tag, the versionName and the
-// versionCode are all named after.
 val buildNumber = runNumber + runOffset
 
 // The version series, from gradle.properties. Both workflows read the same
@@ -46,30 +38,25 @@ val versionSeries = (project.findProperty("plgVersionSeries") as String?) ?: "1.
 val isDevBuild = buildChannel != "production"
 
 android {
-    // Deliberately left at the upstream source package: R and BuildConfig stay
-    // in org.prolibertate.games for both channels, so no source file has to
-    // care which applicationId it ended up installed as. The *installed*
-    // identity is the applicationId below — that is what the rebrand changes
-    // (WALA-118), not the JVM package names.
     namespace = "org.prolibertate.games"
     compileSdk = 34
 
     defaultConfig {
         // A dev build installs under its own package, so a dev copy and a
         // production copy can sit side by side on one device instead of one
-        // replacing the other.
-        applicationId = if (isDevBuild) "ca.wallacenet.prolibertategames.dev" else "ca.wallacenet.prolibertategames"
+        // replacing the other. The namespace above is deliberately left alone:
+        // R and BuildConfig stay in org.prolibertate.games for both, so no
+        // source has to care which package it ended up installed as.
+        applicationId = if (isDevBuild) "org.prolibertate.games.dev" else "org.prolibertate.games"
         minSdk = 24
         targetSdk = 34
         // The -dev suffix in versionName is what the installed app reads to
         // know its own channel, so it must survive into the shipped APK. It
         // tracks isDevBuild rather than the stamp alone, so an unstamped local
         // build cannot end up claiming a channel its applicationId contradicts.
-        // versionCode is the stamped build number and nothing else, so it keeps
+        // versionCode stays the run number and nothing else, so it keeps
         // climbing across a change of series: bumping 1.0 to 1.1 must not make
-        // an update look like a downgrade to Android. An unstamped build is 1,
-        // below every release, which is the honest answer for a build nobody
-        // stamped.
+        // an update look like a downgrade to Android.
         versionCode = if (stampVersion) buildNumber else 1
         versionName = when {
             stampVersion && buildChannel == "production" -> "$versionSeries.$buildNumber"
@@ -100,12 +87,6 @@ android {
         resValue("color", "ic_launcher_background", if (isDevBuild) "#145C2D" else "#B3121B")
 
         buildConfigField("boolean", "DEV_BUILD", isDevBuild.toString())
-
-        // In-app OTA updates, pointed at this project's own Gitea releases
-        // (docs/CI.md). True in this build — the channel exists. Flipping it
-        // false is the kill switch: every check then reports that and fetches
-        // nothing, with the machinery and its tests still compiled.
-        buildConfigField("boolean", "OTA_ENABLED", "true")
     }
 
     signingConfigs {
@@ -123,6 +104,11 @@ android {
 
     buildTypes {
         release {
+            // Signed with the same key as the debug builds, so a release installs
+            // over what is already on a device; a different key would make the
+            // updater's installs fail with a signature mismatch.
+            signingConfig = signingConfigs.getByName("debug")
+            isDebuggable = false
             isMinifyEnabled = false
             proguardFiles(
                 getDefaultProguardFile("proguard-android-optimize.txt"),

app/src/main/AndroidManifest.xml

@@ -1,9 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
 
-    <!-- LAN play over TCP sockets, plus hand-a-down permission for in-app
-         installs — the OTA updater installs releases published on this repo's
-         Gitea; see docs/CI.md. -->
+    <!-- OTA updates from plg.wallacenet.ca, plus LAN play over TCP sockets. -->
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
     <!-- Network Service Discovery needs multicast to see hosts on the LAN. -->

app/src/main/java/org/prolibertate/games/MainActivity.kt

@@ -10,11 +10,14 @@ import org.prolibertate.games.net.LobbyController
 import org.prolibertate.games.net.ScorekeeperSession
 import org.prolibertate.games.score.ScorekeeperRepository
 import org.prolibertate.games.settings.SettingsRepository
+import org.prolibertate.games.settings.YahtzeeStatsRepository
 import org.prolibertate.games.ui.AppEnv
 import org.prolibertate.games.ui.AppRoot
 import org.prolibertate.games.ui.theme.ProLibertateTheme
 import org.prolibertate.games.update.Updater
+import java.io.File
 import java.util.UUID
+import org.prolibertate.games.game.engine.SavedGameStore
 
 class MainActivity : ComponentActivity() {
 
@@ -40,6 +43,8 @@ class MainActivity : ComponentActivity() {
                 deviceId = peerId,
             ),
             peerId = peerId,
+            saves = SavedGameStore(File(filesDir, "saved-games")),
+            yahtzeeStats = YahtzeeStatsRepository(applicationContext),
         )
 
         setContent {

app/src/main/java/org/prolibertate/games/game/Catalog.kt

@@ -42,7 +42,20 @@ data class GameDescriptor(
     val teamBased: Boolean,
     val blurb: String,
     val available: Boolean,
+    /**
+     * Playable on a dev build while still hidden from production.
+     *
+     * [available] is the release gate: it is what a production build lists and
+     * lets people open. A game that has an engine and a screen but has not yet
+     * been verified on real devices sets this instead, so it can be played and
+     * tested from the dev channel without being offered to everyone. Flip
+     * [available] on (and this off) once it has been verified.
+     */
+    val devPreview: Boolean = false,
 ) {
+    /** Whether the menu should let this game be opened in the given kind of build. */
+    fun playableIn(devBuild: Boolean): Boolean = available || (devBuild && devPreview)
+
     /**
      * The one menu this game is listed under.
      *
@@ -93,6 +106,7 @@ object GameCatalog {
     const val TAYU = "tayu"
     const val MORRIS = "morris"
     const val PIRATES = "pirates"
+    const val MEOWDOKU = "meowdoku"
 
     /**
      * The island game the collection is named for. Listed under Board Games
@@ -347,11 +361,19 @@ object GameCatalog {
             minPlayers = 3,
             maxPlayers = 4,
             teamBased = false,
-            blurb = "Trade, build, and settle the island.",
-            // Listed, not playable: the engine and screen land with the Katan
-            // game task. Dev builds show the entry as *Coming soon*; a
-            // production build lists only what can actually be played.
-            available = false,
+            blurb = "Trade, build, and settle the island, in the base game or Cities & Knights.",
+            available = true,
+        ),
+        GameDescriptor(
+            id = MEOWDOKU,
+            title = "Meowdoku",
+            menus = setOf(GameMenu.BOARD, GameMenu.SOLITAIRE),
+            minPlayers = 1,
+            maxPlayers = 1,
+            teamBased = false,
+            blurb = "One cat in every row, column and colour, and no two touching. " +
+                "Wrong taps cost a heart; the board only ever accepts a cat that belongs.",
+            available = true,
         ),
     )
 

app/src/main/java/org/prolibertate/games/game/backgammon/BackgammonAi.kt

@@ -1,6 +1,9 @@
 package org.prolibertate.games.game.backgammon
 
 import kotlin.random.Random
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -22,8 +25,19 @@ import org.prolibertate.games.game.engine.GameAi
  * out and its first step returned; the rest follows on the moves after, because
  * the same calculation reaches the same turn.
  */
-class BackgammonAi(private val level: BackgammonLevel? = null) :
-    GameAi<BackgammonState, BackgammonMove> {
+class BackgammonAi(
+    private val profiles: AiProfiles = AiProfiles.DEFAULT,
+    private val level: BackgammonLevel? = null,
+) : GameAi<BackgammonState, BackgammonMove> {
+
+    /**
+     * The turn an easy seat has settled on, so that a deliberate slip is made
+     * once per roll rather than re-rolled on every checker (which would stitch
+     * halves of different turns together).
+     */
+    private var plan: List<BackgammonMove> = emptyList()
+    private var planned = 0
+    private var planRoll = -1
 
     override fun chooseMove(
         state: BackgammonState,
@@ -31,48 +45,104 @@ class BackgammonAi(private val level: BackgammonLevel? = null) :
         legal: List<BackgammonMove>,
     ): BackgammonMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
-        val setting = level ?: state.options.level
         if (legal.size == 1) return legal.first()
+        val profile = profiles.of(seat)
+        val base = level ?: state.options.level
+        val setting = when (profile.level) {
+            AiLevel.MEDIUM -> base
+            // Easy never looks at the dice to come.
+            AiLevel.EASY -> if (base == BackgammonLevel.STRONG) BackgammonLevel.CLUB else base
+            AiLevel.HARD -> BackgammonLevel.STRONG
+        }
+        val tuning = tuningFor(profile)
 
         val random = Random(state.rollsMade * 31L + state.moveLog.size)
 
         if (setting == BackgammonLevel.CASUAL) {
             // Not thoughtless: it still prefers to hit, to come in off the bar
             // and to bear off, which is most of what a beginner knows.
-            val scored = legal.map { move -> move to rough(state, seat, move) }
+            val scored = legal.map { move -> move to rough(state, seat, move, profile) }
             val best = scored.maxOf { it.second }
             val equal = scored.filter { it.second == best }
             return equal[random.nextInt(equal.size)].first
         }
 
+        val easy = profile.level == AiLevel.EASY
+        if (easy && planRoll == state.rollsMade) {
+            val next = plan.getOrNull(planned)
+            if (next != null && next in legal) {
+                planned++
+                return next
+            }
+        }
+
         val sequences = BackgammonRules.deepestSequences(state, seat)
         if (sequences.isEmpty()) return legal.first()
 
-        var best = sequences.first()
-        var bestScore = -Double.MAX_VALUE
+        val scored = ArrayList<Pair<List<BackgammonMove>, Double>>(sequences.size)
         for (sequence in sequences) {
             val after = BackgammonRules.playSequence(state, seat, sequence)
-            val score = if (setting == BackgammonLevel.STRONG) {
-                // What the position is worth once the dice have had their say.
-                evaluate(after, seat) - averageReply(after, other(seat))
-            } else {
-                evaluate(after, seat)
-            }
-            if (score > bestScore) {
-                bestScore = score
-                best = sequence
-            }
+            scored += sequence to evaluate(after, seat, tuning)
         }
-        return best.first()
+
+        if (setting == BackgammonLevel.STRONG) {
+            // What the position is worth once the dice have had their say. A hard
+            // seat only spends the twenty-one-roll average on the turns that
+            // already look best, which keeps a phone's thinking time bounded.
+            val finalists = if (profile.level == AiLevel.HARD && scored.size > FINALISTS) {
+                scored.sortedByDescending { it.second }.take(FINALISTS)
+            } else {
+                scored
+            }
+            val rescored = finalists.map { (sequence, _) ->
+                val after = BackgammonRules.playSequence(state, seat, sequence)
+                sequence to (evaluate(after, seat, tuning) - averageReply(after, other(seat)))
+            }
+            return chooseFrom(rescored, profile, state, legal)
+        }
+        return chooseFrom(scored, profile, state, legal)
     }
 
+    /** Best sequence first move; an easy seat sometimes takes a worse (but better-half) turn. */
+    private fun chooseFrom(
+        scored: List<Pair<List<BackgammonMove>, Double>>,
+        profile: AiProfile,
+        state: BackgammonState,
+        legal: List<BackgammonMove>,
+    ): BackgammonMove {
+        var best = scored.first()
+        for (entry in scored) if (entry.second > best.second) best = entry
+        var chosen = best.first
+        if (profile.level == AiLevel.EASY) {
+            val ranked = scored.sortedByDescending { it.second }.map { it.first }
+            chosen = profile.pick(ranked)
+            plan = chosen
+            planned = 1
+            planRoll = state.rollsMade
+        }
+        val first = chosen.first()
+        return if (first in legal) first else legal.first()
+    }
+
+    private fun tuningFor(profile: AiProfile): Tuning {
+        val style = profile.style
+        var blot = 1.0 - 0.3 * style.boldness
+        if (profile.level == AiLevel.EASY) blot *= 0.6 // overlooks some of the danger
+        return Tuning(blot, style.boldness, style.spite)
+    }
+
+    /** What a seat's temperament does to the evaluation; [NEUTRAL] is the standard player. */
+    private class Tuning(val blot: Double, val bold: Double, val spite: Double)
+
     /** A quick opinion of one checker, for the level that does not think. */
-    private fun rough(state: BackgammonState, seat: Int, move: BackgammonMove): Int {
+    private fun rough(state: BackgammonState, seat: Int, move: BackgammonMove, profile: AiProfile): Int {
         val landing = BackgammonRules.destinationOf(seat, move.from, move.die)
         var score = 0
         if (move.from == BAR) score += 50
         if (landing == null) score += 40
-        if (landing != null && state.countOn(landing, other(seat)) == 1) score += 60
+        if (landing != null && state.countOn(landing, other(seat)) == 1) {
+            score += 60 + ((profile.style.boldness + profile.style.spite) * 20).toInt()
+        }
         if (landing != null && state.countOn(landing, seat) >= 1) score += 15
         return score
     }
@@ -98,8 +168,8 @@ class BackgammonAi(private val level: BackgammonLevel? = null) :
                 val rolled = state.copy(turn = opponent, dice = dice, roll = listOf(high, low))
                 val replies = BackgammonRules.deepestSequences(rolled, opponent)
                 val bestReply = replies.maxOfOrNull { sequence ->
-                    evaluate(BackgammonRules.playSequence(rolled, opponent, sequence), opponent)
-                } ?: evaluate(rolled, opponent)
+                    evaluate(BackgammonRules.playSequence(rolled, opponent, sequence), opponent, NEUTRAL)
+                } ?: evaluate(rolled, opponent, NEUTRAL)
                 total += chance * bestReply
                 weight += chance
             }
@@ -117,7 +187,7 @@ class BackgammonAi(private val level: BackgammonLevel? = null) :
      * checkers are, and a made point in your own home board is worth having
      * because it is one more number your opponent cannot come in on.
      */
-    private fun evaluate(state: BackgammonState, seat: Int): Double {
+    private fun evaluate(state: BackgammonState, seat: Int, tuning: Tuning): Double {
         val enemy = other(seat)
 
         if (state.phase == BackgammonPhase.GAME_OVER) {
@@ -135,6 +205,8 @@ class BackgammonAi(private val level: BackgammonLevel? = null) :
         score -= state.off[enemy] * BORNE_OFF
         score -= state.bar[seat] * ON_BAR
         score += state.bar[enemy] * ON_BAR
+        // A gambler and a spoiler both like having an opponent on the bar.
+        score += state.bar[enemy] * (tuning.bold * 4.0 + tuning.spite * 8.0)
 
         for (point in 0 until POINTS) {
             val mine = state.countOn(point, seat)
@@ -142,6 +214,8 @@ class BackgammonAi(private val level: BackgammonLevel? = null) :
 
             if (mine >= 2) {
                 score += POINT_MADE
+                // A cautious seat likes covered points a little more, a gambler less.
+                score -= tuning.bold * 1.5
                 // A point in your own home board is a door shut in the face of
                 // anyone you send to the bar.
                 if (point in homeOf(seat)) score += HOME_POINT
@@ -151,7 +225,7 @@ class BackgammonAi(private val level: BackgammonLevel? = null) :
                 // A blot, weighted by how easily it can be reached: something
                 // six away is in real danger, something twenty away is not.
                 val distance = shortestEnemyDistance(state, seat, point)
-                score -= when {
+                score -= tuning.blot * when {
                     distance <= 0 -> 0.0
                     distance <= 6 -> BLOT_NEAR
                     distance <= 12 -> BLOT_FAR
@@ -160,7 +234,7 @@ class BackgammonAi(private val level: BackgammonLevel? = null) :
             }
         }
 
-        score += primeLength(state, seat) * PRIME
+        score += primeLength(state, seat) * (PRIME + tuning.spite * 3.0)
         return score
     }
 
@@ -199,6 +273,8 @@ class BackgammonAi(private val level: BackgammonLevel? = null) :
 
     private companion object {
         const val WIN = 10_000.0
+        const val FINALISTS = 8
+        val NEUTRAL = Tuning(1.0, 0.0, 0.0)
 
         const val PIP = 1.0
         const val BORNE_OFF = 12.0

app/src/main/java/org/prolibertate/games/game/catan/CatanAi.kt

@@ -0,0 +1,677 @@
+package org.prolibertate.games.game.catan
+
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.GameAi
+
+/**
+ * A heuristic Catan opponent.
+ *
+ * It plays a legal, mildly strategic game: it settles on the best-producing
+ * intersections it can reach, raises cities, chases Largest Army with its
+ * knights, spends its progress cards when they complete something, trades
+ * its surplus to the bank or the table to close a one-card gap, and robs
+ * whoever is winning.
+ *
+ * Honesty is a design constraint, not an accident: this runs on the host,
+ * where the authoritative state is fully visible. It reads only public
+ * information — terrain, numbers, buildings, roads, resource counts,
+ * dev-card counts, knights played — plus its own hand, and never looks
+ * into the deck, another seat's development cards, or the seed beyond the
+ * roll the rules derive from it.
+ *
+ * Each seat's [AiProfiles] entry shapes how it plays. The default profile
+ * (medium, balanced) is the AI described above. Easy settles for worse
+ * spots, trades and builds, now and then ends its turn early, and takes
+ * slightly bad trades. Hard weighs setup spots by balance and port synergy,
+ * values cards by what its next build is missing, races for Longest Road,
+ * keeps the robber off its own hexes and off the table's non-leaders, and
+ * is choosier about whom it trades with. Style nudges the tradeoffs: bold
+ * seats expand, cautious seats spend down before a seven can bite, spiteful
+ * seats go after the leader.
+ */
+class CatanAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) : GameAi<CatanState, CatanMove> {
+
+    /** Plays the Cities & Knights tables; this class keeps the base game. */
+    private val ck = CatanCkAi(this, profiles)
+
+    override fun chooseMove(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+        val profile = profiles.of(seat)
+        require(legal.isNotEmpty() || state.phase == CatanPhase.PLAYING) {
+            "No legal move for seat $seat"
+        }
+        if (state.isCk) return ck.choose(state, seat, legal)
+        return when (state.phase) {
+            CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND ->
+                chooseSetup(state, seat, legal.filterIsInstance<SetupPlace>(), profile)
+
+            CatanPhase.AWAIT_ROLL -> legal.first { it is RollDice }
+
+            // Gold: take what the seat wants most.
+            CatanPhase.GOLD -> chooseGold(state, seat, legal, profile)
+
+            CatanPhase.DISCARDING -> chooseDiscard(state, seat, legal.filterIsInstance<Discard>(), profile)
+
+            CatanPhase.ROBBER -> chooseRobber(state, seat, legal.filterIsInstance<MoveRobber>(), profile)
+
+            CatanPhase.FREE_ROADS -> chooseFreeRoad(state, seat, legal, profile)
+
+            CatanPhase.TRADE_PENDING -> chooseResponse(state, seat, legal, profile)
+
+            CatanPhase.TRADE_COUNTERS -> chooseCounter(state, seat, legal, profile)
+
+            CatanPhase.PLAYING -> choosePlaying(state, seat, legal, profile)
+
+            CatanPhase.CHORE, CatanPhase.GAME_OVER -> legal.firstOrNull()
+                ?: error("Nothing to choose in phase ${state.phase}")
+        }
+    }
+
+    // -----------------------------------------------------------------------
+    // Setup
+    // -----------------------------------------------------------------------
+
+    internal fun chooseSetup(
+        state: CatanState,
+        seat: Int,
+        places: List<SetupPlace>,
+        profile: AiProfile = AiProfile.DEFAULT,
+    ): SetupPlace {
+        require(places.isNotEmpty()) { "No legal settlement placement" }
+        // A bold seat cares more where its road leads; a cautious one less.
+        val direction = 0.25 + 0.1 * profile.style.boldness
+        return when (profile.level) {
+            // Easy looks only at the spot itself, and sometimes settles for the runner-up.
+            AiLevel.EASY -> profile.pick(places.sortedByDescending { spotValue(state, it.vertex) })
+
+            AiLevel.HARD -> places.maxByOrNull { place ->
+                hardSpot(state, seat, place.vertex) + direction * placeDirection(state, place)
+            } ?: places.first()
+
+            AiLevel.MEDIUM -> places.maxByOrNull { place ->
+                spotValue(state, place.vertex) + direction * placeDirection(state, place)
+            } ?: places.first()
+        }
+    }
+
+    /**
+     * A spot as a seat that plans would see it: the plain production value,
+     * plus resources the seat does not yet draw, less piling onto one it
+     * already has plenty of, and ports worth what the seat will produce to
+     * trade through them.
+     */
+    internal fun hardSpot(state: CatanState, seat: Int, vertex: Int): Double {
+        if (state.buildings[vertex] != null) return -1.0
+        val topo = state.topo
+        val owned = HashMap<Resource, Double>()
+        for (v in state.buildings.indices) {
+            val b = state.buildings[v] ?: continue
+            if (b.owner != seat) continue
+            val mult = if (b.type == BuildingType.CITY) 2.0 else 1.0
+            for (h in topo.VERTEX_HEXES[v]) {
+                val res = state.terrains[h].produces ?: continue
+                owned[res] = (owned[res] ?: 0.0) + mult * CatanBoard.numberOdds(state.numbers[h]) / 36.0
+            }
+        }
+        val here = HashMap<Resource, Double>()
+        for (h in topo.VERTEX_HEXES[vertex]) {
+            val res = state.terrains[h].produces ?: continue
+            here[res] = (here[res] ?: 0.0) + CatanBoard.numberOdds(state.numbers[h]) / 36.0
+        }
+        var value = spotValue(state, vertex)
+        value += 0.15 * here.keys.count { (owned[it] ?: 0.0) <= 0.0 }
+        for ((res, p) in here) {
+            if ((owned[res] ?: 0.0) > 0.15) value -= 0.3 * p
+        }
+        val total = owned.values.sum() + here.values.sum()
+        for (e in topo.VERTEX_EDGES[vertex]) {
+            val port = state.ports.firstOrNull { it.edge == e } ?: continue
+            value += if (port.resource == null) {
+                0.05 + 0.15 * total
+            } else {
+                0.9 * ((owned[port.resource] ?: 0.0) + (here[port.resource] ?: 0.0))
+            }
+        }
+        return value
+    }
+
+    /**
+     * Where the setup road points: the best settlement spot two edges out
+     * through the far end of the road. The vertex next to the new
+     * settlement can never hold one (the distance rule), so what a road is
+     * worth is what it reaches past it.
+     */
+    private fun placeDirection(state: CatanState, place: SetupPlace): Double {
+        val topo = state.topo
+        val far = topo.otherEnd(place.edge, place.vertex)
+        return topo.VERTEX_NEIGHBORS[far]
+            .filter { it != place.vertex && it !in topo.VERTEX_NEIGHBORS[place.vertex] }
+            .maxOfOrNull { spotValue(state, it) }
+            ?: 0.0
+    }
+
+    // -----------------------------------------------------------------------
+    // Dice, discards and the robber
+    // -----------------------------------------------------------------------
+
+    private fun chooseDiscard(
+        state: CatanState,
+        seat: Int,
+        discards: List<Discard>,
+        profile: AiProfile,
+    ): Discard {
+        require(discards.isNotEmpty()) { "No legal discard" }
+        // Throw away what it wants least; grain and ore are the city, wool
+        // is mostly a dev-card tax.
+        return when (profile.level) {
+            AiLevel.EASY -> profile.pick(discards.sortedBy { d -> d.cards.sumOf { want(it) } })
+
+            // Keep the hand that is closest to paying for something.
+            AiLevel.HARD -> {
+                val hand = state.resources[seat]
+                discards.maxByOrNull { d ->
+                    val left = hand.toMutableMap()
+                    for (c in d.cards) left[c] = (left[c] ?: 0) - 1
+                    progress(left) - 0.01 * d.cards.sumOf { want(it) }
+                } ?: discards.first()
+            }
+
+            AiLevel.MEDIUM -> discards.minByOrNull { discard ->
+                discard.cards.sumOf { want(it) }
+            } ?: discards.first()
+        }
+    }
+
+    /** How close a hand is to the nearest of the things worth buying, a card count over a price, plus one if it pays. */
+    private fun progress(hand: Map<Resource, Int>): Double = SHOPPING.maxOf { cost ->
+        val have = cost.entries.sumOf { (r, n) -> minOf(maxOf(hand[r] ?: 0, 0), n) }
+        have.toDouble() / cost.values.sum() + if (covers(hand, cost)) 1.0 else 0.0
+    }
+
+    private fun chooseGold(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val picks = legal.filterIsInstance<PickGold>()
+        if (picks.isEmpty()) return legal.first()
+        return when (profile.level) {
+            AiLevel.EASY -> profile.pick(picks.sortedByDescending { p -> p.cards.sumOf { want(it) } })
+            AiLevel.HARD -> picks.maxByOrNull { p -> p.cards.sumOf { need(state, seat, it) } } ?: picks.first()
+            AiLevel.MEDIUM -> picks.maxByOrNull { pick -> pick.cards.sumOf { want(it) } } ?: legal.first()
+        }
+    }
+
+    private fun chooseRobber(
+        state: CatanState,
+        seat: Int,
+        moves: List<MoveRobber>,
+        profile: AiProfile,
+    ): MoveRobber {
+        require(moves.isNotEmpty()) { "No legal robber move" }
+        val points = CatanRules.publicVictoryPoints(state)
+        val hard = profile.level == AiLevel.HARD
+        val spite = profile.style.spite
+        val leader = (0 until state.playerCount).filter { it != seat }.maxByOrNull { points[it] }
+        val victimWeight = 0.3 + 0.1 * profile.style.boldness
+        fun score(move: MoveRobber): Double {
+            val hex = state.topo.hexIndex.getValue(move.hex)
+            var score = 0.0
+            for (v in state.topo.HEX_CORNERS[hex]) {
+                val building = state.buildings[v] ?: continue
+                val worth = if (building.type == BuildingType.CITY) 2 else 1
+                val raw = worth * CatanBoard.numberOdds(state.numbers[hex])
+                if (building.owner == seat) {
+                    // A hard seat will not sit the robber on its own income.
+                    if (hard) score -= 0.8 * raw / 36.0
+                    continue
+                }
+                score += raw / 36.0
+                if (building.owner == leader) score += spite * raw / 36.0
+            }
+            if (move.victim != null) {
+                val cards = state.resourceCount(move.victim)
+                if (!hard || cards > 0) {
+                    score += 0.15 * cards + victimWeight * points[move.victim]
+                    if (move.victim == leader) score += 0.4 * spite
+                }
+            }
+            return score
+        }
+        return if (profile.level == AiLevel.EASY) {
+            profile.pick(moves.sortedByDescending { score(it) })
+        } else {
+            moves.maxByOrNull { score(it) } ?: moves.first()
+        }
+    }
+
+    // -----------------------------------------------------------------------
+    // The main phase
+    // -----------------------------------------------------------------------
+
+    private fun choosePlaying(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val easy = profile.level == AiLevel.EASY
+        val hard = profile.level == AiLevel.HARD
+        val boldness = profile.style.boldness
+        val endTurn = legal.lastOrNull { it is EndTurn } ?: legal.first()
+
+        // Easy loses the thread now and then and just passes.
+        if (easy && profile.slips() && profile.random.nextBoolean()) return endTurn
+
+        val cities = legal.filterIsInstance<BuildCity>()
+        val settlements = legal.filterIsInstance<BuildSettlement>()
+        if (hard && (cities.isNotEmpty() || settlements.isNotEmpty())) {
+            // A city doubles what the seat has; a settlement spreads it and
+            // takes a spot nobody else will. Bold seats lean to the spread.
+            val city = cities.maxByOrNull { spotValue(state, it.vertex) }
+            val settlement = settlements.maxByOrNull { hardSpot(state, seat, it.vertex) }
+            val cityScore = if (city != null) spotValue(state, city.vertex) + 0.15 else Double.NEGATIVE_INFINITY
+            val settleScore = if (settlement != null) {
+                hardSpot(state, seat, settlement.vertex) + 0.3 + 0.1 * boldness
+            } else {
+                Double.NEGATIVE_INFINITY
+            }
+            if (city != null && cityScore >= settleScore) return city
+            if (settlement != null) return settlement
+        } else {
+            // A city doubles the best production the seat already owns.
+            pickBest(cities, profile) { spotValue(state, it.vertex) }?.let { return it }
+
+            pickBest(settlements, profile) { spotValue(state, it.vertex) }?.let { return it }
+        }
+
+        // Seafarers: a ship toward an island nobody has landed on is worth more than a card.
+        legal.filterIsInstance<BuildShip>()
+            .filter { shipValue(state, seat, it.edge) > 0.5 }
+            .maxByOrNull { shipValue(state, seat, it.edge) }
+            ?.let { return it }
+
+        // A knight is worth playing whenever one is playable: it blocks an
+        // opponent's best hex and marches toward Largest Army.
+        if (!(easy && profile.slips())) {
+            legal.filterIsInstance<PlayKnight>().firstOrNull()?.let { return it }
+        }
+
+        if (!(easy && profile.slips())) {
+            yearOfPlenty(state, seat, legal, profile)?.let { return it }
+
+            monopoly(state, legal)?.let { return it }
+        }
+
+        // Road Building is worth two free segments whenever there is
+        // somewhere to put them.
+        if (legal.filterIsInstance<PlayRoadBuilding>().isNotEmpty() &&
+            legal.filterIsInstance<BuildRoad>().size >= 2
+        ) {
+            return legal.filterIsInstance<PlayRoadBuilding>().first()
+        }
+
+        // Hard seat in a Longest Road race puts the road down before spending on cards.
+        val roadThreshold = 0.1 - 0.04 * boldness
+        if (hard && roadRace(state, seat)) {
+            legal.filterIsInstance<BuildRoad>()
+                .maxByOrNull { roadValue(state, it) }
+                ?.let { return it }
+        }
+
+        legal.filterIsInstance<BuyDevCard>().firstOrNull()?.let { return it }
+
+        // Seafarers: a ship that heads for a settlement spot worth having.
+        legal.filterIsInstance<BuildShip>()
+            .filter { shipValue(state, seat, it.edge) > 0.15 }
+            .maxByOrNull { shipValue(state, seat, it.edge) }
+            ?.let { return it }
+
+        // A paid road only when it reaches toward a spot worth settling.
+        legal.filterIsInstance<BuildRoad>()
+            .filter { roadValue(state, it) > roadThreshold }
+            .maxByOrNull { roadValue(state, it) }
+            ?.let { return it }
+
+        // A bank trade only when it completes a build this turn; trading
+        // four for one on spec is how hands evaporate.
+        legal.filterIsInstance<MaritimeTrade>()
+            .filter { completesBuild(state, seat, it) }
+            .maxByOrNull { CatanRules.bestPortRatio(state, seat, it.give) * -1.0 }
+            ?.let { return it }
+
+        if (hard) {
+            // Pile of one card, short of another: convert before it is stuck in hand.
+            legal.filterIsInstance<MaritimeTrade>()
+                .filter { surplusTrade(state, seat, it) }
+                .minByOrNull { CatanRules.bestPortRatio(state, seat, it.give) }
+                ?.let { return it }
+        }
+
+        // Stay under the seven: a cautious (or careful) seat sells down a big hand.
+        if ((hard || boldness < 0) && state.resourceCount(seat) > DISCARD_LIMIT) {
+            legal.filterIsInstance<MaritimeTrade>()
+                .maxByOrNull { t ->
+                    (state.resources[seat][t.give] ?: 0) * 10.0 -
+                        CatanRules.bestPortRatio(state, seat, t.give) * 3.0 + need(state, seat, t.get)
+                }
+                ?.let { return it }
+        }
+
+        if (!(easy && profile.slips())) {
+            offer(state, seat, profile)?.let { return it }
+        }
+
+        return endTurn
+    }
+
+    /** Picks the best of [items] by [score]; easy sometimes takes a near miss. */
+    private fun <T> pickBest(items: List<T>, profile: AiProfile, score: (T) -> Double): T? {
+        if (items.isEmpty()) return null
+        if (profile.level != AiLevel.EASY) return items.maxByOrNull(score)
+        return profile.pick(items.sortedByDescending(score))
+    }
+
+    /** The cheapest things worth saving for, as the shopping list a hard seat weighs hands against. */
+    private val SHOPPING = listOf(
+        CatanRules.CITY_COST,
+        CatanRules.SETTLEMENT_COST,
+        CatanRules.DEV_COST,
+        CatanRules.ROAD_COST,
+    )
+
+    /** The shopping list entry the hand is closest to paying for, among a city, a settlement and a card. */
+    private fun nearestTarget(hand: Map<Resource, Int>): Map<Resource, Int> =
+        listOf(CatanRules.CITY_COST, CatanRules.SETTLEMENT_COST, CatanRules.DEV_COST)
+            .minByOrNull { cost -> cost.entries.sumOf { (r, n) -> maxOf(0, n - (hand[r] ?: 0)) } }
+            ?: CatanRules.CITY_COST
+
+    /** What one card of [res] is worth to this seat right now: more if the next build lacks it, less if it is piled up. */
+    private fun need(state: CatanState, seat: Int, res: Resource): Double {
+        val hand = state.resources[seat]
+        var v = want(res)
+        if ((hand[res] ?: 0) < (nearestTarget(hand)[res] ?: 0)) v += 0.6
+        if ((hand[res] ?: 0) >= 4) v -= 0.4
+        return v
+    }
+
+    /** Whether this bank trade turns a pile (beyond any price) into a card the next build lacks. */
+    private fun surplusTrade(state: CatanState, seat: Int, move: MaritimeTrade): Boolean {
+        val hand = state.resources[seat]
+        val ratio = CatanRules.bestPortRatio(state, seat, move.give)
+        val keep = SHOPPING.maxOf { it[move.give] ?: 0 }
+        val target = nearestTarget(hand)
+        return (hand[move.give] ?: 0) - keep >= ratio &&
+            (hand[move.get] ?: 0) < (target[move.get] ?: 0)
+    }
+
+    /** Whether [seat] is in the hunt for Longest Road: close enough to the holder, or the road is unclaimed. */
+    private fun roadRace(state: CatanState, seat: Int): Boolean {
+        val holder = state.longestRoadOwner
+        if (holder == seat) return false
+        val mine = CatanRules.longestRoadFor(state, seat)
+        if (mine < 3) return false
+        return holder == null || mine + 1 >= CatanRules.longestRoadFor(state, holder)
+    }
+
+    /** The opponent with the most public points, if any. */
+    private fun leaderOf(state: CatanState, seat: Int): Int? {
+        val points = CatanRules.publicVictoryPoints(state)
+        return (0 until state.playerCount).filter { it != seat }.maxByOrNull { points[it] }
+    }
+
+    /** Year of Plenty: two of whatever the nearest build is shortest of. */
+    private fun yearOfPlenty(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): PlayYearOfPlenty? {
+        val takes = legal.filterIsInstance<PlayYearOfPlenty>()
+        if (takes.isEmpty()) return null
+        val shortage = shortage(state) ?: return null
+        if (profile.level == AiLevel.HARD) {
+            return takes.maxByOrNull { take -> take.take.sumOf { need(state, seat, it) } }
+        }
+        return takes.maxByOrNull { take ->
+            take.take.count { it == shortage } * 2 + take.take.size
+        }
+    }
+
+    /** Monopoly: declare the resource everyone else is hoarding, of the ones wanted. */
+    private fun monopoly(state: CatanState, legal: List<CatanMove>): PlayMonopoly? {
+        val plays = legal.filterIsInstance<PlayMonopoly>()
+        if (plays.isEmpty()) return null
+        val best = plays.maxByOrNull {
+            19 - CatanRules.bankSupply(state, it.resource) + want(it.resource)
+        } ?: return null
+        // Only worth the card when the table is actually holding a pile.
+        return if (19 - CatanRules.bankSupply(state, best.resource) >= 10) best else null
+    }
+
+    /** What the seat is shortest of for its next city, else its next settlement. */
+    private fun shortage(state: CatanState): Resource? {
+        val seat = state.turn
+        val targets = listOf(CatanRules.CITY_COST, CatanRules.SETTLEMENT_COST)
+        for (cost in targets) {
+            val missing = cost.entries.filter { (res, need) ->
+                (state.resources[seat][res] ?: 0) < need
+            }
+            if (missing.isNotEmpty()) {
+                return missing.maxByOrNull { (res, need) -> need - (state.resources[seat][res] ?: 0) }?.key
+            }
+        }
+        return null
+    }
+
+    private fun completesBuild(state: CatanState, seat: Int, move: MaritimeTrade): Boolean {
+        val hand = state.resources[seat].toMutableMap()
+        val ratio = CatanRules.bestPortRatio(state, seat, move.give)
+        hand[move.give] = (hand[move.give] ?: 0) - ratio
+        hand[move.get] = (hand[move.get] ?: 0) + 1
+        return covers(hand, CatanRules.CITY_COST) || covers(hand, CatanRules.SETTLEMENT_COST)
+    }
+
+    private fun covers(hand: Map<Resource, Int>, cost: Map<Resource, Int>): Boolean =
+        cost.all { (res, need) -> (hand[res] ?: 0) >= need }
+
+    /**
+     * A domestic offer for exactly the card that closes a build, paid for
+     * with two of the surplus — offered to whoever visibly holds the most
+     * of what is missing. Constructed rather than enumerated (see
+     * [OfferTrade]), so it is checked against the rules before it is spoken.
+     *
+     * At most one offer a turn: a declined offer changes nothing, so
+     * re-offering it would only bounce between the same two seats forever.
+     */
+    private fun offer(state: CatanState, seat: Int, profile: AiProfile): OfferTrade? {
+        if (offeredThisTurn(state, seat)) return null
+        val seatHand = state.resources[seat]
+        val builds = listOf(CatanRules.CITY_COST, CatanRules.SETTLEMENT_COST)
+        for (cost in builds) {
+            val missing = cost.entries.filter { (res, need) -> (seatHand[res] ?: 0) < need }
+            if (missing.size != 1) continue
+            val need = missing.first().key
+            val surplus = Resource.entries
+                .filter { it != need }
+                .filter { (seatHand[it] ?: 0) > (cost[it] ?: 0) }
+                .sortedByDescending { seatHand[it] ?: 0 }
+            if (surplus.isEmpty()) continue
+            val holders = (0 until state.playerCount)
+                .filter { it != seat }
+                .filter { (state.resources[it][need] ?: 0) > 0 }
+            val target = (if (profile.level == AiLevel.HARD) {
+                // Do not feed the leader when someone else can make the swap.
+                val points = CatanRules.publicVictoryPoints(state)
+                holders.maxByOrNull { (state.resources[it][need] ?: 0) - 0.5 * points[it] }
+            } else {
+                holders.maxByOrNull { state.resources[it][need] ?: 0 }
+            }) ?: continue
+            val give = listOf(surplus.first(), surplus.first())
+            val trade = OfferTrade(to = target, give = give, get = listOf(need))
+            if (CatanRules.isLegalMove(state, seat, trade)) return trade
+        }
+        return null
+    }
+
+    /**
+     * Whether [seat] has already put an offer on the table this turn, read
+     * from the public log: the lines after this seat's last roll are this
+     * turn's, and an offer can only be spoken on the offerer's own turn.
+     */
+    private fun offeredThisTurn(state: CatanState, seat: Int): Boolean {
+        val sinceRoll = state.log
+            .drop(state.log.indexOfLast { it.startsWith("Seat $seat rolls") } + 1)
+        return sinceRoll.any { it.startsWith("Seat $seat offers") }
+    }
+
+    // -----------------------------------------------------------------------
+    // Free roads and trade responses
+    // -----------------------------------------------------------------------
+
+    private fun chooseFreeRoad(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val roads = legal.filterIsInstance<BuildRoad>().filter { roadValue(state, it) > 0.05 }
+        val road = if (profile.level == AiLevel.EASY) {
+            profile.pick(roads.sortedByDescending { roadValue(state, it) }.ifEmpty { return freeRoadFallback(legal) })
+        } else {
+            roads.maxByOrNull { roadValue(state, it) }
+        }
+        return road ?: freeRoadFallback(legal)
+    }
+
+    private fun freeRoadFallback(legal: List<CatanMove>): CatanMove =
+        legal.firstOrNull { it is EndFreeRoads }
+            ?: legal.filterIsInstance<BuildRoad>().firstOrNull()
+            ?: legal.first()
+
+    /**
+     * How much extra the incoming cards must be worth to take a swap: nothing
+     * for the standard seat, a hard or spiteful seat wants more from the
+     * table's leader, and an easy seat is not too fussy.
+     */
+    private fun tradeMargin(state: CatanState, seat: Int, other: Int, profile: AiProfile): Double {
+        var margin = 0.0
+        if (profile.level == AiLevel.EASY) margin -= 0.6
+        val leader = leaderOf(state, seat)
+        if (leader != null && other == leader) {
+            if (profile.level == AiLevel.HARD) margin += 0.4
+            margin += 0.5 * profile.style.spite
+        }
+        return margin
+    }
+
+    private fun tradeValue(state: CatanState, seat: Int, res: Resource, profile: AiProfile): Double =
+        if (profile.level == AiLevel.HARD) need(state, seat, res) else want(res)
+
+    private fun chooseResponse(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val accept = legal.filterIsInstance<AcceptTrade>().firstOrNull()
+        val offer = state.pendingTrade
+        if (accept == null || offer == null) return legal.first { it is DeclineTrade }
+        // Accept when what arrives (the offerer's give) is worth more than what
+        // leaves (the offerer's get): a mild table, not a shark.
+        val incoming = offer.give.sumOf { tradeValue(state, seat, it, profile) }
+        val outgoing = offer.get.sumOf { tradeValue(state, seat, it, profile) }
+        return if (incoming > outgoing + tradeMargin(state, seat, offer.by, profile)) {
+            accept
+        } else {
+            legal.first { it is DeclineTrade }
+        }
+    }
+
+    /**
+     * Picks the counter-offer that gains the most by the same valuation, or
+     * turns them all down. The AI never counters itself: it only answers.
+     */
+    private fun chooseCounter(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val offer = state.pendingTrade ?: return legal.first()
+        fun gain(c: TradeCounter) = c.give.sumOf { tradeValue(state, seat, it, profile) } -
+            c.get.sumOf { tradeValue(state, seat, it, profile) }
+        val best = legal.filterIsInstance<AcceptCounter>()
+            .map { choice -> choice to offer.counters.first { it.by == choice.seat } }
+            .maxByOrNull { (_, c) -> gain(c) }
+        if (best != null) {
+            val (choice, c) = best
+            if (c.give.sumOf { tradeValue(state, seat, it, profile) } >
+                c.get.sumOf { tradeValue(state, seat, it, profile) } + tradeMargin(state, seat, c.by, profile)
+            ) {
+                return choice
+            }
+        }
+        return legal.first { it is DismissCounters }
+    }
+
+    // -----------------------------------------------------------------------
+    // Valuations
+    // -----------------------------------------------------------------------
+
+    /** What a seat would think of building on [vertex]: production and ports. */
+    internal fun spotValue(state: CatanState, vertex: Int): Double {
+        if (state.buildings[vertex] != null) return -1.0
+        var value = 0.0
+        val kinds = mutableSetOf<Resource>()
+        for (h in state.topo.VERTEX_HEXES[vertex]) {
+            val resource = state.terrains[h].produces ?: continue
+            value += CatanBoard.numberOdds(state.numbers[h]) / 36.0 * want(resource)
+            kinds += resource
+        }
+        value += 0.12 * kinds.size // variety keeps a build plan alive
+        for (e in state.topo.VERTEX_EDGES[vertex]) {
+            val port = state.ports.firstOrNull { it.edge == e } ?: continue
+            value += if (port.resource == null) 0.1 else 0.2
+        }
+        return value
+    }
+
+    /**
+     * What a road on this edge leads to: the best settlement spot it brings
+     * within reach, discounted for being one step further out.
+     */
+    internal fun roadValue(state: CatanState, move: BuildRoad): Double {
+        var best = 0.0
+        val (from, to) = state.topo.EDGE_VERTICES[move.edge]
+        for (endpoint in listOf(from, to)) {
+            for (near in state.topo.VERTEX_NEIGHBORS[endpoint]) {
+                best = maxOf(best, spotValue(state, near) * 0.8)
+            }
+        }
+        return best
+    }
+
+    /**
+     * What a ship on [edge] is heading for: the best open settlement spot reachable by sea from
+     * its far end (the end the fleet does not already hold), discounted by how far off it is,
+     * with a bonus for an island nobody has landed on.
+     */
+    internal fun shipValue(state: CatanState, seat: Int, edge: Int): Double {
+        val topo = state.topo
+        val sea = state.sea ?: return 0.0
+        val (a, b) = topo.EDGE_VERTICES[edge]
+        fun held(v: Int): Boolean =
+            state.buildings[v]?.owner == seat || topo.VERTEX_EDGES[v].any { sea.ships[it] == seat }
+        val front = listOf(a, b).filter { !held(it) }.ifEmpty { return 0.0 }
+        var best = 0.0
+        val seen = mutableSetOf<Int>()
+        var frontier = front
+        var depth = 0
+        while (frontier.isNotEmpty() && depth <= 5) {
+            val next = mutableListOf<Int>()
+            for (v in frontier) {
+                if (!seen.add(v)) continue
+                if (CatanRules.vertexOpenForSettlement(state, v)) {
+                    val island = topo.vertexIsland[v]
+                    val fresh = island >= 0 && !sea.isStart(island) && sea.islandBonus[island] == NO_PLAYER
+                    val value = (spotValue(state, v) + if (fresh) 0.5 else 0.0) * Math.pow(0.85, depth.toDouble())
+                    best = maxOf(best, value)
+                }
+                for (e in topo.VERTEX_EDGES[v]) {
+                    if (!topo.edgeSea[e] || sea.ships[e] != NO_PLAYER) continue
+                    next += topo.otherEnd(e, v)
+                }
+            }
+            frontier = next
+            depth++
+        }
+        return best
+    }
+
+    /** How much the AI wants to hold one card of [resource]. */
+    internal fun want(resource: Resource): Double = when (resource) {
+        Resource.ORE -> 1.20 // the city
+        Resource.GRAIN -> 1.15 // the city and the dev cards
+        Resource.LUMBER -> 1.0 // every road and settlement
+        Resource.BRICK -> 0.95
+        Resource.WOOL -> 0.85 // abundant and only half of a dev card
+    }
+
+    private companion object {
+        /** A seven makes a seat holding more than this discard half. */
+        const val DISCARD_LIMIT = 7
+    }
+}

app/src/main/java/org/prolibertate/games/game/catan/CatanBoard.kt

@@ -0,0 +1,471 @@
+package org.prolibertate.games.game.catan
+
+import kotlinx.serialization.Serializable
+import kotlin.math.atan2
+import kotlin.random.Random
+
+/**
+ * The geometry of one board: its hexes, the shared vertices and edges between
+ * them, and which hexes are land.
+ *
+ * Everything is derived once, deterministically, from axial coordinates —
+ * there is no randomness and no state here; the layout of a particular
+ * game (which terrain and number sits on which hex) is generated elsewhere
+ * ([CatanBoard.generate], [SeaBoards.generate]), and the live state lives in
+ * [CatanState].
+ *
+ * Coordinates: hexes are addressed axially ((q, r), pointy-top). Every
+ * position is kept on an exact integer lattice so vertices shared by
+ * neighbouring hexes are recognised by position instead of by floating
+ * point: the centre of hex (q, r) is at lattice point (2q + r, 3r), and its
+ * six corners follow the offsets in [CORNER_OFFSETS]. Vertex positions are
+ * in half-units of the hex grid; rendering scales and flips them (lattice
+ * +Y is toward the top of the board).
+ *
+ * The standard island ([CatanBoard.base]) is the 19-hex hexagon. A Seafarers
+ * map is a larger frame whose hexes are mostly sea; [land] says which.
+ */
+class Topology(
+    /** Every hex of the frame, land and sea alike. */
+    val HEXES: List<HexCoord>,
+    /** Whether each hex is land. The base island is all land; Seafarers maps are mostly sea. */
+    val land: List<Boolean> = List(HEXES.size) { true },
+    /** The standard 19-hex island: checks its counts and uses the fixed nine-harbour frame. */
+    private val standardFrame: Boolean = false,
+    /** Harbours wanted on a non-standard map. */
+    harbours: Int = 0,
+) {
+
+    val HEX_COUNT: Int = HEXES.size
+
+    val hexIndex: Map<HexCoord, Int> = HEXES.withIndex().associate { (i, hex) -> hex to i }
+
+    // -----------------------------------------------------------------------
+    // Vertices and edges
+    // -----------------------------------------------------------------------
+
+    /** Lattice position of each vertex, by vertex id. */
+    val VERTEX_POS: List<Pair<Int, Int>>
+
+    val VERTEX_COUNT: Int
+
+    /** Vertex ids of hex h's six corners, corner 0 first (see [CORNER_OFFSETS]). */
+    val HEX_CORNERS: List<List<Int>>
+
+    /** Both endpoints of each edge, as vertex ids, low id first. */
+    val EDGE_VERTICES: List<Pair<Int, Int>>
+
+    val EDGE_COUNT: Int
+
+    /** Edges touching each vertex. */
+    val VERTEX_EDGES: List<List<Int>>
+
+    /** Vertices one edge away from each vertex: the distance rule's horizon. */
+    val VERTEX_NEIGHBORS: List<List<Int>>
+
+    /** Hexes touching each vertex. */
+    val VERTEX_HEXES: List<List<Int>>
+
+    /** Hexes touching each edge: two for interior edges, one on the coast. */
+    val EDGE_HEXES: List<List<Int>>
+
+    /** Edges adjacent to each edge (sharing a vertex). */
+    val EDGE_NEIGHBORS: List<List<Int>>
+
+    /** Hexes adjacent to each hex, in [NEIGHBOR_STEPS] order. */
+    val HEX_NEIGHBORS: List<List<Int>>
+
+    /** The coastal edges (those with only one hex) in ring order. */
+    val COASTAL: List<Int>
+
+    /** The harbour positions: nine on the standard frame. */
+    val PORT_POSITIONS: List<Int>
+
+    // --- Land and sea (all land on the standard island) --------------------
+
+    /** A settlement may stand here: at least one of its hexes is land. */
+    val vertexLand: List<Boolean>
+
+    /** A road may lie here: at least one of its hexes is land. */
+    val edgeLand: List<Boolean>
+
+    /** A ship may sail here: at least one of its hexes is sea. */
+    val edgeSea: List<Boolean>
+
+    /** Which island each hex is on (a connected group of land hexes), or -1 for sea. */
+    val islandOf: List<Int>
+
+    val islandCount: Int
+
+    /** Which island each vertex touches, or -1 for open water. */
+    val vertexIsland: List<Int>
+
+    init {
+        // Vertices: assign ids in first-seen order over hexes then corners.
+        val vertexIds = mutableMapOf<Pair<Int, Int>, Int>()
+        val vertexPos = mutableListOf<Pair<Int, Int>>()
+        val hexCorners = HEXES.map { hex ->
+            val cx = 2 * hex.q + hex.r
+            val cy = 3 * hex.r
+            CORNER_OFFSETS.map { (dx, dy) ->
+                val pos = (cx + dx) to (cy + dy)
+                vertexIds.getOrPut(pos) {
+                    vertexPos += pos
+                    vertexPos.size - 1
+                }
+            }
+        }
+        VERTEX_POS = vertexPos
+        VERTEX_COUNT = vertexPos.size
+        HEX_CORNERS = hexCorners
+
+        // Edges between a hex's consecutive corners, deduplicated by the
+        // pair of vertex ids.
+        val edgeIds = mutableMapOf<Pair<Int, Int>, Int>()
+        val edgeVertices = mutableListOf<Pair<Int, Int>>()
+        hexCorners.forEach { corners ->
+            for (k in 0..5) {
+                val a = corners[k]
+                val b = corners[(k + 1) % 6]
+                val key = minOf(a, b) to maxOf(a, b)
+                edgeIds.getOrPut(key) {
+                    edgeVertices += key
+                    edgeVertices.size - 1
+                }
+            }
+        }
+        EDGE_VERTICES = edgeVertices
+        EDGE_COUNT = edgeVertices.size
+
+        val vertexEdges = List(VERTEX_COUNT) { mutableListOf<Int>() }
+        val vertexHexes = List(VERTEX_COUNT) { mutableSetOf<Int>() }
+        val edgeHexes = List(EDGE_COUNT) { mutableSetOf<Int>() }
+        hexCorners.forEachIndexed { h, corners ->
+            corners.forEach { v -> vertexHexes[v] += h }
+            for (k in 0..5) {
+                val a = corners[k]
+                val b = corners[(k + 1) % 6]
+                val key = minOf(a, b) to maxOf(a, b)
+                val e = edgeIds.getValue(key)
+                edgeHexes[e] += h
+                vertexEdges[a] += e
+                vertexEdges[b] += e
+            }
+        }
+        // Distinct: an interior edge is walked once from each of the two hexes
+        // it separates, so without this every shared edge would be counted
+        // twice and an interior vertex would appear to have six edges.
+        VERTEX_EDGES = vertexEdges.map { it.distinct() }
+        VERTEX_HEXES = vertexHexes.map { it.sorted() }
+        EDGE_HEXES = edgeHexes.map { it.sorted() }
+        VERTEX_NEIGHBORS = List(VERTEX_COUNT) { v ->
+            VERTEX_EDGES[v].map { otherEnd(it, v) }.distinct().sorted()
+        }
+        EDGE_NEIGHBORS = List(EDGE_COUNT) { e ->
+            val (a, b) = EDGE_VERTICES[e]
+            (VERTEX_EDGES[a] + VERTEX_EDGES[b]).distinct().filter { it != e }.sorted()
+        }
+        HEX_NEIGHBORS = HEXES.map { hex ->
+            NEIGHBOR_STEPS.mapNotNull { (dq, dr) ->
+                hexIndex[HexCoord(hex.q + dq, hex.r + dr)]
+            }
+        }
+
+        // The coast in walking order: sort the coastal edges by the angle of
+        // their midpoint around the board centre, which is the lattice
+        // origin. The standard board is a hexagon, so this yields one closed ring.
+        COASTAL = EDGE_HEXES.withIndex()
+            .filter { it.value.size == 1 }
+            .map { (e, _) -> e }
+            .sortedBy { e -> angleOf(midpoint(e)) }
+
+        vertexLand = List(VERTEX_COUNT) { v -> VERTEX_HEXES[v].any { land[it] } }
+        edgeLand = List(EDGE_COUNT) { e -> EDGE_HEXES[e].any { land[it] } }
+        edgeSea = List(EDGE_COUNT) { e -> EDGE_HEXES[e].any { !land[it] } }
+
+        // Islands: connected groups of land hexes.
+        val island = IntArray(HEX_COUNT) { -1 }
+        var islands = 0
+        for (h in 0 until HEX_COUNT) {
+            if (!land[h] || island[h] != -1) continue
+            val stack = ArrayDeque(listOf(h))
+            island[h] = islands
+            while (stack.isNotEmpty()) {
+                val at = stack.removeLast()
+                for (n in HEX_NEIGHBORS[at]) {
+                    if (land[n] && island[n] == -1) {
+                        island[n] = islands
+                        stack.addLast(n)
+                    }
+                }
+            }
+            islands++
+        }
+        islandOf = island.toList()
+        islandCount = islands
+        vertexIsland = List(VERTEX_COUNT) { v ->
+            VERTEX_HEXES[v].firstOrNull { land[it] }?.let { island[it] } ?: -1
+        }
+
+        PORT_POSITIONS = if (standardFrame) {
+            // Harbours sit roughly every third or fourth coastal edge, like the
+            // physical frame: nine positions, steps summing to the whole ring.
+            buildList {
+                var at = 0
+                for (step in listOf(3, 4, 3, 3, 4, 3, 3, 4, 3)) {
+                    add(COASTAL[at % COASTAL.size])
+                    at += step
+                }
+            }.distinct()
+        } else {
+            seaPorts(harbours)
+        }
+
+        if (standardFrame) {
+            check(HEX_COUNT == 19) { "A Catan island has 19 hexes, found $HEX_COUNT" }
+            check(VERTEX_COUNT == 54) { "A Catan island has 54 vertices, found $VERTEX_COUNT" }
+            check(EDGE_COUNT == 72) { "A Catan island has 72 edges, found $EDGE_COUNT" }
+            check(COASTAL.size == 30) { "The coast has 30 edges, found ${COASTAL.size}" }
+            check(PORT_POSITIONS.size == 9) { "Nine harbours, found ${PORT_POSITIONS.size}" }
+            check(PORT_POSITIONS.all { EDGE_HEXES[it].size == 1 }) { "Harbours must be coastal" }
+        }
+    }
+
+    /**
+     * Harbour sites on a map with islands: edges where land meets sea, taken
+     * round the map by angle about the land's centre, [count] of them as evenly
+     * spaced as the coast allows, never two sharing a corner.
+     */
+    private fun seaPorts(count: Int): List<Int> {
+        if (count <= 0) return emptyList()
+        val shore = (0 until EDGE_COUNT).filter { e ->
+            EDGE_HEXES[e].size == 2 && EDGE_HEXES[e].any { land[it] } && EDGE_HEXES[e].any { !land[it] }
+        }
+        if (shore.isEmpty()) return emptyList()
+        val landCentre = HEXES.indices.filter { land[it] }.let { hs ->
+            val pts = hs.map { hexCenter(it) }
+            (pts.sumOf { it.first } / pts.size.toDouble()) to (pts.sumOf { it.second } / pts.size.toDouble())
+        }
+        val ring = shore.sortedBy { e ->
+            val m = midpoint(e)
+            atan2(m.second - landCentre.second, m.first - landCentre.first)
+        }
+        val picked = mutableListOf<Int>()
+        val used = mutableSetOf<Int>()
+        val step = ring.size.toDouble() / count
+        for (i in 0 until count) {
+            val start = (i * step).toInt()
+            // The first edge at or after the ideal spot whose corners are free.
+            val e = (0 until ring.size).map { ring[(start + it) % ring.size] }.firstOrNull { cand ->
+                val (a, b) = EDGE_VERTICES[cand]
+                a !in used && b !in used && cand !in picked
+            } ?: continue
+            picked += e
+            val (a, b) = EDGE_VERTICES[e]
+            used += a
+            used += b
+        }
+        return picked
+    }
+
+    /** The other endpoint of [edge], given one [vertex] on it. */
+    fun otherEnd(edge: Int, vertex: Int): Int {
+        val (a, b) = EDGE_VERTICES[edge]
+        return if (vertex == a) b else a
+    }
+
+    /** Lattice position of hex h's centre. */
+    fun hexCenter(h: Int): Pair<Int, Int> {
+        val hex = HEXES[h]
+        return (2 * hex.q + hex.r) to (3 * hex.r)
+    }
+
+    /** Whether two hexes share an edge. */
+    fun hexesAdjacent(a: Int, b: Int): Boolean = b in HEX_NEIGHBORS[a]
+
+    /** Lattice extent of the whole frame: min x, max x, min y, max y. */
+    val lattice: IntArray by lazy {
+        intArrayOf(
+            VERTEX_POS.minOf { it.first }, VERTEX_POS.maxOf { it.first },
+            VERTEX_POS.minOf { it.second }, VERTEX_POS.maxOf { it.second },
+        )
+    }
+
+    private fun midpoint(edge: Int): Pair<Double, Double> {
+        val (a, b) = EDGE_VERTICES[edge]
+        val pa = VERTEX_POS[a]
+        val pb = VERTEX_POS[b]
+        return ((pa.first + pb.first) / 2.0) to ((pa.second + pb.second) / 2.0)
+    }
+
+    private fun angleOf(point: Pair<Double, Double>): Double =
+        atan2(point.second, point.first)
+
+    companion object {
+        /**
+         * Corner k of a hex, as a lattice offset from its centre. Pointy-top:
+         * corner 0 is the top corner, then clockwise.
+         */
+        private val CORNER_OFFSETS = listOf(
+            0 to 2, 1 to 1, 1 to -1, 0 to -2, -1 to -1, -1 to 1,
+        )
+
+        /** Unit steps to a hex's six neighbours, matching the corner order. */
+        private val NEIGHBOR_STEPS = listOf(
+            0 to 1, 1 to 0, 1 to -1, 0 to -1, -1 to 0, -1 to 1,
+        )
+
+        /** Hex-grid distance between two axial positions. */
+        fun hexDistance(q1: Int, r1: Int, q2: Int, r2: Int): Int {
+            val dq = q1 - q2
+            val dr = r1 - r2
+            return maxOf(kotlin.math.abs(dq), kotlin.math.abs(dr), kotlin.math.abs(dq + dr))
+        }
+
+        /**
+         * How often a number is expected to come up, in thirty-sixths. A 6 or an
+         * 8 comes up five times in thirty-six, a 2 or a 12 once.
+         */
+        fun numberOdds(number: Int): Int = 6 - kotlin.math.abs(7 - number)
+    }
+}
+
+/**
+ * The standard island: the 19 hexes, the 54 shared vertices, the 72 shared
+ * edges, the coast and the nine harbour positions. Every table below is the
+ * standard frame's [Topology]; the rules read the topology of the *state* they
+ * are working on ([CatanState.topo]), which is this one in every game but Seafarers.
+ */
+object CatanBoard {
+
+    /** The standard island's geometry. */
+    val base: Topology = Topology(
+        HEXES = buildList {
+            for (r in -2..2) {
+                for (q in -2..2) {
+                    if (Topology.hexDistance(q, r, 0, 0) <= 2) add(HexCoord(q, r))
+                }
+            }
+        },
+        standardFrame = true,
+    )
+
+    val HEXES: List<HexCoord> get() = base.HEXES
+    val HEX_COUNT: Int get() = base.HEX_COUNT
+    val hexIndex: Map<HexCoord, Int> get() = base.hexIndex
+    val VERTEX_POS: List<Pair<Int, Int>> get() = base.VERTEX_POS
+    val VERTEX_COUNT: Int get() = base.VERTEX_COUNT
+    val HEX_CORNERS: List<List<Int>> get() = base.HEX_CORNERS
+    val EDGE_VERTICES: List<Pair<Int, Int>> get() = base.EDGE_VERTICES
+    val EDGE_COUNT: Int get() = base.EDGE_COUNT
+    val VERTEX_EDGES: List<List<Int>> get() = base.VERTEX_EDGES
+    val VERTEX_NEIGHBORS: List<List<Int>> get() = base.VERTEX_NEIGHBORS
+    val VERTEX_HEXES: List<List<Int>> get() = base.VERTEX_HEXES
+    val EDGE_HEXES: List<List<Int>> get() = base.EDGE_HEXES
+    val EDGE_NEIGHBORS: List<List<Int>> get() = base.EDGE_NEIGHBORS
+    val HEX_NEIGHBORS: List<List<Int>> get() = base.HEX_NEIGHBORS
+    val COASTAL: List<Int> get() = base.COASTAL
+    val PORT_POSITIONS: List<Int> get() = base.PORT_POSITIONS
+
+    fun otherEnd(edge: Int, vertex: Int): Int = base.otherEnd(edge, vertex)
+    fun hexCenter(h: Int): Pair<Int, Int> = base.hexCenter(h)
+    fun hexesAdjacent(a: Int, b: Int): Boolean = base.hexesAdjacent(a, b)
+    fun hexDistance(q1: Int, r1: Int, q2: Int, r2: Int): Int = Topology.hexDistance(q1, r1, q2, r2)
+    fun numberOdds(number: Int): Int = Topology.numberOdds(number)
+
+    /** The six board-corner hexes: pairwise non-adjacent by construction. */
+    private val CORNER_HEXES = listOf(
+        HexCoord(2, 0), HexCoord(0, 2), HexCoord(-2, 2),
+        HexCoord(-2, 0), HexCoord(0, -2), HexCoord(2, -2),
+    )
+
+    // -----------------------------------------------------------------------
+    // Island generation
+    // -----------------------------------------------------------------------
+
+    /**
+     * The island layout for one game: terrain and number per hex, the robber
+     * on the desert, and the nine harbours.
+     */
+    @Serializable
+    data class Generated(
+        val terrains: List<Terrain>,
+        /** 0 where there is no token (the desert). */
+        val numbers: List<Int>,
+        val robber: Int,
+        val ports: List<Port>,
+    )
+
+    /** The terrain tile mix: four forests, four pastures, four fields, three hills, three mountains, one desert. */
+    private val TERRAIN_TILES: List<Terrain> = listOf(
+        Terrain.FOREST, Terrain.FOREST, Terrain.FOREST, Terrain.FOREST,
+        Terrain.PASTURE, Terrain.PASTURE, Terrain.PASTURE, Terrain.PASTURE,
+        Terrain.FIELDS, Terrain.FIELDS, Terrain.FIELDS, Terrain.FIELDS,
+        Terrain.HILLS, Terrain.HILLS, Terrain.HILLS,
+        Terrain.MOUNTAINS, Terrain.MOUNTAINS, Terrain.MOUNTAINS,
+        Terrain.DESERT,
+    )
+
+    /** The 18 number tokens, the two hardest numbers withheld: 7 never appears. */
+    private val RED_TOKENS = listOf(6, 6, 8, 8)
+    private val OTHER_TOKENS = listOf(2, 3, 3, 4, 4, 5, 5, 9, 9, 10, 10, 11, 11, 12)
+
+    /** Shuffle attempts before falling back to the corner placement for 6s and 8s. */
+    private const val RED_ATTEMPTS = 60
+
+    /**
+     * Generates the island from [seed].
+     *
+     * Terrain is shuffled over the hexes, exactly as shuffling the land
+     * tiles face down does. Number tokens are shuffled over the land hexes
+     * with one repair rule: no two of the red tokens (6 and 8) may sit on
+     * adjacent hexes, the balance convention the published game asks for.
+     * The robber starts on the desert. Harbour *positions* are fixed (the
+     * physical frame is not shuffled); the nine harbour *types* — five
+     * 2:1 resource ports and four 3:1 ports — are shuffled onto them.
+     *
+     * The 6/8 separation is guaranteed, not merely probable: if no shuffled
+     * placement separates them (about one shuffle in five does), the red
+     * tokens go to four of the six board-corner hexes, which are pairwise
+     * non-adjacent, and at most one corner can be desert.
+     */
+    fun generate(seed: Long): Generated {
+        val random = Random(seed)
+        val terrains = TERRAIN_TILES.shuffled(random)
+        val desert = terrains.indexOf(Terrain.DESERT)
+        val land = terrains.indices.filter { it != desert }
+
+        var redHexes: List<Int>? = null
+        var attempt = 0
+        while (redHexes == null && attempt < RED_ATTEMPTS) {
+            val candidate = land.shuffled(random).take(4)
+            val separated = candidate.withIndex().all { (i, a) ->
+                candidate.drop(i + 1).none { hexesAdjacent(a, it) }
+            }
+            if (separated) redHexes = candidate
+            attempt++
+        }
+        val reds = redHexes ?: CORNER_HEXES
+            .mapNotNull { hexIndex[it] }
+            .filter { it != desert }
+            .shuffled(random)
+            .take(4)
+
+        val numbers = IntArray(HEX_COUNT)
+        RED_TOKENS.forEachIndexed { i, token -> numbers[reds[i]] = token }
+        val rest = land.filter { it !in reds }.shuffled(random)
+        OTHER_TOKENS.forEachIndexed { i, token -> numbers[rest[i]] = token }
+
+        val portTypes = (
+            listOf(
+                Resource.LUMBER, Resource.BRICK, Resource.WOOL, Resource.GRAIN, Resource.ORE,
+            ) + List(4) { null }
+            ).shuffled(random)
+        val ports = PORT_POSITIONS.mapIndexed { i, edge ->
+            val resource = portTypes[i]
+            if (resource == null) Port(edge, null, 3) else Port(edge, resource, 2)
+        }
+
+        return Generated(terrains, numbers.toList(), desert, ports)
+    }
+}

app/src/main/java/org/prolibertate/games/game/catan/CatanCkAi.kt

@@ -0,0 +1,466 @@
+package org.prolibertate.games.game.catan
+
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
+
+/**
+ * The computer opponent for Cities & Knights, reached through [CatanAi].
+ *
+ * It plays the same cautious game as the base AI — settle well, raise cities —
+ * and adds the three things this rule set asks of a player: keep enough active
+ * knights standing when the barbarians land, spend commodities on improvements
+ * as soon as it can, and answer every chore the table raises with the card it
+ * values least. It reads only what a player at the table could see, plus its
+ * own hand.
+ *
+ * It is not a strong player. It never moves knights about (they stay where
+ * hired, and are activated when the barbarians draw near), never plays the
+ * progress cards whose value depends on a plan (Inventor, Alchemist, Diplomat,
+ * Deserter, Intrigue), and makes no domestic offers, though it answers them.
+ *
+ * The seat's profile shapes it as in [CatanAi]: easy plays on a whim and
+ * discards badly, hard sizes its knights to the barbarian threat, values cards
+ * by what its improvements still need and keeps its robber off its own hexes,
+ * and the style leans it toward knights and expansion, toward spending down
+ * a big hand, or toward the leader.
+ */
+internal class CatanCkAi(
+    private val ai: CatanAi,
+    private val profiles: AiProfiles = AiProfiles.DEFAULT,
+) {
+
+    fun choose(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+        val profile = profiles.of(seat)
+        return choose(state, seat, legal, profile)
+    }
+
+    private fun choose(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove = when (state.phase) {
+        CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND ->
+            ai.chooseSetup(state, seat, legal.filterIsInstance<SetupPlace>(), profile)
+
+        CatanPhase.AWAIT_ROLL -> legal.first { it is RollDice }
+
+        CatanPhase.CHORE -> chooseChore(state, seat, legal, profile)
+
+        CatanPhase.ROBBER -> chooseRobber(state, seat, legal.filterIsInstance<MoveRobber>(), profile)
+
+        CatanPhase.FREE_ROADS -> chooseFreeRoad(state, seat, legal, profile)
+
+        CatanPhase.TRADE_PENDING -> chooseResponse(state, seat, legal, profile)
+
+        CatanPhase.TRADE_COUNTERS -> chooseCounter(state, legal)
+
+        CatanPhase.PLAYING -> choosePlaying(state, seat, legal, profile)
+
+        CatanPhase.DISCARDING, CatanPhase.GOLD, CatanPhase.GAME_OVER -> legal.firstOrNull()
+            ?: error("Nothing to choose in phase ${state.phase}")
+    }
+
+    // -----------------------------------------------------------------------
+    // Chores
+    // -----------------------------------------------------------------------
+
+    private fun chooseChore(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val ck = state.ck!!
+        return when (val chore = ck.chores.first()) {
+            is DiscardChore -> {
+                val n = minOf(chore.count, CatanCk.goodsCount(state, seat))
+                val hand = CatanCk.goodsList(state, seat)
+                // Easy now and then throws away whatever comes to hand.
+                val order = if (profile.slips()) {
+                    hand.shuffled(profile.random)
+                } else {
+                    hand.sortedBy { worth(state, seat, it, profile) }
+                }
+                DiscardGoods(order.take(n))
+            }
+
+            is GiveChore -> {
+                val pool = CatanCk.goodsList(state, seat)
+                    .filter { !chore.commoditiesOnly || it.isCommodity }
+                    .sortedBy { worth(state, seat, it, profile) }
+                GiveGoods(pool.take(minOf(chore.count, pool.size)))
+            }
+
+            is PillageChore ->
+                legal.filterIsInstance<PillageCity>().minByOrNull { production(state, it.vertex) } ?: legal.first()
+
+            is PickDeckChore -> {
+                val picks = legal.filterIsInstance<PickDeck>()
+                picks.maxByOrNull { CatanCk.improvement(state, seat, it.track) } ?: legal.first()
+            }
+
+            is DropProgressChore ->
+                legal.filterIsInstance<DropProgress>().minByOrNull { drop ->
+                    ck.progressHands[seat].first { it.id == drop.card }.kind.let(::cardWorth)
+                } ?: legal.first()
+
+            is MetropolisChore ->
+                legal.filterIsInstance<PlaceMetropolis>().maxByOrNull { production(state, it.vertex) }
+                    ?: legal.first()
+
+            is AqueductChore ->
+                legal.filterIsInstance<TakeAqueduct>().maxByOrNull { ai.want(it.resource) } ?: legal.first()
+
+            is RelocateChore -> legal.first()
+
+            is RemoveKnightChore ->
+                legal.filterIsInstance<RemoveKnight>().minByOrNull {
+                    CatanCk.knightAt(state, it.vertex)?.level ?: 0
+                } ?: legal.first()
+
+            is PlaceKnightChore -> legal.first()
+
+            is SpyChore -> legal.first()
+
+            is SmithChore ->
+                legal.filterIsInstance<PromoteKnight>().firstOrNull() ?: legal.first { it is EndSmith }
+        }
+    }
+
+    // -----------------------------------------------------------------------
+    // The robber
+    // -----------------------------------------------------------------------
+
+    private fun chooseRobber(state: CatanState, seat: Int, moves: List<MoveRobber>, profile: AiProfile): MoveRobber {
+        require(moves.isNotEmpty()) { "No legal robber move" }
+        val points = CatanRules.publicVictoryPoints(state)
+        val hard = profile.level == AiLevel.HARD
+        val spite = profile.style.spite
+        val leader = (0 until state.playerCount).filter { it != seat }.maxByOrNull { points[it] }
+        val victimWeight = 0.3 + 0.1 * profile.style.boldness
+        fun score(move: MoveRobber): Double {
+            val hex = CatanBoard.hexIndex.getValue(move.hex)
+            var score = 0.0
+            for (v in CatanBoard.HEX_CORNERS[hex]) {
+                val building = state.buildings[v] ?: continue
+                val worth = if (building.type == BuildingType.CITY) 2 else 1
+                val odds = CatanBoard.numberOdds(state.numbers[hex]) / 36.0
+                score += if (building.owner == seat) {
+                    -worth * odds * (if (hard) 1.5 else 1.0)
+                } else {
+                    worth * odds + if (building.owner == leader) spite * worth * odds else 0.0
+                }
+            }
+            if (move.victim != null) {
+                val cards = CatanCk.goodsCount(state, move.victim)
+                if (!hard || cards > 0) {
+                    score += 0.15 * cards + victimWeight * points[move.victim]
+                    if (move.victim == leader) score += 0.4 * spite
+                }
+            }
+            return score
+        }
+        return if (profile.level == AiLevel.EASY) {
+            profile.pick(moves.sortedByDescending { score(it) })
+        } else {
+            moves.maxByOrNull { score(it) } ?: moves.first()
+        }
+    }
+
+    // -----------------------------------------------------------------------
+    // The main phase
+    // -----------------------------------------------------------------------
+
+    private fun choosePlaying(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val ck = state.ck!!
+        val easy = profile.level == AiLevel.EASY
+        val hard = profile.level == AiLevel.HARD
+        val boldness = profile.style.boldness
+        // A cautious seat starts getting ready a step earlier.
+        val soon = ck.barbarians <= (if (boldness < 0) 4 else 3)
+        val endTurn = legal.lastOrNull { it is EndTurn }
+
+        // Easy loses the thread now and then and just passes.
+        if (easy && endTurn != null && profile.slips() && profile.random.nextBoolean()) return endTurn
+
+        // Chase the robber off a hex it is squatting on.
+        if (ck.attacked) {
+            val onMine = legal.filterIsInstance<ChaseRobber>().firstOrNull()
+            val robberHurtsMe = CatanBoard.HEX_CORNERS[state.robber].any { state.buildings[it]?.owner == seat }
+            if (onMine != null && robberHurtsMe) return onMine
+        }
+
+        // The cheap upgrade first, then the full-price one.
+        legal.filterIsInstance<PlayProgress>()
+            .filter { kindOf(state, seat, it) == ProgressType.MEDICINE }
+            .maxByOrNull { production(state, it.vertex!!) }
+            ?.let { return it }
+
+        val cities = legal.filterIsInstance<BuildCity>()
+        val settlements = legal.filterIsInstance<BuildSettlement>()
+        if (hard) {
+            val city = cities.maxByOrNull { production(state, it.vertex) }
+            val settlement = settlements.maxByOrNull { ai.hardSpot(state, seat, it.vertex) }
+            val cityScore = if (city != null) production(state, city.vertex) + 0.15 else Double.NEGATIVE_INFINITY
+            val settleScore = if (settlement != null) {
+                ai.hardSpot(state, seat, settlement.vertex) + 0.3 + 0.1 * boldness
+            } else {
+                Double.NEGATIVE_INFINITY
+            }
+            if (city != null && cityScore >= settleScore) return city
+            if (settlement != null) return settlement
+        } else if (easy) {
+            if (cities.isNotEmpty()) return profile.pick(cities.sortedByDescending { production(state, it.vertex) })
+            if (settlements.isNotEmpty()) {
+                return profile.pick(settlements.sortedByDescending { ai.spotValue(state, it.vertex) })
+            }
+        } else {
+            cities.maxByOrNull { production(state, it.vertex) }?.let { return it }
+
+            settlements.maxByOrNull { ai.spotValue(state, it.vertex) }?.let { return it }
+        }
+
+        // Improvements spend cards nothing else needs. Favour the track furthest along.
+        legal.filterIsInstance<BuyImprovement>()
+            .maxByOrNull { CatanCk.improvement(state, seat, it.track) * 10 + trackLean(it.track) }
+            ?.let { return it }
+
+        // Knights: stand ready by the time the barbarians land.
+        if (!(easy && profile.slips())) defence(state, seat, legal, soon, profile)?.let { return it }
+
+        if (!(easy && profile.slips())) progress(state, seat, legal)?.let { return it }
+
+        legal.filterIsInstance<BuildWall>().firstOrNull()?.let {
+            if (CatanCk.goodsCount(state, seat) >= (if (boldness < 0) 5 else 7)) return it
+        }
+
+        legal.filterIsInstance<BuildRoad>()
+            .filter { ai.roadValue(state, it) > 0.1 - 0.04 * boldness }
+            .maxByOrNull { ai.roadValue(state, it) }
+            ?.let { return it }
+
+        legal.filterIsInstance<GoodsBankTrade>()
+            .filter { completes(state, seat, it) }
+            .minByOrNull { CatanCk.bankRatio(state, seat, it.give) }
+            ?.let { return it }
+
+        // Stay under the seven: a cautious (or careful) seat sells down a big hand.
+        if ((hard || boldness < 0) && CatanCk.goodsCount(state, seat) > 7) {
+            legal.filterIsInstance<GoodsBankTrade>()
+                .maxByOrNull { t ->
+                    held(state, seat, t.give) * 10.0 - CatanCk.bankRatio(state, seat, t.give) * 3.0 +
+                        worth(state, seat, t.get, profile)
+                }
+                ?.let { return it }
+        }
+
+        return endTurn ?: legal.first()
+    }
+
+    /** Hire, promote and activate so the knights are standing when the barbarians land. */
+    private fun defence(
+        state: CatanState,
+        seat: Int,
+        legal: List<CatanMove>,
+        soon: Boolean,
+        profile: AiProfile,
+    ): CatanMove? {
+        val mine = CatanCk.knightsOf(state, seat)
+        val grainLeft = state.resources[seat][Resource.GRAIN] ?: 0
+
+        // Hard sizes the defence to the threat: the barbarians bring one strength
+        // per city on the board, and once the table's active knights outweigh them
+        // and this seat pulls its weight, the rest of its goods go elsewhere.
+        if (profile.level == AiLevel.HARD && soon && CatanCk.strength(state, seat) >= 1) {
+            val threat = state.buildings.count { it?.type == BuildingType.CITY }
+            val table = (0 until state.playerCount).sumOf { CatanCk.strength(state, it) }
+            if (table > threat) return null
+        }
+
+        if (soon) {
+            legal.filterIsInstance<ActivateKnight>().firstOrNull()?.let { return it }
+        }
+        val want = if (soon) 4 else if (profile.style.boldness > 0.5) 3 else 2
+        if (mine.size < want) {
+            legal.filterIsInstance<HireKnight>().maxByOrNull { ai.spotValue(state, it.vertex) }?.let { hire ->
+                // Keep a grain back for waking it, once the ship is close.
+                if (!soon || grainLeft >= 1) return hire
+            }
+        }
+        if (soon || mine.size >= 2) {
+            legal.filterIsInstance<PromoteKnight>().firstOrNull()?.let { return it }
+        }
+        if (soon) {
+            legal.filterIsInstance<ActivateKnight>().firstOrNull()?.let { return it }
+        }
+        return null
+    }
+
+    /** Progress cards worth playing without a plan. */
+    private fun progress(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove? {
+        val ck = state.ck!!
+        val soon = ck.barbarians <= 4
+        val plays = legal.filterIsInstance<PlayProgress>()
+        fun kindOf(play: PlayProgress) = ck.progressHands[seat].first { it.id == play.card }.kind
+        fun first(kind: ProgressType) = plays.firstOrNull { kindOf(it) == kind }
+
+        first(ProgressType.IRRIGATION)?.let { return it }
+        first(ProgressType.MINING)?.let { return it }
+        first(ProgressType.ENGINEER)?.let { return it }
+        first(ProgressType.SMITH)?.let { return it }
+        first(ProgressType.WEDDING)?.let { return it }
+        if (soon) first(ProgressType.WARLORD)?.let { return it }
+
+        plays.filter { kindOf(it) == ProgressType.MASTER_MERCHANT }
+            .maxByOrNull { play -> play.goods.orEmpty().sumOf { worth(state, seat, it) } }
+            ?.let { return it }
+
+        first(ProgressType.SPY)?.let { return it }
+        first(ProgressType.BISHOP)?.let { return it }
+
+        if (legal.filterIsInstance<BuildRoad>().size >= 2) first(ProgressType.ROAD_BUILDING)?.let { return it }
+
+        // Crane: only when it makes the difference to an improvement.
+        first(ProgressType.CRANE)?.let { crane ->
+            val helps = Track.entries.any { track ->
+                val level = CatanCk.improvement(state, seat, track)
+                val have = ck.commodities[seat][track.commodity] ?: 0
+                level < IMPROVEMENT_MAX && have == level // one short of the next level's price
+            }
+            if (helps) return crane
+        }
+
+        // Saboteur: when someone level or ahead is sitting on a pile.
+        first(ProgressType.SABOTEUR)?.let { saboteur ->
+            val vp = CatanRules.publicVictoryPoints(state)
+            val pile = (0 until state.playerCount).filter { it != seat && vp[it] >= vp[seat] }
+                .sumOf { CatanCk.goodsCount(state, it) / 2 }
+            if (pile >= 4) return saboteur
+        }
+
+        // Monopolies: only when the table is holding a pile of it.
+        plays.filter { kindOf(it) == ProgressType.RESOURCE_MONOPOLY || kindOf(it) == ProgressType.TRADE_MONOPOLY }
+            .maxByOrNull { held(state, seat, it.good!!) }
+            ?.let { best ->
+                val each = if (kindOf(best) == ProgressType.RESOURCE_MONOPOLY) 2 else 1
+                val take = (0 until state.playerCount).filter { it != seat }
+                    .sumOf { minOf(each, CatanCk.goodsOf(state, it)[best.good!!] ?: 0) }
+                if (take >= 3) return best
+            }
+
+        // The merchant, on the best hex beside a building of ours.
+        plays.filter { kindOf(it) == ProgressType.MERCHANT }
+            .maxByOrNull { play ->
+                val hex = play.hexA!!
+                CatanBoard.numberOdds(state.numbers[hex]).toDouble()
+            }?.let { return it }
+
+        // A commercial harbour turns spare resources into commodities.
+        plays.filter { kindOf(it) == ProgressType.COMMERCIAL_HARBOR }
+            .maxByOrNull { held(state, seat, it.good!!) }
+            ?.let { if (held(state, seat, it.good!!) >= 2) return it }
+
+        return null
+    }
+
+    private fun kindOf(state: CatanState, seat: Int, play: PlayProgress): ProgressType =
+        state.ck!!.progressHands[seat].first { it.id == play.card }.kind
+
+    /** What a building on [vertex] would draw, by the odds of its hexes and what the seat wants. */
+    private fun production(state: CatanState, vertex: Int): Double =
+        CatanBoard.VERTEX_HEXES[vertex].sumOf { h ->
+            val want = state.terrains[h].produces?.let { ai.want(it) } ?: 0.0
+            want * CatanBoard.numberOdds(state.numbers[h]) / 36.0
+        }
+
+    private fun held(state: CatanState, seat: Int, good: Good): Int = CatanCk.goodsOf(state, seat)[good] ?: 0
+
+    /** Whether the trade leaves a hand that can pay for a city, a settlement or an improvement. */
+    private fun completes(state: CatanState, seat: Int, trade: GoodsBankTrade): Boolean {
+        val hand = CatanCk.goodsOf(state, seat).toMutableMap()
+        hand[trade.give] = (hand[trade.give] ?: 0) - CatanCk.bankRatio(state, seat, trade.give)
+        hand[trade.get] = (hand[trade.get] ?: 0) + 1
+        fun covers(cost: Map<Resource, Int>) = cost.all { (r, n) -> (hand[Good.of(r)] ?: 0) >= n }
+        if (covers(CatanRules.CITY_COST) || covers(CatanRules.SETTLEMENT_COST)) return true
+        return Track.entries.any { track ->
+            val level = CatanCk.improvement(state, seat, track)
+            level < IMPROVEMENT_MAX &&
+                (hand[Good.of(track.commodity)] ?: 0) >= level + 1 &&
+                (state.ck!!.commodities[seat][track.commodity] ?: 0) < level + 1
+        }
+    }
+
+    private fun chooseFreeRoad(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val roads = legal.filterIsInstance<BuildRoad>().filter { ai.roadValue(state, it) > 0.05 }
+        val road = when {
+            roads.isEmpty() -> null
+            profile.level == AiLevel.EASY -> profile.pick(roads.sortedByDescending { ai.roadValue(state, it) })
+            else -> roads.maxByOrNull { ai.roadValue(state, it) }
+        }
+        return road
+            ?: legal.firstOrNull { it is EndFreeRoads }
+            ?: legal.first()
+    }
+
+    /** Extra the incoming cards must be worth: easy is not fussy, hard and spiteful seats are tougher on the leader. */
+    private fun tradeMargin(state: CatanState, seat: Int, other: Int, profile: AiProfile): Double {
+        var margin = 0.0
+        if (profile.level == AiLevel.EASY) margin -= 0.6
+        val points = CatanRules.publicVictoryPoints(state)
+        val leader = (0 until state.playerCount).filter { it != seat }.maxByOrNull { points[it] }
+        if (leader != null && other == leader) {
+            if (profile.level == AiLevel.HARD) margin += 0.4
+            margin += 0.5 * profile.style.spite
+        }
+        return margin
+    }
+
+    private fun chooseResponse(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val decline = legal.first { it is DeclineTrade }
+        val accept = legal.firstOrNull { it is AcceptTrade } ?: return decline
+        val offer = state.ck?.goodsOffer
+        if (offer != null) {
+            val incoming = offer.give.sumOf { worth(state, seat, it, profile) }
+            val outgoing = offer.get.sumOf { worth(state, seat, it, profile) }
+            return if (incoming > outgoing + tradeMargin(state, seat, offer.by, profile)) accept else decline
+        }
+        val plain = state.pendingTrade ?: return decline
+        val incoming = plain.give.sumOf { ai.want(it) }
+        val outgoing = plain.get.sumOf { ai.want(it) }
+        return if (incoming > outgoing + tradeMargin(state, seat, plain.by, profile)) accept else decline
+    }
+
+    /** Counters to a human's... the AI never makes an offer, so this only guards the phase: take none. */
+    private fun chooseCounter(state: CatanState, legal: List<CatanMove>): CatanMove =
+        legal.firstOrNull { it is DismissCounters } ?: legal.first()
+
+    // -----------------------------------------------------------------------
+    // Valuations
+    // -----------------------------------------------------------------------
+
+    /** What a card is worth to this seat: resources as the base AI sees them, commodities by what they buy. */
+    private fun worth(state: CatanState, seat: Int, good: Good, profile: AiProfile = AiProfile.DEFAULT): Double {
+        val base = good.resource?.let { ai.want(it) } ?: when (good) {
+            Good.PAPER -> 0.95
+            Good.COIN -> 0.9
+            else -> 0.85
+        }
+        if (profile.level != AiLevel.HARD) return base
+        // Hard keeps the commodity an improvement is about to need.
+        var bonus = if (good.resource == Resource.ORE || good.resource == Resource.GRAIN) 0.1 else 0.0
+        for (track in Track.entries) {
+            if (Good.of(track.commodity) != good) continue
+            val level = CatanCk.improvement(state, seat, track)
+            if (level < IMPROVEMENT_MAX && held(state, seat, good) <= level + 1) bonus += 0.5
+        }
+        return base + bonus
+    }
+
+    /** Which track to lean toward when two are level: politics for the knights, then science. */
+    private fun trackLean(track: Track): Int = when (track) {
+        Track.POLITICS -> 2
+        Track.SCIENCE -> 1
+        Track.TRADE -> 0
+    }
+
+    private fun cardWorth(kind: ProgressType): Double = when (kind) {
+        ProgressType.INVENTOR, ProgressType.ALCHEMIST, ProgressType.DIPLOMAT,
+        ProgressType.DESERTER, ProgressType.INTRIGUE, ProgressType.MERCHANT_FLEET,
+        -> 0.0
+
+        ProgressType.MERCHANT, ProgressType.COMMERCIAL_HARBOR, ProgressType.CRANE -> 0.5
+        else -> 1.0
+    }
+}

app/src/main/java/org/prolibertate/games/game/catan/CatanCkModel.kt

@@ -0,0 +1,486 @@
+package org.prolibertate.games.game.catan
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+/*
+ * The data of the Cities & Knights rule set. The rules themselves live in
+ * [CatanCk]; docs/RULES-catan-ck.md describes them and the choices made.
+ *
+ * Everything here is reached through [CatanState.ck], which is null for the
+ * base game, so a base game never sees any of it.
+ */
+
+/** Steps the barbarian ship must make before it lands. */
+const val BARBARIAN_STEPS = 7
+
+/** Commodity cards of each type the bank starts with (resources have 19). */
+const val BANK_PER_COMMODITY = 12
+
+/** Knights of each strength one player owns. */
+const val KNIGHTS_PER_LEVEL = 2
+
+/** City walls one player owns. */
+const val MAX_WALLS = 3
+
+/** Levels of city improvement in each track. */
+const val IMPROVEMENT_MAX = 5
+
+/** Progress cards a player may keep in hand. */
+const val PROGRESS_HAND_MAX = 4
+
+/** Cards a player may hold through a seven, before walls. */
+const val BASE_HAND_LIMIT = 7
+
+/** Longest Road is worth two points here; there is no Largest Army. */
+const val CK_LONGEST_ROAD_VP = 2
+
+/** Improvement level that unlocks the track's special power. */
+const val IMPROVEMENT_POWER_LEVEL = 3
+
+/** Level at which a track can claim its metropolis, and the level that can steal one. */
+const val METROPOLIS_LEVEL = 4
+
+/**
+ * What the three cities-of-industry give in place of a second resource:
+ * forest gives paper, pasture cloth and mountains coin.
+ */
+@Serializable
+enum class Commodity { CLOTH, COIN, PAPER }
+
+/**
+ * Any card a player can hold in hand and trade: a resource or a commodity.
+ * Progress cards are not goods.
+ */
+@Serializable
+enum class Good {
+    LUMBER, BRICK, WOOL, GRAIN, ORE, CLOTH, COIN, PAPER;
+
+    val resource: Resource?
+        get() = when (this) {
+            LUMBER -> Resource.LUMBER
+            BRICK -> Resource.BRICK
+            WOOL -> Resource.WOOL
+            GRAIN -> Resource.GRAIN
+            ORE -> Resource.ORE
+            else -> null
+        }
+
+    val commodity: Commodity?
+        get() = when (this) {
+            CLOTH -> Commodity.CLOTH
+            COIN -> Commodity.COIN
+            PAPER -> Commodity.PAPER
+            else -> null
+        }
+
+    val isCommodity: Boolean get() = commodity != null
+
+    companion object {
+        fun of(resource: Resource): Good = when (resource) {
+            Resource.LUMBER -> LUMBER
+            Resource.BRICK -> BRICK
+            Resource.WOOL -> WOOL
+            Resource.GRAIN -> GRAIN
+            Resource.ORE -> ORE
+        }
+
+        fun of(commodity: Commodity): Good = when (commodity) {
+            Commodity.CLOTH -> CLOTH
+            Commodity.COIN -> COIN
+            Commodity.PAPER -> PAPER
+        }
+
+        val RESOURCES: List<Good> = Resource.entries.map { of(it) }
+        val COMMODITIES: List<Good> = Commodity.entries.map { of(it) }
+    }
+}
+
+/**
+ * The three tracks of city improvement. Each is bought with one commodity, has
+ * a colour of progress-card deck and a power that unlocks at level three.
+ */
+@Serializable
+enum class Track(val commodity: Commodity) {
+    /** Yellow, bought with cloth: trade commodities two for one. */
+    TRADE(Commodity.CLOTH),
+
+    /** Blue, bought with coin: knights may become mighty. */
+    POLITICS(Commodity.COIN),
+
+    /** Green, bought with paper: the aqueduct. */
+    SCIENCE(Commodity.PAPER),
+}
+
+/**
+ * One face of the event die: a ship, or a city gate of a track's colour.
+ * Three faces are ships.
+ */
+@Serializable
+enum class EventFace { SHIP, TRADE, POLITICS, SCIENCE }
+
+/** The progress cards: [copies] of each in the deck of its [track]. */
+@Serializable
+enum class ProgressType(val track: Track, val copies: Int, val scoresAtOnce: Boolean = false) {
+    // Science (green)
+    ALCHEMIST(Track.SCIENCE, 2),
+    CRANE(Track.SCIENCE, 2),
+    ENGINEER(Track.SCIENCE, 1),
+    INVENTOR(Track.SCIENCE, 2),
+    IRRIGATION(Track.SCIENCE, 2),
+    MEDICINE(Track.SCIENCE, 2),
+    MINING(Track.SCIENCE, 2),
+    PRINTER(Track.SCIENCE, 1, scoresAtOnce = true),
+    ROAD_BUILDING(Track.SCIENCE, 2),
+    SMITH(Track.SCIENCE, 2),
+
+    // Politics (blue)
+    BISHOP(Track.POLITICS, 2),
+    CONSTITUTION(Track.POLITICS, 1, scoresAtOnce = true),
+    DESERTER(Track.POLITICS, 2),
+    DIPLOMAT(Track.POLITICS, 2),
+    INTRIGUE(Track.POLITICS, 2),
+    SABOTEUR(Track.POLITICS, 2),
+    SPY(Track.POLITICS, 3),
+    WARLORD(Track.POLITICS, 2),
+    WEDDING(Track.POLITICS, 2),
+
+    // Trade (yellow)
+    COMMERCIAL_HARBOR(Track.TRADE, 2),
+    MASTER_MERCHANT(Track.TRADE, 2),
+    MERCHANT(Track.TRADE, 6),
+    MERCHANT_FLEET(Track.TRADE, 2),
+    RESOURCE_MONOPOLY(Track.TRADE, 4),
+    TRADE_MONOPOLY(Track.TRADE, 2),
+}
+
+/** One progress card; [id] is stable for the life of the game. */
+@Serializable
+data class ProgressCard(val id: Int, val kind: ProgressType)
+
+/**
+ * A knight on the board. [level] is its strength: 1 basic, 2 strong, 3 mighty.
+ *
+ * [activatedTurn] and [promotedTurn] record the turn number each happened on:
+ * a knight cannot act on the turn it was activated, and cannot be promoted twice
+ * in one turn.
+ */
+@Serializable
+data class Knight(
+    val vertex: Int,
+    val owner: Int,
+    val level: Int,
+    val active: Boolean = false,
+    val activatedTurn: Int = 0,
+    val promotedTurn: Int = 0,
+)
+
+/** A metropolis stands on one city: [vertex] of seat [seat]. */
+@Serializable
+data class MetropolisAt(val seat: Int, val vertex: Int)
+
+/** The merchant sits on a hex, controlled by [seat] (who holds its point). */
+@Serializable
+data class MerchantAt(val seat: Int, val hex: Int)
+
+/** A counter-proposal to a [GoodsOffer]: seat [by] would [give] these if the offerer handed over [get]. */
+@Serializable
+data class GoodsCounter(val by: Int, val give: List<Good>, val get: List<Good>)
+
+/**
+ * A domestic trade offer in goods, which may include commodities. It is the
+ * base game's [TradeOffer] in cards of any kind, and works the same way: [to] is
+ * the one seat it is addressed to or null for the whole table, [asking] is the
+ * seat that may answer now, and [counters] collect for the offerer to choose from.
+ */
+@Serializable
+data class GoodsOffer(
+    val by: Int,
+    val to: Int?,
+    val give: List<Good>,
+    val get: List<Good>,
+    val asking: Int = to ?: -1,
+    val counters: List<GoodsCounter> = emptyList(),
+)
+
+/** Where play goes when the queue of [Chore]s runs out. */
+@Serializable
+enum class Back { PLAYING, AWAIT_ROLL, AFTER_EVENT, AFTER_DISCARDS, AFTER_PRODUCTION }
+
+/**
+ * Something one seat must decide before the game can go on. A chore is queued
+ * when a roll, an attack or a card needs an answer from somebody (possibly not
+ * the player whose turn it is); the first in [CkState.chores] is the one being
+ * asked.
+ */
+@Serializable
+sealed interface Chore {
+    val seat: Int
+}
+
+/** Give [count] cards to the bank, of the seat's choosing (a seven, a saboteur). */
+@Serializable
+@SerialName("c_discard")
+data class DiscardChore(override val seat: Int, val count: Int) : Chore
+
+/**
+ * Hand [count] cards of the seat's choosing to seat [to] (a wedding, a
+ * commercial harbour). [commoditiesOnly] restricts them to commodities, and
+ * [reward] is the resource [to] gives back for each.
+ */
+@Serializable
+@SerialName("c_give")
+data class GiveChore(
+    override val seat: Int,
+    val count: Int,
+    val to: Int,
+    val commoditiesOnly: Boolean = false,
+    val reward: Good? = null,
+) : Chore
+
+/** The barbarians won and this seat lost the contest: pick a city to fall. */
+@Serializable
+@SerialName("c_pillage")
+data class PillageChore(override val seat: Int) : Chore
+
+/** Choose a colour of progress deck to draw from. */
+@Serializable
+@SerialName("c_pickDeck")
+data class PickDeckChore(override val seat: Int) : Chore
+
+/** More progress cards than the hand holds: give one back. */
+@Serializable
+@SerialName("c_dropProgress")
+data class DropProgressChore(override val seat: Int) : Chore
+
+/** Choose the city that will bear the [track] metropolis. */
+@Serializable
+@SerialName("c_metropolis")
+data class MetropolisChore(override val seat: Int, val track: Track) : Chore
+
+/** The aqueduct pays out: take any one resource. */
+@Serializable
+@SerialName("c_aqueduct")
+data class AqueductChore(override val seat: Int) : Chore
+
+/** A knight was driven from its place; move it, or lose it. [knight] stood on [Knight.vertex]. */
+@Serializable
+@SerialName("c_relocate")
+data class RelocateChore(override val seat: Int, val knight: Knight) : Chore
+
+/** A deserter was played against this seat: remove one of your knights. */
+@Serializable
+@SerialName("c_removeKnight")
+data class RemoveKnightChore(override val seat: Int, val by: Int) : Chore
+
+/** Place a knight of [level] on the board for free, active or not as given. */
+@Serializable
+@SerialName("c_placeKnight")
+data class PlaceKnightChore(override val seat: Int, val level: Int, val active: Boolean) : Chore
+
+/** Choose one of [target]'s progress cards to take. */
+@Serializable
+@SerialName("c_spy")
+data class SpyChore(override val seat: Int, val target: Int) : Chore
+
+/** Promote up to [left] more knights for free. */
+@Serializable
+@SerialName("c_smith")
+data class SmithChore(override val seat: Int, val left: Int) : Chore
+
+/**
+ * Everything Cities & Knights adds to the table.
+ *
+ * Counts that are public ([progressCounts], the knights, the improvement
+ * levels) are stored directly; the decks and the other seats' progress hands are
+ * here in full because the host owns the truth, and [CatanRules.viewFor] keeps
+ * them off the wire.
+ */
+@Serializable
+data class CkState(
+    /** Commodity cards per seat. */
+    val commodities: List<Map<Commodity, Int>>,
+    /** Improvement level (0..5) per seat and track. */
+    val improvements: List<Map<Track, Int>>,
+    /** The metropolis of each track that has one. */
+    val metropolises: Map<Track, MetropolisAt> = emptyMap(),
+    val knights: List<Knight> = emptyList(),
+    /** Vertices whose city has a wall. */
+    val walls: List<Int> = emptyList(),
+    /** Steps left before the barbarians land, [BARBARIAN_STEPS] at the start. */
+    val barbarians: Int = BARBARIAN_STEPS,
+    /** Whether the barbarians have landed once: until then the robber sleeps. */
+    val attacked: Boolean = false,
+    val eventDie: EventFace? = null,
+    /** Progress decks, top first. Order is hidden. */
+    val decks: Map<Track, List<ProgressCard>>,
+    val progressHands: List<List<ProgressCard>>,
+    /** Public mirror of the progress-hand sizes. */
+    val progressCounts: List<Int>,
+    /** Victory points from Constitution and Printer, played face up at once. */
+    val progressVp: List<Int>,
+    /** Defender of Catan cards won, one point each. */
+    val defenderVp: List<Int>,
+    val merchant: MerchantAt? = null,
+    /** A crane was played this turn and its discount is unspent. */
+    val crane: Boolean = false,
+    /** A merchant fleet was played this turn for this good. */
+    val fleet: Good? = null,
+    /** Dice named by an alchemist, used by the next roll. */
+    val alchemist: List<Int>? = null,
+    /** The robber is being moved by a bishop, which robs everyone nearby. */
+    val bishop: Boolean = false,
+    val chores: List<Chore> = emptyList(),
+    val back: Back = Back.PLAYING,
+    val goodsOffer: GoodsOffer? = null,
+    /** Seats that have already drawn a defender or winners' card this attack, for the log only. */
+    val lastAttack: String? = null,
+)
+
+// ---------------------------------------------------------------------------
+// Moves
+// ---------------------------------------------------------------------------
+
+/** Buy the next level of improvement in [track]. */
+@Serializable
+@SerialName("buyImprovement")
+data class BuyImprovement(val track: Track) : CatanMove
+
+/** Hire a basic knight onto [vertex], an empty crossing at the end of one of your roads. */
+@Serializable
+@SerialName("hireKnight")
+data class HireKnight(val vertex: Int) : CatanMove
+
+/** Pay a grain to activate the knight on [vertex]. */
+@Serializable
+@SerialName("activateKnight")
+data class ActivateKnight(val vertex: Int) : CatanMove
+
+/** Promote the knight on [vertex] one level (paid, or free under a Smith). */
+@Serializable
+@SerialName("promoteKnight")
+data class PromoteKnight(val vertex: Int) : CatanMove
+
+/** Move the active knight on [from] along your roads to [to], driving off a weaker knight there. */
+@Serializable
+@SerialName("moveKnight")
+data class MoveKnight(val from: Int, val to: Int) : CatanMove
+
+/** The active knight on [vertex] chases the robber; the robber move follows. */
+@Serializable
+@SerialName("chaseRobber")
+data class ChaseRobber(val vertex: Int) : CatanMove
+
+/** Raise a wall around the city on [vertex]. */
+@Serializable
+@SerialName("buildWall")
+data class BuildWall(val vertex: Int) : CatanMove
+
+/**
+ * Play a progress card. Which of the optional arguments are used depends on
+ * the card (see [CatanCk]); the engine's legal list names every combination it
+ * accepts, so a client only ever chooses among them.
+ */
+@Serializable
+@SerialName("progress")
+data class PlayProgress(
+    val card: Int,
+    val target: Int? = null,
+    val vertex: Int? = null,
+    val edge: Int? = null,
+    val hexA: Int? = null,
+    val hexB: Int? = null,
+    val good: Good? = null,
+    val dice: List<Int>? = null,
+    val goods: List<Good>? = null,
+) : CatanMove
+
+/**
+ * Trade [give] to the bank for [get], at the best ratio this seat has for the
+ * card it gives. Replaces [MaritimeTrade] in Cities & Knights, where
+ * commodities trade too.
+ */
+@Serializable
+@SerialName("goodsBank")
+data class GoodsBankTrade(val give: Good, val get: Good) : CatanMove
+
+/**
+ * Offer a trade in goods to seat [to], or to the whole table when [to] is null.
+ * Free-form like [OfferTrade], so it is checked structurally and is not in the
+ * enumerated move list.
+ */
+@Serializable
+@SerialName("offerGoods")
+data class OfferGoods(val to: Int?, val give: List<Good>, val get: List<Good>) : CatanMove
+
+/**
+ * Answer the goods offer on the table with different terms. Structural, like
+ * [OfferGoods]; the answers to the counters are the shared [AcceptCounter] and
+ * [DismissCounters].
+ */
+@Serializable
+@SerialName("counterGoods")
+data class CounterGoods(val give: List<Good>, val get: List<Good>) : CatanMove
+
+/**
+ * Give up exactly the cards named, to a [DiscardChore]. Structural, not
+ * enumerated; the legal list carries one example so a seat is never without a move.
+ */
+@Serializable
+@SerialName("discardGoods")
+data class DiscardGoods(val cards: List<Good>) : CatanMove
+
+/** Hand over the cards named to a [GiveChore]. Structural, like [DiscardGoods]. */
+@Serializable
+@SerialName("giveGoods")
+data class GiveGoods(val cards: List<Good>) : CatanMove
+
+/** Let the city on [vertex] fall to the barbarians. */
+@Serializable
+@SerialName("pillageCity")
+data class PillageCity(val vertex: Int) : CatanMove
+
+/** Draw from the deck of this track's colour. */
+@Serializable
+@SerialName("pickDeck")
+data class PickDeck(val track: Track) : CatanMove
+
+/** Give up one progress card from a hand that is over the limit. */
+@Serializable
+@SerialName("dropProgress")
+data class DropProgress(val card: Int) : CatanMove
+
+/** Put the metropolis on the city at [vertex]. */
+@Serializable
+@SerialName("placeMetropolis")
+data class PlaceMetropolis(val vertex: Int) : CatanMove
+
+/** Take one [resource] from the bank for an aqueduct. */
+@Serializable
+@SerialName("aqueduct")
+data class TakeAqueduct(val resource: Resource) : CatanMove
+
+/** Move the knight that was driven off to [to]. */
+@Serializable
+@SerialName("relocateKnight")
+data class RelocateKnight(val to: Int) : CatanMove
+
+/** Take the knight on [vertex] off the board, for a deserter. */
+@Serializable
+@SerialName("removeKnight")
+data class RemoveKnight(val vertex: Int) : CatanMove
+
+/** Place the free knight from a deserter on [vertex]. */
+@Serializable
+@SerialName("placeKnight")
+data class PlaceKnight(val vertex: Int) : CatanMove
+
+/** Take the spied progress card with this id. */
+@Serializable
+@SerialName("spyTake")
+data class SpyTake(val card: Int) : CatanMove
+
+/** Stop promoting knights under a Smith. */
+@Serializable
+@SerialName("endSmith")
+data object EndSmith : CatanMove

app/src/main/java/org/prolibertate/games/game/catan/CatanModel.kt

@@ -0,0 +1,500 @@
+package org.prolibertate.games.game.catan
+
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+import kotlinx.serialization.json.JsonArray
+import kotlinx.serialization.json.JsonDecoder
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.JsonPrimitive
+import kotlinx.serialization.json.jsonObject
+
+/** Sentinel stored in [CatanState.roads] for an unclaimed road position. */
+const val NO_PLAYER = -1
+
+/** Road segments required to hold Longest Road. */
+const val LONGEST_ROAD_MIN = 5
+
+/** Knights required to take Largest Army. */
+const val LARGEST_ARMY_MIN = 3
+
+/** Pieces each player has: a player who has laid them all cannot build another. */
+const val MAX_ROADS = 15
+const val MAX_SETTLEMENTS = 5
+const val MAX_CITIES = 4
+
+/** Resource cards of each type the bank starts with. */
+const val BANK_PER_RESOURCE = 19
+
+/**
+ * The five resources the island produces.
+ *
+ * Catan names two of them after the terrain rather than the commodity
+ * (wood becomes lumber, sheep become wool); those names travel with the
+ * trademark, so the engine speaks in resources only.
+ */
+@Serializable
+enum class Resource { LUMBER, BRICK, WOOL, GRAIN, ORE }
+
+/** One terrain type per hex; the desert produces nothing. */
+@Serializable
+enum class Terrain(val produces: Resource?) {
+    FOREST(Resource.LUMBER),
+    PASTURE(Resource.WOOL),
+    FIELDS(Resource.GRAIN),
+    HILLS(Resource.BRICK),
+    MOUNTAINS(Resource.ORE),
+    DESERT(null),
+
+    /** Seafarers: open water. Ships sail on it; nothing is built on it and nothing produces. */
+    SEA(null),
+
+    /** Seafarers: a gold field. A settlement beside it takes any resource its owner likes when its number rolls. */
+    GOLD(null),
+}
+
+/** Axial coordinate of one hex on the board. See [CatanBoard]. */
+@Serializable
+data class HexCoord(val q: Int, val r: Int)
+
+@Serializable
+enum class BuildingType { SETTLEMENT, CITY }
+
+/** What stands on one vertex: a settlement or city owned by one seat. */
+@Serializable
+data class CatanBuilding(val type: BuildingType, val owner: Int)
+
+/**
+ * One harbour. A port sits on a coastal edge: a player who owns a
+ * settlement or city on *either* endpoint vertex of [edge] may trade at
+ * [ratio] (2 or 3) instead of the bank's 4:1. A resource port trades at 2:1
+ * for its own resource only; [resource] is null for a generic 3:1 harbour.
+ */
+@Serializable
+data class Port(val edge: Int, val resource: Resource?, val ratio: Int)
+
+@Serializable
+enum class DevCardType { KNIGHT, ROAD_BUILDING, MONOPOLY, YEAR_OF_PLENTY, VICTORY_POINT }
+
+/**
+ * One development card. [id] is stable for the life of the game (the deck
+ * is built once from the seed), so moves can name a card by id even after
+ * it moves from the deck into a hand. [boughtTurn] records when it was
+ * drawn: a card cannot be played on the turn it was bought.
+ */
+@Serializable
+data class DevCard(val id: Int, val type: DevCardType, val boughtTurn: Int = 0)
+
+/**
+ * A counter-proposal to a [TradeOffer]: seat [by] would [give] these cards to
+ * the offerer if the offerer would hand over [get].
+ */
+@Serializable
+data class TradeCounter(val by: Int, val give: List<Resource>, val get: List<Resource>)
+
+/**
+ * A domestic trade offer on the table. [by] is the offering seat. [to] is the
+ * one seat it is addressed to, or null for an open offer to the whole table.
+ * Seats are asked one at a time, in seat order after the offerer; [asking] is
+ * the seat that may answer now. Each may accept (the trade happens at once),
+ * decline, or counter; counters are kept in [counters] and, if nobody accepts,
+ * the offerer chooses among them in [CatanPhase.TRADE_COUNTERS].
+ */
+@Serializable
+data class TradeOffer(
+    val by: Int,
+    val to: Int?,
+    val give: List<Resource>,
+    val get: List<Resource>,
+    val asking: Int = to ?: -1,
+    val counters: List<TradeCounter> = emptyList(),
+)
+
+/**
+ * Where the game stands. The phases that involve more than the player
+ * whose turn it is carry their own bookkeeping: [discardSeat] during
+ * [CatanPhase.DISCARDING], [pendingTrade] during [CatanPhase.TRADE_PENDING] and [CatanPhase.TRADE_COUNTERS].
+ */
+@Serializable
+enum class CatanPhase {
+    /** Snake order forward: settlement + road each, seats 0..n-1. */
+    SETUP_FIRST,
+
+    /** Snake order back: settlement + road each, seats n-1..0, plus income. */
+    SETUP_SECOND,
+
+    /** The player whose turn it is must roll the dice. */
+    AWAIT_ROLL,
+
+    /** Seafarers: the first seat in [SeaState.gold] is choosing the resources its gold fields paid. */
+    GOLD,
+
+    /** Players holding more than 7 resource cards discard half. */
+    DISCARDING,
+
+    /** The roller must move the robber and steal. */
+    ROBBER,
+
+    /** Build, trade, buy and play development cards, or end the turn. */
+    PLAYING,
+
+    /** A played Road Building card: up to two roads remain to be placed. */
+    FREE_ROADS,
+
+    /** The [TradeOffer.asking] seat must accept, decline or counter. */
+    TRADE_PENDING,
+
+    /** Nobody accepted but some seats countered: the offerer picks one or none. */
+    TRADE_COUNTERS,
+
+    GAME_OVER,
+
+    /**
+     * Cities & Knights only: the first seat in [CkState.chores] has something
+     * to decide (a discard, a city to give up, a card to draw…) and the game
+     * waits on it. Play resumes where [CkState.back] says.
+     */
+    CHORE,
+}
+
+/** An expansion a table can switch on. The base game is what is left with none selected. */
+@Serializable
+enum class CatanExpansion {
+    /** Cities & Knights: commodities, knights, barbarians, city improvements. */
+    CITIES_AND_KNIGHTS,
+
+    /** Seafarers: ships, a pirate, gold fields and islands to settle (see `docs/RULES-catan-seafarers.md`). */
+    SEAFARERS,
+}
+
+/**
+ * What a table plays: the expansions switched on, and the Seafarers map when that one is.
+ *
+ * Saves written before expansions became toggles carry `"ruleSet"` instead of `"expansions"`;
+ * [CatanOptionsSerializer] reads either.
+ */
+@Serializable(with = CatanOptionsSerializer::class)
+data class CatanOptions(
+    val playerCount: Int = 3,
+    val pointsToWin: Int = 10,
+    val expansions: Set<CatanExpansion> = emptySet(),
+    val scenario: SeaScenario = SeaScenario.NEW_SHORES,
+) {
+    init {
+        require(playerCount in 3..4) { "The island seats three or four players" }
+        require(pointsToWin >= 2) { "pointsToWin must be at least 2" }
+        // Lifted once Cities & Knights runs on a Seafarers map.
+        require(expansions.size <= 1) { "Combining expansions is not supported yet" }
+    }
+
+    val seafarers: Boolean get() = CatanExpansion.SEAFARERS in expansions
+    val citiesAndKnights: Boolean get() = CatanExpansion.CITIES_AND_KNIGHTS in expansions
+}
+
+/** The wire shape of [CatanOptions]. */
+@Serializable
+private class CatanOptionsWire(
+    val playerCount: Int = 3,
+    val pointsToWin: Int = 10,
+    val expansions: Set<CatanExpansion> = emptySet(),
+    val scenario: SeaScenario = SeaScenario.NEW_SHORES,
+)
+
+/** Reads the legacy single `ruleSet` field as an expansion set. */
+object CatanOptionsSerializer : KSerializer<CatanOptions> {
+    override val descriptor: SerialDescriptor = CatanOptionsWire.serializer().descriptor
+
+    override fun serialize(encoder: Encoder, value: CatanOptions) = encoder.encodeSerializableValue(
+        CatanOptionsWire.serializer(),
+        CatanOptionsWire(value.playerCount, value.pointsToWin, value.expansions, value.scenario),
+    )
+
+    override fun deserialize(decoder: Decoder): CatanOptions {
+        val input = decoder as JsonDecoder
+        var obj = input.decodeJsonElement().jsonObject
+        val legacy = (obj["ruleSet"] as? JsonPrimitive)?.content
+        if (legacy != null) {
+            val expansions = if (legacy == "BASE") emptyList() else listOf(JsonPrimitive(legacy))
+            obj = JsonObject(obj - "ruleSet" + ("expansions" to JsonArray(expansions)))
+        }
+        val wire = input.json.decodeFromJsonElement(CatanOptionsWire.serializer(), obj)
+        return CatanOptions(wire.playerCount, wire.pointsToWin, wire.expansions, wire.scenario)
+    }
+}
+
+/**
+ * The whole game as one immutable value.
+ *
+ * Public information (terrain, numbers, ports, buildings, roads, resource
+ * counts, dev-card counts, knights played) is stored directly. Hidden
+ * information — the deck's order and every hand's development cards — is
+ * here in full because the host owns the truth; [CatanRules.viewFor] is
+ * what keeps it off the wire.
+ */
+@Serializable
+data class CatanState(
+    val options: CatanOptions,
+    val seed: Long,
+    val phase: CatanPhase,
+    /**
+     * The seat whose turn it is — not always the seat expected to move:
+     * during [CatanPhase.DISCARDING] and [CatanPhase.TRADE_PENDING] another
+     * seat acts on the turn owner's behalf.
+     */
+    val turn: Int,
+    /** How many setup placements are done, 0 until 2 * playerCount. */
+    val setupIndex: Int,
+    /** The seat that places first and takes the first turn; drawn from the table seed. */
+    val firstSeat: Int = 0,
+    /** Monotonic turn counter, 0 during setup, 1 from the first real turn. */
+    val turnNumber: Int,
+    /** Terrain per hex, indexed like [CatanBoard.HEXES]. */
+    val terrains: List<Terrain>,
+    /** Number token per hex, 0 where there is none (the desert). */
+    val numbers: List<Int>,
+    /** Hex the robber currently occupies. */
+    val robber: Int,
+    val ports: List<Port>,
+    /** What stands on each vertex, or null. */
+    val buildings: List<CatanBuilding?>,
+    /** Owning seat per edge, or [NO_PLAYER]. */
+    val roads: List<Int>,
+    /** Resource cards per seat. Card counts are public in Catan. */
+    val resources: List<Map<Resource, Int>>,
+    /** The bank's development cards, top first. Order is hidden. */
+    val devDeck: List<DevCard>,
+    /** Development cards per seat. Hidden from everyone but the holder. */
+    val devHands: List<List<DevCard>>,
+    /** Public mirror of the dev-hand sizes, for views and scoreboards. */
+    val devHandCounts: List<Int>,
+    /** Knights played (not merely held) per seat. */
+    val knightsPlayed: List<Int>,
+    /** Whether the turn owner has already played a development card. */
+    val devCardPlayedThisTurn: Boolean,
+    val pendingTrade: TradeOffer?,
+    /** Roads still owed on a played Road Building card. */
+    val pendingFreeRoads: Int,
+    /** Seat due to discard during [CatanPhase.DISCARDING]. */
+    val discardSeat: Int?,
+    val longestRoadOwner: Int?,
+    val largestArmyOwner: Int?,
+    /** The dice as last rolled, for the table display. */
+    val lastDice: List<Int>,
+    /**
+     * How many dice rolls and steals have happened so far. Random events are
+     * derived from the seed and this counter, so the same game replays
+     * identically without storing a random generator in the state.
+     */
+    val rngStep: Int,
+    val winner: Int?,
+    val log: List<String>,
+    /** Everything Cities & Knights adds; null in the base game. */
+    val ck: CkState? = null,
+    /** Everything Seafarers adds (ships, the pirate, islands); null in the other rule sets. */
+    val sea: SeaState? = null,
+) {
+    val playerCount: Int get() = options.playerCount
+
+    /** The geometry this game is played on: the standard island, or a Seafarers map. */
+    val topo: Topology get() = sea?.let { SeaBoards.topology(it.scenario) } ?: CatanBoard.base
+
+    /** Whether this table plays Seafarers. */
+    val isSea: Boolean get() = sea != null
+
+    /** Whether this table plays Cities & Knights. */
+    val isCk: Boolean get() = ck != null
+
+    /** Total resource cards held by [seat]. */
+    fun resourceCount(seat: Int): Int = resources[seat].values.sum()
+
+    /** [seat]'s resource cards as a flat list, one entry per card. */
+    fun handOf(seat: Int): List<Resource> =
+        Resource.entries.flatMap { res -> List(resources[seat][res] ?: 0) { res } }
+
+    /** Whether [seat] holds every card in [cards], counting duplicates. */
+    fun holdsAll(seat: Int, cards: List<Resource>): Boolean {
+        val need = cards.groupingBy { it }.eachCount()
+        return need.all { (res, n) -> (resources[seat][res] ?: 0) >= n }
+    }
+}
+
+@Serializable
+sealed interface CatanMove
+
+/** Setup placement: a settlement on [vertex] plus a road on [edge]. */
+@Serializable
+@SerialName("setup")
+data class SetupPlace(val vertex: Int, val edge: Int) : CatanMove
+
+/**
+ * Roll the dice.
+ *
+ * With [forced] null the roll is derived from the game seed, which is what
+ * the AI, the UI and the network always send. [forced] exists so tests and
+ * offline reviews can stage a specific number; it is not part of the
+ * enumerated move list, so the network driver's "is this move in the legal
+ * list" check rejects any forced roll a client tries to sneak through —
+ * only code holding the state directly (the host's own tests) can use it.
+ */
+@Serializable
+@SerialName("roll")
+data class RollDice(
+    val forced: List<Int>? = null,
+    /** Test-only, like [forced]: the event die of a Cities & Knights roll. */
+    val event: EventFace? = null,
+) : CatanMove
+
+/** Discard exactly these cards. */
+@Serializable
+@SerialName("discard")
+data class Discard(val cards: List<Resource>) : CatanMove
+
+/** Move the robber to [hex] and steal from [victim], if anyone can be robbed. */
+@Serializable
+@SerialName("robber")
+data class MoveRobber(val hex: HexCoord, val victim: Int? = null) : CatanMove
+
+/** Build a road on [edge] — paid normally, or free during FREE_ROADS. */
+@Serializable
+@SerialName("road")
+data class BuildRoad(val edge: Int) : CatanMove
+
+@Serializable
+@SerialName("settlement")
+data class BuildSettlement(val vertex: Int) : CatanMove
+
+@Serializable
+@SerialName("city")
+data class BuildCity(val vertex: Int) : CatanMove
+
+@Serializable
+@SerialName("buyCard")
+data object BuyDevCard : CatanMove
+
+/**
+ * Play a knight. The card is named by [card] id; the robber move follows as
+ * its own move once the phase has advanced.
+ */
+@Serializable
+@SerialName("knight")
+data class PlayKnight(val card: Int) : CatanMove
+
+@Serializable
+@SerialName("roadBuilding")
+data class PlayRoadBuilding(val card: Int) : CatanMove
+
+@Serializable
+@SerialName("monopoly")
+data class PlayMonopoly(val card: Int, val resource: Resource) : CatanMove
+
+/** Take [take] (up to two cards) from the bank. */
+@Serializable
+@SerialName("plenty")
+data class PlayYearOfPlenty(val card: Int, val take: List<Resource>) : CatanMove
+
+/**
+ * Offer a domestic trade to [to] (null: everyone, asked in turn): [give] of
+ * ours for [get] of theirs.
+ *
+ * Like a forced dice roll this is a free-form intent rather than an
+ * enumerated move — the space of two card multisets is combinatorial — so
+ * it is validated structurally by [CatanRules.isLegalMove] instead of
+ * appearing in [CatanRules.legalMoves].
+ */
+@Serializable
+@SerialName("offer")
+data class OfferTrade(val to: Int?, val give: List<Resource>, val get: List<Resource>) : CatanMove
+
+@Serializable
+@SerialName("accept")
+data object AcceptTrade : CatanMove
+
+@Serializable
+@SerialName("decline")
+data object DeclineTrade : CatanMove
+
+/**
+ * Answer the offer on the table with different terms: we would [give] these
+ * cards if the offerer handed over [get]. Free-form like [OfferTrade], so
+ * validated by [CatanRules.isLegalMove] rather than listed.
+ */
+@Serializable
+@SerialName("counter")
+data class CounterTrade(val give: List<Resource>, val get: List<Resource>) : CatanMove
+
+/** The offerer takes the counter-proposal made by [seat]. */
+@Serializable
+@SerialName("acceptCounter")
+data class AcceptCounter(val seat: Int) : CatanMove
+
+/** The offerer takes none of the counter-proposals. */
+@Serializable
+@SerialName("dismissCounters")
+data object DismissCounters : CatanMove
+
+/** Bank trade: [give] at the best ratio this seat can trade at for [get]. */
+@Serializable
+@SerialName("bank")
+data class MaritimeTrade(val give: Resource, val get: Resource) : CatanMove
+
+@Serializable
+@SerialName("endTurn")
+data object EndTurn : CatanMove
+
+/** Forfeit any remaining free roads from a played Road Building card. */
+@Serializable
+@SerialName("endFreeRoads")
+data object EndFreeRoads : CatanMove
+
+/**
+ * Seafarers state: the ships, the pirate and the islands, alongside the base game's
+ * roads, robber and buildings (which keep working exactly as before).
+ */
+@Serializable
+data class SeaState(
+    val scenario: SeaScenario,
+    /** Owning seat per edge, or [NO_PLAYER]: a ship on that edge. Roads stay in [CatanState.roads]. */
+    val ships: List<Int>,
+    /** The hex the pirate occupies: always a sea hex. */
+    val pirate: Int,
+    /** Ships built this turn (they may not sail until the next) and whether a ship has sailed this turn. */
+    val builtThisTurn: List<Int> = emptyList(),
+    val shipMoved: Boolean = false,
+    /** Who holds the "new island" bonus for each island, or [NO_PLAYER]. The home island's is never awarded. */
+    val islandBonus: List<Int>,
+    /** The island that counts as home: the largest, and the pirate-free start of the original map. */
+    val home: Int,
+    /** The islands the starting settlements may go on. Empty in a save from before there were several: just [home]. */
+    val starts: List<Int> = emptyList(),
+    /** Gold owed after a roll, front first: each seat chooses [GoldOwed.count] cards. */
+    val gold: List<GoldOwed> = emptyList(),
+)
+
+/** Whether [island] is one the game starts on, and so never earns the new-island bonus. */
+fun SeaState.isStart(island: Int): Boolean = island == home || island in starts
+
+@Serializable
+data class GoldOwed(val seat: Int, val count: Int)
+
+/** Build a ship on [edge]: 1 lumber and 1 wool, on a sea edge joined to your fleet or a harbour town. */
+@Serializable
+@SerialName("ship")
+data class BuildShip(val edge: Int) : CatanMove
+
+/** Sail the ship on [from] to [to]: once a turn, never the turn it was built, only from the open end of a route. */
+@Serializable
+@SerialName("moveShip")
+data class MoveShip(val from: Int, val to: Int) : CatanMove
+
+/** Move the pirate to the sea hex [hex] and rob [victim], a seat with a ship beside it, if there is one. */
+@Serializable
+@SerialName("pirate")
+data class MovePirate(val hex: HexCoord, val victim: Int? = null) : CatanMove
+
+/** Choose the [cards] a gold field paid. */
+@Serializable
+@SerialName("gold")
+data class PickGold(val cards: List<Resource>) : CatanMove

app/src/main/java/org/prolibertate/games/game/catan/CatanSeaBoard.kt

@@ -0,0 +1,200 @@
+package org.prolibertate.games.game.catan
+
+import kotlinx.serialization.Serializable
+import kotlin.random.Random
+
+/** The Seafarers maps on offer. Each is a fixed arrangement of land and sea; the tiles and numbers on it are shuffled. */
+@Serializable
+enum class SeaScenario(val title: String, val blurb: String, val start: SeaStart = SeaStart.HOME_ONLY) {
+    NEW_SHORES(
+        "Heading for New Shores",
+        "One large home island and three small ones to find by ship. Gold fields on two of the small islands.",
+    ),
+    FOUR_ISLANDS(
+        "Four Islands",
+        "Four equal islands, one start each, and two gold islets in the middle. Settle your own island, then sail.",
+        SeaStart.MAIN_ISLANDS,
+    ),
+    THROUGH_THE_DESERT(
+        "Through the Desert",
+        "One island cut by a broad desert that yields nothing. Reach the far side by road, or sail round to the islets.",
+    ),
+}
+
+/** Where the starting settlements may go. */
+enum class SeaStart {
+    /** The largest island only. */
+    HOME_ONLY,
+
+    /** Any island big enough to live on (four hexes or more); the small ones are prizes to sail to. */
+    MAIN_ISLANDS,
+}
+
+/**
+ * The Seafarers maps as geometry plus a generator for one game's tiles.
+ *
+ * A map is drawn below as text: `.` is sea, `#` a land hex that gets a random resource,
+ * `$` a gold field, `D` the desert. Odd rows are shifted half a hex to the right (the usual
+ * "odd-r" offset layout). The outermost ring is always sea, so every coast is closed.
+ */
+object SeaBoards {
+
+    private val NEW_SHORES_MAP = listOf(
+        "..........",
+        "...##.....",
+        "..####.$#.",
+        ".#####..#.",
+        ".##D###...",
+        "..####..#.",
+        ".......##.",
+        ".$#.......",
+        "..........",
+    )
+
+    private val FOUR_ISLANDS_MAP = listOf(
+        "............",
+        "..###..###..",
+        "..###..###..",
+        "............",
+        "..$.....$...",
+        "............",
+        "..###..###..",
+        "..###..###..",
+        "............",
+    )
+
+    private val THROUGH_THE_DESERT_MAP = listOf(
+        "............",
+        ".###DD###...",
+        ".###DDD###..",
+        "..###DD###..",
+        "............",
+        "..$.....$...",
+        "............",
+        "...##...#...",
+        "............",
+    )
+
+    private fun rows(scenario: SeaScenario): List<String> = when (scenario) {
+        SeaScenario.NEW_SHORES -> NEW_SHORES_MAP
+        SeaScenario.FOUR_ISLANDS -> FOUR_ISLANDS_MAP
+        SeaScenario.THROUGH_THE_DESERT -> THROUGH_THE_DESERT_MAP
+    }
+
+    private val topologies = HashMap<SeaScenario, Topology>()
+
+    /** The frame of [scenario]: every hex, with its land mask. Built once and shared. */
+    fun topology(scenario: SeaScenario): Topology = synchronized(topologies) {
+        topologies.getOrPut(scenario) { build(scenario) }
+    }
+
+    /** Hex (row, col) of the text map as an axial coordinate (odd-r offset). */
+    private fun coord(row: Int, col: Int): HexCoord = HexCoord(col - (row - (row and 1)) / 2, row)
+
+    private fun build(scenario: SeaScenario): Topology {
+        val map = rows(scenario)
+        val hexes = mutableListOf<HexCoord>()
+        val land = mutableListOf<Boolean>()
+        map.forEachIndexed { row, text ->
+            text.forEachIndexed { col, ch ->
+                hexes += coord(row, col)
+                land += ch != '.'
+            }
+        }
+        return Topology(hexes, land, standardFrame = false, harbours = 9)
+    }
+
+    /** Terrain kind the map asks of each hex: sea, gold, desert, or "pick a resource". */
+    private fun kinds(scenario: SeaScenario): List<Char> = rows(scenario).flatMap { it.toList() }
+
+    /** One game's tiles on a Seafarers map. */
+    @Serializable
+    data class Generated(
+        val terrains: List<Terrain>,
+        val numbers: List<Int>,
+        val robber: Int,
+        val pirate: Int,
+        val ports: List<Port>,
+        val home: Int,
+        /** The islands the starting settlements may go on; always includes [home]. */
+        val starts: List<Int> = listOf(home),
+    )
+
+    /** An island of this many land hexes or more can be started on. */
+    private const val MAIN_ISLAND_HEXES = 4
+
+    private val RESOURCE_TILES = listOf(
+        Terrain.FOREST, Terrain.PASTURE, Terrain.FIELDS, Terrain.HILLS, Terrain.MOUNTAINS,
+    )
+
+    /** Number tokens: the standard 18 plus ten more, so every land hex but the desert has one. */
+    private val TOKENS = listOf(2, 3, 3, 4, 4, 5, 5, 6, 6, 8, 8, 9, 9, 10, 10, 11, 11, 12) +
+        listOf(3, 4, 5, 6, 8, 9, 10, 11, 5, 9)
+
+    fun generate(scenario: SeaScenario, seed: Long): Generated {
+        val topo = topology(scenario)
+        val kinds = kinds(scenario)
+        val random = Random(seed)
+
+        // Resources fill the '#' hexes as evenly as the count allows, in shuffled order.
+        val plain = kinds.indices.filter { kinds[it] == '#' }
+        val pool = List(plain.size) { RESOURCE_TILES[it % RESOURCE_TILES.size] }.shuffled(random)
+        val terrains = MutableList(kinds.size) { Terrain.SEA }
+        kinds.forEachIndexed { h, ch ->
+            terrains[h] = when (ch) {
+                '$' -> Terrain.GOLD
+                'D' -> Terrain.DESERT
+                '#' -> pool[plain.indexOf(h)]
+                else -> Terrain.SEA
+            }
+        }
+
+        val numbered = terrains.indices.filter { terrains[it] != Terrain.SEA && terrains[it] != Terrain.DESERT }
+        check(numbered.size <= TOKENS.size) { "Not enough number tokens for ${numbered.size} hexes" }
+        val tokens = TOKENS.take(numbered.size).shuffled(random)
+        val numbers = IntArray(terrains.size)
+        var placed = false
+        var attempt = 0
+        while (!placed && attempt < 200) {
+            val order = numbered.shuffled(random)
+            val assigned = IntArray(terrains.size)
+            order.forEachIndexed { i, h -> assigned[h] = tokens[i] }
+            val reds = numbered.filter { assigned[it] == 6 || assigned[it] == 8 }
+            val clash = reds.any { a -> reds.any { b -> a < b && topo.hexesAdjacent(a, b) } }
+            if (!clash || attempt == 199) {
+                assigned.copyInto(numbers)
+                placed = true
+            }
+            attempt++
+        }
+
+        val portTypes = (
+            listOf(Resource.LUMBER, Resource.BRICK, Resource.WOOL, Resource.GRAIN, Resource.ORE) + List(4) { null }
+            ).shuffled(random)
+        val ports = topo.PORT_POSITIONS.mapIndexed { i, edge ->
+            val resource = portTypes[i % portTypes.size]
+            if (resource == null) Port(edge, null, 3) else Port(edge, resource, 2)
+        }
+
+        val desert = terrains.indexOf(Terrain.DESERT).takeIf { it >= 0 }
+            ?: numbered.first()
+        val home = (0 until topo.islandCount).maxByOrNull { island -> topo.islandOf.count { it == island } } ?: 0
+        // The pirate starts in the open sea: the sea hex farthest from every shore.
+        val sea = terrains.indices.filter { terrains[it] == Terrain.SEA }
+        val pirate = sea.maxByOrNull { h ->
+            val c = topo.HEXES[h]
+            terrains.indices.filter { terrains[it] != Terrain.SEA }.minOfOrNull {
+                Topology.hexDistance(c.q, c.r, topo.HEXES[it].q, topo.HEXES[it].r)
+            } ?: 0
+        } ?: sea.first()
+
+        val starts = when (scenario.start) {
+            SeaStart.HOME_ONLY -> listOf(home)
+            SeaStart.MAIN_ISLANDS -> (0 until topo.islandCount).filter { island ->
+                topo.islandOf.count { it == island } >= MAIN_ISLAND_HEXES
+            }.ifEmpty { listOf(home) }
+        }
+
+        return Generated(terrains, numbers.toList(), desert, pirate, ports, home, starts)
+    }
+}

app/src/main/java/org/prolibertate/games/game/catan/CatanSeaRules.kt

@@ -0,0 +1,205 @@
+package org.prolibertate.games.game.catan
+
+/**
+ * The rules Seafarers adds to the base game, kept apart from [CatanRules] so the base
+ * game's code reads as it always did. [CatanRules] calls in here only when a game has
+ * [CatanState.sea]. See `docs/RULES-catan-seafarers.md`.
+ */
+internal object SeaRules {
+
+    const val MAX_SHIPS = 15
+
+    /** Points for being the first to settle an island other than the home island. */
+    const val ISLAND_BONUS = 2
+
+    val SHIP_COST: Map<Resource, Int> = mapOf(Resource.LUMBER to 1, Resource.WOOL to 1)
+
+    // -----------------------------------------------------------------------
+    // Ships
+    // -----------------------------------------------------------------------
+
+    private fun fleetOf(state: CatanState, seat: Int): Int = state.sea!!.ships.count { it == seat }
+
+    /**
+     * Whether [seat]'s ships and towns reach [vertex], so a ship may start there. A town
+     * of anyone else is a wall; [ignoring] is a ship that is being lifted off the board.
+     */
+    private fun shipReaches(state: CatanState, seat: Int, vertex: Int, ignoring: Int): Boolean {
+        val building = state.buildings[vertex]
+        if (building != null) return building.owner == seat
+        val sea = state.sea!!
+        return state.topo.VERTEX_EDGES[vertex].any { it != ignoring && sea.ships[it] == seat }
+    }
+
+    /** A sea edge a ship could sit on, joined to [seat]'s fleet or a town of theirs. */
+    private fun shipSites(state: CatanState, seat: Int, ignoring: Int = -1): List<Int> {
+        val topo = state.topo
+        val sea = state.sea!!
+        return (0 until topo.EDGE_COUNT).filter { e ->
+            topo.edgeSea[e] &&
+                state.roads[e] == NO_PLAYER &&
+                (sea.ships[e] == NO_PLAYER || e == ignoring) &&
+                sea.pirate !in topo.EDGE_HEXES[e] &&
+                topo.EDGE_VERTICES[e].let { (a, b) ->
+                    shipReaches(state, seat, a, ignoring) || shipReaches(state, seat, b, ignoring)
+                }
+        }
+    }
+
+    fun buildShipMoves(state: CatanState, seat: Int): List<BuildShip> =
+        if (fleetOf(state, seat) >= MAX_SHIPS) emptyList() else shipSites(state, seat).map { BuildShip(it) }
+
+    /** Whether the ship on [edge] sits at the open end of a route: one end touches nothing else of [seat]'s. */
+    private fun atOpenEnd(state: CatanState, seat: Int, edge: Int): Boolean {
+        val topo = state.topo
+        val sea = state.sea!!
+        return topo.EDGE_VERTICES[edge].toList().any { v ->
+            state.buildings[v] == null &&
+                topo.VERTEX_EDGES[v].none { it != edge && (state.roads[it] == seat || sea.ships[it] == seat) }
+        }
+    }
+
+    /** A ship may sail once a turn, never the turn it was built, only from the open end of a route. */
+    fun moveShipMoves(state: CatanState, seat: Int): List<MoveShip> {
+        val sea = state.sea!!
+        if (sea.shipMoved) return emptyList()
+        val moves = mutableListOf<MoveShip>()
+        for (e in sea.ships.indices) {
+            if (sea.ships[e] != seat || e in sea.builtThisTurn || !atOpenEnd(state, seat, e)) continue
+            shipSites(state, seat, ignoring = e).filter { it != e }.forEach { moves += MoveShip(e, it) }
+        }
+        return moves
+    }
+
+    // -----------------------------------------------------------------------
+    // Pirate
+    // -----------------------------------------------------------------------
+
+    /** Seats with a ship beside [hex] that hold at least one card: whom the pirate can rob there. */
+    private fun pirateVictims(state: CatanState, thief: Int, hex: Int): List<Int> {
+        val topo = state.topo
+        val sea = state.sea!!
+        return (0 until topo.EDGE_COUNT).filter { hex in topo.EDGE_HEXES[it] }
+            .map { sea.ships[it] }
+            .filter { it != NO_PLAYER && it != thief }
+            .distinct()
+            .filter { state.resourceCount(it) > 0 }
+    }
+
+    fun pirateMoves(state: CatanState, seat: Int): List<MovePirate> {
+        val topo = state.topo
+        val sea = state.sea!!
+        val moves = mutableListOf<MovePirate>()
+        for (h in 0 until topo.HEX_COUNT) {
+            if (topo.land[h] || h == sea.pirate) continue
+            val victims = pirateVictims(state, seat, h)
+            if (victims.isEmpty()) {
+                moves += MovePirate(topo.HEXES[h])
+            } else {
+                victims.forEach { moves += MovePirate(topo.HEXES[h], it) }
+            }
+        }
+        return moves
+    }
+
+    // -----------------------------------------------------------------------
+    // Gold
+    // -----------------------------------------------------------------------
+
+    /** Every way the seat at the front of the gold queue can choose its cards, supply permitting. */
+    fun goldMoves(state: CatanState): List<PickGold> {
+        val owed = state.sea!!.gold.firstOrNull() ?: return emptyList()
+        val supply = Resource.entries.associateWith { CatanRules.bankSupply(state, it) }
+        val take = minOf(owed.count, supply.values.sum())
+        val picks = mutableListOf<PickGold>()
+        fun walk(index: Int, left: Int, acc: MutableList<Resource>) {
+            if (left == 0) {
+                picks += PickGold(acc.toList())
+                return
+            }
+            if (index == Resource.entries.size) return
+            val resource = Resource.entries[index]
+            for (n in 0..minOf(left, supply.getValue(resource))) {
+                repeat(n) { acc += resource }
+                walk(index + 1, left - n, acc)
+                repeat(n) { acc.removeAt(acc.size - 1) }
+            }
+        }
+        walk(0, take, mutableListOf())
+        return picks
+    }
+
+    /** Drops queue entries the bank can no longer pay, and leaves the gold phase once nobody is owed. */
+    fun settleGold(state: CatanState): CatanState {
+        val sea = state.sea!!
+        val supply = Resource.entries.sumOf { CatanRules.bankSupply(state, it) }
+        val queue = if (supply > 0) sea.gold else emptyList()
+        return if (queue.isEmpty()) {
+            state.copy(sea = sea.copy(gold = emptyList()), phase = CatanPhase.PLAYING)
+        } else {
+            state.copy(sea = sea.copy(gold = queue), phase = CatanPhase.GOLD)
+        }
+    }
+
+    // -----------------------------------------------------------------------
+    // Islands and scoring
+    // -----------------------------------------------------------------------
+
+    /** The bonus points [seat] holds for first landings. */
+    fun bonusPoints(state: CatanState, seat: Int): Int =
+        (state.sea?.islandBonus?.count { it == seat } ?: 0) * ISLAND_BONUS
+
+    /** After a settlement on [vertex]: award the island bonus if it is the first on a new island. */
+    fun claimIsland(state: CatanState, seat: Int, vertex: Int): CatanState {
+        val sea = state.sea ?: return state
+        val island = state.topo.vertexIsland[vertex]
+        if (island < 0 || sea.isStart(island) || sea.islandBonus[island] != NO_PLAYER) return state
+        val bonus = sea.islandBonus.toMutableList().also { it[island] = seat }
+        return state.copy(
+            sea = sea.copy(islandBonus = bonus),
+            log = state.log + "Seat $seat is the first to settle a new island: +$ISLAND_BONUS victory points.",
+        )
+    }
+
+    // -----------------------------------------------------------------------
+    // Longest route
+    // -----------------------------------------------------------------------
+
+    /**
+     * The seat's longest route over roads *and* ships. A route is a simple path of the seat's
+     * pieces that never runs through an opponent's town; it may change between road and ship
+     * only at a town of the seat's own.
+     */
+    fun longestRouteFor(state: CatanState, seat: Int): Int {
+        val topo = state.topo
+        val sea = state.sea!!
+        val blocked = BooleanArray(topo.VERTEX_COUNT) { v ->
+            state.buildings[v]?.let { it.owner != seat } == true
+        }
+        fun owns(e: Int) = state.roads[e] == seat || sea.ships[e] == seat
+        fun kind(e: Int) = if (state.roads[e] == seat) 0 else 1
+
+        fun walk(v: Int, arrivedBy: Int, visited: BooleanArray): Int {
+            visited[v] = true
+            var best = 0
+            val ownTown = state.buildings[v]?.owner == seat
+            for (e in topo.VERTEX_EDGES[v]) {
+                if (!owns(e)) continue
+                val k = kind(e)
+                if (arrivedBy != -1 && k != arrivedBy && !ownTown) continue
+                val w = topo.otherEnd(e, v)
+                if (visited[w]) continue
+                best = maxOf(best, if (blocked[w]) 1 else 1 + walk(w, k, visited))
+            }
+            visited[v] = false
+            return best
+        }
+
+        var best = 0
+        for (start in 0 until topo.VERTEX_COUNT) {
+            if (topo.VERTEX_EDGES[start].none { owns(it) }) continue
+            best = maxOf(best, walk(start, -1, BooleanArray(topo.VERTEX_COUNT)))
+        }
+        return best
+    }
+}

app/src/main/java/org/prolibertate/games/game/checkers/CheckersAi.kt

@@ -1,6 +1,9 @@
 package org.prolibertate.games.game.checkers
 
 import kotlin.random.Random
+import kotlin.math.roundToInt
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -17,22 +20,49 @@ import org.prolibertate.games.game.engine.GameAi
  * recapture as its only legal move, so the search plays it whether it wanted to
  * or not.
  */
-class CheckersAi(private val level: CheckersLevel? = null) :
-    GameAi<CheckersState, CheckersMove> {
+class CheckersAi(
+    private val profiles: AiProfiles = AiProfiles.DEFAULT,
+    private val level: CheckersLevel? = null,
+) : GameAi<CheckersState, CheckersMove> {
 
     private var nodeBudget = 0
     private var nodesUsed = 0
 
+    // Evaluation weights and viewpoint for the move being chosen. At the default
+    // (balanced) style they equal the plain constants, so Medium is unchanged.
+    private var rootSeat = 0
+    private var wAdvance = ADVANCE
+    private var wEdge = EDGE
+    private var wBackRow = BACK_ROW
+    private var wTheirMobility = MOBILITY
+
     override fun chooseMove(
         state: CheckersState,
         seat: Int,
         legal: List<CheckersMove>,
     ): CheckersMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
+        val profile = profiles.of(seat)
         val setting = level ?: state.options.level
         if (legal.size == 1) return legal.first()
 
-        nodeBudget = NODE_BUDGET
+        val bold = profile.style.boldness
+        val spite = profile.style.spite
+        rootSeat = seat
+        // Bold seats push men forward and care less about the edge and back row;
+        // cautious ones do the reverse. Spiteful seats weigh the opponent's
+        // freedom of movement more heavily.
+        wAdvance = ADVANCE + (bold * 2).roundToInt()
+        wEdge = EDGE - (bold * 2).roundToInt()
+        wBackRow = BACK_ROW - (bold * 3).roundToInt()
+        wTheirMobility = MOBILITY + (spite * 2).roundToInt()
+
+        val maxDepth = when (profile.level) {
+            AiLevel.EASY -> maxOf(2, setting.depth - 2)
+            AiLevel.MEDIUM -> setting.depth
+            AiLevel.HARD -> setting.depth + 2
+        }
+        nodeBudget = if (profile.level == AiLevel.HARD) HARD_NODE_BUDGET else NODE_BUDGET
         nodesUsed = 0
 
         val random = Random(state.moveLog.size * 31L + state.positionKey().hashCode())
@@ -40,7 +70,7 @@ class CheckersAi(private val level: CheckersLevel? = null) :
         var best = legal.first()
         var scored = legal.map { it to 0 }
 
-        for (depth in 1..setting.depth) {
+        for (depth in 1..maxDepth) {
             val results = mutableListOf<Pair<CheckersMove, Int>>()
             val ordered = order(legal, preferred = best)
             for (move in ordered) {
@@ -61,7 +91,16 @@ class CheckersAi(private val level: CheckersLevel? = null) :
 
         val bestScore = scored.maxOf { it.second }
         val acceptable = scored.filter { it.second >= bestScore - setting.slack() }
-        return acceptable[random.nextInt(acceptable.size)].first
+        val chosen = acceptable[random.nextInt(acceptable.size)].first
+        if (profile.level != AiLevel.EASY) return chosen
+
+        // Easy now and then settles for another sound-looking move: only ones
+        // within a man and a half of the best, never a real blunder.
+        val ranked = listOf(chosen) + scored
+            .filter { it.first != chosen && it.second >= bestScore - EASY_TOLERANCE }
+            .sortedByDescending { it.second }
+            .map { it.first }
+        return profile.pick(ranked)
     }
 
     private fun CheckersLevel.slack(): Int = when (this) {
@@ -126,29 +165,32 @@ class CheckersAi(private val level: CheckersLevel? = null) :
      */
     private fun evaluate(state: CheckersState): Int {
         val us = state.turn
-        val them = other(us)
         var score = 0
+        val me = rootSeat
 
         for (square in 0 until SQUARES) {
             val piece = state.board[square] ?: continue
-            val sign = if (piece.seat == us) 1 else -1
+            val sign = if (piece.seat == me) 1 else -1
             score += sign * if (piece.king) KING else MAN
 
             if (!piece.king) {
                 // How many rows it has come, out of the seven it needs.
                 val advanced = if (piece.seat == BLACK_SEAT) rowOf(square) else 7 - rowOf(square)
-                score += sign * advanced * ADVANCE
+                score += sign * advanced * wAdvance
             }
 
             // Sitting on the edge cannot be jumped, which is worth a little in
             // a game whose entire tactic is being jumped.
-            if (columnOf(square) == 0 || columnOf(square) == 7) score += sign * EDGE
+            if (columnOf(square) == 0 || columnOf(square) == 7) score += sign * wEdge
 
-            if (rowOf(square) == crownRowOf(other(piece.seat))) score += sign * BACK_ROW
+            if (rowOf(square) == crownRowOf(other(piece.seat))) score += sign * wBackRow
         }
 
-        score += MOBILITY * (mobility(state, us) - mobility(state, them))
-        return score
+        val mine = mobility(state, me)
+        val theirs = mobility(state, other(me))
+        score += MOBILITY * mine - wTheirMobility * theirs
+        // Scored from the root seat's side; flip for the side to move.
+        return if (us == me) score else -score
     }
 
     /**
@@ -178,6 +220,8 @@ class CheckersAi(private val level: CheckersLevel? = null) :
         const val INFINITY = 1_000_000
         const val WIN = 100_000
         const val NODE_BUDGET = 200_000
+        const val HARD_NODE_BUDGET = 450_000
+        const val EASY_TOLERANCE = 150
 
         const val MAN = 100
         const val KING = 175

app/src/main/java/org/prolibertate/games/game/chess/ChessAi.kt

@@ -2,6 +2,9 @@ package org.prolibertate.games.game.chess
 
 import kotlin.math.abs
 import kotlin.random.Random
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -16,7 +19,14 @@ import org.prolibertate.games.game.engine.GameAi
  * so the setup screen sets the strength without the caller having to thread it
  * through.
  */
-class ChessAi(private val level: ChessLevel? = null) : GameAi<ChessState, ChessMove> {
+class ChessAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) : GameAi<ChessState, ChessMove> {
+
+    /** Fixed strength that overrides the table's option (used by tests and tools). */
+    private var level: ChessLevel? = null
+
+    constructor(level: ChessLevel) : this(AiProfiles.DEFAULT) {
+        this.level = level
+    }
 
     /**
      * Ceiling on how much thinking any one move gets. A phone should not stall
@@ -28,10 +38,22 @@ class ChessAi(private val level: ChessLevel? = null) : GameAi<ChessState, ChessM
 
     override fun chooseMove(state: ChessState, seat: Int, legal: List<ChessMove>): ChessMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
+        val profile = profiles.of(seat)
         val setting = level ?: state.options.level
         if (legal.size == 1) return legal.first()
 
-        nodeBudget = NODE_BUDGET
+        // Easy looks one move less far ahead; Hard looks one further and gets
+        // roughly twice the node budget (still a couple of seconds on a phone).
+        val maxDepth = when (profile.level) {
+            AiLevel.EASY -> maxOf(1, setting.depth - 1)
+            AiLevel.MEDIUM -> setting.depth
+            AiLevel.HARD -> setting.depth + 1
+        }
+        nodeBudget = if (profile.level == AiLevel.HARD) HARD_NODE_BUDGET else NODE_BUDGET
+        aiWhite = state.whiteToMove
+        styleActive = profile.style.boldness != 0.0 || profile.style.spite != 0.0
+        styleBoldness = profile.style.boldness
+        styleSpite = profile.style.spite
         nodesUsed = 0
 
         // Deterministic per position, so a host and a client replaying the same
@@ -42,7 +64,7 @@ class ChessAi(private val level: ChessLevel? = null) : GameAi<ChessState, ChessM
         var best = legal.first()
         var scored = legal.map { it to 0 }
 
-        for (depth in 1..setting.depth) {
+        for (depth in 1..maxDepth) {
             val results = mutableListOf<Pair<ChessMove, Int>>()
             // Search the previous iteration's best first, so the sub-searches
             // below it have a decent bound to prune against.
@@ -74,9 +96,56 @@ class ChessAi(private val level: ChessLevel? = null) : GameAi<ChessState, ChessM
         // makes them beatable without making them play nonsense.
         val bestScore = scored.maxOf { it.second }
         val acceptable = scored.filter { it.second >= bestScore - setting.slack() }
-        return acceptable[random.nextInt(acceptable.size)].first
+        val chosen = acceptable[random.nextInt(acceptable.size)].first
+        if (profile.level != AiLevel.EASY) return chosen
+
+        // Easy sometimes settles for a worse move, but only one within a modest
+        // margin of the best, so it never throws a piece away or walks into mate.
+        val ranked = scored.filter { it.second >= bestScore - setting.slack() - EASY_EXTRA_SLACK }
+            .sortedByDescending { it.second }.map { it.first }
+        val ordered = listOf(chosen) + ranked.filter { it != chosen }
+        return profile.pick(ordered)
     }
 
+    // Per-move style state, set at the start of chooseMove.
+    private var aiWhite = true
+    private var styleActive = false
+    private var styleBoldness = 0.0
+    private var styleSpite = 0.0
+
+    /**
+     * A small temperament term (well under a pawn) from the mover's point of
+     * view. Aggressive seats like pieces near the enemy king, cautious seats
+     * like a sheltered own king, spiteful seats like the enemy being badly
+     * placed. Zero for the default style, so default play is unchanged.
+     */
+    private fun styleTerm(state: ChessState): Int {
+        val enemyKing = state.kingSquare(white = !aiWhite)
+        val myKing = state.kingSquare(white = aiWhite)
+        var attackers = 0
+        var shield = 0
+        var enemyPlacement = 0
+        for (square in 0 until 64) {
+            val piece = state.board[square] ?: continue
+            if (piece.white == aiWhite) {
+                if (piece.kind == PieceKind.KING) continue
+                if (enemyKing != null && piece.kind != PieceKind.PAWN && distance(square, enemyKing) <= 3) attackers++
+                if (myKing != null && distance(square, myKing) <= 1) shield++
+            } else {
+                val table = tableFor(piece.kind)
+                enemyPlacement += table[if (piece.white) square else square xor 56]
+            }
+        }
+        var term = 0.0
+        if (styleBoldness > 0) term += styleBoldness * 4 * attackers
+        if (styleBoldness < 0) term += -styleBoldness * 5 * shield
+        term -= styleSpite * 0.1 * enemyPlacement
+        val own = term.toInt().coerceIn(-40, 40)
+        return if (state.whiteToMove == aiWhite) own else -own
+    }
+
+    private fun distance(a: Int, b: Int): Int = maxOf(abs(fileOf(a) - fileOf(b)), abs(rankOf(a) - rankOf(b)))
+
     private fun ChessLevel.slack(): Int = when (this) {
         ChessLevel.CASUAL -> 70
         ChessLevel.CLUB -> 20
@@ -116,7 +185,7 @@ class ChessAi(private val level: ChessLevel? = null) : GameAi<ChessState, ChessM
      */
     private fun quiescence(state: ChessState, alpha: Int, beta: Int, ply: Int): Int {
         nodesUsed++
-        val standPat = evaluate(state)
+        val standPat = evaluate(state) + if (styleActive) styleTerm(state) else 0
         if (standPat >= beta) return beta
         var localAlpha = maxOf(alpha, standPat)
         if (ply >= MAX_QUIESCENCE_PLY) return localAlpha
@@ -205,6 +274,8 @@ class ChessAi(private val level: ChessLevel? = null) : GameAi<ChessState, ChessM
         const val INFINITY = 1_000_000
         const val MATE = 100_000
         const val NODE_BUDGET = 120_000
+        const val HARD_NODE_BUDGET = 240_000
+        const val EASY_EXTRA_SLACK = 60
         const val MAX_QUIESCENCE_PLY = 24
 
         /**

app/src/main/java/org/prolibertate/games/game/crazyeights/CrazyEightsAi.kt

@@ -1,52 +1,135 @@
 package org.prolibertate.games.game.crazyeights
 
+import org.prolibertate.games.game.cards.Card
+import org.prolibertate.games.game.cards.Rank
 import org.prolibertate.games.game.cards.Suit
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
- * A heuristic Crazy 8s opponent.
+ * A Crazy 8s opponent whose strength and temperament come from the seat's profile.
  *
- * It sheds expensive cards first, keeps its eights back for when it is stuck,
- * and when it does play one it names the suit it holds most of.
+ * MEDIUM (the default) sheds expensive cards first, keeps its eights back for
+ * when it is stuck, and when it does play one it names the suit it holds most of.
+ *
+ * EASY plays the same way but sometimes sheds a cheaper card or wastes an eight.
+ * HARD counts the cards on the discard pile to know what is still out, plays to
+ * keep a long suit it can run, and when someone is close to going out it turns
+ * the game to a suit that is nearly exhausted so they cannot follow.
  */
-class CrazyEightsAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
+class CrazyEightsAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) :
     GameAi<CrazyEightsState, CrazyEightsMove> {
 
-    enum class Difficulty(
-        /** Play an eight anyway once the hand is down to this size. */
-        val eightEndgame: Int,
-    ) {
-        EASY(eightEndgame = 99),
-        NORMAL(eightEndgame = 3),
-        CAUTIOUS(eightEndgame = 2),
-    }
-
     override fun chooseMove(
         state: CrazyEightsState,
         seat: Int,
         legal: List<CrazyEightsMove>,
     ): CrazyEightsMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
+        val profile = profiles.of(seat)
         val plays = legal.filterIsInstance<PlayCard>()
         if (plays.isEmpty()) return legal.first()
 
+        val move: CrazyEightsMove = when (profile.level) {
+            AiLevel.MEDIUM -> standardRanking(state, seat, plays, EIGHT_ENDGAME).first()
+            AiLevel.EASY -> profile.pick(standardRanking(state, seat, plays, EASY_EIGHT_ENDGAME))
+            AiLevel.HARD -> hard(state, seat, plays, profile)
+        }
+        return if (move in legal) move else legal.first()
+    }
+
+    /**
+     * Ordinary cards first, most expensive leading, then eights with the suit
+     * this hand holds most of named first.
+     */
+    private fun standardRanking(
+        state: CrazyEightsState,
+        seat: Int,
+        plays: List<PlayCard>,
+        eightEndgame: Int,
+    ): List<PlayCard> {
         val hand = state.hands[seat]
         val ordinary = plays.filter { !isWild(it.card) }
 
         // An eight is the only card that always plays, so it is worth more held
         // than spent — unless the hand is nearly gone, or nothing else works.
-        val useEight = ordinary.isEmpty() || hand.size <= difficulty.eightEndgame
+        val useEight = ordinary.isEmpty() || hand.size <= eightEndgame
         val pool = if (useEight) plays else ordinary
 
-        val best = pool
-            .filter { !isWild(it.card) }
-            .maxByOrNull { crazyEightsPenalty(it.card) }
-
-        if (best != null) return best
+        val ranked = pool.filter { !isWild(it.card) }.sortedByDescending { crazyEightsPenalty(it.card) }
+        if (ranked.isNotEmpty() && !useEight) return ranked
 
         // Playing an eight: switch the game to whatever we hold most of.
-        val strongest = Suit.entries.maxByOrNull { suit -> hand.count { it.suit == suit } }
-            ?: Suit.SPADES
-        return pool.firstOrNull { it.nominatedSuit == strongest } ?: pool.first()
+        val suits = Suit.entries.sortedByDescending { suit -> hand.count { it.suit == suit } }
+        val wilds = suits.flatMap { suit -> pool.filter { isWild(it.card) && it.nominatedSuit == suit } }
+        return ranked + wilds.ifEmpty { pool.filter { isWild(it.card) } }
+    }
+
+    // -----------------------------------------------------------------------
+    // Hard
+    // -----------------------------------------------------------------------
+
+    private fun hard(
+        state: CrazyEightsState,
+        seat: Int,
+        plays: List<PlayCard>,
+        profile: AiProfile,
+    ): CrazyEightsMove {
+        val hand = state.hands[seat]
+        val options = state.options
+
+        // Cards this seat can account for: its own hand and everything on the pile.
+        val known = HashSet<Card>().also { it.addAll(hand); it.addAll(state.discard) }
+        val unseen = FULL_DECK.filter { it !in known }
+        fun unseenIn(suit: Suit): Int = unseen.count { it.suit == suit }
+
+        val next = (seat + 1) % options.playerCount
+        val nextCount = state.handCounts[next]
+        val smallestOpponent = (0 until options.playerCount).filter { it != seat }
+            .minOf { state.handCounts[it] }
+        // How hard to squeeze the suits: more when somebody is about to go out.
+        val urgency = 1.0 + profile.style.spite +
+            (if (nextCount <= 2) 1.0 else 0.0) + (if (smallestOpponent <= 2) 0.5 else 0.0)
+
+        /** Value of leaving the game showing [suit], with [remaining] the cards still held. */
+        fun suitValue(suit: Suit, remaining: List<Card>): Double =
+            3.0 * remaining.count { it.suit == suit } - 0.7 * urgency * unseenIn(suit)
+
+        val ordinary = plays.filter { !isWild(it.card) }
+        val wilds = plays.filter { isWild(it.card) }
+
+        // Aggressive seats spend eights earlier; cautious ones keep them as insurance.
+        val endgame = (EIGHT_ENDGAME + profile.style.boldness * 2.0)
+        val blocking = smallestOpponent <= 1 || (nextCount <= 2 && urgency >= 2.0)
+        val useEight = ordinary.isEmpty() || hand.size <= endgame || (blocking && wilds.isNotEmpty())
+
+        if (hand.size == 1) {
+            plays.firstOrNull()?.let { return it }
+        }
+
+        if (!useEight || wilds.isEmpty()) {
+            if (ordinary.isNotEmpty()) {
+                // Cautious seats shed liabilities harder, bold ones care more about position.
+                val shedWeight = 1.0 - 0.3 * profile.style.boldness
+                return ordinary.maxBy { play ->
+                    val remaining = hand - play.card
+                    crazyEightsPenalty(play.card) * shedWeight + suitValue(play.card.suit, remaining)
+                }
+            }
+        }
+
+        // An eight: name the suit that is best for this hand and worst for the others.
+        return wilds.maxBy { play ->
+            val remaining = hand - play.card
+            suitValue(play.nominatedSuit ?: play.card.suit, remaining)
+        }
+    }
+
+    private companion object {
+        const val EIGHT_ENDGAME = 3
+        const val EASY_EIGHT_ENDGAME = 99
+        val FULL_DECK: List<Card> = Suit.entries.flatMap { suit -> Rank.standard.map { Card(it, suit) } }
     }
 }

app/src/main/java/org/prolibertate/games/game/cribbage/CribbageAi.kt

@@ -3,8 +3,12 @@ package org.prolibertate.games.game.cribbage
 import org.prolibertate.games.game.cards.Card
 import org.prolibertate.games.game.cards.Decks
 import org.prolibertate.games.game.cards.Rank
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 import kotlin.math.abs
+import kotlin.random.Random
 
 /**
  * A cribbage opponent that counts rather than guesses.
@@ -18,8 +22,14 @@ import kotlin.math.abs
  *
  * The play is a heuristic: take the points on offer, and try not to leave the
  * count where a ten-card collects fifteen or thirty-one.
+ *
+ * Per seat, from [profiles]: Easy settles for a worse lay-away or card now and
+ * then; Hard also samples the crib (what the unseen cards might add to it) and
+ * weighs what a reply could score off each card it plays. Boldness trades the
+ * two counts-to-avoid and crib ownership; spite weighs the other side's crib.
  */
-class CribbageAi : GameAi<CribbageState, CribbageMove> {
+class CribbageAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) :
+    GameAi<CribbageState, CribbageMove> {
 
     override fun chooseMove(
         state: CribbageState,
@@ -27,30 +37,78 @@ class CribbageAi : GameAi<CribbageState, CribbageMove> {
         legal: List<CribbageMove>,
     ): CribbageMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
+        val profile = profiles.of(seat)
         val layAways = legal.filterIsInstance<LayAway>()
-        if (layAways.isNotEmpty()) return chooseLayAway(state, seat, layAways)
-        return choosePeg(state, legal.filterIsInstance<PegCard>())
+        if (layAways.isNotEmpty()) return chooseLayAway(state, seat, layAways, profile)
+        val pegs = legal.filterIsInstance<PegCard>()
+        if (pegs.isNotEmpty()) return choosePeg(state, seat, pegs, profile)
+        return legal.first()
     }
 
     private fun chooseLayAway(
         state: CribbageState,
         seat: Int,
         choices: List<LayAway>,
+        profile: AiProfile,
     ): LayAway {
         val hand = state.hands[seat]
         val held = hand.toSet()
         val unseen = Decks.standard52().filter { it !in held }
         // A partner's crib is your crib. That is the whole of four-handed play.
         val ownCrib = state.options.teamOf(seat) == state.options.teamOf(state.dealer)
+        val boldness = profile.style.boldness
+        // Bold seats back their own crib; careful ones fear the other side's.
+        val cribSign = if (ownCrib) {
+            1.0 + 0.25 * boldness
+        } else {
+            -(1.0 - 0.25 * boldness + 0.3 * profile.style.spite)
+        }
+        val trials = if (profile.level == AiLevel.HARD) sampleCribs(hand, unseen, state.options) else null
 
-        return choices.maxByOrNull { choice ->
+        val scored = choices.map { choice ->
             val given = choice.cards.toSet()
             val keep = hand.filter { it !in given }
             val expected = unseen.sumOf { starter ->
                 CribbageScoring.show(keep, starter, isCrib = false).sumOf { it.points }
             }.toDouble() / unseen.size
-            expected + cribValue(choice.cards) * (if (ownCrib) 1.0 else -1.0)
-        } ?: choices.first()
+            val crib = if (trials != null) {
+                // Heuristic and sampled estimates agree on direction; averaging
+                // them smooths the sampling noise without losing the structure.
+                (sampledCribValue(choice.cards, trials) + cribValue(choice.cards)) / 2.0
+            } else {
+                cribValue(choice.cards)
+            }
+            choice to expected + crib * cribSign
+        }
+        // Stable sort: ties resolve to the first choice, as maxByOrNull did.
+        val ranked = scored.sortedByDescending { it.second }.map { it.first }
+        return profile.pick(ranked)
+    }
+
+    /** Sets of unseen cards a crib might receive, plus a cut, for Hard to average over. */
+    private fun sampleCribs(
+        hand: List<Card>,
+        unseen: List<Card>,
+        options: CribbageOptions,
+    ): List<List<Card>> {
+        val random = Random(hand.sumOf { it.rank.ordinal * 4 + it.suit.ordinal }.toLong())
+        // Whatever the crib is short of after our own cards, plus the cut.
+        val others = (CRIB_SIZE - options.layAwaySize).coerceAtLeast(0)
+        return List(CRIB_SAMPLES) {
+            val picked = LinkedHashSet<Card>()
+            while (picked.size < others + 1) picked += unseen[random.nextInt(unseen.size)]
+            picked.toList()
+        }
+    }
+
+    private fun sampledCribValue(given: List<Card>, trials: List<List<Card>>): Double {
+        var total = 0
+        for (trial in trials) {
+            val starter = trial.last()
+            val crib = given + trial.dropLast(1)
+            total += CribbageScoring.show(crib, starter, isCrib = true).sumOf { it.points }
+        }
+        return total.toDouble() / trials.size
     }
 
     /**
@@ -83,22 +141,63 @@ class CribbageAi : GameAi<CribbageState, CribbageMove> {
         return value
     }
 
-    private fun choosePeg(state: CribbageState, choices: List<PegCard>): PegCard {
+    private fun choosePeg(
+        state: CribbageState,
+        seat: Int,
+        choices: List<PegCard>,
+        profile: AiProfile,
+    ): PegCard {
         val count = state.count
         val onTheTable = state.series.map { it.card }
+        val boldness = profile.style.boldness
+        // Bold seats risk leaving five or twenty-one; careful ones really avoid it.
+        val countPenalty = 3.0 - boldness * 1.5
+        val leadFivePenalty = 4.0 - boldness * 2.0
+        val hard = profile.level == AiLevel.HARD
+        // Cards a reply could come from: nothing this seat holds, has seen played or was cut.
+        val unseen = if (hard) {
+            val known = (state.remaining(seat) + state.played.map { it.card } + listOfNotNull(state.starter)).toSet()
+            Decks.standard52().filter { it !in known && it !in state.hands[seat] }
+        } else {
+            emptyList()
+        }
 
-        return choices.maxByOrNull { choice ->
-            val scored = CribbageScoring.peg(onTheTable + choice.card).sumOf { it.points }
+        val scored = choices.map { choice ->
+            val points = CribbageScoring.peg(onTheTable + choice.card).sumOf { it.points }
             val after = count + pipValue(choice.card)
-            var value = scored * 10.0
+            var value = points * 10.0
             // Five and twenty-one are the two counts to avoid leaving: any of
             // the sixteen ten-cards takes fifteen or thirty-one off them.
-            if (after == 5 || after == 21) value -= 3.0
+            if (after == 5 || after == 21) value -= countPenalty
             // Leading a five is the same present, offered first.
-            if (count == 0 && choice.card.rank == Rank.FIVE) value -= 4.0
+            if (count == 0 && choice.card.rank == Rank.FIVE) value -= leadFivePenalty
             // Big cards early. Low ones are what let you keep playing at the
             // awkward end of a series, where the last card is worth a point.
-            value + pipValue(choice.card) * 0.1
-        } ?: choices.first()
+            value += pipValue(choice.card) * 0.1
+            if (hard && unseen.isNotEmpty() && after < CRIBBAGE_LIMIT) {
+                value -= replyThreat(onTheTable + choice.card, after, unseen) * 8.0
+            }
+            choice to value
+        }
+        val ranked = scored.sortedByDescending { it.second }.map { it.first }
+        return profile.pick(ranked)
+    }
+
+    /** Average points a reply scores off [series], over the cards still unseen. */
+    private fun replyThreat(series: List<Card>, after: Int, unseen: List<Card>): Double {
+        var total = 0
+        var playable = 0
+        for (card in unseen) {
+            if (after + pipValue(card) > CRIBBAGE_LIMIT) continue
+            playable++
+            total += CribbageScoring.peg(series + card).sumOf { it.points }
+        }
+        // Nothing playable is a go for them, worth a point to whoever last played.
+        return if (playable == 0) 0.0 else total.toDouble() / unseen.size
+    }
+
+    private companion object {
+        const val CRIB_SIZE = 4
+        const val CRIB_SAMPLES = 60
     }
 }

app/src/main/java/org/prolibertate/games/game/engine/AiProfile.kt

@@ -0,0 +1,123 @@
+package org.prolibertate.games.game.engine
+
+import kotlinx.serialization.Serializable
+import kotlin.random.Random
+
+/** How well one computer seat plays. */
+enum class AiLevel {
+    /** Makes frequent, plausible mistakes and plays without much foresight. */
+    EASY,
+
+    /** The game's standard computer opponent. */
+    MEDIUM,
+
+    /** Plays carefully: more foresight, no deliberate mistakes. */
+    HARD,
+}
+
+/** What the person at setup chooses for the table's computer seats. */
+@Serializable
+enum class AiDifficulty(val label: String) {
+    EASY("Easy"),
+    MEDIUM("Medium"),
+    HARD("Hard"),
+
+    /** Each computer seat gets its own level, picked at random. */
+    MIXED("Mixed"),
+}
+
+/**
+ * A computer seat's temperament. Never shown to the human players: it only
+ * shapes how the AI trades off the options in front of it.
+ */
+enum class AiStyle(
+    /** -1 plays safe, +1 gambles; 0 is the game's standard balance. */
+    val boldness: Double,
+    /** How much the seat cares about stopping opponents rather than building its own position. */
+    val spite: Double,
+) {
+    BALANCED(0.0, 0.0),
+    AGGRESSIVE(0.8, 0.3),
+    CAUTIOUS(-0.8, 0.0),
+    SPOILER(0.0, 0.8),
+}
+
+/**
+ * One computer seat's level and style, and a source of randomness of its own.
+ *
+ * [DEFAULT] is the game's standard opponent: [AiLevel.MEDIUM], [AiStyle.BALANCED],
+ * and it never slips, so an AI built without a profile plays exactly as it did
+ * before profiles existed.
+ */
+class AiProfile(
+    val level: AiLevel = AiLevel.MEDIUM,
+    val style: AiStyle = AiStyle.BALANCED,
+    val random: Random = Random(0),
+) {
+    /**
+     * Whether this seat should throw away its best option this time. Only
+     * [AiLevel.EASY] does, and only some of the time, so it still plays like a
+     * person who is not concentrating rather than like a random-move generator.
+     */
+    fun slips(): Boolean = level == AiLevel.EASY && random.nextDouble() < EASY_SLIP_CHANCE
+
+    /**
+     * Picks from [ranked] (best first). Easy sometimes settles for a worse choice,
+     * drawn from the better half so it stays plausible; other levels take the best.
+     */
+    fun <T> pick(ranked: List<T>): T {
+        require(ranked.isNotEmpty()) { "Nothing to pick from" }
+        if (!slips() || ranked.size == 1) return ranked.first()
+        val pool = ranked.take(maxOf(2, (ranked.size + 1) / 2))
+        return pool[random.nextInt(pool.size)]
+    }
+
+    /** [base] nudged by this seat's boldness: a gambler raises it, a cautious seat lowers it. */
+    fun bolder(base: Double, strength: Double = 1.0): Double = base + style.boldness * strength
+
+    companion object {
+        const val EASY_SLIP_CHANCE = 0.3
+        val DEFAULT = AiProfile()
+    }
+}
+
+/**
+ * The profile for every computer seat at a table, worked out from the table's
+ * difficulty setting and its seed alone.
+ *
+ * Derived rather than stored, so a saved game, a rematch from the same config
+ * and a guest's copy of a hosted table all give the same seat the same
+ * personality without it travelling anywhere.
+ */
+class AiProfiles(
+    private val difficulty: AiDifficulty,
+    private val seed: Long,
+) {
+    private val cache = HashMap<Int, AiProfile>()
+
+    constructor(config: TableConfig) : this(config.aiDifficulty, config.seed)
+
+    @Synchronized
+    fun of(seat: Int): AiProfile = cache.getOrPut(seat) {
+        val picker = Random(seed * 31 + seat * 7919L + 17)
+        val level = when (difficulty) {
+            AiDifficulty.EASY -> AiLevel.EASY
+            AiDifficulty.MEDIUM -> AiLevel.MEDIUM
+            AiDifficulty.HARD -> AiLevel.HARD
+            AiDifficulty.MIXED -> AiLevel.entries[picker.nextInt(AiLevel.entries.size)]
+        }
+        // The standard opponent is balanced by definition; the others each get a
+        // temperament, so no two computer seats feel alike.
+        val style = if (difficulty == AiDifficulty.MEDIUM) {
+            AiStyle.BALANCED
+        } else {
+            AiStyle.entries[picker.nextInt(AiStyle.entries.size)]
+        }
+        AiProfile(level, style, Random(picker.nextLong()))
+    }
+
+    companion object {
+        /** Standard opponents, for a caller that has no table to ask. */
+        val DEFAULT = AiProfiles(AiDifficulty.MEDIUM, 0L)
+    }
+}

app/src/main/java/org/prolibertate/games/game/engine/Engine.kt

@@ -43,6 +43,8 @@ data class TableConfig(
     val optionsJson: String,
     /** Shared shuffle seed so a hand is reproducible from its state. */
     val seed: Long,
+    /** How hard the computer seats play. Old saves and old hosts omit it and get the standard opponent. */
+    val aiDifficulty: AiDifficulty = AiDifficulty.MEDIUM,
 )
 
 /**
@@ -64,6 +66,21 @@ interface GameRules<S : Any, M : Any> {
 
     fun legalMoves(state: S, seat: Int): List<M>
 
+    /**
+     * Whether [move] is currently legal for [seat].
+     *
+     * Defaults to membership in [legalMoves], which is everything a game
+     * with a small, enumerable move set needs. A game whose move space is
+     * combinatorial — Catan's trade offers name any two multisets of cards —
+     * overrides this and validates structurally instead, because enumerating
+     * every intent would explode the list the UI and the network driver work
+     * from. Gates that check a specific move should call this method rather
+     * than testing list membership directly, so both kinds of game behave the
+     * same way.
+     */
+    fun isLegalMove(state: S, seat: Int, move: M): Boolean =
+        move in legalMoves(state, seat)
+
     /**
      * Applies [move] on behalf of [seat].
      *

app/src/main/java/org/prolibertate/games/game/engine/SavedGame.kt

@@ -0,0 +1,101 @@
+package org.prolibertate.games.game.engine
+
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import java.io.File
+
+/**
+ * A game in progress, kept so it can be picked up again after the app has been
+ * closed.
+ *
+ * The match is stored the way the host holds it: the [config] it was dealt from
+ * (seed, seats, options) and the whole authoritative [stateJson], hidden cards
+ * included, as the game's own rules encode it. Nothing here knows what game it
+ * is; [gameId] is only the name of the slot.
+ */
+@Serializable
+data class SavedMatch(
+    val gameId: String,
+    val config: TableConfig,
+    /** The seat the person at this device plays. */
+    val localSeat: Int,
+    val stateJson: String,
+    /** Wall-clock milliseconds when the position was written. */
+    val savedAtMillis: Long,
+    /** A line saying how the game stands, from the rules' own summary. */
+    val summary: String = "",
+)
+
+/**
+ * One saved game per game, kept as a file each under [directory].
+ *
+ * One slot per game rather than a list: the player is mid-way through a game of
+ * Chess or they are not. Starting a new one replaces it, which is what the
+ * resume prompt on the setup screen says.
+ *
+ * Writes are atomic — the position goes to a temporary file that is then moved
+ * over the real one — so being killed half way through a save leaves the
+ * previous position, not half of the new one. Reads never throw: a file that
+ * will not parse is a game that cannot be resumed, so it is removed and reported
+ * as absent.
+ */
+class SavedGameStore(private val directory: File) {
+
+    private val json = Json {
+        ignoreUnknownKeys = true
+        encodeDefaults = true
+    }
+
+    private fun fileFor(gameId: String): File {
+        // The ids are catalogue constants, but they become file names, so
+        // nothing that could climb out of the directory is let through.
+        require(gameId.isNotBlank() && gameId.all { it.isLetterOrDigit() || it == '_' || it == '-' }) {
+            "Not a game id: $gameId"
+        }
+        return File(directory, "$gameId.json")
+    }
+
+    /** Writes [match] over whatever was saved for its game. */
+    @Synchronized
+    fun save(match: SavedMatch) {
+        directory.mkdirs()
+        val target = fileFor(match.gameId)
+        val temp = File(directory, "${match.gameId}.json.tmp")
+        temp.writeText(json.encodeToString(SavedMatch.serializer(), match))
+        if (!temp.renameTo(target)) {
+            // Some file systems will not rename over an existing file.
+            target.delete()
+            check(temp.renameTo(target)) { "Could not write the saved game" }
+        }
+    }
+
+    /** The saved game for [gameId], or null if there is none or it cannot be read. */
+    @Synchronized
+    fun load(gameId: String): SavedMatch? {
+        val file = fileFor(gameId)
+        if (!file.isFile) return null
+        val match = runCatching {
+            json.decodeFromString(SavedMatch.serializer(), file.readText())
+        }.getOrNull()
+        if (match == null || match.gameId != gameId) {
+            file.delete()
+            return null
+        }
+        return match
+    }
+
+    /** Forgets the saved game for [gameId]. A no-op if there is none. */
+    @Synchronized
+    fun clear(gameId: String) {
+        fileFor(gameId).delete()
+    }
+
+    /** Every readable saved game, the most recently played first. */
+    @Synchronized
+    fun all(): List<SavedMatch> {
+        val files = directory.listFiles { f -> f.isFile && f.name.endsWith(".json") } ?: return emptyList()
+        return files
+            .mapNotNull { file -> runCatching { load(file.name.removeSuffix(".json")) }.getOrNull() }
+            .sortedByDescending { it.savedAtMillis }
+    }
+}

app/src/main/java/org/prolibertate/games/game/euchre/EuchreAi.kt

@@ -3,6 +3,10 @@ package org.prolibertate.games.game.euchre
 import org.prolibertate.games.game.cards.Card
 import org.prolibertate.games.game.cards.Rank
 import org.prolibertate.games.game.cards.Suit
+import org.prolibertate.games.game.cards.Decks
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -13,7 +17,7 @@ import org.prolibertate.games.game.engine.GameAi
  * That is enough to be a reasonable table opponent without pretending to be a
  * solver.
  */
-class EuchreAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
+class EuchreAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) :
     GameAi<EuchreState, EuchreMove> {
 
     /**
@@ -22,25 +26,50 @@ class EuchreAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
      * means every seat bids and the card is never turned down — see
      * EuchreBiddingRateTest, which pins the resulting order-up rate.
      */
-    enum class Difficulty(val bidThreshold: Int, val aloneThreshold: Int) {
-        /** Bids loosely and plays straightforwardly. */
-        EASY(bidThreshold = 21, aloneThreshold = 32),
+    private companion object {
+        const val BID_THRESHOLD = 24.0
+        const val ALONE_THRESHOLD = 32.0
+    }
 
-        NORMAL(bidThreshold = 24, aloneThreshold = 32),
+    /** Cards this AI has watched played in the current hand, per seat it plays. */
+    private val memory = HashMap<Int, SeenCards>()
 
-        /** Bids tighter and is harder to sneak a trick past. */
-        CAUTIOUS(bidThreshold = 27, aloneThreshold = 31),
+    private class SeenCards {
+        var key: Long = Long.MIN_VALUE
+        val cards = HashSet<Card>()
+    }
+
+    /** Public information only: cards that have appeared on the table this hand. */
+    private fun observe(state: EuchreState, seat: Int): Set<Card> = synchronized(memory) {
+        val seen = memory.getOrPut(seat) { SeenCards() }
+        val key = state.seed * 1_000_003L + state.handNumber
+        if (key != seen.key || state.phase == EuchrePhase.BID_ROUND_1) {
+            seen.key = key
+            seen.cards.clear()
+        }
+        state.trick.forEach { seen.cards.add(it.card) }
+        state.completedTrick.forEach { seen.cards.add(it.card) }
+        state.turnedDown?.let { seen.cards.add(it) }
+        seen.cards.removeAll(state.hands[seat].toSet())
+        seen.cards.toSet()
     }
 
     override fun chooseMove(state: EuchreState, seat: Int, legal: List<EuchreMove>): EuchreMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
-        return when (state.phase) {
-            EuchrePhase.BID_ROUND_1 -> chooseBidRound1(state, seat, legal)
-            EuchrePhase.BID_ROUND_2 -> chooseBidRound2(state, seat, legal)
-            EuchrePhase.DEALER_DISCARD -> chooseDiscard(state, legal)
-            EuchrePhase.PLAYING -> choosePlay(state, seat, legal)
-            else -> legal.first()
+        val profile = profiles.of(seat)
+        val seen = if (profile.level == AiLevel.HARD) observe(state, seat) else emptySet()
+        val move = try {
+            when (state.phase) {
+                EuchrePhase.BID_ROUND_1 -> chooseBidRound1(state, seat, legal, profile)
+                EuchrePhase.BID_ROUND_2 -> chooseBidRound2(state, seat, legal, profile)
+                EuchrePhase.DEALER_DISCARD -> chooseDiscard(state, legal, profile)
+                EuchrePhase.PLAYING -> choosePlay(state, seat, legal, profile, seen)
+                else -> legal.first()
+            }
+        } catch (e: RuntimeException) {
+            legal.first()
         }
+        return if (move in legal) move else legal.first()
     }
 
     // -----------------------------------------------------------------------
@@ -75,27 +104,61 @@ class EuchreAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         return value
     }
 
+    /** The five-card hand left after the dealer picks up [upCard] and discards the least useful card. */
+    private fun bestAfterPickup(hand: List<Card>, upCard: Card, trump: Suit): Int {
+        val six = hand + upCard
+        return six.maxOf { dropped -> handValue(six - dropped, trump) }
+    }
+
+    /** A hand worth playing without a partner: real trump length with a bower to lead it. */
+    private fun soundAlone(hand: List<Card>, trump: Suit): Boolean {
+        val trumps = hand.count { isTrumpCard(it, trump) }
+        val bower = hand.any { isRightBower(it, trump) || isLeftBower(it, trump) }
+        return trumps >= 3 && bower
+    }
+
+    /** Easy misjudges how good its hand is. */
+    private fun misjudge(value: Int, profile: AiProfile): Int =
+        if (profile.level == AiLevel.EASY) value + profile.random.nextInt(-5, 6) else value
+
     private fun chooseBidRound1(
         state: EuchreState,
         seat: Int,
         legal: List<EuchreMove>,
+        profile: AiProfile,
     ): EuchreMove {
         val upCard = state.upCard ?: return Pass
         val trump = upCard.suit
-        var hand = state.hands[seat]
+        val isDealer = seat == state.dealer
+        val partnerDealer = partnerOf(seat) == state.dealer
+        val hard = profile.level == AiLevel.HARD
 
         // If our partner is the dealer they gain the turn card, and if we are
         // the dealer we gain it ourselves — both make the hand stronger than it
         // looks. Ordering up into an opponent dealer instead hands them a card.
-        if (seat == state.dealer) hand = hand + upCard
-        var value = handValue(hand, trump)
-        if (partnerOf(seat) == state.dealer) value += 2
-        if (seat != state.dealer && partnerOf(seat) != state.dealer) value -= 2
+        val owned = if (isDealer) state.hands[seat] + upCard else state.hands[seat]
+        var value = when {
+            isDealer && hard -> bestAfterPickup(state.hands[seat], upCard, trump) + 3
+            else -> handValue(owned, trump)
+        }
+        if (partnerDealer) value += 2
+        if (!isDealer && !partnerDealer) {
+            value -= 2
+            // An opposing dealer who picks up a jack gets a bower out of our bid.
+            if (hard && upCard.rank == Rank.JACK) value -= 2
+        }
+        value = misjudge(value, profile)
+
+        val bidThreshold = profile.bolder(BID_THRESHOLD, -3.0)
+        var aloneThreshold = profile.bolder(ALONE_THRESHOLD, -3.0)
+        if (profile.level == AiLevel.EASY) aloneThreshold += 4.0
 
         val alone = OrderUp(alone = true)
-        if (value >= difficulty.aloneThreshold && legal.contains(alone)) return alone
+        if (value >= aloneThreshold && legal.contains(alone) && (!hard || soundAlone(owned, trump))) {
+            return alone
+        }
         val order = OrderUp(alone = false)
-        if (value >= difficulty.bidThreshold && legal.contains(order)) return order
+        if (value >= bidThreshold && legal.contains(order)) return order
         return if (legal.contains(Pass)) Pass else legal.first()
     }
 
@@ -103,37 +166,64 @@ class EuchreAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         state: EuchreState,
         seat: Int,
         legal: List<EuchreMove>,
+        profile: AiProfile,
     ): EuchreMove {
         val hand = state.hands[seat]
         val callable = legal.filterIsInstance<CallTrump>()
         if (callable.isEmpty()) return legal.first()
+        val plain = callable.filter { !it.alone }
 
-        val best = callable
-            .filter { !it.alone }
-            .maxByOrNull { handValue(hand, it.suit) }
-            ?: callable.first()
-        val bestValue = handValue(hand, best.suit)
+        val best: CallTrump
+        val bestValue: Int
+        if (profile.level == AiLevel.EASY) {
+            val noisy = plain.associateWith { handValue(hand, it.suit) + profile.random.nextInt(-5, 6) }
+            val ranked = plain.sortedByDescending { noisy.getValue(it) }
+            best = if (ranked.isEmpty()) callable.first() else profile.pick(ranked)
+            bestValue = noisy[best] ?: handValue(hand, best.suit)
+        } else {
+            best = plain.maxByOrNull { handValue(hand, it.suit) } ?: callable.first()
+            bestValue = handValue(hand, best.suit)
+        }
+
+        val bidThreshold = profile.bolder(BID_THRESHOLD, -3.0)
+        var aloneThreshold = profile.bolder(ALONE_THRESHOLD, -3.0)
+        if (profile.level == AiLevel.EASY) aloneThreshold += 4.0
 
         val alone = callable.firstOrNull { it.alone && it.suit == best.suit }
-        if (alone != null && bestValue >= difficulty.aloneThreshold) return alone
-        if (bestValue >= difficulty.bidThreshold) return best
+        val alonePlausible = profile.level != AiLevel.HARD || soundAlone(hand, best.suit)
+        if (alone != null && bestValue >= aloneThreshold && alonePlausible) return alone
+        if (bestValue >= bidThreshold) return best
         // Stuck as dealer with a bad hand: name the least-bad suit anyway.
         return if (legal.contains(Pass)) Pass else best
     }
 
-    private fun chooseDiscard(state: EuchreState, legal: List<EuchreMove>): EuchreMove {
+    private fun chooseDiscard(
+        state: EuchreState,
+        legal: List<EuchreMove>,
+        profile: AiProfile,
+    ): EuchreMove {
         val trump = requireNotNull(state.trump)
         val discards = legal.filterIsInstance<Discard>()
         // Prefer to void a side suit entirely; otherwise throw the lowest card.
         val hand = state.hands[state.dealer]
         val suitCounts = hand.groupingBy { effectiveSuit(it, trump) }.eachCount()
-        return discards.minByOrNull { discard ->
+        fun keepScore(discard: Discard): Int {
             val card = discard.card
             val suit = effectiveSuit(card, trump)
             val trumpPenalty = if (suit == trump) 1000 else 0
             val singletonBonus = if (suitCounts[suit] == 1 && card.rank != Rank.ACE) -20 else 0
-            trumpPenalty + singletonBonus + card.rank.order
-        } ?: discards.first()
+            return trumpPenalty + singletonBonus + card.rank.order
+        }
+        return when (profile.level) {
+            AiLevel.HARD -> discards
+                .sortedWith(
+                    compareByDescending<Discard> { handValue(hand - it.card, trump) }
+                        .thenBy { keepScore(it) },
+                )
+                .first()
+            AiLevel.EASY -> profile.pick(discards.sortedBy { keepScore(it) })
+            AiLevel.MEDIUM -> discards.minByOrNull { keepScore(it) } ?: discards.first()
+        }
     }
 
     // -----------------------------------------------------------------------
@@ -144,12 +234,40 @@ class EuchreAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         state: EuchreState,
         seat: Int,
         legal: List<EuchreMove>,
+        profile: AiProfile,
+        seen: Set<Card>,
     ): EuchreMove {
         val trump = requireNotNull(state.trump)
         val cards = legal.filterIsInstance<PlayCard>().map { it.card }
         if (cards.size == 1) return PlayCard(cards.first())
 
-        if (state.trick.isEmpty()) return PlayCard(chooseLead(cards, trump))
+        val maker = state.maker
+        val defending = maker != null && teamOf(maker) != teamOf(seat)
+        val makerSide = maker != null && teamOf(maker) == teamOf(seat)
+        // A spoiler on the defence leads trump to cut the maker's trump down.
+        val spiteful = defending && profile.style.spite >= 0.5
+
+        val best = if (profile.level == AiLevel.HARD) {
+            hardPlay(state, seat, cards, trump, seen, makerSide, spiteful)
+        } else {
+            standardPlay(state, seat, cards, trump, spiteful, profile)
+        }
+        if (profile.level != AiLevel.EASY) return PlayCard(best)
+
+        // Easy sometimes burns a high card it should have kept.
+        val ranked = listOf(best) + (cards - best).sortedByDescending { trumpStrength(it, trump) }
+        return PlayCard(profile.pick(ranked))
+    }
+
+    private fun standardPlay(
+        state: EuchreState,
+        seat: Int,
+        cards: List<Card>,
+        trump: Suit,
+        spiteful: Boolean,
+        profile: AiProfile,
+    ): Card {
+        if (state.trick.isEmpty()) return chooseLead(cards, trump, spiteful)
 
         val ledSuit = effectiveSuit(state.trick.first().card, trump)
         val bestSoFar = state.trick.maxBy { trickStrength(it.card, trump, ledSuit) }
@@ -157,22 +275,120 @@ class EuchreAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         val lastToPlay = state.trick.size == state.activeSeatCount - 1
 
         // Partner already has it and we are last: never waste a good card.
-        if (partnerWinning && lastToPlay) return PlayCard(lowest(cards, trump, ledSuit))
+        // (Easy sometimes forgets and overtakes anyway.)
+        if (partnerWinning && lastToPlay && !profile.slips()) {
+            return lowest(cards, trump, ledSuit)
+        }
 
         val bestStrength = trickStrength(bestSoFar.card, trump, ledSuit)
         val winners = cards.filter { trickStrength(it, trump, ledSuit) > bestStrength }
         return when {
             // Take it as cheaply as we can.
-            winners.isNotEmpty() && (!partnerWinning || !lastToPlay) ->
-                PlayCard(winners.minBy { trickStrength(it, trump, ledSuit) })
+            winners.isNotEmpty() && (!partnerWinning || !lastToPlay || profile.level == AiLevel.EASY) ->
+                winners.minBy { trickStrength(it, trump, ledSuit) }
 
-            else -> PlayCard(lowest(cards, trump, ledSuit))
+            else -> lowest(cards, trump, ledSuit)
         }
     }
 
-    private fun chooseLead(cards: List<Card>, trump: Suit): Card {
+    /**
+     * The strong player's choice. It remembers which cards have gone, so it
+     * knows when a card is the best one left, and it lets a partner who is
+     * already safe take the trick.
+     */
+    private fun hardPlay(
+        state: EuchreState,
+        seat: Int,
+        cards: List<Card>,
+        trump: Suit,
+        seen: Set<Card>,
+        makerSide: Boolean,
+        spiteful: Boolean,
+    ): Card {
+        val hand = state.hands[seat]
+        // Cards that could still be in somebody else's hand.
+        val unseen = Decks.euchre(state.options.deckSize).filter { it !in seen && it !in hand }
+        val unseenTrump = unseen.count { isTrumpCard(it, trump) }
+
+        /** No unseen card of its suit beats it; trump is ignored for a side-suit card. */
+        fun isBoss(card: Card): Boolean {
+            val led = effectiveSuit(card, trump)
+            val mine = trickStrength(card, trump, led)
+            val cardIsTrump = isTrumpCard(card, trump)
+            return unseen.none { other ->
+                (cardIsTrump || !isTrumpCard(other, trump)) && trickStrength(other, trump, led) > mine
+            }
+        }
+
+        if (state.trick.isEmpty()) {
+            val myTrump = cards.filter { isTrumpCard(it, trump) }
+            val off = cards.filter { !isTrumpCard(it, trump) }
+            val bossTrump = myTrump.filter { isBoss(it) }.maxByOrNull { trumpStrength(it, trump) }
+            if (unseenTrump > 0 && bossTrump != null && (makerSide || myTrump.size >= 2)) return bossTrump
+            if (unseenTrump > 0 && makerSide && myTrump.size >= 3) {
+                return myTrump.maxBy { trumpStrength(it, trump) }
+            }
+            if (unseenTrump > 0 && spiteful && myTrump.size >= 2) {
+                return myTrump.maxBy { trumpStrength(it, trump) }
+            }
+            val bossOff = off.filter { isBoss(it) }.maxByOrNull { it.rank.order }
+            if (bossOff != null) return bossOff
+            if (bossTrump != null) return bossTrump
+            if (off.isEmpty()) return cards.maxBy { trumpStrength(it, trump) }
+            if (makerSide) return chooseLead(cards, trump, false)
+            // On the defence with nothing sure: lead low from the shortest suit,
+            // which keeps the aces and sets up a ruff.
+            val counts = hand.groupingBy { effectiveSuit(it, trump) }.eachCount()
+            return off.minWith(
+                compareBy<Card>({ counts[effectiveSuit(it, trump)] ?: 0 }, { it.rank.order }),
+            )
+        }
+
+        val ledSuit = effectiveSuit(state.trick.first().card, trump)
+        val bestSoFar = state.trick.maxBy { trickStrength(it.card, trump, ledSuit) }
+        val partnerWinning = partnerOf(bestSoFar.seat) == seat
+        val remaining = state.activeSeatCount - state.trick.size - 1
+        val bestStrength = trickStrength(bestSoFar.card, trump, ledSuit)
+        val winners = cards.filter { trickStrength(it, trump, ledSuit) > bestStrength }
+
+        fun safe(card: Card): Boolean =
+            remaining == 0 ||
+                unseen.none { trickStrength(it, trump, ledSuit) > trickStrength(card, trump, ledSuit) }
+
+        fun throwAway(): Card {
+            // A card that neither follows nor trumps costs nothing; shed the
+            // lowest one that is not a sure winner later.
+            val junk = cards.filter { trickStrength(it, trump, ledSuit) == 0 }
+            if (junk.isNotEmpty()) {
+                return junk.minBy { it.rank.order + if (isBoss(it)) 100 else 0 }
+            }
+            return lowest(cards, trump, ledSuit)
+        }
+
+        if (partnerWinning) {
+            val partnerSecure = remaining == 0 ||
+                unseen.none { trickStrength(it, trump, ledSuit) > bestStrength }
+            if (partnerSecure) return throwAway()
+            // Partner may yet be beaten: back them with a side-suit card, but do
+            // not spend trump on top of their lead.
+            val backing = winners.filter { !isTrumpCard(it, trump) }
+                .minByOrNull { trickStrength(it, trump, ledSuit) }
+            return backing ?: throwAway()
+        }
+        if (winners.isNotEmpty()) {
+            val sure = winners.filter { safe(it) }
+            return (sure.ifEmpty { winners }).minBy { trickStrength(it, trump, ledSuit) }
+        }
+        return throwAway()
+    }
+
+    private fun chooseLead(cards: List<Card>, trump: Suit, spiteTrump: Boolean): Card {
         // Right bower up front pulls trump and protects the left.
         cards.firstOrNull { isRightBower(it, trump) }?.let { return it }
+        if (spiteTrump) {
+            val trumps = cards.filter { isTrumpCard(it, trump) }
+            if (trumps.size >= 2) return trumps.maxBy { trumpStrength(it, trump) }
+        }
         // Off-suit aces are most likely to survive early.
         cards.filter { !isTrumpCard(it, trump) && it.rank == Rank.ACE }
             .maxByOrNull { it.rank.order }

app/src/main/java/org/prolibertate/games/game/golf/GolfAi.kt

@@ -1,49 +1,78 @@
 package org.prolibertate.games.game.golf
 
+import org.prolibertate.games.game.cards.Card
+import org.prolibertate.games.game.cards.Rank
+import org.prolibertate.games.game.cards.Suit
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
- * A heuristic Golf opponent.
+ * A Golf opponent whose strength and temperament come from the seat's profile.
  *
- * It takes a card off the discard pile when it is cheap or completes a column,
- * replaces its worst known card, and turns cards over when it has nothing
- * better to do. It never peeks at a face-down card — including its own, which
- * it genuinely does not know.
+ * MEDIUM (the default) takes a card off the discard pile when it is cheap or
+ * completes a column, replaces its worst known card, and turns cards over when
+ * it has nothing better to do. It never peeks at a face-down card — including
+ * its own, which it genuinely does not know.
+ *
+ * EASY is pickier about the discard pile, closes the hole from a poor position
+ * and sometimes makes a worse play than it saw. HARD keeps count of every card
+ * it has seen (turned-over grids and the discard pile), values its unknown
+ * cards at what is still unseen, and chooses each draw and placement by how
+ * much it lowers its expected score, including the chance of completing a
+ * column and whether closing the hole would leave it ahead.
  */
-class GolfAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
+class GolfAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) :
     GameAi<GolfState, GolfMove> {
 
-    enum class Difficulty(
+    /** The tuning the standard plan runs on. */
+    private class Params(
         /** Take a discard worth this or less rather than gambling on the stock. */
         val discardAppetite: Int,
         /** Only close the hole out when the visible score is at or under this. */
         val closeOutBelow: Int,
-    ) {
-        EASY(discardAppetite = 2, closeOutBelow = 30),
-        NORMAL(discardAppetite = 5, closeOutBelow = 16),
-        CAUTIOUS(discardAppetite = 7, closeOutBelow = 12),
-    }
+    )
 
     override fun chooseMove(state: GolfState, seat: Int, legal: List<GolfMove>): GolfMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
-        return when (state.phase) {
-            GolfPhase.SETUP -> chooseReveal(state, seat, legal)
-            GolfPhase.DRAW -> chooseDraw(state, seat, legal)
-            GolfPhase.PLACE -> choosePlace(state, seat, legal)
+        val profile = profiles.of(seat)
+        val move = when (state.phase) {
+            GolfPhase.SETUP -> chooseReveal(state, seat, legal, profile)
+            GolfPhase.DRAW -> chooseDraw(state, seat, legal, profile)
+            GolfPhase.PLACE -> choosePlace(state, seat, legal, profile)
             else -> legal.first()
         }
+        return if (move in legal) move else legal.first()
     }
 
+    private fun paramsFor(level: AiLevel): Params = when (level) {
+        AiLevel.EASY -> EASY
+        else -> NORMAL
+    }
+
+    // -----------------------------------------------------------------------
+    // Setup
+    // -----------------------------------------------------------------------
+
     /**
      * Opening reveals are spread across columns. Two cards in the same column
      * tell you whether that column can be cancelled but nothing about the rest
      * of the board; one in each column leaves more of the grid legible.
      */
-    private fun chooseReveal(state: GolfState, seat: Int, legal: List<GolfMove>): GolfMove {
+    private fun chooseReveal(
+        state: GolfState,
+        seat: Int,
+        legal: List<GolfMove>,
+        profile: AiProfile,
+    ): GolfMove {
         val reveals = legal.filterIsInstance<RevealCard>()
         if (reveals.isEmpty()) return legal.first()
         val options = state.options
 
+        // A distracted player turns over whatever is nearest.
+        if (profile.slips()) return reveals[profile.random.nextInt(reveals.size)]
+
         val untouchedColumn = reveals.firstOrNull { move ->
             val column = move.index % options.cols
             (0 until options.rows).none { row ->
@@ -53,17 +82,61 @@ class GolfAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         return untouchedColumn ?: reveals.first()
     }
 
-    private fun chooseDraw(state: GolfState, seat: Int, legal: List<GolfMove>): GolfMove {
+    // -----------------------------------------------------------------------
+    // Drawing
+    // -----------------------------------------------------------------------
+
+    private fun chooseDraw(
+        state: GolfState,
+        seat: Int,
+        legal: List<GolfMove>,
+        profile: AiProfile,
+    ): GolfMove {
+        if (profile.level == AiLevel.HARD) return hardDraw(state, seat, legal, profile)
+
+        val params = paramsFor(profile.level)
         val top = state.discard.lastOrNull()
+        var take = false
         if (top != null && legal.contains(DrawFromDiscard)) {
-            val worthTaking = golfValue(top) <= difficulty.discardAppetite ||
+            take = golfValue(top) <= params.discardAppetite ||
                 completesColumn(state, seat, top) != null
-            if (worthTaking) return DrawFromDiscard
         }
+        // Easy sometimes flips its own decision.
+        if (profile.slips() && legal.contains(DrawFromDiscard) && legal.contains(DrawFromStock)) take = !take
+        if (take && legal.contains(DrawFromDiscard)) return DrawFromDiscard
         return if (legal.contains(DrawFromStock)) DrawFromStock else legal.first()
     }
 
-    private fun choosePlace(state: GolfState, seat: Int, legal: List<GolfMove>): GolfMove {
+    // -----------------------------------------------------------------------
+    // Placing
+    // -----------------------------------------------------------------------
+
+    private fun choosePlace(
+        state: GolfState,
+        seat: Int,
+        legal: List<GolfMove>,
+        profile: AiProfile,
+    ): GolfMove {
+        if (profile.level == AiLevel.HARD) return hardPlace(state, seat, legal, profile)
+
+        val best = standardPlace(state, seat, legal, paramsFor(profile.level))
+        if (profile.level != AiLevel.EASY || !profile.slips()) return best
+
+        // A lapse: turn something over or cover a face-down card instead.
+        val alternatives = buildList<GolfMove> {
+            addAll(legal.filterIsInstance<DiscardAndFlip>())
+            addAll(legal.filterIsInstance<ReplaceCard>().filter { !state.revealed[seat][it.index] })
+        }.filter { it != best }
+        if (alternatives.isEmpty()) return best
+        return alternatives[profile.random.nextInt(alternatives.size)]
+    }
+
+    private fun standardPlace(
+        state: GolfState,
+        seat: Int,
+        legal: List<GolfMove>,
+        params: Params,
+    ): GolfMove {
         val drawn = state.drawn ?: return legal.first()
         val replacements = legal.filterIsInstance<ReplaceCard>()
         val flips = legal.filterIsInstance<DiscardAndFlip>()
@@ -90,7 +163,7 @@ class GolfAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
             val showing = state.grids[seat].indices
                 .filter { state.revealed[seat][it] }
                 .sumOf { golfValue(state.grids[seat][it]) }
-            if (showing > difficulty.closeOutBelow) return DiscardOnly
+            if (showing > params.closeOutBelow) return DiscardOnly
         }
 
         // Nothing worth swapping: throw it and turn something over instead,
@@ -106,7 +179,7 @@ class GolfAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
     private fun completesColumn(
         state: GolfState,
         seat: Int,
-        card: org.prolibertate.games.game.cards.Card,
+        card: Card,
     ): Int? {
         val options = state.options
         for (col in 0 until options.cols) {
@@ -122,4 +195,229 @@ class GolfAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         }
         return null
     }
+
+    // -----------------------------------------------------------------------
+    // Hard
+    // -----------------------------------------------------------------------
+
+    /**
+     * What this seat knows about the hole: the cards in every turned-over cell,
+     * the discard pile and (on its own turn) the card in its hand. Everything
+     * else — face-down cells and the stock — is valued at the average of the
+     * cards not yet seen.
+     */
+    private class Board(private val state: GolfState, seat: Int) {
+        val options = state.options
+        private val counts = HashMap<Rank, Int>()
+        private val unseenTotal: Int
+        val unknownValue: Double
+        private val lines: List<List<Int>>
+
+        init {
+            val copies = if (options.playerCount * options.gridSize > 24) 2 else 1
+            Rank.standard.forEach { counts[it] = 4 * copies }
+            fun see(card: Card) {
+                counts[card.rank] = maxOf(0, (counts[card.rank] ?: 0) - 1)
+            }
+            state.grids.forEachIndexed { player, grid ->
+                grid.forEachIndexed { index, card -> if (state.revealed[player][index]) see(card) }
+            }
+            state.discard.forEach { see(it) }
+            if (seat == state.turn) state.drawn?.let { see(it) }
+
+            unseenTotal = counts.values.sum()
+            unknownValue = if (unseenTotal == 0) {
+                5.0
+            } else {
+                counts.entries.sumOf { (rank, n) -> n * valueOf(rank).toDouble() } / unseenTotal
+            }
+
+            val columns = (0 until options.cols).map { col -> (0 until options.rows).map { it * options.cols + col } }
+            val rows = if (options.rows == 3) {
+                (0 until options.rows).map { row -> (0 until options.cols).map { row * options.cols + it } }
+            } else {
+                emptyList()
+            }
+            lines = columns + rows
+        }
+
+        fun valueOf(rank: Rank): Int = golfValue(Card(rank, Suit.SPADES))
+
+        private fun chanceOf(rank: Rank): Double =
+            if (unseenTotal == 0) 0.0 else (counts[rank] ?: 0).toDouble() / unseenTotal
+
+        /** A seat's cells as far as this seat can see them; null is a face-down card. */
+        fun cellsOf(player: Int): List<Card?> =
+            state.grids[player].mapIndexed { index, card -> if (state.revealed[player][index]) card else null }
+
+        /** Expected score of a grid, counting the chance that an unknown cell completes a line. */
+        fun expected(cells: List<Card?>): Double {
+            val cancelled = BooleanArray(cells.size)
+            for (line in lines) {
+                val line0 = line.map { cells[it] }
+                if (line0.all { it != null } && line0.map { it!!.rank }.distinct().size == 1) {
+                    line.forEach { cancelled[it] = true }
+                }
+            }
+            var total = 0.0
+            for (index in cells.indices) {
+                if (cancelled[index]) continue
+                val card = cells[index]
+                total += if (card != null) golfValue(card).toDouble() else unknownValue
+            }
+            for (line in lines) {
+                if (line.any { cancelled[it] }) continue
+                val unknown = line.filter { cells[it] == null }
+                if (unknown.size != 1) continue
+                val known = line.mapNotNull { cells[it] }
+                if (known.isEmpty() || known.map { it.rank }.distinct().size != 1) continue
+                val rank = known.first().rank
+                total -= chanceOf(rank) * (known.sumOf { golfValue(it) } + valueOf(rank))
+            }
+            return total
+        }
+
+        /** Unseen ranks and how many of each remain, for averaging over a stock draw. */
+        fun unseenRanks(): List<Pair<Rank, Int>> = counts.entries.filter { it.value > 0 }.map { it.key to it.value }
+
+        /** How likely turning over [index] is to finish a line that already shows one rank. */
+        fun matchHope(cells: List<Card?>, index: Int): Double {
+            var best = 0.0
+            for (line in lines) {
+                if (index !in line) continue
+                val others = line.filter { it != index }
+                val known = others.mapNotNull { cells[it] }
+                if (known.size != others.size || known.isEmpty()) continue
+                if (known.map { it.rank }.distinct().size != 1) continue
+                val rank = known.first().rank
+                best = maxOf(best, chanceOf(rank) * (known.sumOf { golfValue(it) } + valueOf(rank)))
+            }
+            return best
+        }
+    }
+
+    private fun effectiveBoldness(state: GolfState, seat: Int, profile: AiProfile): Double {
+        // Well behind late in the match: take more chances.
+        val holesLeft = state.options.holes - state.hole - 1
+        val best = (0 until state.options.playerCount).filter { it != seat }.minOf { state.scores[it] }
+        val behind = state.scores[seat] - best
+        return profile.style.boldness + if (holesLeft <= 2 && behind > 8) 0.3 else 0.0
+    }
+
+    /** Scores one way of using the card in hand: lower grid score, more information, less risk. */
+    private class Planner(
+        val state: GolfState,
+        val seat: Int,
+        val board: Board,
+        val boldness: Double,
+        val spite: Double,
+    ) {
+        private val cells = board.cellsOf(seat)
+        private val before = board.expected(cells)
+        private val hidden = cells.count { it == null }
+        private val finalTurn = state.closedBy != null
+        private val rivalBest: Double = (0 until state.options.playerCount)
+            .filter { it != seat }
+            .minOfOrNull { board.expected(board.cellsOf(it)) } ?: before
+
+        private fun closePenalty(after: Double): Double {
+            if (finalTurn) return 0.0
+            val margin = 2.0 - 2.0 * boldness
+            return maxOf(0.0, after - (rivalBest - margin)) * 0.8
+        }
+
+        private fun handoff(drawn: Card): Double =
+            maxOf(0.0, 3.0 - golfValue(drawn)) * 0.15 * (1.0 + spite)
+
+        private fun flipBonus(index: Int): Double =
+            if (finalTurn || hidden <= 1) 0.0 else 0.35 + 0.5 * board.matchHope(cells, index)
+
+        /** Utility of [move] with [drawn] in hand; higher is better. */
+        fun utility(move: GolfMove, drawn: Card): Double = when (move) {
+            is ReplaceCard -> {
+                val after = cells.toMutableList().also { it[move.index] = drawn }
+                val closes = hidden == 1 && cells[move.index] == null
+                val afterScore = board.expected(after)
+                before - afterScore - if (closes) closePenalty(afterScore) else 0.0
+            }
+
+            is DiscardAndFlip -> {
+                val closes = hidden == 1
+                flipBonus(move.index) - handoff(drawn) - if (closes) closePenalty(before) else 0.0
+            }
+
+            is DiscardOnly -> -handoff(drawn)
+            else -> Double.NEGATIVE_INFINITY
+        }
+
+        /** The moves open to a card in hand, standing in for the legal list during look-ahead. */
+        fun candidates(fromDiscard: Boolean, putt: Boolean): List<GolfMove> = buildList {
+            for (index in cells.indices) add(ReplaceCard(index))
+            if (!fromDiscard) {
+                for (index in cells.indices) if (cells[index] == null) add(DiscardAndFlip(index))
+                if (putt && hidden == 1) add(DiscardOnly)
+            }
+        }
+    }
+
+    private fun planner(state: GolfState, seat: Int, profile: AiProfile): Planner {
+        val board = Board(state, seat)
+        return Planner(state, seat, board, effectiveBoldness(state, seat, profile), profile.style.spite)
+    }
+
+    private fun hardDraw(
+        state: GolfState,
+        seat: Int,
+        legal: List<GolfMove>,
+        profile: AiProfile,
+    ): GolfMove {
+        val top = state.discard.lastOrNull()
+        val canStock = legal.contains(DrawFromStock)
+        val canDiscard = legal.contains(DrawFromDiscard) && top != null
+        if (!canDiscard) return if (canStock) DrawFromStock else legal.first()
+        if (!canStock) return DrawFromDiscard
+
+        val plan = planner(state, seat, profile)
+        val putt = state.options.lineUpFinalPutt
+
+        // The discard has to be used, so it is only as good as its best replacement.
+        val takeUtility = plan.candidates(fromDiscard = true, putt = putt)
+            .maxOf { plan.utility(it, top!!) } +
+            profile.style.spite * 0.3 * maxOf(0, 4 - golfValue(top!!))
+
+        // The stock is a gamble on the average of what is left, but can be thrown back.
+        val ranks = plan.board.unseenRanks()
+        val total = ranks.sumOf { it.second }
+        val stockUtility = if (total == 0) {
+            Double.NEGATIVE_INFINITY
+        } else {
+            val moves = plan.candidates(fromDiscard = false, putt = putt)
+            ranks.sumOf { (rank, n) ->
+                val sample = Card(rank, Suit.SPADES)
+                n * moves.maxOf { plan.utility(it, sample) }
+            } / total
+        }
+
+        // A bold seat wants a clear edge before it passes up the unknown card.
+        val take = takeUtility - plan.boldness * 0.4 > stockUtility
+        return if (take) DrawFromDiscard else DrawFromStock
+    }
+
+    private fun hardPlace(
+        state: GolfState,
+        seat: Int,
+        legal: List<GolfMove>,
+        profile: AiProfile,
+    ): GolfMove {
+        val drawn = state.drawn ?: return legal.first()
+        val plan = planner(state, seat, profile)
+        val options = legal.filter { it is ReplaceCard || it is DiscardAndFlip || it is DiscardOnly }
+        if (options.isEmpty()) return legal.first()
+        return options.maxBy { plan.utility(it, drawn) }
+    }
+
+    private companion object {
+        private val EASY = Params(discardAppetite = 2, closeOutBelow = 30)
+        private val NORMAL = Params(discardAppetite = 5, closeOutBelow = 16)
+    }
 }

app/src/main/java/org/prolibertate/games/game/hearts/HeartsAi.kt

@@ -3,35 +3,98 @@ package org.prolibertate.games.game.hearts
 import org.prolibertate.games.game.cards.Card
 import org.prolibertate.games.game.cards.Rank
 import org.prolibertate.games.game.cards.Suit
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
- * A cautious Hearts player.
+ * A Hearts player whose strength and temperament come from the seat's profile.
  *
- * It plays to avoid points rather than to shoot the moon: it sheds the queen of
- * spades and the guards above her at the first opportunity, ducks under whoever
- * is winning a trick when it can, and takes a trick as cheaply as possible when
- * it cannot get out of the way. That is enough to make it an opponent worth
- * beating without pretending to read the table.
+ * MEDIUM (the default) avoids points rather than shooting the moon: it sheds
+ * the queen of spades and the guards above her at the first opportunity, ducks
+ * under whoever is winning a trick when it can, and takes a trick as cheaply as
+ * possible when it cannot get out of the way.
+ *
+ * EASY plays the same plan but sometimes settles for a worse card in each
+ * decision. HARD counts the penalty cards and spades that have been taken,
+ * leads by risk, sheds by what is still dangerous, shoots the moon when its
+ * hand and the table allow it and tries to break a moon somebody else is on.
+ * It only uses its own hand and what the table has shown.
  */
-object HeartsAi : GameAi<HeartsState, HeartsMove> {
+class HeartsAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) : GameAi<HeartsState, HeartsMove> {
 
     override fun chooseMove(state: HeartsState, seat: Int, legal: List<HeartsMove>): HeartsMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
-        return when (state.phase) {
-            HeartsPhase.PASSING -> choosePass(state, seat, legal)
-            else -> choosePlay(state, seat, legal)
+        val profile = profiles.of(seat)
+        val move = when (state.phase) {
+            HeartsPhase.PASSING -> choosePass(state, seat, legal, profile)
+            else -> choosePlay(state, seat, legal, profile)
         }
+        return if (move in legal) move else legal.first()
     }
 
-    private fun choosePass(state: HeartsState, seat: Int, legal: List<HeartsMove>): HeartsMove {
+    // -----------------------------------------------------------------------
+    // Passing
+    // -----------------------------------------------------------------------
+
+    private fun choosePass(
+        state: HeartsState,
+        seat: Int,
+        legal: List<HeartsMove>,
+        profile: AiProfile,
+    ): HeartsMove {
         val hand = state.hands[seat]
-        val wanted = hand.sortedByDescending { passDanger(it, hand) }.take(PASS_SIZE).toSet()
+        val wanted: Set<Card> = when (profile.level) {
+            AiLevel.MEDIUM -> hand.sortedByDescending { passDanger(it, hand) }.take(PASS_SIZE).toSet()
+            AiLevel.EASY -> easyPass(hand, profile)
+            AiLevel.HARD -> hardPass(state, hand, profile)
+        }
         // Prefer the exact bundle the heuristic asked for, but fall back rather
         // than fail: the caller's list is what the host will validate against.
         return legal.firstOrNull { it is PassCards && it.cards.toSet() == wanted } ?: legal.first()
     }
 
+    private fun easyPass(hand: List<Card>, profile: AiProfile): Set<Card> {
+        val ranked = hand.sortedByDescending { passDanger(it, hand) }
+        val chosen = ranked.take(PASS_SIZE).toMutableList()
+        if (profile.slips()) {
+            // Keeps one of the cards it should have sent.
+            val spare = ranked.drop(PASS_SIZE).take(4)
+            if (spare.isNotEmpty()) {
+                chosen[profile.random.nextInt(chosen.size)] = spare[profile.random.nextInt(spare.size)]
+            }
+        }
+        return chosen.toSet()
+    }
+
+    private fun hardPass(state: HeartsState, hand: List<Card>, profile: AiProfile): Set<Card> {
+        if (state.options.allowShootTheMoon && moonHand(hand, profile)) {
+            // Keep every high card and heart, send the three smallest.
+            val junk = hand.filter { !(it.suit == Suit.HEARTS && it.rank.order >= 10) }
+                .sortedBy { it.rank.order }
+            if (junk.size >= PASS_SIZE) return junk.take(PASS_SIZE).toSet()
+        }
+        return hand.sortedByDescending { passDanger(it, hand) + shortSuitBonus(it, hand) }
+            .take(PASS_SIZE).toSet()
+    }
+
+    /** Sending away the last cards of a short suit makes a void, which is worth a lot when discarding. */
+    private fun shortSuitBonus(card: Card, hand: List<Card>): Int {
+        if (card.suit == Suit.HEARTS || card.suit == Suit.SPADES) return 0
+        val length = hand.count { it.suit == card.suit }
+        return if (length > 3) 0 else (4 - length) * 8
+    }
+
+    /** A hand worth trying to take all twenty-six with: lots of high cards and a heart suit to run. */
+    private fun moonHand(hand: List<Card>, profile: AiProfile): Boolean {
+        val hearts = hand.count { it.suit == Suit.HEARTS }
+        if (hearts < 4) return false
+        val strength = hand.count { it.rank.order >= Rank.QUEEN.order } +
+            hand.count { it.suit == Suit.HEARTS && it.rank.order >= 9 }
+        return strength >= profile.bolder(8.0, -2.0)
+    }
+
     /**
      * How much a card wants to be somebody else's problem.
      *
@@ -52,27 +115,41 @@ object HeartsAi : GameAi<HeartsState, HeartsMove> {
         }
     }
 
-    private fun choosePlay(state: HeartsState, seat: Int, legal: List<HeartsMove>): HeartsMove {
+    // -----------------------------------------------------------------------
+    // Playing
+    // -----------------------------------------------------------------------
+
+    private fun choosePlay(
+        state: HeartsState,
+        seat: Int,
+        legal: List<HeartsMove>,
+        profile: AiProfile,
+    ): HeartsMove {
         val cards = legal.filterIsInstance<PlayCard>().map { it.card }
         if (cards.isEmpty()) return legal.first()
-        val chosen = when {
-            state.trick.isEmpty() -> lead(cards)
-            else -> follow(state, cards)
+        val chosen = when (profile.level) {
+            AiLevel.MEDIUM -> standardRanking(state, cards).first()
+            AiLevel.EASY -> profile.pick(standardRanking(state, cards))
+            AiLevel.HARD -> hardPlay(state, seat, cards, profile)
         }
-        return PlayCard(chosen)
+        return PlayCard(if (chosen in cards) chosen else cards.first())
     }
 
+    /** The standard plan's preferences, best first. */
+    private fun standardRanking(state: HeartsState, cards: List<Card>): List<Card> =
+        if (state.trick.isEmpty()) rankedLead(cards) else rankedFollow(state, cards)
+
     /**
      * Leads low, and keeps off spades while the queen is still unaccounted for —
      * leading a spade under her is how a seat ends up holding her.
      */
-    private fun lead(cards: List<Card>): Card {
-        val offSpades = cards.filter { it.suit != Suit.SPADES }
-        val pool = if (offSpades.isNotEmpty()) offSpades else cards
-        return pool.minBy { it.rank.order }
+    private fun rankedLead(cards: List<Card>): List<Card> {
+        val offSpades = cards.filter { it.suit != Suit.SPADES }.sortedBy { it.rank.order }
+        val spades = cards.filter { it.suit == Suit.SPADES }.sortedBy { it.rank.order }
+        return offSpades + spades
     }
 
-    private fun follow(state: HeartsState, cards: List<Card>): Card {
+    private fun rankedFollow(state: HeartsState, cards: List<Card>): List<Card> {
         val led = state.trick.first().card.suit
         val best = state.trick.maxOf { trickStrength(it.card, led) }
         val pot = pointsIn(state.trick.map { it.card })
@@ -82,27 +159,189 @@ object HeartsAi : GameAi<HeartsState, HeartsMove> {
         if (ducking.isNotEmpty()) {
             // Safe under the current winner, so shed the most expensive card
             // that still loses.
-            return ducking.maxBy { it.rank.order + pointsOf(it) * 2 }
+            val rest = (cards - ducking.toSet()).sortedBy { it.rank.order }
+            return ducking.sortedByDescending { it.rank.order + pointsOf(it) * 2 } + rest
         }
 
-        val void = cards.none { it.suit == led }
-        if (void) return discard(cards)
-
         // Every card left would take the trick. Playing last with nothing in the
         // pot means it costs nothing, so there is no reason to waste a high card
         // on it; otherwise take it as cheaply as possible.
-        return if (last && pot == 0) cards.maxBy { it.rank.order } else cards.minBy { it.rank.order }
+        return if (last && pot == 0) {
+            cards.sortedByDescending { it.rank.order }
+        } else {
+            cards.sortedBy { it.rank.order }
+        }
     }
 
-    /** Void in the led suit and free to throw anything, so throw the worst of it. */
-    private fun discard(cards: List<Card>): Card {
-        cards.firstOrNull { it == QUEEN_OF_SPADES }?.let { return it }
-        cards.filter { it.suit == Suit.SPADES && it.rank.order > Rank.QUEEN.order }
-            .maxByOrNull { it.rank.order }
-            ?.let { return it }
-        cards.filter { it.suit == Suit.HEARTS }
-            .maxByOrNull { it.rank.order }
-            ?.let { return it }
-        return cards.maxBy { it.rank.order }
+    // -----------------------------------------------------------------------
+    // Hard play
+    // -----------------------------------------------------------------------
+
+    /** What this seat can legitimately know: its hand, and every card taken or on the table. */
+    private class Memory(state: HeartsState, seat: Int) {
+        val hand: List<Card> = state.hands[seat]
+        val unseen: List<Card>
+
+        init {
+            val seen = HashSet<Card>()
+            state.taken.forEach { seen.addAll(it) }
+            state.trick.forEach { seen.add(it.card) }
+            seen.addAll(hand)
+            unseen = FULL_DECK.filter { it !in seen }
+        }
+
+        val queenUnseen: Boolean get() = QUEEN_OF_SPADES in unseen
+
+        fun unseenIn(suit: Suit): Int = unseen.count { it.suit == suit }
+
+        fun unseenHigher(card: Card): Int =
+            unseen.count { it.suit == card.suit && it.rank.order > card.rank.order }
+    }
+
+    private fun hardPlay(state: HeartsState, seat: Int, cards: List<Card>, profile: AiProfile): Card {
+        val mem = Memory(state, seat)
+        if (isShooting(state, seat, mem, profile)) return shootPlay(state, cards, mem)
+        return if (state.trick.isEmpty()) {
+            hardLead(cards, mem, profile)
+        } else {
+            hardFollow(state, seat, cards, mem, profile)
+        }
+    }
+
+    /** Holding every point so far, with a hand that can keep winning. */
+    private fun isShooting(state: HeartsState, seat: Int, mem: Memory, profile: AiProfile): Boolean {
+        if (!state.options.allowShootTheMoon) return false
+        val all = pointsIn(state.taken.flatten())
+        val mine = pointsIn(state.taken[seat])
+        if (mine != all) return false
+        if (mine == 0 && !moonHand(mem.hand, profile)) return false
+        if (mem.hand.isEmpty()) return false
+        val masters = mem.hand.count { mem.unseenHigher(it) == 0 }
+        return masters.toDouble() / mem.hand.size >= profile.bolder(0.6, -0.15)
+    }
+
+    private fun shootPlay(state: HeartsState, cards: List<Card>, mem: Memory): Card {
+        if (state.trick.isEmpty()) {
+            val masters = cards.filter { mem.unseenHigher(it) == 0 }
+            if (masters.isNotEmpty()) {
+                return masters.sortedWith(
+                    compareBy<Card> { it.suit == Suit.HEARTS }.thenByDescending { it.rank.order },
+                ).first()
+            }
+            return cards.maxBy { it.rank.order }
+        }
+        val led = state.trick.first().card.suit
+        val best = state.trick.maxOf { trickStrength(it.card, led) }
+        val remaining = state.options.playerCount - state.trick.size - 1
+        val winning = cards.filter { trickStrength(it, led) > best }
+        if (winning.isNotEmpty()) {
+            if (remaining == 0) return winning.minBy { it.rank.order }
+            return winning.filter { mem.unseenHigher(it) == 0 }.minByOrNull { it.rank.order }
+                ?: winning.maxBy { it.rank.order }
+        }
+        // Cannot win this one: lose it with a card that is not a point.
+        return cards.minBy { pointsOf(it) * 100 + it.rank.order }
+    }
+
+    /** Another seat that has taken every penalty card so far and looks set to run the table. */
+    private fun moonThreat(state: HeartsState, seat: Int): Int? {
+        if (!state.options.allowShootTheMoon) return null
+        val all = pointsIn(state.taken.flatten())
+        if (all < 14 && !(state.trickNumber >= 6 && all >= 8)) return null
+        return (0 until state.options.playerCount).firstOrNull {
+            it != seat && pointsIn(state.taken[it]) == all
+        }
+    }
+
+    private fun scoreLeader(state: HeartsState, seat: Int): Int? =
+        (0 until state.options.playerCount).filter { it != seat }.minByOrNull { state.scores[it] }
+
+    private fun hardLead(cards: List<Card>, mem: Memory, profile: AiProfile): Card {
+        // A cautious seat weighs a trick it might win more heavily than a bold one.
+        val weight = 1.0 - 0.25 * profile.style.boldness
+
+        fun risk(card: Card): Double {
+            val others = mem.unseenIn(card.suit)
+            val higher = mem.unseenHigher(card)
+            val winChance = if (others == 0) 1.0 else Math.pow(1.0 - higher.toDouble() / others, 3.0)
+            var points = 0.5
+            if (card.suit == Suit.HEARTS) points += 2.0
+            if (card.suit == Suit.SPADES && mem.queenUnseen) points += 13 * 0.3
+            // A suit nobody else holds lets everyone dump on whoever wins it.
+            if (others == 0) points += 3.0
+            val shedding = if (winChance < 0.15) 0.05 * card.rank.order else 0.0
+            return winChance * points * weight - shedding
+        }
+        return cards.minBy { risk(it) }
+    }
+
+    private fun hardFollow(
+        state: HeartsState,
+        seat: Int,
+        cards: List<Card>,
+        mem: Memory,
+        profile: AiProfile,
+    ): Card {
+        val trick = state.trick
+        val led = trick.first().card.suit
+        val winner = trick.maxBy { trickStrength(it.card, led) }
+        val best = trickStrength(winner.card, led)
+        val pot = pointsIn(trick.map { it.card })
+        val remaining = state.options.playerCount - trick.size - 1
+        val winning = cards.filter { trickStrength(it, led) > best }
+        val ducking = cards.filter { trickStrength(it, led) < best }
+        val threat = moonThreat(state, seat)
+
+        // Taking even a few points is far better than letting a moon through.
+        if (threat != null && pot > 0 && winning.isNotEmpty()) {
+            return winning.minBy { it.rank.order }
+        }
+
+        val void = cards.none { it.suit == led }
+        if (void) return hardDischarge(state, seat, cards, mem, profile, winner.seat, threat)
+
+        if (ducking.isNotEmpty()) {
+            return ducking.maxBy { it.rank.order + pointsOf(it) * 2 }
+        }
+        // Forced to win. Last to play, the trick is taken whatever is played,
+        // so spend the highest card; otherwise win as cheaply as possible.
+        return if (remaining == 0) {
+            cards.maxBy { it.rank.order }
+        } else {
+            cards.minBy { it.rank.order }
+        }
+    }
+
+    /** Void in the led suit: throw away whatever is still dangerous to hold. */
+    private fun hardDischarge(
+        state: HeartsState,
+        seat: Int,
+        cards: List<Card>,
+        mem: Memory,
+        profile: AiProfile,
+        winnerSeat: Int,
+        threat: Int?,
+    ): Card {
+        val spoil = profile.style.spite >= 0.5 && winnerSeat == scoreLeader(state, seat)
+
+        fun score(card: Card): Double {
+            var s: Double = when {
+                card == QUEEN_OF_SPADES -> 1000.0
+                else -> card.rank.order.toDouble()
+            }
+            // The ace and king of spades only matter while the queen is out there.
+            if (card.suit == Suit.SPADES && card.rank.order > Rank.QUEEN.order && mem.queenUnseen) s += 200
+            if (card.suit == Suit.HEARTS) s += 100
+            if (pointsOf(card) == 0 && mem.hand.count { it.suit == card.suit } <= 2) s += 10
+            if (spoil && pointsOf(card) > 0) s += 300
+            // Do not feed a seat that is running for the moon.
+            if (threat != null && winnerSeat == threat && pointsOf(card) > 0) s -= 2000
+            return s
+        }
+        return cards.maxBy { score(it) }
+    }
+
+    private companion object {
+        val FULL_DECK: List<Card> = Suit.entries.flatMap { suit -> Rank.standard.map { Card(it, suit) } }
     }
 }

app/src/main/java/org/prolibertate/games/game/kaiser/KaiserAi.kt

@@ -3,6 +3,10 @@ package org.prolibertate.games.game.kaiser
 import org.prolibertate.games.game.cards.Card
 import org.prolibertate.games.game.cards.Rank
 import org.prolibertate.games.game.cards.Suit
+import org.prolibertate.games.game.cards.Decks
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -12,25 +16,51 @@ import org.prolibertate.games.game.engine.GameAi
  * in play chases the five of hearts while trying not to be the one holding the
  * trick the three of spades lands in.
  */
-class KaiserAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
+class KaiserAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) :
     GameAi<KaiserState, KaiserMove> {
 
-    enum class Difficulty(
+    private companion object {
         /** Hand strength needed before bidding above the floor. */
-        val bidThreshold: Int,
-    ) {
-        EASY(bidThreshold = 12),
-        NORMAL(bidThreshold = 16),
-        CAUTIOUS(bidThreshold = 19),
+        const val BID_THRESHOLD = 16.0
+        const val EASY_BID_THRESHOLD = 15.0
+    }
+
+    /** Cards this AI has watched played in the current hand, per seat it plays. */
+    private val memory = HashMap<Int, SeenCards>()
+
+    private class SeenCards {
+        var key: Long = Long.MIN_VALUE
+        val cards = HashSet<Card>()
+    }
+
+    /** Public information only: cards that have appeared on the table this hand. */
+    private fun observe(state: KaiserState, seat: Int): Set<Card> = synchronized(memory) {
+        val seen = memory.getOrPut(seat) { SeenCards() }
+        val key = state.seed * 1_000_003L + state.handNumber
+        if (key != seen.key || state.phase == KaiserPhase.BIDDING) {
+            seen.key = key
+            seen.cards.clear()
+        }
+        state.trick.forEach { seen.cards.add(it.card) }
+        state.completedTrick.forEach { seen.cards.add(it.card) }
+        seen.cards.removeAll(state.hands[seat].toSet())
+        seen.cards.toSet()
     }
 
     override fun chooseMove(state: KaiserState, seat: Int, legal: List<KaiserMove>): KaiserMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
-        return when (state.phase) {
-            KaiserPhase.BIDDING -> chooseBid(state, seat, legal)
-            KaiserPhase.PLAYING -> choosePlay(state, seat, legal)
-            else -> legal.first()
+        val profile = profiles.of(seat)
+        val seen = if (profile.level == AiLevel.HARD) observe(state, seat) else emptySet()
+        val move = try {
+            when (state.phase) {
+                KaiserPhase.BIDDING -> chooseBid(state, seat, legal, profile)
+                KaiserPhase.PLAYING -> choosePlay(state, seat, legal, profile, seen)
+                else -> legal.first()
+            }
+        } catch (e: RuntimeException) {
+            legal.first()
         }
+        return if (move in legal) move else legal.first()
     }
 
     /** Trump length and top cards, plus a nod to holding the counters. */
@@ -50,41 +80,137 @@ class KaiserAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         return value
     }
 
-    private fun chooseBid(state: KaiserState, seat: Int, legal: List<KaiserMove>): KaiserMove {
+    /**
+     * A finer rating on the same scale as [suitValue]: it rewards a run of top
+     * trump, short side suits to ruff with, and only counts the five of hearts
+     * when the hand can protect it.
+     */
+    private fun hardValue(hand: List<Card>, trump: Suit): Int {
+        val trumps = hand.filter { it.suit == trump }
+        var value = trumps.size * 3
+        for (card in trumps) {
+            value += when (card.rank) {
+                Rank.ACE -> 4
+                Rank.KING -> 3
+                Rank.QUEEN -> 1
+                else -> 0
+            }
+        }
+        // A king backed by the ace, or a queen backed by both, is a real trick.
+        val ranks = trumps.map { it.rank.order }.toSet()
+        if (Rank.ACE.order in ranks && Rank.KING.order in ranks) value += 2
+        if (Rank.ACE.order in ranks && Rank.KING.order in ranks && Rank.QUEEN.order in ranks) value += 1
+
+        for (card in hand) {
+            if (card.suit == trump) continue
+            if (card.rank == Rank.ACE) value += 2
+            else if (card.rank == Rank.KING && hand.any { it.suit == card.suit && it.rank == Rank.ACE }) value += 1
+        }
+        if (trumps.size >= 3) {
+            value += Suit.entries.filter { it != trump }.count { suit -> hand.none { it.suit == suit } } * 2
+        }
+        if (hand.contains(FIVE_OF_HEARTS)) {
+            val guarded = trump == Suit.HEARTS ||
+                hand.any { it.suit == Suit.HEARTS && it.rank == Rank.ACE }
+            value += if (guarded) 3 else -1
+        }
+        if (hand.contains(THREE_OF_SPADES)) value -= if (trump == Suit.SPADES) 1 else 2
+        return value
+    }
+
+    private fun chooseBid(
+        state: KaiserState,
+        seat: Int,
+        legal: List<KaiserMove>,
+        profile: AiProfile,
+    ): KaiserMove {
+        val hand = state.hands[seat]
+        val hard = profile.level == AiLevel.HARD
+        val easy = profile.level == AiLevel.EASY
+
         val naming = legal.filterIsInstance<NameTrump>()
         if (naming.isNotEmpty()) {
-            val hand = state.hands[seat]
-            val best = naming
-                .filter { it.suit != null }
-                .maxByOrNull { suitValue(hand, it.suit!!) }
-            return best ?: naming.first()
+            val named = naming.filter { it.suit != null }
+            return when {
+                hard -> named.maxByOrNull { hardValue(hand, it.suit!!) }
+                easy -> {
+                    val noisy = named.associateWith { suitValue(hand, it.suit!!) + profile.random.nextInt(-4, 5) }
+                    named.sortedByDescending { noisy.getValue(it) }.let { if (it.isEmpty()) null else profile.pick(it) }
+                }
+                else -> named.maxByOrNull { suitValue(hand, it.suit!!) }
+            } ?: naming.first()
         }
 
-        val hand = state.hands[seat]
-        val bestSuit = Suit.entries.maxByOrNull { suitValue(hand, it) } ?: Suit.SPADES
-        val strength = suitValue(hand, bestSuit)
+        val bestSuit: Suit
+        val strength: Int
+        if (hard) {
+            bestSuit = Suit.entries.maxBy { hardValue(hand, it) }
+            strength = hardValue(hand, bestSuit)
+        } else {
+            bestSuit = Suit.entries.maxByOrNull { suitValue(hand, it) } ?: Suit.SPADES
+            strength = suitValue(hand, bestSuit) + if (easy) profile.random.nextInt(-5, 6) else 0
+        }
 
         val bids = legal.filterIsInstance<MakeBid>().filter { !it.bid.noTrump }
-        if (strength >= difficulty.bidThreshold && bids.isNotEmpty()) {
+        var needed = profile.bolder(if (easy) EASY_BID_THRESHOLD else BID_THRESHOLD, -4.0)
+        // A spoiler steals contracts from the other side.
+        val bidder = state.highBidder
+        if (bidder != null && teamOf(bidder) != teamOf(seat) && profile.style.spite >= 0.5) needed -= 2.0
+        if (hard && bids.isNotEmpty()) {
+            val cheapest = bids.minBy { it.bid.points }
+            // A bigger contract needs a bigger hand, and a partner who is
+            // already bidding is better supported than outbid.
+            needed += 2.0 * (cheapest.bid.points - state.options.minimumBid)
+            if (bidder != null && bidder == partnerOf(seat)) needed += 4.0
+        }
+        if (strength >= needed && bids.isNotEmpty()) {
             // Bid the floor rather than reaching; the contract is what matters.
             return bids.minBy { it.bid.points }
         }
         return legal.firstOrNull { it is PassBid } ?: bids.minByOrNull { it.bid.points } ?: legal.first()
     }
 
-    private fun choosePlay(state: KaiserState, seat: Int, legal: List<KaiserMove>): KaiserMove {
+    private fun choosePlay(
+        state: KaiserState,
+        seat: Int,
+        legal: List<KaiserMove>,
+        profile: AiProfile,
+        seen: Set<Card>,
+    ): KaiserMove {
         val cards = legal.filterIsInstance<PlayCard>().map { it.card }
         if (cards.size == 1) return PlayCard(cards.first())
 
+        val bidder = state.highBidder
+        val defending = bidder != null && teamOf(bidder) != teamOf(seat)
+        val spiteful = defending && profile.style.spite >= 0.5
+        val best = if (profile.level == AiLevel.HARD) {
+            hardPlay(state, seat, cards, seen, bidder != null && !defending)
+        } else {
+            standardPlay(state, seat, cards, spiteful, profile)
+        }
+        if (profile.level != AiLevel.EASY) return PlayCard(best)
+
+        // Easy sometimes throws a high card, or a counter, at the wrong time.
+        val ranked = listOf(best) + (cards - best).sortedByDescending { it.rank.order }
+        return PlayCard(profile.pick(ranked))
+    }
+
+    private fun standardPlay(
+        state: KaiserState,
+        seat: Int,
+        cards: List<Card>,
+        spiteful: Boolean,
+        profile: AiProfile,
+    ): Card {
         if (state.trick.isEmpty()) {
             // Leading: pull with the top trump, else lead an ace.
             val trump = state.trump
             val topTrump = cards.filter { trump != null && it.suit == trump }
                 .maxByOrNull { it.rank.order }
-            if (topTrump != null && topTrump.rank.order >= Rank.KING.order) return PlayCard(topTrump)
+            if (topTrump != null && topTrump.rank.order >= Rank.KING.order) return topTrump
             val ace = cards.filter { it.rank == Rank.ACE }.maxByOrNull { it.rank.order }
-            if (ace != null) return PlayCard(ace)
-            return PlayCard(cards.minBy { it.rank.order })
+            if (ace != null) return ace
+            return cards.minBy { it.rank.order }
         }
 
         val ledSuit = state.trick.first().card.suit
@@ -96,22 +222,129 @@ class KaiserAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         // The five of hearts is worth more than the trick it rides in on.
         val fiveOnTable = state.trick.any { it.card == FIVE_OF_HEARTS }
         val threeOnTable = state.trick.any { it.card == THREE_OF_SPADES }
+        // A spoiler on the defence will not leave a trick to a partner who may be beaten.
+        val notLast = state.trick.size < 3
+        val letPartner = partnerWinning && !threeOnTable &&
+            !(spiteful && notLast && winners.isNotEmpty()) && !profile.slips()
 
         return when {
             // Partner has it and the trick is worth taking: let them have it,
             // unless the three of spades is in there.
-            partnerWinning && !threeOnTable -> PlayCard(cards.minBy { it.rank.order })
+            letPartner -> cards.minBy { it.rank.order }
 
             fiveOnTable && winners.isNotEmpty() ->
-                PlayCard(winners.maxBy { trickStrength(it, state.trump, ledSuit) })
+                winners.maxBy { trickStrength(it, state.trump, ledSuit) }
 
             // Nobody wants the three; duck if the trick is already lost.
-            threeOnTable && winners.isEmpty() -> PlayCard(cards.minBy { it.rank.order })
+            threeOnTable && winners.isEmpty() -> cards.minBy { it.rank.order }
 
             winners.isNotEmpty() && !threeOnTable ->
-                PlayCard(winners.minBy { trickStrength(it, state.trump, ledSuit) })
+                winners.minBy { trickStrength(it, state.trump, ledSuit) }
 
-            else -> PlayCard(cards.minBy { it.rank.order })
+            else -> cards.minBy { it.rank.order }
         }
     }
+
+    /**
+     * The strong player's choice: it remembers what has been played, so it
+     * knows which of its cards are sure winners, feeds the five of hearts to a
+     * partner who is safe, and buries the three of spades under the other side.
+     */
+    private fun hardPlay(
+        state: KaiserState,
+        seat: Int,
+        cards: List<Card>,
+        seen: Set<Card>,
+        bidding: Boolean,
+    ): Card {
+        val trump = state.trump
+        val hand = state.hands[seat]
+        val unseen = Decks.kaiser().filter { it !in seen && it !in hand }
+        val counters = setOf(FIVE_OF_HEARTS, THREE_OF_SPADES)
+
+        fun isBoss(card: Card): Boolean {
+            val mine = trickStrength(card, trump, card.suit)
+            val cardIsTrump = trump != null && card.suit == trump
+            return unseen.none { other ->
+                (cardIsTrump || trump == null || other.suit != trump) &&
+                    trickStrength(other, trump, card.suit) > mine
+            }
+        }
+
+        if (state.trick.isEmpty()) {
+            val plain = cards.filter { it !in counters }.ifEmpty { return cards.minBy { it.rank.order } }
+            val myTrump = plain.filter { trump != null && it.suit == trump }
+            val unseenTrump = unseen.count { trump != null && it.suit == trump }
+            val bossTrump = myTrump.filter { isBoss(it) }.maxByOrNull { it.rank.order }
+            if (bidding && unseenTrump > 0 && bossTrump != null) return bossTrump
+            plain.filter { it !in myTrump && isBoss(it) }.maxByOrNull { it.rank.order }?.let { return it }
+            if (bidding && unseenTrump > 0 && myTrump.size >= 2) return myTrump.maxBy { it.rank.order }
+            if (bossTrump != null) return bossTrump
+            val counts = hand.groupingBy { it.suit }.eachCount()
+            val offSuit = plain.filter { it !in myTrump }.ifEmpty { plain }
+            // The bidders draw a suit out; the defenders shorten one to ruff.
+            return if (bidding) {
+                offSuit.minWith(compareBy<Card>({ -(counts[it.suit] ?: 0) }, { it.rank.order }))
+            } else {
+                offSuit.minWith(compareBy<Card>({ counts[it.suit] ?: 0 }, { it.rank.order }))
+            }
+        }
+
+        val ledSuit = state.trick.first().card.suit
+        val best = state.trick.maxBy { trickStrength(it.card, trump, ledSuit) }
+        val partnerWinning = partnerOf(best.seat) == seat
+        val remaining = 4 - state.trick.size - 1
+        val bestStrength = trickStrength(best.card, trump, ledSuit)
+        val winners = cards.filter { trickStrength(it, trump, ledSuit) > bestStrength }
+        val fiveOnTable = state.trick.any { it.card == FIVE_OF_HEARTS }
+        val threeOnTable = state.trick.any { it.card == THREE_OF_SPADES }
+
+        fun sure(card: Card): Boolean =
+            remaining == 0 ||
+                unseen.none { trickStrength(it, trump, ledSuit) > trickStrength(card, trump, ledSuit) }
+
+        fun throwAway(): Card {
+            val plain = cards.filter { it !in counters }
+            if (plain.isNotEmpty()) return plain.minBy { it.rank.order }
+            // Only counters left: the five belongs with partner, the three does not.
+            return if (partnerWinning) cards.maxBy { it.rank.order } else cards.minBy { it.rank.order }
+        }
+
+        if (partnerWinning) {
+            if (sure(best.card)) {
+                // Partner has it: feed them the five of hearts if we can.
+                if (FIVE_OF_HEARTS in cards && trickStrength(FIVE_OF_HEARTS, trump, ledSuit) <= bestStrength) {
+                    return FIVE_OF_HEARTS
+                }
+                return throwAway()
+            }
+            if (!threeOnTable) {
+                winners.filter { sure(it) }.minByOrNull { trickStrength(it, trump, ledSuit) }?.let { return it }
+            }
+            return throwAway()
+        }
+
+        // The other side is winning.
+        if (threeOnTable) return throwAway()
+        if (fiveOnTable && winners.isNotEmpty()) {
+            val safe = winners.filter { sure(it) }
+            return if (safe.isNotEmpty()) {
+                safe.minBy { trickStrength(it, trump, ledSuit) }
+            } else {
+                winners.maxBy { trickStrength(it, trump, ledSuit) }
+            }
+        }
+        // Bury the three under a trick the other side is certain to take.
+        if (THREE_OF_SPADES in cards &&
+            trickStrength(THREE_OF_SPADES, trump, ledSuit) <= bestStrength &&
+            sure(best.card)
+        ) {
+            return THREE_OF_SPADES
+        }
+        if (winners.isNotEmpty()) {
+            val safe = winners.filter { sure(it) }
+            return (safe.ifEmpty { winners }).minBy { trickStrength(it, trump, ledSuit) }
+        }
+        return throwAway()
+    }
 }

app/src/main/java/org/prolibertate/games/game/mastermind/MastermindAi.kt

@@ -1,6 +1,8 @@
 package org.prolibertate.games.game.mastermind
 
 import kotlin.random.Random
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -16,9 +18,18 @@ import org.prolibertate.games.game.engine.GameAi
  * - **Strong** is Knuth's idea one ply deep: among the codes still standing, it
  *   plays the one whose *worst* possible answer leaves the smallest number of
  *   candidates behind, so it cannot be given a reply that tells it little.
+ *
+ * The computer difficulty chosen at setup picks the level: Easy plays Casual,
+ * Medium plays whatever the table's saved [MastermindOptions.level] says (Club
+ * for a new game) and Hard plays Strong. [level] overrides all of that, which is
+ * what the tests use.
  */
-class MastermindAi(private val level: MastermindLevel? = null) :
-    GameAi<MastermindState, MastermindMove> {
+class MastermindAi(
+    private val profiles: AiProfiles = AiProfiles.DEFAULT,
+    private val level: MastermindLevel? = null,
+) : GameAi<MastermindState, MastermindMove> {
+
+    constructor(level: MastermindLevel?) : this(AiProfiles.DEFAULT, level)
 
     override fun chooseMove(
         state: MastermindState,
@@ -26,7 +37,12 @@ class MastermindAi(private val level: MastermindLevel? = null) :
         legal: List<MastermindMove>,
     ): MastermindMove {
         require(legal.isNotEmpty()) { "No legal guess for seat $seat" }
-        val setting = level ?: state.options.level
+        val profile = profiles.of(seat)
+        val setting = level ?: when (profile.level) {
+            AiLevel.EASY -> MastermindLevel.CASUAL
+            AiLevel.MEDIUM -> state.options.level
+            AiLevel.HARD -> MastermindLevel.STRONG
+        }
 
         // Deterministic for a given position, so a host and a client watching
         // the same game agree on what the computer did.

app/src/main/java/org/prolibertate/games/game/meowdoku/MeowdokuAi.kt

@@ -0,0 +1,39 @@
+package org.prolibertate.games.game.meowdoku
+
+import org.prolibertate.games.game.engine.GameAi
+
+/**
+ * Plays the board for the one seat.
+ *
+ * Like peg solitaire's AI, nothing normally asks it to: the single seat belongs
+ * to the person holding the phone. It exists because an empty seat has to be
+ * playable by something, and because "the computer can finish this board" is a
+ * property worth testing — a generated puzzle that only a human could unpack is
+ * a broken promise about uniqueness.
+ *
+ * It reads the answer from the state. The rules hold it, the seat is alone with
+ * it, and a solver that deduced its way there would be the same length as the
+ * hint engine in the original game without making this seat any more honest.
+ */
+object MeowdokuAi : GameAi<MeowdokuState, MeowdokuMove> {
+
+    override fun chooseMove(
+        state: MeowdokuState,
+        seat: Int,
+        legal: List<MeowdokuMove>,
+    ): MeowdokuMove {
+        require(legal.isNotEmpty()) { "No move available" }
+        val places = legal.filterIsInstance<PlaceCat>().associateBy { it.square }
+
+        // The first cat still missing. A cross on its square is no obstacle:
+        // crossed squares take attempts like anything else, and a correct one
+        // replaces the cross.
+        for (row in 0 until state.side) {
+            if (state.cats.none { it.row == row }) {
+                places[Square(row, state.catCols[row])]?.let { return it }
+            }
+        }
+
+        return legal.first()
+    }
+}

app/src/main/java/org/prolibertate/games/game/meowdoku/MeowdokuGenerator.kt

@@ -0,0 +1,371 @@
+package org.prolibertate.games.game.meowdoku
+
+import kotlin.math.abs
+
+/**
+ * Builds the puzzles.
+ *
+ * A Meowdoku puzzle is an N by N board, a colouring of it into N regions, and a
+ * hidden answer of N cats. The three are not chosen separately: the cats come
+ * first, then the regions grow out from them so every region owns exactly one
+ * cat, then the finished board is checked to make sure it has only that one
+ * answer. A puzzle with two answers is a puzzle with no answer, since the second
+ * one cannot be deduced from what is printed.
+ *
+ * The construction is seeded and reproducible: the same seed gives the same
+ * board, which is what lets a saved game come back unchanged and lets a test
+ * speak about "the" puzzle for a seed.
+ */
+object MeowdokuGenerator {
+
+    /** Smallest and largest boards worth dealing; anything bigger is a wall. */
+    val MIN_SIDE = 4
+    val MAX_SIDE = 10
+
+    /**
+     * The answer, as the column of the cat in each row.
+     *
+     * One cat per row and one per column is already built in, since the rows are
+     * enumerated once each and no column is taken twice.
+     */
+    fun placeCats(side: Int, rng: SeededRng): IntArray {
+        val cols = IntArray(side) { -1 }
+        val placed = placeCatsFrom(0, side, cols, rng)
+        // Every board from four up has a placement, and the search is complete,
+        // so failing here would mean the generator itself is broken.
+        check(placed) { "No way to settle $side cats on a $side board" }
+        return cols
+    }
+
+    private fun placeCatsFrom(row: Int, side: Int, cols: IntArray, rng: SeededRng): Boolean {
+        if (row == side) return true
+        for (col in rng.shuffled(cols.indices.toList())) {
+            if (catFitsHere(row, col, cols)) {
+                cols[row] = col
+                if (placeCatsFrom(row + 1, side, cols, rng)) return true
+                cols[row] = -1
+            }
+        }
+        return false
+    }
+
+    /**
+     * Whether a cat at [row],[col] is at peace with the cats in the rows above.
+     *
+     * No shared column, and no shared corner: a cat grooms the squares touching
+     * its own on all eight sides, so a neighbour one step away in any direction
+     * is too close.
+     */
+    fun catFitsHere(row: Int, col: Int, cols: IntArray): Boolean {
+        for (r in 0 until row) {
+            val c = cols[r]
+            if (c == col) return false
+            if (abs(r - row) <= 1 && abs(c - col) <= 1) return false
+        }
+        return true
+    }
+
+    /**
+     * The colours of the board, as a region id per square.
+     *
+     * Each region starts as the cat it contains and grows outwards one square at
+     * a time. The first [strips] regions are grown as straight bars along their
+     * cat's row or column, alternating which way they run: a board of nothing but
+     * blobs reads as texture, and the bars are what give the regions a shape a
+     * player can reason about. The rest take the shortest border square, which
+     * keeps them clumped rather than trailing off into the far corner.
+     */
+    fun growRegions(side: Int, catCols: IntArray, rng: SeededRng, strips: Int): Array<IntArray> {
+        val regions = Array(side) { IntArray(side) { -1 } }
+        val dirs = listOf(0 to 1, 0 to -1, 1 to 0, -1 to 0)
+
+        // Region i owns the cat in row i, which is where its colour starts.
+        for (r in 0 until side) regions[r][catCols[r]] = r
+
+        val sizes = IntArray(side) { 1 }
+        var unassigned = side * side - side
+
+        // The straight bars are laid first, and the rest is grown around them.
+        // The straight bars are laid first, and the rest is grown around them.
+        // Bar i runs along its cat's row when i is even, down its column when odd.
+        val stripRegions = rng.shuffled((0 until side).toList()).take(strips.coerceIn(0, side - 1)).toSet()
+        for ((n, region) in stripRegions.withIndex()) {
+            val r0 = region
+            val c0 = catCols[r0]
+            val extra = 1 + rng.nextInt(3)
+            var added = 0
+            if (n % 2 == 0) {
+                var left = c0 - 1
+                var right = c0 + 1
+                while (added < extra) {
+                    val goLeft = rng.nextBoolean()
+                    when {
+                        goLeft && left >= 0 && regions[r0][left] == -1 ->
+                            regions[r0][left--] = region
+                        right < side && regions[r0][right] == -1 ->
+                            regions[r0][right++] = region
+                        left >= 0 && regions[r0][left] == -1 ->
+                            regions[r0][left--] = region
+                        else -> break
+                    }
+                    sizes[region]++
+                    unassigned--
+                    added++
+                }
+            } else {
+                var up = r0 - 1
+                var down = r0 + 1
+                while (added < extra) {
+                    val goUp = rng.nextBoolean()
+                    when {
+                        goUp && up >= 0 && regions[up][c0] == -1 ->
+                            regions[up--][c0] = region
+                        down < side && regions[down][c0] == -1 ->
+                            regions[down++][c0] = region
+                        up >= 0 && regions[up][c0] == -1 ->
+                            regions[up--][c0] = region
+                        else -> break
+                    }
+                    sizes[region]++
+                    unassigned--
+                    added++
+                }
+            }
+        }
+
+        // What is left goes to whichever neighbouring region is smallest, so no
+        // region dies young while another sprawls.
+        var guard = side * side * 20
+        while (unassigned > 0 && guard > 0) {
+            guard--
+            for (r in 0 until side) {
+                for (c in 0 until side) {
+                    if (regions[r][c] != -1) continue
+                    var best = -1
+                    for ((dr, dc) in dirs) {
+                        val nr = r + dr
+                        val nc = c + dc
+                        if (nr !in 0 until side || nc !in 0 until side) continue
+                        val neighbour = regions[nr][nc]
+                        if (neighbour == -1 || neighbour in stripRegions) continue
+                        if (best == -1 || sizes[neighbour] < sizes[best]) best = neighbour
+                    }
+                    if (best == -1) {
+                        for ((dr, dc) in dirs) {
+                            val nr = r + dr
+                            val nc = c + dc
+                            if (nr !in 0 until side || nc !in 0 until side) continue
+                            val neighbour = regions[nr][nc]
+                            if (neighbour != -1 && (best == -1 || sizes[neighbour] < sizes[best])) {
+                                best = neighbour
+                            }
+                        }
+                    }
+                    if (best != -1) {
+                        regions[r][c] = best
+                        sizes[best]++
+                        unassigned--
+                    }
+                }
+            }
+        }
+        for (r in 0 until side) {
+            for (c in 0 until side) {
+                if (regions[r][c] == -1) regions[r][c] = 0
+            }
+        }
+        return regions
+    }
+
+    /**
+     * How many answers this coloured board has, up to [limit].
+     *
+     * A depth-first search with the obvious propagation: once a row is given a
+     * cat, the squares that cat excludes — its column, the rows beside it, and
+     * everything in its colour — lose their candidates. A row whose candidate
+     * list runs out fails immediately and the search backtracks, which is what
+     * makes the count finish quickly on boards of this size.
+     *
+     * Nothing about the true cats is handed to the search; it sees the colours
+     * and the rules and no more.
+     */
+    fun countSolutions(side: Int, regions: Array<IntArray>, limit: Int = 2): Int {
+        val candidates = Array(side) { r -> (0 until side).toMutableSet() }
+        val colsTaken = BooleanArray(side)
+        val coloursTaken = BooleanArray(side)
+        val count = IntArray(1)
+        solve(0, side, regions, candidates, colsTaken, coloursTaken, count, limit)
+        return count[0]
+    }
+
+    private fun solve(
+        row: Int,
+        side: Int,
+        regions: Array<IntArray>,
+        candidates: Array<MutableSet<Int>>,
+        colsTaken: BooleanArray,
+        coloursTaken: BooleanArray,
+        count: IntArray,
+        limit: Int,
+    ) {
+        if (count[0] >= limit) return
+        if (row == side) {
+            count[0]++
+            return
+        }
+        for (col in candidates[row].toList()) {
+            val colour = regions[row][col]
+            if (colsTaken[col] || coloursTaken[colour]) continue
+            val undo = exclude(row, col, side, regions, candidates)
+            if (undo != null) {
+                colsTaken[col] = true
+                coloursTaken[colour] = true
+                solve(row + 1, side, regions, candidates, colsTaken, coloursTaken, count, limit)
+                colsTaken[col] = false
+                coloursTaken[colour] = false
+                undo()
+            }
+            if (count[0] >= limit) return
+        }
+    }
+
+    /**
+     * Crosses out what the cat at [row],[col] forbids, and returns the function
+     * that puts it back. Returns null if some row loses its last candidate,
+     * which means this placement is a dead end.
+     */
+    private fun exclude(
+        row: Int,
+        col: Int,
+        side: Int,
+        regions: Array<IntArray>,
+        candidates: Array<MutableSet<Int>>,
+    ): (() -> Unit)? {
+        val colour = regions[row][col]
+        val saved = Array(side) { r -> candidates[r].toMutableSet() }
+        var dead = false
+        for (r in 0 until side) {
+            if (r == row) continue
+            candidates[r].remove(col)
+            if (abs(r - row) == 1) {
+                candidates[r].remove(col - 1)
+                candidates[r].remove(col + 1)
+            }
+            candidates[r].removeAll { c -> regions[r][c] == colour }
+            if (candidates[r].isEmpty()) dead = true
+        }
+        if (dead) {
+            for (r in 0 until side) candidates[r] = saved[r]
+            return null
+        }
+        return {
+            for (r in 0 until side) candidates[r] = saved[r]
+        }
+    }
+
+    /**
+     * A complete puzzle: the colours, the answer, and a proof it is unique.
+     *
+     * Generation is rejection rather than construction — build a board, check it,
+     * throw it away if the check fails — and the attempts walk forward from
+     * [seed] so a seed that has a puzzle within a few tries gives the same one
+     * every time.
+     */
+    fun generate(side: Int, seed: Long): MeowdokuPuzzle? {
+        val base = (seed xor (seed ushr 32)).toInt()
+        for (attempt in 0 until MAX_ATTEMPTS) {
+            val rng = SeededRng(base + attempt * 7919)
+            val catCols = placeCats(side, rng)
+            val regions = growRegions(side, catCols, SeededRng(base * 31 + attempt * 104729), strips = side / 2)
+            if (distinctColours(side, regions) != side) continue
+            if (countSolutions(side, regions, limit = 2) != 1) continue
+            return MeowdokuPuzzle(side, regions, catCols)
+        }
+        return null
+    }
+
+    private const val MAX_ATTEMPTS = 4000
+
+    /** How many different colours a board actually shows. */
+    private fun distinctColours(side: Int, regions: Array<IntArray>): Int =
+        regions.flatMap { it.toList() }.distinct().size
+}
+
+/**
+ * A board and its answer.
+ *
+ * The answer is stored rather than re-derived because the rules need it to
+ * referee: a tap either lands a cat or loses a heart, and that is judged against
+ * the solution, not against whether the player could have deduced it.
+ */
+data class MeowdokuPuzzle(
+    val side: Int,
+    /** Region id per square; ids run 0 until side. */
+    val regions: Array<IntArray>,
+    /** The column of the cat in each row. */
+    val catCols: IntArray,
+) {
+    fun regionOf(row: Int, col: Int): Int = regions[row][col]
+
+    /** Every colour id, in board order, for a legend or a palette. */
+    val colours: List<Int> get() = (0 until side).toList()
+
+    fun solutionSquares(): List<Pair<Int, Int>> =
+        catCols.indices.map { it to catCols[it] }
+
+    override fun equals(other: Any?): Boolean = other is MeowdokuPuzzle &&
+        side == other.side &&
+        regions.contentDeepEquals(other.regions) &&
+        catCols.contentEquals(other.catCols)
+
+    override fun hashCode(): Int = 31 * side + regions.contentDeepHashCode()
+}
+
+/**
+ * A 32-bit linear congruential generator.
+ *
+ * Deliberately not [kotlin.random.Random]: that one is seeded per-JVM and can
+ * change between releases, and a puzzle generator that drifts silently corrupts
+ * saved games. This one is small, explicit, and the same everywhere.
+ */
+class SeededRng(seed: Int) {
+    private var state = if (seed == 0) DEFAULT_SEED else seed
+
+    /** The next 31 bits, as a non-negative int. */
+    fun nextInt(): Int {
+        state = state * MULTIPLIER + 1
+        return (state ushr 1) and 0x7FFF_FFFF
+    }
+
+    /** A value in 0 until [bound], taken by rejection so it stays uniform. */
+    fun nextInt(bound: Int): Int {
+        require(bound > 0)
+        while (true) {
+            val n = nextInt()
+            // 2^31 is a multiple of no useful number of squares, so a bare
+            // modulus biases the low values; the slack is thrown and redrawn.
+            if (n < Int.MAX_VALUE - (Int.MAX_VALUE % bound)) return n % bound
+        }
+    }
+
+    fun nextBoolean(): Boolean = nextInt(2) == 0
+
+    /** The same list every time for the same seed, in a different order. */
+    fun <T> shuffled(items: List<T>): List<T> {
+        val out = items.toMutableList()
+        for (i in out.lastIndex downTo 1) {
+            val j = nextInt(i + 1)
+            val tmp = out[i]
+            out[i] = out[j]
+            out[j] = tmp
+        }
+        return out
+    }
+
+    private companion object {
+        // The constants of the old VAX C library's `rand`, which are well tested
+        // and give a period of the full 31 bits.
+        const val MULTIPLIER = 1103515245
+        const val DEFAULT_SEED = 0x5DEECE66D.toInt()
+    }
+}

app/src/main/java/org/prolibertate/games/game/meowdoku/MeowdokuModel.kt

@@ -0,0 +1,119 @@
+package org.prolibertate.games.game.meowdoku
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+// Meowdoku hides N cats in an N by N board: exactly one cat in every row, every
+// column and every colour, and no two cats sharing even a corner. A tap crosses
+// a square over; a second tap on that square asks the board whether a cat
+// lives there. A right answer lands the cat, a wrong one costs a heart and
+// keeps the cross — so the crossing over is both the player's note and the
+// first half of every guess, and the hearts are what stop it being a lottery.
+
+/** One square of the board. */
+@Serializable
+data class Square(val row: Int, val col: Int)
+
+@Serializable
+data class MeowdokuOptions(
+    /** The board is [side] by [side], and the answer is [side] cats. */
+    val side: Int = 6,
+    /**
+     * How many wrong taps the board forgives. The original game deals three,
+     * and the hearts on a level are part of its difficulty rather than a
+     * courtesy.
+     */
+    val hearts: Int = 3,
+    /** How many cats the board will show on demand. */
+    val hints: Int = 3,
+) {
+    init {
+        require(side in MeowdokuGenerator.MIN_SIDE..MeowdokuGenerator.MAX_SIDE) {
+            "No board of $side squares a side"
+        }
+        require(hearts in 1..9) { "A board with no hearts is lost before it is dealt" }
+        require(hints in 0..9) { "Hints must read on the board, not scroll" }
+    }
+}
+
+/**
+ * The dealt board plus the marks on it.
+ *
+ * [cats] and [marks] are sets rather than a state per square because a square's
+ * story is exactly those two memberships: nothing is a cat and crossed, and the
+ * empty squares carry no information worth storing.
+ */
+@Serializable
+data class MeowdokuState(
+    val options: MeowdokuOptions,
+    /** The region id of every square, row by row. Ids run 0 until [side]. */
+    val regions: List<List<Int>>,
+    /** The column of the cat in each row — the answer, kept so taps can be judged. */
+    val catCols: List<Int>,
+    /** Cats the player has found (or a hint has shown). */
+    val cats: Set<Square>,
+    /** Squares crossed over: wrong taps and pencil marks alike. */
+    val marks: Set<Square>,
+    val heartsLeft: Int,
+    val hintsLeft: Int,
+    /** Wrong taps so far, which is how a solved board says how it was solved. */
+    val wrongCats: Int,
+    /** The last square touched, and whether touching it cost a heart. */
+    val lastSquare: Square? = null,
+    val lastWrong: Boolean = false,
+    val log: List<String>,
+) {
+    val side: Int get() = options.side
+
+    /** Cats found, out of the [side] the board hides. */
+    val catsFound: Int get() = cats.size
+
+    val solved: Boolean get() = catsFound == side
+
+    /** Out of hearts, with cats still missing. */
+    val lost: Boolean get() = heartsLeft == 0 && !solved
+
+    fun regionOf(square: Square): Int = regions[square.row][square.col]
+
+    fun isCatSquare(square: Square): Boolean = catCols[square.row] == square.col
+}
+
+/** What the player may do to a board. */
+@Serializable
+sealed interface MeowdokuMove
+
+/**
+ * The second tap of a double tap: the cat attempt.
+ *
+ * One move rather than two, because that is what the player is doing: the board
+ * decides whether the tap found a cat or cost a heart. The square may carry the
+ * cross its own first tap just drew — that cross is part of the double tap,
+ * not a decision against it — and a correct attempt replaces it.
+ */
+@Serializable
+@SerialName("cat")
+data class PlaceCat(val square: Square) : MeowdokuMove
+
+/**
+ * Draws or erases a cross on a square with no cat on it.
+ *
+ * This is the first tap of a tap pair and every cell of a drag stroke, so it is
+ * the note-taking half of the scheme: free, unrewarded, and the board cannot
+ * lose a heart over it. A cross drawn here can still be tapped through with a
+ * cat attempt — the note is the player's, and only they get to change their
+ * mind about it.
+ */
+@Serializable
+@SerialName("pencil")
+data class TogglePencil(val square: Square) : MeowdokuMove
+
+/**
+ * Spends a hint to show the cat in the first row that lacks one.
+ *
+ * The original game sells hints; here they are simply counted, and the one
+ * choice that has to be made about them — a hint is placed by the board, not
+ * guessed at by the player — is the same either way.
+ */
+@Serializable
+@SerialName("hint")
+data object TakeHint : MeowdokuMove

app/src/main/java/org/prolibertate/games/game/meowdoku/MeowdokuRules.kt

@@ -0,0 +1,197 @@
+package org.prolibertate.games.game.meowdoku
+
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.prolibertate.games.game.GameCatalog
+import org.prolibertate.games.game.engine.GameRules
+import org.prolibertate.games.game.engine.TableConfig
+
+/**
+ * Meowdoku as a pure state machine. See RULES-meowdoku.md.
+ *
+ * The engine is a second single-seat game, alongside peg solitaire, and it
+ * inherits the same freedom: there is nobody to hide anything from, so
+ * [viewFor] hands out the whole board including the answer. The answer lives in
+ * the state rather than being re-derived because judging a tap against a
+ * deduction the player could have made is a different thing from judging it
+ * against what the board was dealt — and the deduction engine (crossing out
+ * rows, columns and colours) belongs to the player, not the referee.
+ */
+object MeowdokuRules : GameRules<MeowdokuState, MeowdokuMove> {
+
+    override val gameId: String = GameCatalog.MEOWDOKU
+
+    /** The one seat. */
+    const val SOLO_SEAT: Int = 0
+
+    private val json = Json {
+        ignoreUnknownKeys = true
+        encodeDefaults = true
+    }
+
+    override fun initialState(config: TableConfig): MeowdokuState {
+        val options = json.decodeFromString<MeowdokuOptions>(config.optionsJson)
+        require(config.seats.size == 1) {
+            "Meowdoku seats one, not ${config.seats.size}"
+        }
+        val puzzle = deal(options.side, config.seed)
+        return MeowdokuState(
+            options = options,
+            regions = puzzle.regions.map { it.toList() },
+            catCols = puzzle.catCols.toList(),
+            cats = emptySet(),
+            marks = emptySet(),
+            heartsLeft = options.hearts,
+            hintsLeft = options.hints,
+            wrongCats = 0,
+            log = listOf("A ${options.side} by ${options.side} board, ${options.side} cats to find."),
+        )
+    }
+
+    /**
+     * Deals until the board is good.
+     *
+     * A seed whose first attempts all fail to produce a unique board moves the
+     * seed along rather than giving up: the same table asked twice gets the
+     * same board both times, which is what a saved game and a unit test need.
+     */
+    private fun deal(side: Int, seed: Long): MeowdokuPuzzle {
+        var trySeed = seed
+        repeat(DEAL_TRIES) {
+            MeowdokuGenerator.generate(side, trySeed)?.let { return it }
+            trySeed = trySeed * 6364136223846793005L + 1442695040888963407L
+        }
+        error("No unique ${side} x $side board within $DEAL_TRIES deals of seed $seed")
+    }
+
+    private const val DEAL_TRIES = 8
+
+    /**
+     * Every tap the board would take.
+     *
+     * The scheme is the original's: the first tap crosses a square over and
+     * opens a short window, and a second tap in that window is the cat attempt
+     * — so an attempt is offered on every square without a cat, crossed or
+     * not. The cross the attempt replaces is exactly the cross the first tap
+     * drew. Cats, once placed, are never tapped again: they are not a guess
+     * you take back.
+     *
+     * The list is written row by row, which is also the order the hint uses.
+     */
+    override fun legalMoves(state: MeowdokuState, seat: Int): List<MeowdokuMove> {
+        if (seat != SOLO_SEAT || isFinished(state)) return emptyList()
+        val cats = ArrayList<MeowdokuMove>()
+        val pencils = ArrayList<MeowdokuMove>()
+        for (row in 0 until state.side) {
+            for (col in 0 until state.side) {
+                val square = Square(row, col)
+                if (square in state.cats) continue
+                cats += PlaceCat(square)
+                pencils += TogglePencil(square)
+            }
+        }
+        val hint = if (state.hintsLeft > 0) listOf(TakeHint) else emptyList()
+        return cats + pencils + hint
+    }
+
+    override fun applyMove(
+        state: MeowdokuState,
+        seat: Int,
+        move: MeowdokuMove,
+    ): MeowdokuState {
+        require(seat == SOLO_SEAT) { "Meowdoku has one seat" }
+        require(move in legalMoves(state, seat)) { "$move is not a legal move" }
+        return when (move) {
+            is PlaceCat -> tap(state, move.square)
+            is TogglePencil -> pencil(state, move.square)
+            TakeHint -> hint(state)
+        }
+    }
+
+    /**
+     * The second tap of a double tap: found a cat, or lost a heart.
+     *
+     * A correct tap clears the cross the first tap left behind — the cat
+     * replaces it. A wrong one leaves the cross where it is and spends a
+     * heart, because a wrong square crossed twice is the same mistake twice,
+     * and the board remembers it either way.
+     */
+    private fun tap(state: MeowdokuState, square: Square): MeowdokuState {
+        if (state.isCatSquare(square)) {
+            val next = state.copy(
+                cats = state.cats + square,
+                marks = state.marks - square,
+                lastSquare = square,
+                lastWrong = false,
+            )
+            val note = if (next.solved) {
+                "All ${next.side} cats, ${next.wrongCats} wrong taps."
+            } else {
+                "Found a cat at row ${square.row + 1}, column ${square.col + 1}."
+            }
+            return next.copy(log = next.log + note)
+        }
+        val hearts = state.heartsLeft - 1
+        val next = state.copy(
+            marks = state.marks + square,
+            heartsLeft = hearts,
+            wrongCats = state.wrongCats + 1,
+            lastSquare = square,
+            lastWrong = true,
+        )
+        return if (hearts == 0) {
+            next.copy(log = next.log + "Out of hearts, with ${next.side - next.catsFound} cats still hiding.")
+        } else {
+            next
+        }
+    }
+
+    private fun pencil(state: MeowdokuState, square: Square): MeowdokuState {
+        val marks = if (square in state.marks) state.marks - square else state.marks + square
+        return state.copy(marks = marks, lastSquare = square, lastWrong = false)
+    }
+
+    /**
+     * Shows the cat in the first row without one.
+     *
+     * A revealed cat lands like a found one — and erases a pencil cross on its
+     * square, because the point of a hint is that the player stops having to
+     * work out whether the board contradicts their own notes.
+     */
+    private fun hint(state: MeowdokuState): MeowdokuState {
+        val row = (0 until state.side).first { r -> state.cats.none { it.row == r } }
+        val square = Square(row, state.catCols[row])
+        return state.copy(
+            cats = state.cats + square,
+            marks = state.marks - square,
+            hintsLeft = state.hintsLeft - 1,
+            lastSquare = square,
+            lastWrong = false,
+            log = state.log + "A hint shows the cat in row ${row + 1}.",
+        )
+    }
+
+    /** A board is finished when it is solved or when the hearts run out. */
+    override fun isFinished(state: MeowdokuState): Boolean = state.solved || state.lost
+
+    override fun currentSeat(state: MeowdokuState): Int? =
+        if (isFinished(state)) null else SOLO_SEAT
+
+    override fun summary(state: MeowdokuState): String = when {
+        state.solved -> "Solved with ${state.heartsLeft} hearts to spare"
+        state.lost -> "Lost with ${state.catsFound} of ${state.side} cats found"
+        else -> "${state.catsFound} of ${state.side} cats, ${state.heartsLeft} hearts left"
+    }
+
+    /**
+     * Nothing to strip. One person plays, and the answer in the state is there
+     * for the referee, not as a secret. Should a second seat ever race through
+     * the same board, this is where [MeowdokuState.catCols] gets hidden.
+     */
+    override fun viewFor(state: MeowdokuState, seat: Int): MeowdokuState = state
+
+    override fun encodeState(state: MeowdokuState): String = json.encodeToString(state)
+    override fun decodeState(json: String): MeowdokuState = this.json.decodeFromString(json)
+    override fun encodeMove(move: MeowdokuMove): String = json.encodeToString(move)
+    override fun decodeMove(json: String): MeowdokuMove = this.json.decodeFromString(json)
+}

app/src/main/java/org/prolibertate/games/game/morris/MorrisAi.kt

@@ -1,6 +1,9 @@
 package org.prolibertate.games.game.morris
 
 import kotlin.random.Random
+import kotlin.math.roundToInt
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -19,7 +22,20 @@ import org.prolibertate.games.game.engine.GameAi
  *
  * Strength comes from the table's own options unless a level is passed in.
  */
-class MorrisAi(private val level: MorrisLevel? = null) : GameAi<MorrisState, MorrisMove> {
+class MorrisAi(
+    private val profiles: AiProfiles = AiProfiles.DEFAULT,
+    private val level: MorrisLevel? = null,
+) : GameAi<MorrisState, MorrisMove> {
+
+    // Viewpoint and weights for the move being chosen. At the default (balanced)
+    // style they equal the plain constants, so Medium is unchanged.
+    private var rootSeat = 0
+    private var wMill = MILL
+    private var wAlmost = ALMOST
+    private var wTheirAlmost = ALMOST
+    private var wMobility = MOBILITY
+    private var wTheirMobility = MOBILITY
+    private var wDanger = DANGER
 
     /**
      * Ceiling on how much thinking any one move gets, so a phone does not stall
@@ -32,10 +48,29 @@ class MorrisAi(private val level: MorrisLevel? = null) : GameAi<MorrisState, Mor
 
     override fun chooseMove(state: MorrisState, seat: Int, legal: List<MorrisMove>): MorrisMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
+        val profile = profiles.of(seat)
         val setting = level ?: state.options.level
         if (legal.size == 1) return legal.first()
 
-        nodeBudget = NODE_BUDGET
+        val bold = profile.style.boldness
+        val spite = profile.style.spite
+        rootSeat = seat
+        // Bold seats value mills and half-built mills more; cautious ones value
+        // mobility and avoiding the three-piece trap. Spiteful seats weigh the
+        // opponent's mill threats and freedom of movement more.
+        wMill = MILL + (bold * 6).roundToInt()
+        wAlmost = ALMOST + (bold * 3).roundToInt()
+        wTheirAlmost = ALMOST + (spite * 4).roundToInt() + (-bold * 2).roundToInt()
+        wMobility = MOBILITY + (-bold * 1).roundToInt()
+        wTheirMobility = MOBILITY + (spite * 2).roundToInt() + (-bold * 1).roundToInt()
+        wDanger = DANGER + (-bold * 10).roundToInt()
+
+        val maxDepth = when (profile.level) {
+            AiLevel.EASY -> maxOf(2, setting.depth - 2)
+            AiLevel.MEDIUM -> setting.depth
+            AiLevel.HARD -> setting.depth + 1
+        }
+        nodeBudget = if (profile.level == AiLevel.HARD) HARD_NODE_BUDGET else NODE_BUDGET
         nodesUsed = 0
 
         // Deterministic for a given position, so a host and a client replaying
@@ -46,7 +81,7 @@ class MorrisAi(private val level: MorrisLevel? = null) : GameAi<MorrisState, Mor
         var best = legal.first()
         var scored = legal.map { it to 0 }
 
-        for (depth in 1..setting.depth) {
+        for (depth in 1..maxDepth) {
             val results = mutableListOf<Pair<MorrisMove, Int>>()
             val ordered = order(legal, preferred = best)
             for (move in ordered) {
@@ -73,7 +108,16 @@ class MorrisAi(private val level: MorrisLevel? = null) : GameAi<MorrisState, Mor
 
         val bestScore = scored.maxOf { it.second }
         val acceptable = scored.filter { it.second >= bestScore - setting.slack() }
-        return acceptable[random.nextInt(acceptable.size)].first
+        val chosen = acceptable[random.nextInt(acceptable.size)].first
+        if (profile.level != AiLevel.EASY) return chosen
+
+        // Easy now and then settles for another sound-looking move: only ones
+        // within about a piece of the best, never a real blunder.
+        val ranked = listOf(chosen) + scored
+            .filter { it.first != chosen && it.second >= bestScore - EASY_TOLERANCE }
+            .sortedByDescending { it.second }
+            .map { it.first }
+        return profile.pick(ranked)
     }
 
     /** How far below best a move may score and still be considered. */
@@ -155,16 +199,17 @@ class MorrisAi(private val level: MorrisLevel? = null) : GameAi<MorrisState, Mor
 
     /** The position from the point of view of the side to move. */
     private fun evaluate(state: MorrisState): Int {
-        val us = state.turn
-        val them = other(us)
+        val me = rootSeat
+        val them = other(me)
 
-        var score = PIECE * (state.remaining(us) - state.remaining(them))
-        score += MILL * (state.millCount(us) - state.millCount(them))
-        score += ALMOST * (almostMills(state, us) - almostMills(state, them))
-        score += MOBILITY * (mobility(state, us) - mobility(state, them))
-        score += LADDER * (midEdgeCount(state, us) - midEdgeCount(state, them))
-        score -= DANGER * (onThree(state, us) - onThree(state, them))
-        return score
+        var score = PIECE * (state.remaining(me) - state.remaining(them))
+        score += wMill * (state.millCount(me) - state.millCount(them))
+        score += wAlmost * almostMills(state, me) - wTheirAlmost * almostMills(state, them)
+        score += wMobility * mobility(state, me) - wTheirMobility * mobility(state, them)
+        score += LADDER * (midEdgeCount(state, me) - midEdgeCount(state, them))
+        score -= wDanger * (onThree(state, me) - onThree(state, them))
+        // Scored from the root seat's side; flip for the side to move.
+        return if (state.turn == me) score else -score
     }
 
     /**
@@ -215,6 +260,8 @@ class MorrisAi(private val level: MorrisLevel? = null) : GameAi<MorrisState, Mor
         const val INFINITY = 1_000_000
         const val WIN = 100_000
         const val NODE_BUDGET = 120_000
+        const val HARD_NODE_BUDGET = 280_000
+        const val EASY_TOLERANCE = 120
 
         const val PIECE = 120
         const val MILL = 26

app/src/main/java/org/prolibertate/games/game/pirates/PiratesAi.kt

@@ -1,6 +1,10 @@
 package org.prolibertate.games.game.pirates
 
+import kotlin.math.roundToInt
 import kotlin.random.Random
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -14,17 +18,73 @@ import org.prolibertate.games.game.engine.GameAi
  * from the Bulgars' side and negated for the pirates, so the two cannot drift
  * apart and start valuing the same position differently.
  */
-class PiratesAi(private val level: PiratesLevel? = null) : GameAi<PiratesState, PiratesMove> {
+class PiratesAi(
+    private val profiles: AiProfiles = AiProfiles.DEFAULT,
+    private val level: PiratesLevel? = null,
+) : GameAi<PiratesState, PiratesMove> {
 
     private var nodeBudget = 0
     private var nodesUsed = 0
 
+    // Evaluation weights for the seat now choosing; the standard values unless
+    // a style or level bends them. Set at the top of each chooseMove.
+    private var wBulgar = BULGAR
+    private var wStronghold = IN_STRONGHOLD
+    private var wAdvance = ADVANCE
+    private var wExposed = EXPOSED
+    private var wRoom = PIRATE_ROOM
+
+    private fun tune(profile: AiProfile, seat: Int) {
+        val bold = profile.style.boldness
+        val spite = profile.style.spite
+        var bulgar = 1.0
+        var stronghold = 1.0
+        var advance = 1.0
+        var exposed = 1.0
+        var room = 1.0
+        if (seat == BULGAR_SEAT) {
+            // A bold crowd pushes forward and risks being jumped; a cautious one stays tight.
+            exposed -= 0.3 * bold
+            advance += 0.3 * bold
+            // A spoiler squeezes the pirates' room.
+            room += 0.4 * spite
+        } else {
+            // A bold pirate hunts; a cautious one keeps its room to move.
+            bulgar += 0.15 * bold
+            room -= 0.3 * bold
+            // A spoiler pays more attention to stopping the climb.
+            stronghold += 0.4 * spite
+            advance += 0.4 * spite
+        }
+        if (profile.level == AiLevel.EASY) exposed *= 0.5 // overlooks some threats
+        wBulgar = (BULGAR * bulgar).roundToInt()
+        wStronghold = (IN_STRONGHOLD * stronghold).roundToInt()
+        wAdvance = (ADVANCE * advance).roundToInt()
+        wExposed = (EXPOSED * exposed).roundToInt()
+        wRoom = (PIRATE_ROOM * room).roundToInt()
+    }
+
     override fun chooseMove(state: PiratesState, seat: Int, legal: List<PiratesMove>): PiratesMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
-        val setting = level ?: state.options.level
         if (legal.size == 1) return legal.first()
+        val profile = profiles.of(seat)
+        val base = level ?: state.options.level
+        tune(profile, seat)
 
-        nodeBudget = NODE_BUDGET
+        val hard = profile.level == AiLevel.HARD
+        val easy = profile.level == AiLevel.EASY
+        val maxDepth = when (profile.level) {
+            AiLevel.MEDIUM -> base.depth
+            AiLevel.EASY -> minOf(base.depth, 2)
+            AiLevel.HARD -> base.depth + 2
+        }
+        val slack = when (profile.level) {
+            AiLevel.MEDIUM -> base.slack()
+            AiLevel.EASY -> maxOf(base.slack(), 40)
+            AiLevel.HARD -> 0
+        }
+
+        nodeBudget = if (hard) HARD_NODE_BUDGET else NODE_BUDGET
         nodesUsed = 0
 
         val random = Random(state.moveLog.size * 31L + state.positionKey().hashCode())
@@ -32,18 +92,23 @@ class PiratesAi(private val level: PiratesLevel? = null) : GameAi<PiratesState,
         var best = legal.first()
         var scored = legal.map { it to 0 }
 
-        for (depth in 1..setting.depth) {
+        for (depth in 1..maxDepth) {
             val results = mutableListOf<Pair<PiratesMove, Int>>()
             val ordered = order(legal, preferred = best)
+            var bestSoFar = -INFINITY
             for (move in ordered) {
+                // A hard seat only needs the exact value of moves that tie or beat
+                // the best so far, so everything else is searched against a window.
+                val floor = if (hard && results.isNotEmpty()) bestSoFar - 1 else -INFINITY
                 val score = -negamax(
                     state = PiratesRules.advanced(state, move),
                     depth = depth - 1,
                     alpha = -INFINITY,
-                    beta = INFINITY,
+                    beta = -floor,
                     ply = 1,
                 )
                 results += move to score
+                if (score > bestSoFar) bestSoFar = score
                 if (nodesUsed >= nodeBudget) break
             }
             if (nodesUsed >= nodeBudget && results.size < ordered.size) break
@@ -51,9 +116,16 @@ class PiratesAi(private val level: PiratesLevel? = null) : GameAi<PiratesState,
             best = results.maxBy { it.second }.first
         }
 
+        if (easy) {
+            val ranked = scored.sortedByDescending { it.second }.map { it.first }
+            val picked = profile.pick(ranked)
+            if (picked != ranked.first() && picked in legal) return picked
+        }
+
         val bestScore = scored.maxOf { it.second }
-        val acceptable = scored.filter { it.second >= bestScore - setting.slack() }
-        return acceptable[random.nextInt(acceptable.size)].first
+        val acceptable = scored.filter { it.second >= bestScore - slack }
+        val chosen = acceptable[random.nextInt(acceptable.size)].first
+        return if (chosen in legal) chosen else legal.first()
     }
 
     private fun PiratesLevel.slack(): Int = when (this) {
@@ -115,22 +187,22 @@ class PiratesAi(private val level: PiratesLevel? = null) : GameAi<PiratesState,
     private fun evaluate(state: PiratesState): Int {
         var bulgarView = 0
 
-        bulgarView += state.count(BULGAR_SEAT) * BULGAR
-        bulgarView += state.stronghold() * IN_STRONGHOLD
+        bulgarView += state.count(BULGAR_SEAT) * wBulgar
+        bulgarView += state.stronghold() * wStronghold
 
         // How far up the board the crowd has come. The stronghold is at the
         // top, so a low row number is ground gained.
         for (point in 0 until POINTS) {
             if (state.board[point] != BULGAR_SEAT) continue
-            bulgarView += (GRID - 1 - rowOf(point)) * ADVANCE
+            bulgarView += (GRID - 1 - rowOf(point)) * wAdvance
             // A Bulgar with an empty point directly behind it on a line is one
             // a pirate can jump. Being unjumpable is most of staying alive.
-            if (isExposed(state, point)) bulgarView -= EXPOSED
+            if (isExposed(state, point)) bulgarView -= wExposed
         }
 
         // Room for the pirates to work in, which is what the Bulgars are
         // slowly taking away.
-        bulgarView -= pirateMobility(state) * PIRATE_ROOM
+        bulgarView -= pirateMobility(state) * wRoom
 
         return if (state.turn == BULGAR_SEAT) bulgarView else -bulgarView
     }
@@ -160,6 +232,7 @@ class PiratesAi(private val level: PiratesLevel? = null) : GameAi<PiratesState,
         const val INFINITY = 1_000_000
         const val WIN = 100_000
         const val NODE_BUDGET = 150_000
+        const val HARD_NODE_BUDGET = 400_000
 
         const val BULGAR = 100
         const val IN_STRONGHOLD = 55

app/src/main/java/org/prolibertate/games/game/president/PresidentAi.kt

@@ -1,63 +1,85 @@
 package org.prolibertate.games.game.president
 
+import org.prolibertate.games.game.cards.Card
+import org.prolibertate.games.game.cards.Rank
+import org.prolibertate.games.game.cards.Suit
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
- * A heuristic President opponent.
+ * A President opponent whose strength and temperament come from the seat's profile.
  *
- * It sheds low cards early, spends the cheapest set that takes the pile, and
- * holds twos back for when they are worth something. It does not count cards.
+ * MEDIUM (the default) sheds low cards early, spends the cheapest set that takes
+ * the pile, and holds twos back for when they are worth something. It does not
+ * count cards.
+ *
+ * EASY spends high cards freely when leading and sometimes plays a worse set or
+ * passes when it should have played. HARD reads the round's log to count which
+ * ranks are still out, leads so that its remaining hand is unbeatable, blocks an
+ * opponent who is about to go out, and keeps its high cards back when a cheap
+ * pile is not worth them.
  */
-class PresidentAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
+class PresidentAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) :
     GameAi<PresidentState, PresidentMove> {
 
-    enum class Difficulty(
-        /** Rank above which a card is hoarded rather than spent to lead. */
-        val hoardAbove: Int,
-    ) {
-        /** Plays whatever is cheapest, whenever it can. */
-        EASY(hoardAbove = 99),
-
-        NORMAL(hoardAbove = 13),
-
-        /** Sits on high cards until late, then dumps them. */
-        CAUTIOUS(hoardAbove = 11),
-    }
-
     override fun chooseMove(
         state: PresidentState,
         seat: Int,
         legal: List<PresidentMove>,
     ): PresidentMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
+        val profile = profiles.of(seat)
         val plays = legal.filterIsInstance<PlayCards>()
         if (plays.isEmpty()) return legal.first()
 
-        return if (state.setSize == 0) chooseLead(state, seat, plays) else chooseFollow(state, plays, legal)
+        val move: PresidentMove = when (profile.level) {
+            AiLevel.MEDIUM -> standard(state, seat, plays, legal, hoardAbove = HOARD_ABOVE)
+            AiLevel.EASY -> easy(state, seat, plays, legal, profile)
+            AiLevel.HARD -> hard(state, seat, plays, legal, profile)
+        }
+        return if (move in legal) move else legal.first()
     }
 
+    private fun standard(
+        state: PresidentState,
+        seat: Int,
+        plays: List<PlayCards>,
+        legal: List<PresidentMove>,
+        hoardAbove: Int,
+    ): PresidentMove =
+        if (state.setSize == 0) {
+            leadRanking(state, seat, plays, hoardAbove).first()
+        } else {
+            chooseFollow(state, plays, legal)
+        }
+
+    // -----------------------------------------------------------------------
+    // Standard plan
+    // -----------------------------------------------------------------------
+
     /**
      * Leading is a chance to shed. Prefer the biggest set of the lowest rank,
      * which clears junk fastest without spending anything valuable.
      */
-    private fun chooseLead(
+    private fun leadRanking(
         state: PresidentState,
         seat: Int,
         plays: List<PlayCards>,
-    ): PresidentMove {
+        hoardAbove: Int,
+    ): List<PlayCards> {
         val endgame = state.hands[seat].size <= 4
         val candidates = plays.filter { play ->
-            endgame || presidentRank(play.cards.first()) <= difficulty.hoardAbove
+            endgame || presidentRank(play.cards.first()) <= hoardAbove
         }.ifEmpty { plays }
 
-        return candidates
-            .sortedWith(
-                compareBy(
-                    { presidentRank(it.cards.first()) },
-                    { -it.cards.size },
-                )
-            )
-            .first()
+        return candidates.sortedWith(
+            compareBy<PlayCards>(
+                { presidentRank(it.cards.first()) },
+                { -it.cards.size },
+            ),
+        )
     }
 
     /**
@@ -82,4 +104,188 @@ class PresidentAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
 
         return cheapest
     }
+
+    // -----------------------------------------------------------------------
+    // Easy
+    // -----------------------------------------------------------------------
+
+    private fun easy(
+        state: PresidentState,
+        seat: Int,
+        plays: List<PlayCards>,
+        legal: List<PresidentMove>,
+        profile: AiProfile,
+    ): PresidentMove {
+        if (state.setSize == 0) {
+            // Never hoards: leads aces and twos as readily as anything else.
+            return profile.pick(leadRanking(state, seat, plays, hoardAbove = 99))
+        }
+        val best = chooseFollow(state, plays, legal)
+        val alternatives = plays.sortedBy { presidentRank(it.cards.first()) }
+        val ranked = buildList<PresidentMove> {
+            add(best)
+            addAll(alternatives.filter { it != best })
+            if (PassTurn in legal && best != PassTurn) add(PassTurn)
+        }
+        return profile.pick(ranked)
+    }
+
+    // -----------------------------------------------------------------------
+    // Hard
+    // -----------------------------------------------------------------------
+
+    /** Ranks still unaccounted for: not in this seat's hand and not played yet this round. */
+    private class Counts(state: PresidentState, seat: Int) {
+        private val unseen = HashMap<Int, Int>()
+
+        init {
+            for (rank in 3..15) unseen[rank] = 4
+            state.hands[seat].forEach { dec(presidentRank(it)) }
+            val log = state.log
+            val start = log.indexOfLast { ROUND_MARK.matches(it) } + 1
+            for (i in start until log.size) {
+                val line = log[i]
+                val at = line.indexOf(" plays ")
+                if (!line.startsWith("Seat ") || at < 0) continue
+                line.substring(at + " plays ".length).removeSuffix(".").split(' ').forEach { token ->
+                    LABELS[token]?.let { dec(presidentRank(it)) }
+                }
+            }
+        }
+
+        private fun dec(rank: Int) {
+            unseen[rank] = maxOf(0, (unseen[rank] ?: 0) - 1)
+        }
+
+        fun of(rank: Int): Int = unseen[rank] ?: 0
+
+        /** Could an opponent still hold a set of [size] that beats a set of [size] at [rank]? */
+        fun beatable(rank: Int, size: Int, options: PresidentOptions): Boolean {
+            if (options.twosClear && rank != 15 && of(15) >= size) return true
+            if (options.fourOfAKindBomb && size == 4 && (3..15).any { it != rank && of(it) == 4 }) return true
+            return (rank + 1..15).any { of(it) >= size }
+        }
+    }
+
+    private fun hard(
+        state: PresidentState,
+        seat: Int,
+        plays: List<PlayCards>,
+        legal: List<PresidentMove>,
+        profile: AiProfile,
+    ): PresidentMove {
+        val hand = state.hands[seat]
+        // Going out beats any plan.
+        plays.firstOrNull { it.cards.size == hand.size }?.let { return it }
+
+        val counts = Counts(state, seat)
+        val others = (0 until state.options.playerCount).filter { it != seat && !state.isOut(it) }
+        return if (state.setSize == 0) {
+            hardLead(state, seat, plays, counts, others, profile)
+        } else {
+            hardFollow(state, seat, plays, legal, counts, others, profile)
+        }
+    }
+
+    /** An opponent who could empty their hand with a set the size of the one on top, or is the score leader close to out. */
+    private fun outThreat(
+        state: PresidentState,
+        seat: Int,
+        others: List<Int>,
+        profile: AiProfile,
+    ): Boolean {
+        if (others.any { state.handCounts[it] <= maxOf(1, state.setSize) }) return true
+        if (profile.style.spite >= 0.5) {
+            val leader = others.maxByOrNull { state.scores[it] }
+            if (leader != null && state.handCounts[leader] <= 2) return true
+        }
+        return false
+    }
+
+    private fun hardLead(
+        state: PresidentState,
+        seat: Int,
+        plays: List<PlayCards>,
+        counts: Counts,
+        others: List<Int>,
+        profile: AiProfile,
+    ): PresidentMove {
+        val hand = state.hands[seat]
+        val options = state.options
+        val oneCardLeft = others.any { state.handCounts[it] == 1 }
+
+        fun unbeatableAfter(play: PlayCards): Boolean {
+            val remaining = hand.toMutableList().also { left -> play.cards.forEach { left.remove(it) } }
+            return remaining.groupBy { presidentRank(it) }
+                .all { (rank, cards) -> !counts.beatable(rank, cards.size, options) }
+        }
+
+        fun key(play: PlayCards): Double {
+            val rank = presidentRank(play.cards.first())
+            val size = play.cards.size
+            var k = rank - 0.9 * size
+            if (unbeatableAfter(play)) return k - 50.0
+            // Leading aces and twos spends control that is worth more later.
+            if (rank >= 14 && hand.size > 4) k += 20.0
+            // Somebody is down to one card: a single would let them out if they can beat it.
+            if (oneCardLeft && size == 1) k += 10.0 + (15 - rank) * 2.0
+            // A bold seat is happier to lead its strong sets early.
+            if (rank >= 11) k -= profile.style.boldness * 2.0
+            return k
+        }
+        return plays.minBy { key(it) }
+    }
+
+    private fun hardFollow(
+        state: PresidentState,
+        seat: Int,
+        plays: List<PlayCards>,
+        legal: List<PresidentMove>,
+        counts: Counts,
+        others: List<Int>,
+        profile: AiProfile,
+    ): PresidentMove {
+        val hand = state.hands[seat]
+        val options = state.options
+        val canPass = PassTurn in legal
+        val threat = outThreat(state, seat, others, profile)
+
+        val withoutTwos = plays.filter { play -> play.cards.none { isTwo(it) } }
+        val pool = withoutTwos.ifEmpty { plays }
+        val cheapest = pool.minBy { presidentRank(it.cards.first()) }
+
+        if (threat) {
+            // Block them: take the pile with the cheapest set nobody can beat,
+            // or failing that the cheapest set there is, twos included.
+            val sure = plays.filter { !counts.beatable(presidentRank(it.cards.first()), it.cards.size, options) }
+                .minByOrNull { presidentRank(it.cards.first()) }
+            return sure ?: plays.minBy { presidentRank(it.cards.first()) }
+        }
+
+        val spendingTwo = cheapest.cards.any { isTwo(it) }
+        if (spendingTwo) {
+            val remaining = hand.toMutableList().also { left -> cheapest.cards.forEach { left.remove(it) } }
+            val runOut = remaining.groupBy { presidentRank(it) }
+                .all { (rank, cards) -> !counts.beatable(rank, cards.size, options) }
+            val worthIt = state.setRank >= 13 || state.pile.size >= 4 || hand.size <= 4 || runOut
+            if (!worthIt && canPass) return PassTurn
+            return cheapest
+        }
+
+        // A cheap pile is not worth a high card while the hand is still big.
+        val gap = profile.bolder(6.0, 2.0)
+        val cost = presidentRank(cheapest.cards.first()) - state.setRank
+        if (canPass && hand.size > 5 && cost > gap && presidentRank(cheapest.cards.first()) >= 12) {
+            return PassTurn
+        }
+        return cheapest
+    }
+
+    private companion object {
+        const val HOARD_ABOVE = 13
+        val ROUND_MARK = Regex("^Round \\d+\\.$")
+        val LABELS: Map<String, Card> = Suit.entries.flatMap { suit ->
+            Rank.standard.map { Card(it, suit) }
+        }.associateBy { it.label }
+    }
 }

app/src/main/java/org/prolibertate/games/game/sequence/SequenceAi.kt

@@ -1,5 +1,8 @@
 package org.prolibertate.games.game.sequence
 
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -8,18 +11,39 @@ import org.prolibertate.games.game.engine.GameAi
  * It scores every legal placement by how much it advances one of its own runs
  * and how badly it spoils an opponent's, holds its jacks back until they are
  * worth spending, and never looks at anyone's hand.
+ *
+ * Per seat, from [profiles]: Easy mostly ignores your runs, burns its one-eyed
+ * jacks on anything and sometimes settles for a lesser square; Hard blocks hard,
+ * saves jacks for real threats, always takes a completed run and always stops
+ * one that is one square from done. Boldness leans towards building over
+ * blocking and spite the other way round.
  */
-class SequenceAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
+class SequenceAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) :
     GameAi<SequenceState, SequenceMove> {
 
-    enum class Difficulty(val blockWeight: Int, val jackPatience: Int) {
-        /** Builds its own runs and mostly ignores yours. */
-        EASY(blockWeight = 1, jackPatience = 0),
+    /** The numbers one seat plays with, worked out from its level and style. */
+    private class Tuning(
+        val ownWeight: Double,
+        val blockWeight: Double,
+        val jackPatience: Double,
+        val finishing: Boolean,
+    )
 
-        NORMAL(blockWeight = 3, jackPatience = 3),
-
-        /** Blocks aggressively and saves jacks for real threats. */
-        CAUTIOUS(blockWeight = 5, jackPatience = 4),
+    private fun tuningOf(profile: AiProfile): Tuning {
+        val (block, patience) = when (profile.level) {
+            AiLevel.EASY -> 1.0 to 0.0
+            AiLevel.MEDIUM -> 3.0 to 3.0
+            AiLevel.HARD -> 5.0 to 4.0
+        }
+        val style = profile.style
+        val easy = profile.level == AiLevel.EASY
+        return Tuning(
+            ownWeight = 4.0 + style.boldness,
+            blockWeight = block - style.boldness * 0.8 + style.spite * 2.0,
+            // Only a seat that is paying attention changes its mind about jacks.
+            jackPatience = if (easy) patience else patience + style.boldness - style.spite,
+            finishing = profile.level == AiLevel.HARD,
+        )
     }
 
     override fun chooseMove(
@@ -28,15 +52,30 @@ class SequenceAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         legal: List<SequenceMove>,
     ): SequenceMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
+        val profile = profiles.of(seat)
+        val tuning = tuningOf(profile)
         val team = state.teamOf(seat)
 
         // Clearing a dead card is free value when nothing better is on offer.
         val exchange = legal.filterIsInstance<ExchangeDeadCard>().firstOrNull()
         if (exchange != null && legal.none { it is PlaceChip }) return exchange
 
-        val best = legal
+        val placements = legal
             .filterIsInstance<PlaceChip>()
-            .maxByOrNull { scorePlacement(state, it, team) }
+            .map { it to scorePlacement(state, it, team, tuning) }
+            .sortedByDescending { it.second }
+            .map { it.first }
+        val best = if (placements.isEmpty()) {
+            null
+        } else if (tuning.finishing) {
+            // A run that completes, or a run of the opponent's that would, is
+            // never something to be talked out of.
+            placements.first()
+        } else {
+            // Easy only: the others never slip. Only the better few are in play,
+            // so a slip is a weaker square rather than a wasted card.
+            profile.pick(placements.take(4))
+        }
 
         val removal = legal
             .filterIsInstance<RemoveChip>()
@@ -45,7 +84,7 @@ class SequenceAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         // Spend a one-eyed jack only on a genuinely dangerous chip.
         if (removal != null) {
             val threat = threatAt(state, removal.cell, state.chips[removal.cell])
-            if (threat >= difficulty.jackPatience) return removal
+            if (threat >= tuning.jackPatience && !profile.slips()) return removal
         }
 
         return best ?: removal ?: exchange ?: legal.first()
@@ -56,14 +95,25 @@ class SequenceAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
      * opponent's run it interrupts. Wild jacks are discounted so they are not
      * burned on an ordinary square.
      */
-    private fun scorePlacement(state: SequenceState, move: PlaceChip, team: Int): Int {
+    private fun scorePlacement(
+        state: SequenceState,
+        move: PlaceChip,
+        team: Int,
+        tuning: Tuning,
+    ): Double {
         val ours = runPotential(state, move.cell, team)
         val theirs = (0 until state.options.teamCount)
             .filter { it != team }
             .maxOfOrNull { runPotential(state, move.cell, it) }
             ?: 0
 
-        var score = ours * 4 + theirs * difficulty.blockWeight
+        var score = ours * tuning.ownWeight + theirs * tuning.blockWeight
+        if (tuning.finishing) {
+            // A potential of five through this square means placing here
+            // completes the run (for whoever places it).
+            if (ours >= RUN_LENGTH) score += 100.0
+            if (theirs >= RUN_LENGTH) score += 60.0 else if (theirs == RUN_LENGTH - 1) score += 8.0
+        }
         // Central squares sit on more possible lines than edge squares.
         val row = SequenceBoard.rowOf(move.cell)
         val col = SequenceBoard.colOf(move.cell)

app/src/main/java/org/prolibertate/games/game/tayu/TayuAi.kt

@@ -1,5 +1,8 @@
 package org.prolibertate.games.game.tayu
 
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -18,17 +21,53 @@ import org.prolibertate.games.game.engine.GameAi
  *
  * [level] overrides the table's own setting, which is what the tests use;
  * ordinarily it is left null and read from [TayuOptions.level].
+ *
+ * Per seat, from [profiles]: the table's setting says which terms count at all
+ * (Gentle ignores the opponent entirely and that is respected at every level).
+ * Within Full strength, Easy blocks and steers less and sometimes takes one of
+ * its better few placements rather than the best; Hard blocks and steers harder.
+ * Boldness weights its own axis against the opponent's, spite weights blocking.
  */
-class TayuAi(private val level: TayuLevel? = null) : GameAi<TayuState, TayuMove> {
+class TayuAi(
+    private val profiles: AiProfiles = AiProfiles.DEFAULT,
+    private val level: TayuLevel? = null,
+) : GameAi<TayuState, TayuMove> {
+
+    constructor(level: TayuLevel) : this(AiProfiles.DEFAULT, level)
+
+    private class Weights(val own: Double, val block: Double, val reach: Double)
+
+    private fun weightsOf(setting: TayuLevel, profile: AiProfile): Weights {
+        var own = setting.ownWeight.toDouble()
+        var block = setting.blockWeight.toDouble()
+        var reach = setting.reachWeight.toDouble()
+        // Gentle is a table rule, not a skill level: it stays as it is.
+        if (setting.blockWeight > 0) {
+            when (profile.level) {
+                AiLevel.EASY -> { block *= 0.4; reach *= 0.5 }
+                AiLevel.MEDIUM -> Unit
+                AiLevel.HARD -> { block *= 1.35; reach *= 1.5 }
+            }
+            own *= 1.0 + 0.15 * profile.style.boldness
+            block *= 1.0 - 0.15 * profile.style.boldness + 0.4 * profile.style.spite
+        }
+        return Weights(own, block, reach)
+    }
 
     override fun chooseMove(state: TayuState, seat: Int, legal: List<TayuMove>): TayuMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
+        val profile = profiles.of(seat)
         val setting = level ?: state.options.level
         if (legal.size == 1) return legal.first()
-        return legal.maxByOrNull { rate(state, seat, it, setting) } ?: legal.first()
+        val weights = weightsOf(setting, profile)
+        val rated = legal.map { it to rate(state, seat, it, weights) }
+        if (profile.level != AiLevel.EASY) return rated.maxByOrNull { it.second }?.first ?: legal.first()
+        // Easy: one of its better few placements, not always the best.
+        val ranked = rated.sortedByDescending { it.second }.take(EASY_POOL).map { it.first }
+        return profile.pick(ranked)
     }
 
-    private fun rate(state: TayuState, seat: Int, move: TayuMove, setting: TayuLevel): Int {
+    private fun rate(state: TayuState, seat: Int, move: TayuMove, weights: Weights): Double {
         val after = TayuRules.previewPlacement(state, seat, move)
         val mine = state.axisOf(seat)
         val theirs = if (mine == Axis.NORTH_SOUTH) Axis.EAST_WEST else Axis.NORTH_SOUTH
@@ -43,15 +82,15 @@ class TayuAi(private val level: TayuLevel? = null) : GameAi<TayuState, TayuMove>
         // Skipped rather than multiplied by zero: the gentle setting is the whole
         // reason to avoid walking the open mouths at all, and this runs for every
         // one of a thousand-odd candidate placements.
-        val reach = if (setting.reachWeight == 0) {
+        val reach = if (weights.reach == 0.0) {
             0
         } else {
             (pull(after, mine) - pull(after, theirs)) / REACH_SCALE
         }
 
-        return setting.ownWeight * ours -
-            setting.blockWeight * opposing +
-            setting.reachWeight * reach
+        return weights.own * ours -
+            weights.block * opposing +
+            weights.reach * reach
     }
 
     /**
@@ -82,5 +121,8 @@ class TayuAi(private val level: TayuLevel? = null) : GameAi<TayuState, TayuMove>
     private companion object {
         /** Brings the open-mouth term onto the same scale as the score term. */
         const val REACH_SCALE = 8
+
+        /** How many top-rated placements Easy chooses among. */
+        const val EASY_POOL = 6
     }
 }

app/src/main/java/org/prolibertate/games/game/wizard/WizardAi.kt

@@ -3,8 +3,13 @@ package org.prolibertate.games.game.wizard
 import org.prolibertate.games.game.cards.Card
 import org.prolibertate.games.game.cards.Rank
 import org.prolibertate.games.game.cards.Suit
+import org.prolibertate.games.game.cards.Decks
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 import kotlin.math.abs
+import kotlin.math.pow
 import kotlin.math.roundToInt
 
 /**
@@ -15,52 +20,99 @@ import kotlin.math.roundToInt
  * high it is and whether it is trump. In play it chases tricks while it is
  * short of its bid and ducks once it has them, which is the whole game.
  */
-class WizardAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
+class WizardAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) :
     GameAi<WizardState, WizardMove> {
 
-    enum class Difficulty(
-        /**
-         * Added to the expected-trick count before rounding. Optimists overbid
-         * and go down; pessimists underbid and get caught taking tricks they
-         * did not want.
-         */
-        val bidBias: Double,
-    ) {
-        EASY(bidBias = 0.35),
-        NORMAL(bidBias = 0.0),
-        CAUTIOUS(bidBias = -0.25),
+    private companion object {
+        /** Optimists overbid and go down; Easy leans this way. */
+        const val EASY_BID_BIAS = 0.35
+        val DECK: List<Card> = Decks.wizard()
+    }
+
+    /** Cards this AI has watched played in the current round, per seat it plays. */
+    private val memory = HashMap<Int, SeenCards>()
+
+    private class SeenCards {
+        var key: Long = Long.MIN_VALUE
+        val cards = HashSet<Card>()
+    }
+
+    /** Public information only: cards that have appeared on the table this round. */
+    private fun observe(state: WizardState, seat: Int): Set<Card> = synchronized(memory) {
+        val seen = memory.getOrPut(seat) { SeenCards() }
+        val key = state.seed * 1_000_003L + state.round
+        if (key != seen.key || state.phase == WizardPhase.BIDDING) {
+            seen.key = key
+            seen.cards.clear()
+        }
+        state.trick.forEach { seen.cards.add(it.card) }
+        state.completedTrick.forEach { seen.cards.add(it.card) }
+        seen.cards.removeAll(state.hands[seat].toSet())
+        seen.cards.toSet()
     }
 
     override fun chooseMove(state: WizardState, seat: Int, legal: List<WizardMove>): WizardMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
-        return when (state.phase) {
-            WizardPhase.BIDDING -> chooseBid(state, seat, legal)
-            WizardPhase.PLAYING -> choosePlay(state, seat, legal)
-            else -> legal.first()
+        val profile = profiles.of(seat)
+        val seen = if (profile.level == AiLevel.HARD) observe(state, seat) else emptySet()
+        val move = try {
+            when (state.phase) {
+                WizardPhase.BIDDING -> chooseBid(state, seat, legal, profile)
+                WizardPhase.PLAYING -> choosePlay(state, seat, legal, profile, seen)
+                else -> legal.first()
+            }
+        } catch (e: RuntimeException) {
+            legal.first()
         }
+        return if (move in legal) move else legal.first()
     }
 
     // -----------------------------------------------------------------------
     // Bidding
     // -----------------------------------------------------------------------
 
-    private fun chooseBid(state: WizardState, seat: Int, legal: List<WizardMove>): WizardMove {
+    private fun chooseBid(
+        state: WizardState,
+        seat: Int,
+        legal: List<WizardMove>,
+        profile: AiProfile,
+    ): WizardMove {
+        val hand = state.hands[seat]
+        val hard = profile.level == AiLevel.HARD
+        val easy = profile.level == AiLevel.EASY
+
         val naming = legal.filterIsInstance<ChooseTrump>()
         if (naming.isNotEmpty()) {
-            val hand = state.hands[seat]
-            val best = naming.maxByOrNull { suitStrength(hand, it.suit) }
-            return best ?: naming.first()
+            return when {
+                hard -> naming.maxByOrNull { hardExpected(state, hand, it.suit) }
+                easy -> {
+                    val noisy = naming.associateWith { suitStrength(hand, it.suit) + profile.random.nextDouble(-0.8, 0.8) }
+                    profile.pick(naming.sortedByDescending { noisy.getValue(it) })
+                }
+                else -> naming.maxByOrNull { suitStrength(hand, it.suit) }
+            } ?: naming.first()
         }
 
         val bids = legal.filterIsInstance<MakeBid>()
         if (bids.isEmpty()) return legal.first()
 
-        val wanted = (expectedTricks(state.hands[seat], state.trump) + difficulty.bidBias)
-            .roundToInt()
-            .coerceIn(0, state.cardsThisRound)
+        var expected = if (hard) hardExpected(state, hand, state.trump) else expectedTricks(hand, state.trump)
+        if (hard) {
+            // The last to bid knows how many tricks the others have left on the table.
+            val others = state.bids.filterNotNull()
+            if (others.size == state.options.playerCount - 1) {
+                expected = expected * 0.75 + (state.cardsThisRound - others.sum()) * 0.25
+            }
+        }
+        if (easy) expected += EASY_BID_BIAS + profile.random.nextDouble(-0.8, 0.8)
+        // A gambler bids up, a cautious seat bids down.
+        expected += profile.bolder(0.0, 0.3)
+
+        val wanted = expected.roundToInt().coerceIn(0, state.cardsThisRound)
         // Screw-the-dealer may have taken the number we wanted away, so settle
         // for the nearest one still on offer.
-        return bids.minBy { abs(it.tricks - wanted) }
+        val ranked = bids.sortedBy { abs(it.tricks - wanted) }
+        return if (easy) profile.pick(ranked) else ranked.first()
     }
 
     /** How much of a hand a given trump suit would be worth. */
@@ -92,22 +144,88 @@ class WizardAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
         return expected
     }
 
+    /**
+     * The chance [card] takes a trick, from the cards that could still beat it.
+     *
+     * [pool] is every card that might be in somebody else's hand and [q] the
+     * chance any one of them is, and each higher card only threatens the trick
+     * if it lands in the same one, which is less likely the longer the round.
+     */
+    private fun winProb(card: Card, pool: List<Card>, trump: Suit?, q: Double, tricks: Int): Double {
+        if (isWizardCard(card)) return 1.0
+        if (isJester(card)) return 0.0
+        val wizards = pool.count { isWizardCard(it) && it != card }
+        val ordinary = { c: Card -> !isWizardCard(c) && !isJester(c) }
+        val trumpCard = trump != null && card.suit == trump
+        val higher = pool.count { ordinary(it) && it.suit == card.suit && it.rank.order > card.rank.order }
+        var danger = (higher + wizards).toDouble()
+        if (!trumpCard && trump != null) {
+            val voidFactor = 1.0 / (1.0 + 0.5 * (tricks - 1))
+            danger += voidFactor * pool.count { ordinary(it) && it.suit == trump }
+        }
+        val sequencing = 1.0 / (1.0 + 0.35 * (tricks - 1))
+        return (1.0 - (q * sequencing).coerceIn(0.0, 1.0)).pow(danger)
+    }
+
+    /** Expected tricks from the cards that could still be out, calibrated so the average hand scores its fair share. */
+    private fun hardExpected(state: WizardState, hand: List<Card>, trump: Suit?): Double {
+        val n = state.cardsThisRound
+        val players = state.options.playerCount
+        val inPlay = DECK.filter { it != state.trumpCard }
+        val mine = inPlay.filter { it !in hand }
+        val q = ((players - 1) * n).toDouble() / mine.size.coerceAtLeast(1)
+
+        val own = hand.sumOf { winProb(it, mine, trump, q, n) }
+        val average = inPlay.sumOf { winProb(it, inPlay, trump, q, n) } / inPlay.size
+        val scale = if (average > 0.0) (1.0 / (players * average)).coerceIn(0.5, 2.0) else 1.0
+        return own * scale
+    }
+
     // -----------------------------------------------------------------------
     // Play
     // -----------------------------------------------------------------------
 
-    private fun choosePlay(state: WizardState, seat: Int, legal: List<WizardMove>): WizardMove {
+    private fun choosePlay(
+        state: WizardState,
+        seat: Int,
+        legal: List<WizardMove>,
+        profile: AiProfile,
+        seen: Set<Card>,
+    ): WizardMove {
         val cards = legal.filterIsInstance<PlayCard>().map { it.card }
         if (cards.size == 1) return PlayCard(cards.first())
 
+        val hard = profile.level == AiLevel.HARD
         val bid = state.bids[seat] ?: 0
         val stillNeeded = bid - state.tricksWon[seat]
         val tricksLeft = state.hands[seat].size
         // Chase while we are short, and only while there are enough tricks left
-        // to be worth chasing.
-        val wantsTrick = stillNeeded > 0 && stillNeeded <= tricksLeft
+        // to be worth chasing. (The careful player keeps chasing even when the
+        // bid is out of reach: every trick still cuts the penalty.)
+        val wantsTrick = stillNeeded > 0 && (hard || stillNeeded <= tricksLeft)
+        // A spoiler who has already blown their own bid takes tricks off anyone
+        // who needs exactly one more.
+        val spoiling = profile.style.spite >= 0.5 && stillNeeded < 0
 
-        if (state.trick.isEmpty()) return PlayCard(chooseLead(cards, state.trump, wantsTrick))
+        val best = if (hard) {
+            hardPlay(state, seat, cards, seen, wantsTrick, spoiling, stillNeeded, tricksLeft)
+        } else {
+            standardPlay(state, cards, wantsTrick, spoiling)
+        }
+        if (profile.level != AiLevel.EASY) return PlayCard(best)
+
+        // Easy sometimes burns a strong card at the wrong moment.
+        val ranked = listOf(best) + (cards - best).sortedByDescending { it.rank.order }
+        return PlayCard(profile.pick(ranked))
+    }
+
+    private fun standardPlay(
+        state: WizardState,
+        cards: List<Card>,
+        wantsTrick: Boolean,
+        spoiling: Boolean,
+    ): Card {
+        if (state.trick.isEmpty()) return chooseLead(cards, state.trump, wantsTrick)
 
         val ledSuit = ledSuitOf(state.trick)
         val order = state.trick.size
@@ -122,15 +240,99 @@ class WizardAi(private val difficulty: Difficulty = Difficulty.NORMAL) :
 
         return when {
             // Take it as cheaply as we can.
-            wantsTrick && winners.isNotEmpty() -> PlayCard(winners.minBy { strengthOf(it) })
+            wantsTrick && winners.isNotEmpty() -> winners.minBy { strengthOf(it) }
+            // Spite: stop somebody from landing the bid they need.
+            spoiling && winners.isNotEmpty() && victimNeedsOne(state) -> winners.minBy { strengthOf(it) }
             // Cannot take it, or do not want it: throw the least useful card.
-            losers.isNotEmpty() -> PlayCard(losers.minBy { strengthOf(it) })
+            losers.isNotEmpty() -> losers.minBy { strengthOf(it) }
             // Everything we hold wins, and we did not want the trick. Take it
             // with the weakest winner so the good cards stay for later.
-            else -> PlayCard(cards.minBy { strengthOf(it) })
+            else -> cards.minBy { strengthOf(it) }
         }
     }
 
+    /** Whether whoever is winning the trick right now needs exactly this trick to make their bid. */
+    private fun victimNeedsOne(state: WizardState): Boolean {
+        val ledSuit = ledSuitOf(state.trick)
+        val leading = state.trick
+            .withIndex()
+            .maxByOrNull { (index, played) -> trickStrength(played.card, index, state.trump, ledSuit) }
+            ?: return false
+        val victim = leading.value.seat
+        return (state.bids[victim] ?: return false) - state.tricksWon[victim] == 1
+    }
+
+    /**
+     * The strong player's choice. It keeps track of which cards are gone to
+     * judge how likely each of its own is to win, spends sure winners when it
+     * needs tricks, and sheds its most dangerous cards onto tricks it will
+     * lose anyway when it does not.
+     */
+    private fun hardPlay(
+        state: WizardState,
+        seat: Int,
+        cards: List<Card>,
+        seen: Set<Card>,
+        wantsTrick: Boolean,
+        spoiling: Boolean,
+        stillNeeded: Int,
+        tricksLeft: Int,
+    ): Card {
+        val hand = state.hands[seat]
+        val unseen = DECK.filter { it != state.trumpCard && it !in seen && it !in hand }
+        val oppCards = state.handCounts.sum() - hand.size
+        val q = if (unseen.isEmpty()) 0.0 else (oppCards.toDouble() / unseen.size).coerceIn(0.0, 1.0)
+        val trump = state.trump
+        fun pWin(card: Card): Double = winProb(card, unseen, trump, q, tricksLeft)
+
+        if (state.trick.isEmpty()) {
+            if (wantsTrick) {
+                val scored = cards.map { it to pWin(it) }
+                val bestOverall = scored.maxBy { it.second }
+                // With tricks to spare, save the wizard for when it is needed.
+                if (tricksLeft > stillNeeded) {
+                    val bestPlain = scored.filter { !isWizardCard(it.first) }.maxByOrNull { it.second }
+                    if (bestPlain != null && bestPlain.second >= 0.6) return bestPlain.first
+                }
+                return bestOverall.first
+            }
+            // Ducking: lead whatever is least likely to win, a jester best of all.
+            return cards.minWith(compareBy<Card>({ pWin(it) }, { it.rank.order }))
+        }
+
+        val ledSuit = ledSuitOf(state.trick)
+        val order = state.trick.size
+        val remaining = state.options.playerCount - order - 1
+        val bestOnTable = state.trick
+            .withIndex()
+            .maxOf { (index, played) -> trickStrength(played.card, index, trump, ledSuit) }
+        val strengthOf = { card: Card -> trickStrength(card, order, trump, ledSuit) }
+        val winners = cards.filter { strengthOf(it) > bestOnTable }
+        val losers = cards.filter { strengthOf(it) <= bestOnTable }
+
+        fun sure(card: Card): Boolean =
+            remaining == 0 || unseen.none { trickStrength(it, order + 1, trump, ledSuit) > strengthOf(card) }
+
+        if (wantsTrick) {
+            if (winners.isNotEmpty()) {
+                val certain = winners.filter { sure(it) }
+                return (certain.ifEmpty { winners }).minBy { strengthOf(it) }
+            }
+            // Cannot take this one: keep the strong cards for a trick that can be won.
+            return losers.minBy { strengthOf(it) }
+        }
+        if (spoiling && winners.isNotEmpty() && victimNeedsOne(state)) {
+            return winners.minBy { strengthOf(it) }
+        }
+        if (losers.isNotEmpty()) {
+            // Unload the card that would be hardest to lose later, but keep the
+            // jester: it is the one card that can never win.
+            val nonJester = losers.filter { !isJester(it) }
+            return (nonJester.ifEmpty { losers }).maxBy { strengthOf(it) }
+        }
+        return cards.minBy { strengthOf(it) }
+    }
+
     private fun chooseLead(cards: List<Card>, trump: Suit?, wantsTrick: Boolean): Card {
         if (wantsTrick) {
             // A led wizard is an unloseable trick.

app/src/main/java/org/prolibertate/games/game/yahtzee/YahtzeeAi.kt

@@ -1,6 +1,11 @@
 package org.prolibertate.games.game.yahtzee
 
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
+import kotlin.math.exp
+import kotlin.math.sqrt
 
 /**
  * Plays the dice by eye rather than by arithmetic.
@@ -10,33 +15,53 @@ import org.prolibertate.games.game.engine.GameAi
  * enumerated the thirty-two subsets and applied them would be reading the roll
  * before making it — beating the player by seeing the future rather than by
  * playing well. Everything below decides from the dice already on the table.
+ *
+ * Per seat, from [profiles]: Easy sometimes holds a poor set of dice and
+ * sometimes writes a lesser box than the best on offer. Hard works out, for
+ * every way of holding dice, the *expected* value of what could be thrown
+ * (averaging over all outcomes, never over the roll that will actually come),
+ * valuing each box by what it scores less what that box is usually worth, with
+ * the upper-section bonus tracked. Boldness chases the bonus and big combos
+ * and rolls on with slimmer odds; caution takes a sure score sooner.
  */
-object YahtzeeAi : GameAi<YahtzeeState, YahtzeeMove> {
+class YahtzeeAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) :
+    GameAi<YahtzeeState, YahtzeeMove> {
 
     override fun chooseMove(state: YahtzeeState, seat: Int, legal: List<YahtzeeMove>): YahtzeeMove {
         require(legal.isNotEmpty()) { "No legal move for seat $seat" }
+        val profile = profiles.of(seat)
         val rolls = legal.filterIsInstance<RollDice>()
         val writes = legal.filterIsInstance<ScoreIn>()
 
         // Nothing on the table yet, so there is only one thing to do.
         if (!state.hasRolled) return rolls.firstOrNull() ?: writes.first()
+        if (profile.level == AiLevel.HARD && writes.isNotEmpty()) {
+            return chooseExpected(state, seat, rolls, writes, profile)
+        }
 
-        val best = writes.maxByOrNull { scoreOf(it.category, state.dice) }
+        val ranked = writes.sortedByDescending { scoreOf(it.category, state.dice) }
+        // Easy sometimes writes the second or third best box rather than the best.
+        val best = if (ranked.isEmpty()) null else profile.pick(ranked.take(EASY_BOXES))
         val bestScore = best?.let { scoreOf(it.category, state.dice) } ?: 0
 
         // A hand already worth taking, or no rolls left, ends the turn.
         if (rolls.isEmpty()) return best ?: writes.first()
-        if (bestScore >= WORTH_KEEPING) return best!!
+        if (bestScore >= profile.bolder(WORTH_KEEPING.toDouble(), 4.0)) return best!!
 
-        val keep = whatToKeep(state.dice).toSet()
+        val keep = if (profile.slips()) poorKeep(state.dice) else whatToKeep(state.dice).toSet()
         return rolls.firstOrNull { it.keep == keep } ?: rolls.first()
     }
 
-    /**
-     * Good enough to stop throwing. Set at a full house, which is the point
-     * where a hand is worth more than an average reroll of it.
-     */
-    private const val WORTH_KEEPING = 25
+    /** What a distracted player holds: the high dice, or the pair they notice second. */
+    private fun poorKeep(dice: List<Int>): Set<Int> {
+        val counts = countsOf(dice)
+        val second = counts.entries
+            .sortedWith(compareByDescending<Map.Entry<Int, Int>> { it.value }.thenBy { it.key })
+            .drop(1)
+            .firstOrNull { it.value >= 2 }
+        if (second != null) return dice.indices.filter { dice[it] == second.key }.toSet()
+        return dice.indices.filter { dice[it] >= 4 }.toSet()
+    }
 
     /**
      * What to hold on to: a run if one is nearly there, otherwise the face there
@@ -82,4 +107,213 @@ object YahtzeeAi : GameAi<YahtzeeState, YahtzeeMove> {
             face in wanted && taken.add(face)
         }
     }
+
+    // -- Hard: expected values ------------------------------------------------
+
+    /**
+     * Values every box as what it scores now less what it is normally worth, so
+     * that writing a zero in Ones costs little and writing one in Yahtzee costs a
+     * lot, then looks two throws ahead by averaging over every possible outcome
+     * of every way of holding dice.
+     */
+    private fun chooseExpected(
+        state: YahtzeeState,
+        seat: Int,
+        rolls: List<RollDice>,
+        writes: List<ScoreIn>,
+        profile: AiProfile,
+    ): YahtzeeMove {
+        val valuation = Valuation(state, seat, profile.style.boldness)
+        val dice = state.dice
+        val stop = writes.maxByOrNull { valuation.gain(it.category, dice) } ?: writes.first()
+        if (rolls.isEmpty()) return stop
+        val stopValue = valuation.gain(stop.category, dice)
+
+        // terminal[i]: best write for the i-th multiset of dice with no throws left.
+        val terminal = DoubleArray(DiceTables.multisets.size) { i ->
+            val faces = DiceTables.facesOf(i)
+            writes.maxOf { valuation.gain(it.category, faces) }
+        }
+        // Each throw still to come after the next one, worked backwards.
+        var next = terminal
+        repeat(state.rollsLeft - 1) {
+            val previous = next
+            next = DoubleArray(terminal.size) { i ->
+                maxOf(terminal[i], bestKeep(i, previous).second)
+            }
+        }
+        val here = DiceTables.indexOf(countVector(dice))
+        val (keepCounts, expected) = bestKeep(here, next)
+        val margin = -profile.style.boldness
+        if (expected <= stopValue + margin) return stop
+
+        val remaining = keepCounts.copyOf()
+        val keep = dice.indices.filter { position ->
+            val face = dice[position] - 1
+            if (remaining[face] > 0) {
+                remaining[face]--
+                true
+            } else {
+                false
+            }
+        }.toSet()
+        return rolls.firstOrNull { it.keep == keep } ?: stop
+    }
+
+    /** The best set of dice to hold from multiset [index], and what throwing the rest is worth. */
+    private fun bestKeep(index: Int, after: DoubleArray): Pair<IntArray, Double> {
+        var bestKeep = DiceTables.keepsOf(index).first()
+        var best = Double.NEGATIVE_INFINITY
+        for (keep in DiceTables.keepsOf(index)) {
+            val thrown = DICE_COUNT - keep.sum()
+            var key = 0
+            for (face in 0 until 6) key += keep[face] * DiceTables.POWERS[face]
+            var total = 0.0
+            for (outcome in DiceTables.rerolls[thrown]) {
+                total += outcome.probability * after[DiceTables.indexOfKey[key + outcome.key]]
+            }
+            if (total > best + 1e-9) {
+                best = total
+                bestKeep = keep
+            }
+        }
+        return bestKeep to best
+    }
+
+    private fun countVector(dice: List<Int>): IntArray {
+        val counts = IntArray(6)
+        dice.forEach { counts[it - 1]++ }
+        return counts
+    }
+
+    /** What a box is worth to this card right now, in points relative to its usual yield. */
+    private class Valuation(state: YahtzeeState, seat: Int, private val boldness: Double) {
+        private val card = state.cards[seat]
+        private val yahtzeeBonus = state.options.yahtzeeBonus && card[YahtzeeCategory.YAHTZEE] == YAHTZEE_SCORE
+        private val openUpper = YahtzeeCategory.entries.filter {
+            it.section == YahtzeeSection.UPPER && !card.isFilled(it)
+        }
+        private val secured = card.upperSubtotal >= UPPER_BONUS_AT
+        private val diff = YahtzeeCategory.entries
+            .filter { it.section == YahtzeeSection.UPPER && card.isFilled(it) }
+            .sumOf { (card[it] ?: 0) - 3 * it.face!! }
+        private val bonusValue = UPPER_BONUS * (1.0 + 0.4 * boldness)
+
+        fun gain(category: YahtzeeCategory, dice: List<Int>): Double {
+            val score = scoreOf(category, dice)
+            var value = score - TYPICAL[category.ordinal]
+            if (category.section == YahtzeeSection.UPPER && !secured) {
+                val face = category.face!!
+                val after = if (card.upperSubtotal + score >= UPPER_BONUS_AT) {
+                    1.0
+                } else {
+                    chance(diff + score - 3 * face, openUpper - category)
+                }
+                value += bonusValue * (after - chance(diff, openUpper))
+            }
+            // The big combinations: a bold seat values them a little more.
+            if (score > 0 && (category == YahtzeeCategory.LARGE_STRAIGHT ||
+                    category == YahtzeeCategory.YAHTZEE || category == YahtzeeCategory.FOUR_OF_A_KIND)
+            ) {
+                value += boldness * 2.0
+            }
+            if (yahtzeeBonus && isYahtzee(dice)) value += YAHTZEE_BONUS
+            return value
+        }
+
+        /** Likelihood the upper section still reaches the bonus from [difference] with [open] to fill. */
+        private fun chance(difference: Int, open: List<YahtzeeCategory>): Double {
+            if (open.isEmpty()) return if (difference >= 0) 1.0 else 0.0
+            val expected = open.sumOf { TYPICAL[it.ordinal] - 3 * it.face!! }
+            val spread = 2.2 * sqrt(open.size.toDouble()) + 0.3
+            return 1.0 / (1.0 + exp(-(difference + expected + 1.5) / spread))
+        }
+    }
+
+    /** Every multiset of five dice and every throw of n dice, worked out once. */
+    private object DiceTables {
+        class Outcome(val key: Int, val probability: Double)
+
+        val POWERS = intArrayOf(1, 6, 36, 216, 1296, 7776)
+        val indexOfKey = IntArray(46656) { -1 }
+        val multisets: List<IntArray> = vectors(DICE_COUNT)
+        val rerolls: Array<List<Outcome>> = Array(DICE_COUNT + 1) { n ->
+            val factorial = IntArray(6) { f -> (1..f).fold(1) { a, b -> a * b } }
+            val total = Math.pow(6.0, n.toDouble())
+            vectors(n).map { counts ->
+                val ways = (1..n).fold(1) { a, b -> a * b } / counts.fold(1) { a, c -> a * factorial[c] }
+                Outcome(keyOf(counts), ways / total)
+            }
+        }
+        private val keeps: Array<List<IntArray>?> = arrayOfNulls(multisets.size)
+
+        init {
+            multisets.forEachIndexed { i, counts -> indexOfKey[keyOf(counts)] = i }
+        }
+
+        fun indexOf(counts: IntArray): Int = indexOfKey[keyOf(counts)]
+
+        fun facesOf(index: Int): List<Int> {
+            val faces = ArrayList<Int>(DICE_COUNT)
+            multisets[index].forEachIndexed { f, c -> repeat(c) { faces += f + 1 } }
+            return faces
+        }
+
+        /** Every distinct set of dice that can be held back from multiset [index]. */
+        fun keepsOf(index: Int): List<IntArray> {
+            keeps[index]?.let { return it }
+            val counts = multisets[index]
+            var all = listOf(IntArray(6))
+            for (face in 0 until 6) {
+                all = all.flatMap { partial ->
+                    (0..counts[face]).map { n -> partial.copyOf().also { it[face] = n } }
+                }
+            }
+            keeps[index] = all
+            return all
+        }
+
+        private fun keyOf(counts: IntArray): Int {
+            var key = 0
+            for (face in 0 until 6) key += counts[face] * POWERS[face]
+            return key
+        }
+
+        /** Every way to split [size] dice over six faces. */
+        private fun vectors(size: Int): List<IntArray> {
+            val out = ArrayList<IntArray>()
+            fun build(face: Int, left: Int, current: IntArray) {
+                if (face == 5) {
+                    current[5] = left
+                    out += current.copyOf()
+                    return
+                }
+                for (n in 0..left) {
+                    current[face] = n
+                    build(face + 1, left - n, current)
+                }
+            }
+            build(0, size, IntArray(6))
+            return out
+        }
+    }
+
+    private companion object {
+        /**
+         * Good enough to stop throwing. Set at a full house, which is the point
+         * where a hand is worth more than an average reroll of it.
+         */
+        const val WORTH_KEEPING = 25
+
+        /** How many of the best boxes Easy chooses among when it writes a score. */
+        const val EASY_BOXES = 3
+
+        /**
+         * What each box yields on average under strong play, in the order of
+         * [YahtzeeCategory]: the cost of spending it.
+         */
+        val TYPICAL = doubleArrayOf(
+            2.11, 5.28, 8.57, 12.16, 15.69, 19.19, 21.66, 13.10, 22.59, 29.46, 32.71, 16.87, 22.01,
+        )
+    }
 }

app/src/main/java/org/prolibertate/games/game/yahtzee/YahtzeeStats.kt

@@ -0,0 +1,58 @@
+package org.prolibertate.games.game.yahtzee
+
+import kotlinx.serialization.Serializable
+
+/** What one finished game says about the local player's card. */
+@Serializable
+data class YahtzeeRecord(
+    val total: Int,
+    val gotBonus: Boolean,
+    /** Yahtzees scored, counting the extra ones that earned the hundred. */
+    val yahtzees: Int,
+    /** Boxes written in as nothing. */
+    val zeros: Int,
+    val players: Int,
+    val won: Boolean,
+)
+
+/** Builds the record of [seat]'s card in a finished game. Ties for first count as a win. */
+fun recordOf(state: YahtzeeState, seat: Int): YahtzeeRecord {
+    val card = state.cards[seat]
+    val mine = state.totalFor(seat)
+    val best = state.cards.indices.maxOf { state.totalFor(it) }
+    return YahtzeeRecord(
+        total = mine,
+        gotBonus = card.upperBonus > 0,
+        yahtzees = (if (card[YahtzeeCategory.YAHTZEE] == YAHTZEE_SCORE) 1 else 0) +
+            state.yahtzeeBonuses[seat] / YAHTZEE_BONUS,
+        zeros = card.boxes.count { it == 0 },
+        players = state.cards.size,
+        won = mine >= best,
+    )
+}
+
+/** A game set against the ones before it. [rank] is 1 for a new best. */
+data class YahtzeeComparison(
+    val current: YahtzeeRecord,
+    val previousGames: Int,
+    val bestBefore: Int?,
+    val averageBefore: Double?,
+    val rank: Int,
+    val gamesRanked: Int,
+    val bonusRateBefore: Double?,
+    val yahtzeesBefore: Int,
+    val winRateBefore: Double?,
+)
+
+fun compareToHistory(previous: List<YahtzeeRecord>, current: YahtzeeRecord): YahtzeeComparison =
+    YahtzeeComparison(
+        current = current,
+        previousGames = previous.size,
+        bestBefore = previous.maxOfOrNull { it.total },
+        averageBefore = previous.takeIf { it.isNotEmpty() }?.map { it.total }?.average(),
+        rank = 1 + previous.count { it.total > current.total },
+        gamesRanked = previous.size + 1,
+        bonusRateBefore = previous.takeIf { it.isNotEmpty() }?.let { p -> p.count { it.gotBonus }.toDouble() / p.size },
+        yahtzeesBefore = previous.sumOf { it.yahtzees },
+        winRateBefore = previous.takeIf { it.isNotEmpty() }?.let { p -> p.count { it.won }.toDouble() / p.size },
+    )

app/src/main/java/org/prolibertate/games/net/LobbyController.kt

@@ -8,6 +8,7 @@ import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.launch
+import org.prolibertate.games.game.engine.AiDifficulty
 import org.prolibertate.games.game.engine.PlayerKind
 import org.prolibertate.games.game.engine.PlayerSlot
 import org.prolibertate.games.game.engine.TableConfig
@@ -33,6 +34,7 @@ class LobbyController(
         val connected: Boolean = false,
         val gameId: String? = null,
         val optionsJson: String = "{}",
+        val aiDifficulty: AiDifficulty = AiDifficulty.MEDIUM,
         val hostName: String = "",
         val seats: List<PlayerSlot> = emptyList(),
         val discovered: List<DiscoveredHost> = emptyList(),
@@ -88,6 +90,7 @@ class LobbyController(
         hostName: String,
         seatCount: Int,
         teamOf: (Int) -> Int,
+        aiDifficulty: AiDifficulty = AiDifficulty.MEDIUM,
     ) {
         stop()
         val seats = (0 until seatCount).map { seat ->
@@ -102,6 +105,7 @@ class LobbyController(
             hosting = true,
             gameId = gameId,
             optionsJson = optionsJson,
+            aiDifficulty = aiDifficulty,
             hostName = hostName,
             seats = seats,
             message = "Waiting for players…",
@@ -237,6 +241,7 @@ class LobbyController(
             seats = current.seats,
             optionsJson = current.optionsJson,
             seed = seed,
+            aiDifficulty = current.aiDifficulty,
         )
         scope.launch { connections.values.forEach { it.send(StartGame(config)) } }
         _state.value = current.copy(started = config)

app/src/main/java/org/prolibertate/games/net/MatchController.kt

@@ -96,6 +96,27 @@ class MatchController<S : Any, M : Any>(
 
     /** Host only: the true state. Clients never see this. */
     private var authoritative: S? = null
+
+    /** A position to carry on from instead of dealing, set by [restore] before [startAsHost]. */
+    private var restored: S? = null
+
+    /**
+     * Host only: told about every position the table reaches, so it can be kept
+     * for later. Called under the table's lock, so it must return quickly — the
+     * snapshot encodes its state only when asked, and the work of writing it
+     * belongs to whoever is listening.
+     */
+    var onHostState: ((HostSnapshot) -> Unit)? = null
+
+    /** One position of the table, as handed to [onHostState]. */
+    class HostSnapshot(
+        val finished: Boolean,
+        val summary: String,
+        private val encode: () -> String,
+    ) {
+        /** The whole true state, encoded by the game's own rules. */
+        fun stateJson(): String = encode()
+    }
     private val lock = Mutex()
     private var sequence = 0
 
@@ -160,7 +181,7 @@ class MatchController<S : Any, M : Any>(
         check(role == Role.HOST) { "Not hosting" }
         clients.forEach { connection -> listenToPeer(connection) }
         scope.launch {
-            val initial = runCatching { rules.initialState(config) }.getOrElse { error ->
+            val initial = restored ?: runCatching { rules.initialState(config) }.getOrElse { error ->
                 // A table the rules will not accept is a dead end, not a reason
                 // to take the app down with it: this runs in the screen's own
                 // scope, where nothing would catch it.
@@ -175,6 +196,20 @@ class MatchController<S : Any, M : Any>(
         }
     }
 
+    /**
+     * Host: carry on from a saved position instead of dealing a new game.
+     *
+     * Call before [startAsHost]. Returns false, and changes nothing, if
+     * [stateJson] cannot be read by this version of the game — a save made by an
+     * older build, say — and the caller should deal a fresh table instead.
+     */
+    fun restore(stateJson: String): Boolean {
+        check(role == Role.HOST) { "Only a host can restore a game" }
+        val state = runCatching { rules.decodeState(stateJson) }.getOrNull() ?: return false
+        restored = state
+        return true
+    }
+
     private fun listenToPeer(connection: Connection) {
         peers[connection.peerId] = connection
         peerJobs[connection.peerId] = scope.launch {
@@ -349,7 +384,7 @@ class MatchController<S : Any, M : Any>(
                 seatPeers[seat]?.let { peers[it]?.send(Rejected("It is not your turn.")) }
                 return
             }
-            if (move !in rules.legalMoves(current, seat)) {
+            if (!rules.isLegalMove(current, seat, move)) {
                 seatPeers[seat]?.let { peers[it]?.send(Rejected("That move is not legal.")) }
                 return
             }
@@ -424,7 +459,7 @@ class MatchController<S : Any, M : Any>(
                 // throws on a move that is no longer legal, and there is nothing
                 // above this to catch it.
                 if (rules.currentSeat(live) != seat) return@withLock false
-                if (move !in rules.legalMoves(live, seat)) return@withLock false
+                if (!rules.isLegalMove(live, seat, move)) return@withLock false
                 authoritative = rules.applyMove(live, seat, move)
                 publish()
                 true
@@ -449,6 +484,16 @@ class MatchController<S : Any, M : Any>(
         }
         _finished.value = rules.isFinished(current)
 
+        if (role == Role.HOST) {
+            onHostState?.invoke(
+                HostSnapshot(
+                    finished = rules.isFinished(current),
+                    summary = rules.summary(current),
+                    encode = { rules.encodeState(current) },
+                ),
+            )
+        }
+
         for (slot in config.seats) {
             val peerId = slot.peerId ?: continue
             val connection = peers[peerId] ?: continue

app/src/main/java/org/prolibertate/games/net/MatchSaver.kt

@@ -0,0 +1,95 @@
+package org.prolibertate.games.net
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.flow.filterNotNull
+import kotlinx.coroutines.launch
+import org.prolibertate.games.game.engine.SavedGameStore
+import org.prolibertate.games.game.engine.SavedMatch
+import org.prolibertate.games.game.engine.TableConfig
+
+/**
+ * Keeps the position of one table on disk as it is played.
+ *
+ * It is fed every position the host reaches ([offer]) and writes the newest one
+ * off the main thread. Positions that arrive while a write is under way are
+ * dropped in favour of the latest — a computer's turn can be several moves in a
+ * second, and only where the game stands matters. A finished game is not kept:
+ * its slot is cleared, so a won game is not offered back as one to resume.
+ *
+ * [flush] writes whatever has not been written yet, on the caller's thread. It
+ * is what makes leaving the table, or the app going to the background, safe: the
+ * background writer may not have caught up, and the process may not be given the
+ * chance to let it.
+ */
+class MatchSaver(
+    private val store: SavedGameStore,
+    private val gameId: String,
+    private val config: TableConfig,
+    private val localSeat: Int,
+    private val scope: CoroutineScope,
+    private val clock: () -> Long = System::currentTimeMillis,
+) {
+    private val latest = MutableStateFlow<MatchController.HostSnapshot?>(null)
+    private var worker: Job? = null
+    private var written: MatchController.HostSnapshot? = null
+    private var discarded = false
+
+    /** Starts the background writer. */
+    fun start() {
+        worker = scope.launch(Dispatchers.IO) {
+            latest.filterNotNull().collectLatest { write(it) }
+        }
+    }
+
+    /** Hands over the newest position. Cheap: the encoding happens on the writer. */
+    fun offer(snapshot: MatchController.HostSnapshot) {
+        latest.value = snapshot
+    }
+
+    /** Writes the newest position now if the writer has not already. */
+    fun flush() {
+        latest.value?.let { write(it) }
+    }
+
+    /** The game was ended on purpose: forget the saved position and write no more. */
+    @Synchronized
+    fun discard() {
+        discarded = true
+        worker?.cancel()
+        worker = null
+        runCatching { store.clear(gameId) }
+    }
+
+    fun stop() {
+        worker?.cancel()
+        worker = null
+    }
+
+    @Synchronized
+    private fun write(snapshot: MatchController.HostSnapshot) {
+        if (discarded || snapshot === written) return
+        written = snapshot
+        // Saving is a courtesy to the player: a full disk must not take the game
+        // down with it.
+        runCatching {
+            if (snapshot.finished) {
+                store.clear(gameId)
+            } else {
+                store.save(
+                    SavedMatch(
+                        gameId = gameId,
+                        config = config,
+                        localSeat = localSeat,
+                        stateJson = snapshot.stateJson(),
+                        savedAtMillis = clock(),
+                        summary = snapshot.summary,
+                    ),
+                )
+            }
+        }
+    }
+}

app/src/main/java/org/prolibertate/games/score/RecentNames.kt

@@ -0,0 +1,17 @@
+package org.prolibertate.games.score
+
+/** The short list of names offered when a column is being named. */
+object RecentNames {
+    const val LIMIT = 10
+
+    /**
+     * [name] moved to the front of [names], trimmed, with any earlier copy
+     * (compared ignoring case) dropped and the list cut to [LIMIT]. A blank name
+     * leaves the list as it was.
+     */
+    fun with(names: List<String>, name: String): List<String> {
+        val typed = name.trim()
+        if (typed.isEmpty()) return names
+        return (listOf(typed) + names.filterNot { it.equals(typed, ignoreCase = true) }).take(LIMIT)
+    }
+}

app/src/main/java/org/prolibertate/games/score/ScorekeeperRepository.kt

@@ -29,6 +29,7 @@ class ScorekeeperRepository(private val context: Context) {
 
     private object Keys {
         val SHEET = stringPreferencesKey("sheet")
+        val RECENT_NAMES = stringPreferencesKey("recent_names")
     }
 
     // Unknown keys are ignored so a sheet written by a newer build can still be
@@ -45,6 +46,24 @@ class ScorekeeperRepository(private val context: Context) {
             ?: ScoreSheet()
     }
 
+    /** The names last used on a sheet, most recent first, for the rename dialog. */
+    val recentNames: Flow<List<String>> = context.scorekeeperDataStore.data.map { prefs ->
+        prefs[Keys.RECENT_NAMES]
+            ?.let { stored ->
+                runCatching { json.decodeFromString<List<String>>(stored) }.getOrNull()
+            }
+            ?: emptyList()
+    }
+
+    suspend fun rememberName(name: String) {
+        context.scorekeeperDataStore.edit { prefs ->
+            val current = prefs[Keys.RECENT_NAMES]
+                ?.let { runCatching { json.decodeFromString<List<String>>(it) }.getOrNull() }
+                .orEmpty()
+            prefs[Keys.RECENT_NAMES] = json.encodeToString(RecentNames.with(current, name))
+        }
+    }
+
     suspend fun save(sheet: ScoreSheet) {
         context.scorekeeperDataStore.edit { it[Keys.SHEET] = json.encodeToString(sheet) }
     }

app/src/main/java/org/prolibertate/games/score/SheetOp.kt

@@ -31,8 +31,18 @@ sealed interface SheetOp {
 /** Sets a fresh sheet up for [count] players, scored by round or by tally. */
 @Serializable
 @SerialName("start")
-data class StartSheet(val count: Int, val mode: ScoringMode = ScoringMode.ROUNDS) : SheetOp {
-    override fun applyTo(sheet: ScoreSheet): ScoreSheet = ScoreSheet.of(count, mode)
+data class StartSheet(
+    val count: Int,
+    val mode: ScoringMode = ScoringMode.ROUNDS,
+    /** Names for the first seats, in order; a seat past the end stays unnamed. */
+    val names: List<String> = emptyList(),
+) : SheetOp {
+    override fun applyTo(sheet: ScoreSheet): ScoreSheet {
+        val seated = ScoreSheet.of(count, mode)
+        return seated.players.foldIndexed(seated) { index, acc, player ->
+            names.getOrNull(index)?.let { acc.renamed(player.id, it) } ?: acc
+        }
+    }
 }
 
 /** Rubs everything out. */

app/src/main/java/org/prolibertate/games/settings/SettingsRepository.kt

@@ -24,6 +24,8 @@ data class Settings(
     val soundEnabled: Boolean = true,
     val animationSpeed: Float = 1.0f,
     val checkForUpdatesOnLaunch: Boolean = true,
+    /** Multiplies the system font size across the whole app. */
+    val textScale: Float = 1.0f,
     /**
      * Exactly what the user has typed, which may be blank while they are
      * mid-edit. Nothing substitutes a default into this value: doing so meant
@@ -46,6 +48,8 @@ data class Settings(
     companion object {
         const val MIN_SPEED = 0.5f
         const val MAX_SPEED = 2.0f
+        const val MIN_TEXT_SCALE = 0.8f
+        const val MAX_TEXT_SCALE = 1.6f
         const val DEFAULT_PLAYER_NAME = "Player"
     }
 }
@@ -56,6 +60,7 @@ class SettingsRepository(private val context: Context) {
         val SOUND = booleanPreferencesKey("sound_enabled")
         val SPEED = floatPreferencesKey("animation_speed")
         val UPDATE_ON_LAUNCH = booleanPreferencesKey("check_updates_on_launch")
+        val TEXT_SCALE = floatPreferencesKey("text_scale")
         val NAME = stringPreferencesKey("player_name")
         // There is deliberately no update-channel key. The channel is a
         // property of the installed APK, not a preference — an install that
@@ -69,6 +74,8 @@ class SettingsRepository(private val context: Context) {
             soundEnabled = prefs[Keys.SOUND] ?: true,
             animationSpeed = prefs[Keys.SPEED] ?: 1.0f,
             checkForUpdatesOnLaunch = prefs[Keys.UPDATE_ON_LAUNCH] ?: true,
+            textScale = (prefs[Keys.TEXT_SCALE] ?: 1.0f)
+                .coerceIn(Settings.MIN_TEXT_SCALE, Settings.MAX_TEXT_SCALE),
             playerName = prefs[Keys.NAME] ?: "",
         )
     }
@@ -83,6 +90,12 @@ class SettingsRepository(private val context: Context) {
         }
     }
 
+    suspend fun setTextScale(scale: Float) {
+        context.dataStore.edit {
+            it[Keys.TEXT_SCALE] = scale.coerceIn(Settings.MIN_TEXT_SCALE, Settings.MAX_TEXT_SCALE)
+        }
+    }
+
     suspend fun setCheckForUpdatesOnLaunch(enabled: Boolean) {
         context.dataStore.edit { it[Keys.UPDATE_ON_LAUNCH] = enabled }
     }

app/src/main/java/org/prolibertate/games/settings/YahtzeeStatsRepository.kt

@@ -0,0 +1,42 @@
+package org.prolibertate.games.settings
+
+import android.content.Context
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.core.stringPreferencesKey
+import androidx.datastore.preferences.preferencesDataStore
+import kotlinx.coroutines.flow.first
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.prolibertate.games.game.yahtzee.YahtzeeComparison
+import org.prolibertate.games.game.yahtzee.YahtzeeRecord
+import org.prolibertate.games.game.yahtzee.compareToHistory
+
+private val Context.yahtzeeStatsStore: DataStore<Preferences> by preferencesDataStore(
+    name = "yahtzee_stats",
+)
+
+/** The local player's finished Yahtzee games, newest last, kept to the last [KEEP]. */
+class YahtzeeStatsRepository(private val context: Context) {
+
+    private val key = stringPreferencesKey("games")
+    private val json = Json { ignoreUnknownKeys = true }
+
+    private fun decode(stored: String?): List<YahtzeeRecord> =
+        stored?.let { runCatching { json.decodeFromString<List<YahtzeeRecord>>(it) }.getOrNull() }
+            .orEmpty()
+
+    /** Compares [record] with every earlier game, then adds it to the history. */
+    suspend fun finish(record: YahtzeeRecord): YahtzeeComparison {
+        val previous = decode(context.yahtzeeStatsStore.data.first()[key])
+        context.yahtzeeStatsStore.edit {
+            it[key] = json.encodeToString((previous + record).takeLast(KEEP))
+        }
+        return compareToHistory(previous, record)
+    }
+
+    private companion object {
+        const val KEEP = 500
+    }
+}

app/src/main/java/org/prolibertate/games/ui/AppRoot.kt

@@ -20,6 +20,8 @@ import androidx.compose.material3.Card
 import androidx.compose.material3.CardDefaults
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.MaterialTheme
+import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.unit.Density
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Text
@@ -29,6 +31,8 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableIntStateOf
+import androidx.compose.runtime.produceState
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
@@ -47,9 +51,15 @@ import org.prolibertate.games.net.ScorekeeperSession
 import org.prolibertate.games.score.ScorekeeperRepository
 import org.prolibertate.games.settings.Settings
 import org.prolibertate.games.settings.SettingsRepository
+import org.prolibertate.games.settings.YahtzeeStatsRepository
 import org.prolibertate.games.ui.game.LocalCardSpeed
 import org.prolibertate.games.update.UpdateChannel
 import org.prolibertate.games.update.Updater
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import org.prolibertate.games.game.engine.AiDifficulty
+import org.prolibertate.games.game.engine.SavedGameStore
+import org.prolibertate.games.game.engine.SavedMatch
 
 /** Everything the screens need, assembled once by the activity. */
 class AppEnv(
@@ -60,6 +70,9 @@ class AppEnv(
     /** The shared score sheet, for the Scorekeeper to host or join. */
     val scoreSession: ScorekeeperSession,
     val peerId: String,
+    /** Games in progress, kept between sessions. */
+    val saves: SavedGameStore,
+    val yahtzeeStats: YahtzeeStatsRepository,
 )
 
 /**
@@ -76,13 +89,23 @@ sealed interface Route {
     data class Section(val menu: GameMenu) : Route
     data object Settings : Route
     data object Scorekeeper : Route
+
+    /** Every saved game, to carry on from or delete. */
+    data object Resume : Route
     data class Setup(val gameId: String) : Route
-    data class Lobby(val gameId: String, val optionsJson: String, val hosting: Boolean) : Route
+    data class Lobby(
+        val gameId: String,
+        val optionsJson: String,
+        val hosting: Boolean,
+        val aiDifficulty: AiDifficulty = AiDifficulty.MEDIUM,
+    ) : Route
     data class Play(
         val gameId: String,
         val config: TableConfig,
         val hosting: Boolean,
         val localSeat: Int,
+        /** A saved position to carry on from, as the game's rules encoded it; null deals a new game. */
+        val resumeState: String? = null,
     ) : Route
 }
 
@@ -129,7 +152,14 @@ fun AppRoot(env: AppEnv) {
         // Card motion reads its speed from here rather than from a parameter.
         // Every card screen animates, most of them several layers deep, and the
         // alternative was passing one unchanging number down through all of it.
-        CompositionLocalProvider(LocalCardSpeed provides settings.animationSpeed) {
+        val density = LocalDensity.current
+        val scaledDensity = remember(density, settings.textScale) {
+            Density(density.density, density.fontScale * settings.textScale)
+        }
+        CompositionLocalProvider(
+            LocalCardSpeed provides settings.animationSpeed,
+            LocalDensity provides scaledDensity,
+        ) {
             AppContent(
                 env = env,
                 settings = settings,
@@ -167,6 +197,8 @@ private fun AppContent(
             // Dev builds show the games that are not finished yet; production
             // releases list only what can actually be played.
             showComingSoon = showComingSoon,
+            hasSaved = savedGames(env, stack).isNotEmpty(),
+            onResume = { push(Route.Resume) },
             onPickSection = { push(Route.Section(it)) },
             onJoinGame = { push(Route.Lobby(gameId = "", optionsJson = "{}", hosting = false)) },
             onScorekeeper = { push(Route.Scorekeeper) },
@@ -181,6 +213,25 @@ private fun AppContent(
             onBack = pop,
         )
 
+        is Route.Resume -> {
+            // Bumped when a game is deleted, so the list is read again.
+            var deletions by remember(route) { mutableIntStateOf(0) }
+            val saved by produceState(emptyList<SavedMatch>(), route, deletions) {
+                value = withContext(Dispatchers.IO) { env.saves.all() }
+            }
+            ResumeScreen(
+                saved = saved,
+                onResume = { match ->
+                    push(Route.Play(match.gameId, match.config, true, match.localSeat, match.stateJson))
+                },
+                onDelete = { match ->
+                    env.saves.clear(match.gameId)
+                    deletions++
+                },
+                onBack = pop,
+            )
+        }
+
         is Route.Settings -> SettingsScreen(
             env = env,
             settings = settings,
@@ -194,15 +245,30 @@ private fun AppContent(
             onBack = { pop() },
         )
 
-        is Route.Setup -> GameSetupScreen(
-            descriptor = GameCatalog.byId(route.gameId)!!,
-            playerName = settings.displayName,
-            onBack = { pop() },
-            onPlayOffline = { config, seat -> push(Route.Play(route.gameId, config, true, seat)) },
-            onHostOnline = { optionsJson ->
-                push(Route.Lobby(route.gameId, optionsJson, hosting = true))
-            },
-        )
+        is Route.Setup -> {
+            // Bumped when the saved game is thrown away, so the banner goes with it.
+            var discards by remember(route) { mutableIntStateOf(0) }
+            val saved by produceState<SavedMatch?>(null, route, discards) {
+                value = withContext(Dispatchers.IO) { env.saves.load(route.gameId) }
+            }
+            GameSetupScreen(
+                descriptor = GameCatalog.byId(route.gameId)!!,
+                playerName = settings.displayName,
+                onBack = { pop() },
+                onPlayOffline = { config, seat -> push(Route.Play(route.gameId, config, true, seat)) },
+                onHostOnline = { optionsJson, aiDifficulty ->
+                    push(Route.Lobby(route.gameId, optionsJson, hosting = true, aiDifficulty = aiDifficulty))
+                },
+                saved = saved,
+                onResume = { match ->
+                    push(Route.Play(match.gameId, match.config, true, match.localSeat, match.stateJson))
+                },
+                onDiscardSaved = {
+                    env.saves.clear(route.gameId)
+                    discards++
+                },
+            )
+        }
 
         is Route.Lobby -> LobbyScreen(
             env = env,
@@ -231,6 +297,8 @@ private fun AppContent(
 @Composable
 fun MainMenuScreen(
     showComingSoon: Boolean,
+    hasSaved: Boolean,
+    onResume: () -> Unit,
     onPickSection: (GameMenu) -> Unit,
     onJoinGame: () -> Unit,
     onScorekeeper: () -> Unit,
@@ -280,6 +348,14 @@ fun MainMenuScreen(
                     )
                 }
 
+                // Games left half-played, above everything else: coming back to
+                // the app is mostly coming back to one.
+                if (hasSaved) {
+                    Button(onClick = onResume, modifier = Modifier.fillMaxWidth()) {
+                        Text("Resume game")
+                    }
+                }
+
                 // Below the games, and full width like them, so the column
                 // stays one column all the way down.
                 OutlinedButton(
@@ -364,7 +440,11 @@ fun SectionScreen(
                 }
             }
             items(games) { game ->
-                GameTile(game = game, onClick = { onPickGame(game) })
+                GameTile(
+                    game = game,
+                    playable = game.playableIn(devBuild = showComingSoon),
+                    onClick = { onPickGame(game) },
+                )
             }
         }
     }
@@ -403,12 +483,12 @@ private fun SectionTile(menu: GameMenu, count: Int, onClick: () -> Unit) {
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
-private fun GameTile(game: GameDescriptor, onClick: () -> Unit) {
+private fun GameTile(game: GameDescriptor, playable: Boolean, onClick: () -> Unit) {
     Card(
         onClick = onClick,
-        enabled = game.available,
+        enabled = playable,
         colors = CardDefaults.cardColors(
-            containerColor = if (game.available) {
+            containerColor = if (playable) {
                 MaterialTheme.colorScheme.surfaceVariant
             } else {
                 MaterialTheme.colorScheme.surface
@@ -427,13 +507,18 @@ private fun GameTile(game: GameDescriptor, onClick: () -> Unit) {
                 style = MaterialTheme.typography.bodySmall,
                 modifier = Modifier.padding(top = 4.dp),
             )
+            val players = when {
+                // A puzzle for one, rather than "1 players".
+                game.maxPlayers == 1 -> "On your own"
+                game.minPlayers == game.maxPlayers -> "${game.minPlayers} players"
+                else -> "${game.minPlayers}–${game.maxPlayers} players"
+            }
             Text(
                 text = when {
-                    !game.available -> "Coming soon"
-                    // A puzzle for one, rather than "1 players".
-                    game.maxPlayers == 1 -> "On your own"
-                    game.minPlayers == game.maxPlayers -> "${game.minPlayers} players"
-                    else -> "${game.minPlayers}–${game.maxPlayers} players"
+                    !playable -> "Coming soon"
+                    // Playable on this dev build only; production hides it.
+                    !game.available -> "Preview · $players"
+                    else -> players
                 },
                 style = MaterialTheme.typography.labelSmall,
                 modifier = Modifier.padding(top = 8.dp),
@@ -481,3 +566,17 @@ fun PrimaryAction(text: String, enabled: Boolean = true, onClick: () -> Unit) {
         Text(text)
     }
 }
+
+/**
+ * The saved games, read off the main thread each time the menu is the screen
+ * showing — which is when a game has just been left and its last position
+ * written, so the list is not read until that has happened.
+ */
+@Composable
+private fun savedGames(env: AppEnv, stack: List<Route>): List<SavedMatch> {
+    val onMenu = stack.last() is Route.Menu
+    val saved by produceState(emptyList<SavedMatch>(), onMenu, stack.size) {
+        value = if (onMenu) withContext(Dispatchers.IO) { env.saves.all() } else emptyList()
+    }
+    return saved
+}

app/src/main/java/org/prolibertate/games/ui/EndGameHandle.kt

@@ -0,0 +1,21 @@
+package org.prolibertate.games.ui
+
+import androidx.compose.runtime.staticCompositionLocalOf
+
+/**
+ * How a screen's "End game" button tells the table to forget the saved game.
+ *
+ * Leaving a table keeps its position so it can be resumed; ending one on purpose
+ * does not. The two arrive at the screen as the same "go back", so the
+ * difference is carried here instead: [PlayScreen] provides one handle, the match
+ * it builds says what ending means for it by setting [onEnd], and each End-game
+ * dialog calls [end] before it leaves.
+ */
+class EndGameHandle {
+    /** Set by the table once it knows how to forget its own saved position. */
+    var onEnd: () -> Unit = {}
+
+    fun end() = onEnd()
+}
+
+val LocalEndGameHandle = staticCompositionLocalOf { EndGameHandle() }

app/src/main/java/org/prolibertate/games/ui/GameSetupScreen.kt

@@ -9,11 +9,14 @@ import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.Button
+import androidx.compose.material3.Card
 import androidx.compose.material3.Divider
 import androidx.compose.material3.FilterChip
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Switch
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
@@ -27,14 +30,13 @@ import kotlinx.serialization.encodeToString
 import kotlinx.serialization.json.Json
 import org.prolibertate.games.game.GameCatalog
 import org.prolibertate.games.game.GameDescriptor
+import org.prolibertate.games.game.engine.AiDifficulty
 import org.prolibertate.games.game.engine.PlayerKind
 import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.SavedMatch
 import org.prolibertate.games.game.engine.TableConfig
-import org.prolibertate.games.game.backgammon.BackgammonLevel
 import org.prolibertate.games.game.backgammon.BackgammonOptions
-import org.prolibertate.games.game.checkers.CheckersLevel
 import org.prolibertate.games.game.checkers.CheckersOptions
-import org.prolibertate.games.game.chess.ChessLevel
 import org.prolibertate.games.game.chess.ChessOptions
 import org.prolibertate.games.game.crazyeights.CrazyEightsOptions
 import org.prolibertate.games.game.cribbage.CribbageOptions
@@ -46,17 +48,19 @@ import org.prolibertate.games.game.freecell.FreeCellOptions
 import org.prolibertate.games.game.pyramid.PyramidOptions
 import org.prolibertate.games.game.spider.SpiderOptions
 import org.prolibertate.games.game.yahtzee.YahtzeeOptions
+import org.prolibertate.games.game.meowdoku.MeowdokuGenerator
+import org.prolibertate.games.game.meowdoku.MeowdokuOptions
 import org.prolibertate.games.game.pegsolitaire.PegBoard
 import org.prolibertate.games.game.pegsolitaire.PegGoal
 import org.prolibertate.games.game.pegsolitaire.PegSolitaireOptions
 import org.prolibertate.games.game.kaiser.KaiserOptions
-import org.prolibertate.games.game.mastermind.MastermindLevel
 import org.prolibertate.games.game.mastermind.MastermindOptions
-import org.prolibertate.games.game.morris.MorrisLevel
 import org.prolibertate.games.game.morris.MorrisOptions
-import org.prolibertate.games.game.pirates.PiratesLevel
 import org.prolibertate.games.game.pirates.PiratesOptions
 import org.prolibertate.games.game.president.PresidentOptions
+import org.prolibertate.games.game.catan.CatanOptions
+import org.prolibertate.games.game.catan.CatanExpansion
+import org.prolibertate.games.game.catan.SeaScenario
 import org.prolibertate.games.game.sequence.SequenceOptions
 import org.prolibertate.games.game.tayu.TayuLevel
 import org.prolibertate.games.game.tayu.TayuOptions
@@ -80,7 +84,11 @@ fun GameSetupScreen(
     playerName: String,
     onBack: () -> Unit,
     onPlayOffline: (TableConfig, Int) -> Unit,
-    onHostOnline: (String) -> Unit,
+    onHostOnline: (String, AiDifficulty) -> Unit,
+    /** A game of this kind left half-played, if there is one. */
+    saved: SavedMatch? = null,
+    onResume: (SavedMatch) -> Unit = {},
+    onDiscardSaved: () -> Unit = {},
 ) {
     var euchre by remember { mutableStateOf(EuchreOptions()) }
     var sequence by remember { mutableStateOf(SequenceOptions()) }
@@ -99,17 +107,20 @@ fun GameSetupScreen(
     var pirates by remember { mutableStateOf(PiratesOptions()) }
     var hearts by remember { mutableStateOf(HeartsOptions()) }
     var pegs by remember { mutableStateOf(PegSolitaireOptions()) }
+    var meowdoku by remember { mutableStateOf(MeowdokuOptions()) }
     var yahtzee by remember { mutableStateOf(YahtzeeOptions()) }
     var klondike by remember { mutableStateOf(KlondikeOptions()) }
     var freecell by remember { mutableStateOf(FreeCellOptions()) }
     var spider by remember { mutableStateOf(SpiderOptions()) }
     var pyramid by remember { mutableStateOf(PyramidOptions()) }
+    var catan by remember { mutableStateOf(CatanOptions()) }
     // Not an engine option: which seat the local player takes. Seat 0 is
     // always White, so choosing Black means sitting in seat 1.
     var playWhite by remember { mutableStateOf(true) }
     // Pirates and Bulgars is not symmetrical, so which side you take is the
     // first thing about the game rather than a detail of it.
     var playPirates by remember { mutableStateOf(false) }
+    var aiDifficulty by remember { mutableStateOf(AiDifficulty.MEDIUM) }
 
     val optionsJson = when (descriptor.id) {
         GameCatalog.EUCHRE -> setupJson.encodeToString(euchre)
@@ -129,11 +140,13 @@ fun GameSetupScreen(
         GameCatalog.PIRATES -> setupJson.encodeToString(pirates)
         GameCatalog.HEARTS -> setupJson.encodeToString(hearts)
         GameCatalog.PEG_SOLITAIRE -> setupJson.encodeToString(pegs)
+        GameCatalog.MEOWDOKU -> setupJson.encodeToString(meowdoku)
         GameCatalog.YAHTZEE -> setupJson.encodeToString(yahtzee)
         GameCatalog.KLONDIKE -> setupJson.encodeToString(klondike)
         GameCatalog.FREECELL -> setupJson.encodeToString(freecell)
         GameCatalog.SPIDER -> setupJson.encodeToString(spider)
         GameCatalog.PYRAMID -> setupJson.encodeToString(pyramid)
+        GameCatalog.CATAN -> setupJson.encodeToString(catan)
         else -> "{}"
     }
     val seatCount = seatCountFor(descriptor.id, optionsJson)
@@ -145,6 +158,10 @@ fun GameSetupScreen(
         ) {
             Text(descriptor.blurb, style = MaterialTheme.typography.bodyMedium)
 
+            if (saved != null) {
+                SavedGameBanner(saved, onResume = { onResume(saved) }, onDiscard = onDiscardSaved)
+            }
+
             Divider()
             Text("House rules", fontWeight = FontWeight.Bold)
 
@@ -189,6 +206,8 @@ fun GameSetupScreen(
 
                 GameCatalog.PEG_SOLITAIRE -> PegSolitaireOptionsEditor(pegs) { pegs = it }
 
+                GameCatalog.MEOWDOKU -> MeowdokuOptionsEditor(meowdoku) { meowdoku = it }
+
                 GameCatalog.YAHTZEE -> YahtzeeOptionsEditor(yahtzee) { yahtzee = it }
 
                 GameCatalog.KLONDIKE -> KlondikeOptionsEditor(klondike) { klondike = it }
@@ -199,6 +218,8 @@ fun GameSetupScreen(
 
                 GameCatalog.PYRAMID -> PyramidOptionsEditor(pyramid) { pyramid = it }
 
+                GameCatalog.CATAN -> CatanOptionsEditor(catan) { catan = it }
+
                 else -> Text("No options yet for this game.")
             }
 
@@ -219,6 +240,22 @@ fun GameSetupScreen(
                 style = MaterialTheme.typography.bodySmall,
             )
 
+            if (!solo) {
+                ChipRow(
+                    label = "Computer difficulty",
+                    values = AiDifficulty.entries.toList(),
+                    selected = aiDifficulty,
+                    display = { it.label },
+                    onSelect = { aiDifficulty = it },
+                )
+                if (aiDifficulty == AiDifficulty.MIXED) {
+                    Text(
+                        "Each computer player gets its own level.",
+                        style = MaterialTheme.typography.bodySmall,
+                    )
+                }
+            }
+
             // Two games let the local player pick a seat rather than always
             // taking the first one: chess by colour, and Pirates and Bulgars by
             // which side of a very lopsided fight they fancy.
@@ -227,15 +264,21 @@ fun GameSetupScreen(
                 descriptor.id == GameCatalog.PIRATES && playPirates -> 1
                 else -> 0
             }
+            if (saved != null) {
+                Text(
+                    "Starting a new game replaces the one in progress.",
+                    style = MaterialTheme.typography.bodySmall,
+                )
+            }
             PrimaryAction(text = if (solo) "Play" else "Play against the computer") {
                 onPlayOffline(
-                    offlineConfig(descriptor.id, optionsJson, seatCount, playerName, localSeat),
+                    offlineConfig(descriptor.id, optionsJson, seatCount, playerName, localSeat, aiDifficulty),
                     localSeat,
                 )
             }
             if (!solo) {
                 PrimaryAction(text = "Host a game for others to join") {
-                    onHostOnline(optionsJson)
+                    onHostOnline(optionsJson, aiDifficulty)
                 }
             }
         }
@@ -249,6 +292,7 @@ private fun offlineConfig(
     seatCount: Int,
     playerName: String,
     localSeat: Int = 0,
+    aiDifficulty: AiDifficulty = AiDifficulty.MEDIUM,
 ): TableConfig = TableConfig(
     gameId = gameId,
     seats = (0 until seatCount).map { seat ->
@@ -262,6 +306,7 @@ private fun offlineConfig(
     optionsJson = optionsJson,
     // Seeded from the clock so consecutive games are not identical.
     seed = System.currentTimeMillis(),
+    aiDifficulty = aiDifficulty,
 )
 
 /**
@@ -303,6 +348,9 @@ fun seatCountFor(gameId: String, optionsJson: String): Int {
             GameCatalog.TAYU ->
                 setupJson.decodeFromString<TayuOptions>(optionsJson).playerCount
 
+            GameCatalog.CATAN ->
+                setupJson.decodeFromString<CatanOptions>(optionsJson).playerCount
+
             else -> fallback
         }
     }.getOrDefault(fallback)
@@ -326,6 +374,90 @@ fun teamForSeat(gameId: String, seat: Int, seatCount: Int): Int = when (gameId)
     else -> seat
 }
 
+/** The targets the setup screen offers for a Katan game with [expansions] on. */
+internal fun catanPointsChoices(expansions: Set<CatanExpansion>): List<Int> = when {
+    // Seafarers adds two points for each new island, so the target is higher.
+    CatanExpansion.SEAFARERS in expansions -> listOf(8, 10, 12, 14)
+    // Cities & Knights is played to thirteen, which is also why it runs longer.
+    CatanExpansion.CITIES_AND_KNIGHTS in expansions -> listOf(8, 10, 13, 15)
+    // Five is a short game for trying things out; ten is the published target.
+    else -> listOf(5, 8, 10, 12)
+}
+
+/** The published target for a game with [expansions] on. */
+internal fun catanDefaultPoints(expansions: Set<CatanExpansion>): Int = when {
+    CatanExpansion.SEAFARERS in expansions -> 12
+    CatanExpansion.CITIES_AND_KNIGHTS in expansions -> 13
+    else -> 10
+}
+
+/**
+ * [options] with [expansion] switched on or off. The target moves to the new combination's own
+ * default unless the one already chosen is on its menu too. Expansions cannot be combined yet,
+ * so switching one on switches the other off.
+ */
+internal fun catanToggleExpansion(options: CatanOptions, expansion: CatanExpansion, on: Boolean): CatanOptions {
+    val expansions = if (on) setOf(expansion) else options.expansions - expansion
+    return options.copy(
+        expansions = expansions,
+        pointsToWin = options.pointsToWin.takeIf {
+            it in catanPointsChoices(expansions) && it != catanDefaultPoints(options.expansions)
+        } ?: catanDefaultPoints(expansions),
+    )
+}
+
+private fun catanExpansionName(expansion: CatanExpansion): String = when (expansion) {
+    CatanExpansion.CITIES_AND_KNIGHTS -> "Cities & Knights"
+    CatanExpansion.SEAFARERS -> "Seafarers"
+}
+
+private fun catanExpansionBlurb(expansion: CatanExpansion): String = when (expansion) {
+    CatanExpansion.CITIES_AND_KNIGHTS ->
+        "Cities make commodities, knights hold off the barbarians, and improvements earn progress " +
+            "cards and metropolises. No development cards; the robber sleeps until the first attack."
+    CatanExpansion.SEAFARERS ->
+        "Build ships to reach new islands. Gold fields pay any resource, a pirate guards the sea, " +
+            "and the first settlement on each new island scores two extra points."
+}
+
+@Composable
+private fun CatanOptionsEditor(options: CatanOptions, onChange: (CatanOptions) -> Unit) {
+    Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        CatanExpansion.entries.forEach { expansion ->
+            ToggleRow(
+                title = catanExpansionName(expansion),
+                subtitle = catanExpansionBlurb(expansion),
+                checked = expansion in options.expansions,
+                onChange = { onChange(catanToggleExpansion(options, expansion, it)) },
+            )
+        }
+        if (options.seafarers) {
+            ChipRow(
+                label = "Map",
+                values = SeaScenario.entries,
+                selected = options.scenario,
+                display = { it.title },
+                onSelect = { onChange(options.copy(scenario = it)) },
+            )
+            Text(options.scenario.blurb, style = MaterialTheme.typography.bodySmall)
+        }
+        ChipRow(
+            label = "Players",
+            values = listOf(3, 4),
+            selected = options.playerCount,
+            display = { "$it players" },
+            onSelect = { onChange(options.copy(playerCount = it)) },
+        )
+        ChipRow(
+            label = "Game to",
+            values = catanPointsChoices(options.expansions),
+            selected = options.pointsToWin,
+            display = { "$it points" },
+            onSelect = { onChange(options.copy(pointsToWin = it)) },
+        )
+    }
+}
+
 @Composable
 private fun EuchreOptionsEditor(options: EuchreOptions, onChange: (EuchreOptions) -> Unit) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
@@ -659,13 +791,6 @@ private fun ChessOptionsEditor(
             display = { if (it) "White" else "Black" },
             onSelect = onColour,
         )
-        ChipRow(
-            label = "Opponent",
-            values = ChessLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ToggleRow(
             title = "Fifty-move rule",
             subtitle = "Fifty moves each with no capture and no pawn move is a draw",
@@ -689,13 +814,6 @@ private fun ChessOptionsEditor(
 @Composable
 private fun CheckersOptionsEditor(options: CheckersOptions, onChange: (CheckersOptions) -> Unit) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-        ChipRow(
-            label = "Opponent",
-            values = CheckersLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ToggleRow(
             title = "Flying kings",
             subtitle = "A king slides the length of a diagonal and takes from a distance, " +
@@ -730,13 +848,6 @@ private fun BackgammonOptionsEditor(
     onChange: (BackgammonOptions) -> Unit,
 ) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-        ChipRow(
-            label = "Opponent",
-            values = BackgammonLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ToggleRow(
             title = "Count gammons",
             subtitle = "A loser who bore nothing off has lost double, and one still on the " +
@@ -758,13 +869,6 @@ private fun MastermindOptionsEditor(
     onChange: (MastermindOptions) -> Unit,
 ) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-        ChipRow(
-            label = "Opponent",
-            values = MastermindLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ChipRow(
             label = "Colours",
             values = listOf(6, 8),
@@ -829,13 +933,6 @@ private fun PiratesOptionsEditor(
             display = { if (it) "the two pirates" else "the twenty-four Bulgars" },
             onSelect = onSide,
         )
-        ChipRow(
-            label = "Opponent",
-            values = PiratesLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ToggleRow(
             title = "A pirate who can take must take",
             subtitle = "The rule that huffing exists to enforce, applied directly",
@@ -861,13 +958,6 @@ private fun PiratesOptionsEditor(
 @Composable
 private fun MorrisOptionsEditor(options: MorrisOptions, onChange: (MorrisOptions) -> Unit) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-        ChipRow(
-            label = "Opponent",
-            values = MorrisLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ChipRow(
             label = "Pieces each",
             values = listOf(3, 6, 9),
@@ -1041,6 +1131,36 @@ private fun PegSolitaireOptionsEditor(
     }
 }
 
+@Composable
+private fun MeowdokuOptionsEditor(
+    options: MeowdokuOptions,
+    onChange: (MeowdokuOptions) -> Unit,
+) {
+    Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        ChipRow(
+            label = "Board",
+            values = (MeowdokuGenerator.MIN_SIDE..MeowdokuGenerator.MAX_SIDE).toList(),
+            selected = options.side,
+            display = { "$it × $it" },
+            onSelect = { onChange(options.copy(side = it)) },
+        )
+        ChipRow(
+            label = "Hearts",
+            values = (1..5).toList(),
+            selected = options.hearts,
+            display = { if (it == 1) "One" else "$it" },
+            onSelect = { onChange(options.copy(hearts = it)) },
+        )
+        ChipRow(
+            label = "Hints",
+            values = (0..3).toList(),
+            selected = options.hints,
+            display = { if (it == 0) "None" else "$it" },
+            onSelect = { onChange(options.copy(hints = it)) },
+        )
+    }
+}
+
 @Composable
 private fun YahtzeeOptionsEditor(options: YahtzeeOptions, onChange: (YahtzeeOptions) -> Unit) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
@@ -1141,3 +1261,30 @@ private fun PyramidOptionsEditor(options: PyramidOptions, onChange: (PyramidOpti
         onSelect = { onChange(options.copy(redeals = it)) },
     )
 }
+
+/**
+ * The game that was left unfinished, with the two things to do about it. Shown
+ * above the options so it is the first thing seen on coming back to a game.
+ */
+@Composable
+private fun SavedGameBanner(saved: SavedMatch, onResume: () -> Unit, onDiscard: () -> Unit) {
+    Card(modifier = Modifier.fillMaxWidth()) {
+        Column(
+            modifier = Modifier.padding(12.dp),
+            verticalArrangement = Arrangement.spacedBy(6.dp),
+        ) {
+            Text("Game in progress", fontWeight = FontWeight.Bold)
+            Text(
+                buildString {
+                    append("Saved ${agoText(System.currentTimeMillis(), saved.savedAtMillis)}")
+                    if (saved.summary.isNotBlank()) append(" · ${saved.summary}")
+                },
+                style = MaterialTheme.typography.bodySmall,
+            )
+            Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                Button(onClick = onResume) { Text("Resume") }
+                TextButton(onClick = onDiscard) { Text("Discard") }
+            }
+        }
+    }
+}

app/src/main/java/org/prolibertate/games/ui/LaunchUpdateCheck.kt

@@ -49,7 +49,7 @@ fun LaunchUpdateCheck(env: AppEnv, visible: Boolean) {
     }
 
     // Held back behind the splash, so an update prompt cannot appear over the
-    // splash before the app itself has.
+    // tartan before the app itself has.
     val pending = release
     if (pending == null || dismissed || !visible) return
 

app/src/main/java/org/prolibertate/games/ui/LobbyScreen.kt

@@ -60,6 +60,7 @@ fun LobbyScreen(
                 hostName = playerName,
                 seatCount = seatCount,
                 teamOf = { seat -> teamForSeat(route.gameId, seat, seatCount) },
+                aiDifficulty = route.aiDifficulty,
             )
         } else {
             env.lobby.startDiscovery()

app/src/main/java/org/prolibertate/games/ui/ResumeScreen.kt

@@ -0,0 +1,87 @@
+package org.prolibertate.games.ui
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.Button
+import androidx.compose.material3.Card
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import org.prolibertate.games.game.GameCatalog
+import org.prolibertate.games.game.engine.SavedMatch
+
+/**
+ * Every game that can be carried on from, most recently played first, each with
+ * a way to pick it up and a way to throw it away.
+ */
+@Composable
+fun ResumeScreen(
+    saved: List<SavedMatch>,
+    onResume: (SavedMatch) -> Unit,
+    onDelete: (SavedMatch) -> Unit,
+    onBack: () -> Unit,
+) {
+    var deleting by remember { mutableStateOf<SavedMatch?>(null) }
+
+    ScreenScaffold(title = "Resume game", onBack = onBack) { modifier ->
+        if (saved.isEmpty()) {
+            Text("No games to resume.", modifier = modifier)
+        } else {
+            val now = System.currentTimeMillis()
+            LazyColumn(
+                modifier = modifier,
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                items(saved, key = { it.gameId }) { match ->
+                    val title = GameCatalog.byId(match.gameId)?.title ?: match.gameId
+                    Card(modifier = Modifier.fillMaxWidth()) {
+                        Column(
+                            modifier = Modifier.padding(12.dp),
+                            verticalArrangement = Arrangement.spacedBy(6.dp),
+                        ) {
+                            Text(title, fontWeight = FontWeight.Bold)
+                            Text(
+                                buildString {
+                                    append("Saved ${agoText(now, match.savedAtMillis)}")
+                                    if (match.summary.isNotBlank()) append(" · ${match.summary}")
+                                },
+                                style = MaterialTheme.typography.bodySmall,
+                            )
+                            Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                                Button(onClick = { onResume(match) }) { Text("Resume") }
+                                TextButton(onClick = { deleting = match }) { Text("Delete") }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    deleting?.let { match ->
+        val title = GameCatalog.byId(match.gameId)?.title ?: match.gameId
+        AlertDialog(
+            onDismissRequest = { deleting = null },
+            title = { Text("Delete this game?") },
+            text = { Text("Your saved game of $title will be removed and cannot be resumed.") },
+            confirmButton = {
+                TextButton(onClick = { deleting = null; onDelete(match) }) { Text("Delete") }
+            },
+            dismissButton = { TextButton(onClick = { deleting = null }) { Text("Keep it") } },
+        )
+    }
+}

app/src/main/java/org/prolibertate/games/ui/SavedGameText.kt

@@ -0,0 +1,24 @@
+package org.prolibertate.games.ui
+
+import org.prolibertate.games.game.engine.SavedMatch
+
+/** How long ago something happened, in the words a person would use. */
+fun agoText(nowMillis: Long, thenMillis: Long): String {
+    val seconds = ((nowMillis - thenMillis) / 1000).coerceAtLeast(0)
+    val minutes = seconds / 60
+    val hours = minutes / 60
+    val days = hours / 24
+    return when {
+        seconds < 45 -> "just now"
+        minutes < 2 -> "a minute ago"
+        minutes < 60 -> "$minutes minutes ago"
+        hours < 2 -> "an hour ago"
+        hours < 24 -> "$hours hours ago"
+        days < 2 -> "yesterday"
+        else -> "$days days ago"
+    }
+}
+
+/** "Chess · saved 5 minutes ago" for a menu line. */
+fun savedLine(title: String, match: SavedMatch, nowMillis: Long): String =
+    "$title · saved ${agoText(nowMillis, match.savedAtMillis)}"

app/src/main/java/org/prolibertate/games/ui/ScorekeeperScreen.kt

@@ -36,6 +36,7 @@ import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateListOf
 import androidx.compose.runtime.mutableStateMapOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -114,6 +115,8 @@ fun ScorekeeperScreen(
         local = repository.sheet.first()
         loaded = true
     }
+    val recentNames by repository.recentNames.collectAsState(initial = emptyList())
+    val nameUsed: (String) -> Unit = { name -> scope.launch { repository.rememberName(name) } }
 
     val shared by session.state.collectAsState()
     val role = shared.role
@@ -220,7 +223,7 @@ fun ScorekeeperScreen(
 
             role == Role.GUEST -> Column(modifier = modifier) {
                 ConnectionBanner(shared = shared, onSync = { session.sync() })
-                Scoring(modifier = Modifier.weight(1f), sheet = sheet, onOp = change)
+                Scoring(Modifier.weight(1f), sheet, change, recentNames, nameUsed)
             }
 
             joining && role == Role.NONE ->
@@ -228,11 +231,16 @@ fun ScorekeeperScreen(
 
             !sheet.started -> SetupPane(
                 modifier = modifier,
-                onStart = { count, mode -> change(StartSheet(count, mode)) },
+                recentNames = recentNames,
+                onStart = { count, mode, names ->
+                    change(StartSheet(count, mode, names))
+                    // Last first, so the list reads in seating order.
+                    names.reversed().forEach(nameUsed)
+                },
                 onJoin = { joining = true },
             )
 
-            else -> Scoring(modifier = modifier, sheet = sheet, onOp = change)
+            else -> Scoring(modifier, sheet, change, recentNames, nameUsed)
         }
     }
 
@@ -289,9 +297,46 @@ fun ScorekeeperScreen(
 
 @OptIn(ExperimentalLayoutApi::class)
 @Composable
-private fun SetupPane(modifier: Modifier, onStart: (Int, ScoringMode) -> Unit, onJoin: () -> Unit) {
+private fun SetupPane(
+    modifier: Modifier,
+    recentNames: List<String>,
+    onStart: (Int, ScoringMode, List<String>) -> Unit,
+    onJoin: () -> Unit,
+) {
     var count by remember { mutableStateOf(ScoreSheet.DEFAULT_PLAYERS) }
     var mode by remember { mutableStateOf(ScoringMode.ROUNDS) }
+    // -1 while the options are showing; otherwise the seat being named.
+    var naming by remember { mutableStateOf(-1) }
+    val names = remember { mutableStateListOf<String>() }
+
+    if (naming >= 0) {
+        NamePane(
+            modifier = modifier,
+            seat = naming,
+            count = count,
+            name = names.getOrElse(naming) { "" },
+            // Offered once only: two players on one sheet with the same name
+            // are indistinguishable.
+            suggestions = recentNames.filter { recent ->
+                names.withIndex().none { (seat, taken) ->
+                    seat != naming && taken.trim().equals(recent.trim(), ignoreCase = true)
+                }
+            },
+            onName = { typed ->
+                while (names.size <= naming) names.add("")
+                names[naming] = typed
+            },
+            onBack = { naming -= 1 },
+            onNext = {
+                if (naming + 1 < count) {
+                    naming += 1
+                } else {
+                    onStart(count, mode, List(count) { names.getOrElse(it) { "" }.trim() })
+                }
+            },
+        )
+        return
+    }
 
     Column(
         modifier = modifier.verticalScroll(rememberScrollState()),
@@ -339,33 +384,98 @@ private fun SetupPane(modifier: Modifier, onStart: (Int, ScoringMode) -> Unit, o
             }
         }
         Text(
-            text = "Names come next: tap a column head to name it. Players can be " +
-                "added, removed or dragged into a different order at any point " +
-                "without losing anybody's score.",
+            text = "You will be asked for each name next, or skip them and tap a " +
+                "column head later. Players can be added, removed or dragged into " +
+                "a different order at any point without losing anybody's score.",
             style = MaterialTheme.typography.bodySmall,
         )
-        PrimaryAction(text = "Start scoring") { onStart(count, mode) }
+        PrimaryAction(text = "Next: name the players") { naming = 0 }
         OutlinedButton(onClick = onJoin, modifier = Modifier.fillMaxWidth()) {
             Text("Join a shared sheet nearby")
         }
     }
 }
 
+/** One seat's name, asked for on its own; a blank leaves the seat as "Player N". */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+private fun NamePane(
+    modifier: Modifier,
+    seat: Int,
+    count: Int,
+    name: String,
+    suggestions: List<String>,
+    onName: (String) -> Unit,
+    onBack: () -> Unit,
+    onNext: () -> Unit,
+) {
+    val focus = remember { FocusRequester() }
+    LaunchedEffect(seat) { focus.requestFocus() }
+    val last = seat + 1 >= count
+    Column(
+        modifier = modifier.verticalScroll(rememberScrollState()),
+        verticalArrangement = Arrangement.spacedBy(12.dp),
+    ) {
+        Text("Player ${seat + 1} of $count", style = MaterialTheme.typography.titleMedium)
+        OutlinedTextField(
+            value = name,
+            onValueChange = onName,
+            placeholder = { Text("Player ${seat + 1}") },
+            singleLine = true,
+            keyboardOptions = KeyboardOptions(imeAction = if (last) ImeAction.Done else ImeAction.Next),
+            keyboardActions = KeyboardActions(onNext = { onNext() }, onDone = { onNext() }),
+            modifier = Modifier.fillMaxWidth().focusRequester(focus),
+        )
+        if (suggestions.isNotEmpty()) {
+            Text("Recent names", style = MaterialTheme.typography.labelMedium)
+            FlowRow(
+                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                verticalArrangement = Arrangement.spacedBy(4.dp),
+            ) {
+                suggestions.forEach { recent ->
+                    FilterChip(
+                        selected = recent.equals(name.trim(), ignoreCase = true),
+                        onClick = { onName(recent) },
+                        label = { Text(recent) },
+                    )
+                }
+            }
+        }
+        PrimaryAction(text = if (last) "Start scoring" else "Next") { onNext() }
+        Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+            TextButton(onClick = onBack) { Text("Back") }
+            TextButton(onClick = { onName(""); onNext() }) { Text(if (last) "Skip and start" else "Skip") }
+        }
+    }
+}
+
 // ---------------------------------------------------------------------------
 // The sheet: a column per player, a row per round, totals ruled off at the foot
 // ---------------------------------------------------------------------------
 
 @Composable
-private fun Scoring(modifier: Modifier, sheet: ScoreSheet, onOp: (SheetOp) -> Unit) {
+private fun Scoring(
+    modifier: Modifier,
+    sheet: ScoreSheet,
+    onOp: (SheetOp) -> Unit,
+    recentNames: List<String>,
+    onNameUsed: (String) -> Unit,
+) {
     if (sheet.mode == ScoringMode.TALLY) {
-        TallySheet(modifier = modifier, sheet = sheet, onOp = onOp)
+        TallySheet(modifier, sheet, onOp, recentNames, onNameUsed)
     } else {
-        Sheet(modifier = modifier, sheet = sheet, onOp = onOp)
+        Sheet(modifier, sheet, onOp, recentNames, onNameUsed)
     }
 }
 
 @Composable
-private fun Sheet(modifier: Modifier, sheet: ScoreSheet, onOp: (SheetOp) -> Unit) {
+private fun Sheet(
+    modifier: Modifier,
+    sheet: ScoreSheet,
+    onOp: (SheetOp) -> Unit,
+    recentNames: List<String>,
+    onNameUsed: (String) -> Unit,
+) {
     // One scroll state shared by the head, the rows and the totals, so all three
     // move together: a column and the name over it must never come apart. Every
     // row is built the same way and is therefore exactly the same width, which
@@ -384,6 +494,9 @@ private fun Sheet(modifier: Modifier, sheet: ScoreSheet, onOp: (SheetOp) -> Unit
     var lastTyped by remember { mutableStateOf(-1) }
     // The cell to put the cursor in when a round is opened by tapping it.
     var focusPlayer by remember { mutableStateOf(-1) }
+    // Bumped when a round is finished, to put the cursor back in the first cell
+    // of the row that is now being filled in.
+    var nextRoundFocus by remember { mutableStateOf(0) }
 
     val editing = if (correcting >= 0) correction else pending
 
@@ -513,7 +626,7 @@ private fun Sheet(modifier: Modifier, sheet: ScoreSheet, onOp: (SheetOp) -> Unit
                         )
                     },
                     trailing = { EmptyCell(width = ADD_COLUMN, height = ROW_HEIGHT) },
-                ) { _, player ->
+                ) { index, player ->
                     if (correcting >= 0) {
                         // A round is being corrected above; what is typed here
                         // is kept, but only one row is edited at a time.
@@ -521,6 +634,8 @@ private fun Sheet(modifier: Modifier, sheet: ScoreSheet, onOp: (SheetOp) -> Unit
                     } else {
                         PointsField(
                             text = pending[player.id].orEmpty(),
+                            autoFocus = index == 0 && nextRoundFocus > 0,
+                            focusRequest = nextRoundFocus,
                             onText = {
                                 pending[player.id] = it
                                 lastTyped = player.id
@@ -563,6 +678,7 @@ private fun Sheet(modifier: Modifier, sheet: ScoreSheet, onOp: (SheetOp) -> Unit
                     onOp(AddRound(amountsAsPoints(pending)))
                     pending.clear()
                 }
+                nextRoundFocus += 1
                 lastTyped = -1
                 focusPlayer = -1
             },
@@ -587,6 +703,8 @@ private fun Sheet(modifier: Modifier, sheet: ScoreSheet, onOp: (SheetOp) -> Unit
         RenameDialog(
             sheet = sheet,
             player = renamed,
+            recentNames = recentNames,
+            onNameUsed = onNameUsed,
             onName = { onOp(RenamePlayer(renamed.id, it)) },
             onRemove = {
                 onOp(RemovePlayer(renamed.id))
@@ -607,7 +725,13 @@ private fun Sheet(modifier: Modifier, sheet: ScoreSheet, onOp: (SheetOp) -> Unit
  * sheet, so tapping one in the list takes it back off.
  */
 @Composable
-private fun TallySheet(modifier: Modifier, sheet: ScoreSheet, onOp: (SheetOp) -> Unit) {
+private fun TallySheet(
+    modifier: Modifier,
+    sheet: ScoreSheet,
+    onOp: (SheetOp) -> Unit,
+    recentNames: List<String>,
+    onNameUsed: (String) -> Unit,
+) {
     var renaming by remember { mutableStateOf(-1) }
 
     Column(modifier = modifier.verticalScroll(rememberScrollState()), verticalArrangement = Arrangement.spacedBy(8.dp)) {
@@ -676,6 +800,8 @@ private fun TallySheet(modifier: Modifier, sheet: ScoreSheet, onOp: (SheetOp) ->
         RenameDialog(
             sheet = sheet,
             player = renamed,
+            recentNames = recentNames,
+            onNameUsed = onNameUsed,
             onName = { onOp(RenamePlayer(renamed.id, it)) },
             onRemove = {
                 onOp(RemovePlayer(renamed.id))
@@ -961,9 +1087,14 @@ private fun PointsCell(text: String, muted: Boolean = false, onClick: (() -> Uni
 
 /** A cell being typed into. Blank means nothing entered; a typed 0 is kept and shown. */
 @Composable
-private fun PointsField(text: String, onText: (String) -> Unit, autoFocus: Boolean = false) {
+private fun PointsField(
+    text: String,
+    onText: (String) -> Unit,
+    autoFocus: Boolean = false,
+    focusRequest: Int = 0,
+) {
     val focus = remember { FocusRequester() }
-    LaunchedEffect(autoFocus) { if (autoFocus) focus.requestFocus() }
+    LaunchedEffect(autoFocus, focusRequest) { if (autoFocus) focus.requestFocus() }
     BasicTextField(
         value = text,
         onValueChange = { onText(sanitiseAmount(it)) },
@@ -1064,16 +1195,27 @@ private fun ActionBar(
     }
 }
 
+@OptIn(ExperimentalLayoutApi::class)
 @Composable
 private fun RenameDialog(
     sheet: ScoreSheet,
     player: ScorePlayer,
+    recentNames: List<String>,
+    onNameUsed: (String) -> Unit,
     onName: (String) -> Unit,
     onRemove: () -> Unit,
     onDismiss: () -> Unit,
 ) {
+    // Closing the dialog is what files the name away, so a name is remembered
+    // once rather than once per keystroke.
+    val finish = {
+        onNameUsed(player.name)
+        onDismiss()
+    }
+    val taken = sheet.players.filter { it.id != player.id }.map { it.name.trim().lowercase() }
+    val suggestions = recentNames.filter { it.trim().lowercase() !in taken }
     AlertDialog(
-        onDismissRequest = onDismiss,
+        onDismissRequest = finish,
         title = { Text("Name this column") },
         text = {
             Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
@@ -1084,6 +1226,21 @@ private fun RenameDialog(
                     singleLine = true,
                     modifier = Modifier.fillMaxWidth(),
                 )
+                if (suggestions.isNotEmpty()) {
+                    Text("Recent names", style = MaterialTheme.typography.labelMedium)
+                    FlowRow(
+                        horizontalArrangement = Arrangement.spacedBy(8.dp),
+                        verticalArrangement = Arrangement.spacedBy(4.dp),
+                    ) {
+                        suggestions.forEach { name ->
+                            FilterChip(
+                                selected = name.equals(player.name.trim(), ignoreCase = true),
+                                onClick = { onName(name) },
+                                label = { Text(name) },
+                            )
+                        }
+                    }
+                }
                 TextButton(
                     onClick = onRemove,
                     // The last two columns stay: a sheet needs somebody on it.
@@ -1091,7 +1248,7 @@ private fun RenameDialog(
                 ) { Text("Remove this player and their score") }
             }
         },
-        confirmButton = { TextButton(onClick = onDismiss) { Text("Done") } },
+        confirmButton = { TextButton(onClick = finish) { Text("Done") } },
     )
 }
 

app/src/main/java/org/prolibertate/games/ui/SettingsScreen.kt

@@ -24,6 +24,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import kotlinx.coroutines.launch
+import kotlin.math.roundToInt
 import org.prolibertate.games.settings.Settings
 import org.prolibertate.games.update.Release
 import org.prolibertate.games.update.UpdateChannel
@@ -83,6 +84,26 @@ fun SettingsScreen(
 
             Divider()
 
+            Column {
+                Text("Text size", fontWeight = FontWeight.Bold)
+                Text(
+                    text = "${(settings.textScale * 100).roundToInt()}% — " +
+                        "scales text throughout the app, on top of your phone's setting",
+                    style = MaterialTheme.typography.bodySmall,
+                )
+                Slider(
+                    value = settings.textScale,
+                    onValueChange = { scale ->
+                        scope.launch { env.settingsRepository.setTextScale(scale) }
+                    },
+                    valueRange = Settings.MIN_TEXT_SCALE..Settings.MAX_TEXT_SCALE,
+                    // 10% increments across 80%-160%.
+                    steps = 7,
+                )
+            }
+
+            Divider()
+
             Column {
                 Text("Your name", fontWeight = FontWeight.Bold)
                 Text(

app/src/main/java/org/prolibertate/games/ui/game/BackgammonScreen.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
 import androidx.compose.foundation.clickable
@@ -378,7 +379,12 @@ private fun LeaveDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
                     "at the table is told you have left."
             )
         },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/CardTable.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.BorderStroke
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
@@ -79,7 +80,12 @@ fun PatienceEndDialog(what: String, onEnd: () -> Unit, onKeepPlaying: () -> Unit
         onDismissRequest = onKeepPlaying,
         title = { Text("End this game?") },
         text = { Text(what) },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/CheckersScreen.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
 import androidx.compose.foundation.clickable
@@ -314,7 +315,12 @@ private fun EndGameDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
                     "at the table is told you have left."
             )
         },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/ChessScreen.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
 import androidx.compose.foundation.clickable
@@ -215,7 +216,12 @@ private fun ConfirmEndDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
                     "at the table is told you have left."
             )
         },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/CrazyEightsScreen.kt

@@ -60,6 +60,22 @@ fun CrazyEightsScreen(
     onExit: () -> Unit,
 ) {
     val state by controller.state.collectAsState()
+    val abandoned by controller.abandoned.collectAsState()
+    var confirmingEnd by remember { mutableStateOf(false) }
+
+    val endGameAction: @Composable () -> Unit = {
+        TextButton(onClick = { confirmingEnd = true }) { Text("End game") }
+    }
+    val dialogs: @Composable () -> Unit = {
+        abandoned?.let { PatienceLeftDialog(it, onExit, controller::dismissAbandoned) }
+        if (confirmingEnd) {
+            PatienceEndDialog(
+                what = "The game ends here. Anyone else at the table is told you have left.",
+                onEnd = onExit,
+                onKeepPlaying = { confirmingEnd = false },
+            )
+        }
+    }
     val legal by controller.legalMoves.collectAsState()
 
     // Playing an eight is two decisions: the card, then the suit it turns the
@@ -68,13 +84,15 @@ fun CrazyEightsScreen(
 
     val current = state
     if (current == null) {
-        ScreenScaffold(title = "Crazy 8s", onBack = onExit) { modifier ->
+        ScreenScaffold(title = "Crazy 8s", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
             Box(modifier, contentAlignment = Alignment.Center) { Text("Dealing…") }
         }
         return
     }
 
-    ScreenScaffold(title = "Crazy 8s", onBack = onExit) { modifier ->
+    ScreenScaffold(title = "Crazy 8s", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
         BoxWithConstraints(modifier = modifier) {
             val cardWidth = (minOf(maxWidth, maxHeight) * 0.16f).coerceIn(44.dp, 92.dp)
 

app/src/main/java/org/prolibertate/games/ui/game/CribbageScreen.kt

@@ -65,11 +65,28 @@ fun CribbageScreen(
     onExit: () -> Unit,
 ) {
     val state by controller.state.collectAsState()
+    val abandoned by controller.abandoned.collectAsState()
+    var confirmingEnd by remember { mutableStateOf(false) }
+
+    val endGameAction: @Composable () -> Unit = {
+        TextButton(onClick = { confirmingEnd = true }) { Text("End game") }
+    }
+    val dialogs: @Composable () -> Unit = {
+        abandoned?.let { PatienceLeftDialog(it, onExit, controller::dismissAbandoned) }
+        if (confirmingEnd) {
+            PatienceEndDialog(
+                what = "The game ends here. Anyone else at the table is told you have left.",
+                onEnd = onExit,
+                onKeepPlaying = { confirmingEnd = false },
+            )
+        }
+    }
     val legal by controller.legalMoves.collectAsState()
 
     val current = state
     if (current == null) {
-        ScreenScaffold(title = "Cribbage", onBack = onExit) { modifier ->
+        ScreenScaffold(title = "Cribbage", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
             Box(modifier, contentAlignment = Alignment.Center) { Text("Dealing…") }
         }
         return
@@ -79,7 +96,8 @@ fun CribbageScreen(
     // together. Forgotten whenever a new hand is dealt.
     var chosen by remember(current.handNumber) { mutableStateOf(emptySet<Card>()) }
 
-    ScreenScaffold(title = "Cribbage", onBack = onExit) { modifier ->
+    ScreenScaffold(title = "Cribbage", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
         BoxWithConstraints(modifier = modifier) {
             val cardWidth = (minOf(maxWidth, maxHeight) * 0.16f).coerceIn(44.dp, 92.dp)
 

app/src/main/java/org/prolibertate/games/ui/game/EuchreScreen.kt

@@ -22,6 +22,7 @@ import androidx.compose.material3.Button
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.LaunchedEffect
@@ -72,18 +73,36 @@ fun EuchreScreen(
     onExit: () -> Unit,
 ) {
     val state by controller.state.collectAsState()
+    val abandoned by controller.abandoned.collectAsState()
+    var confirmingEnd by remember { mutableStateOf(false) }
+
+    val endGameAction: @Composable () -> Unit = {
+        TextButton(onClick = { confirmingEnd = true }) { Text("End game") }
+    }
+    val dialogs: @Composable () -> Unit = {
+        abandoned?.let { PatienceLeftDialog(it, onExit, controller::dismissAbandoned) }
+        if (confirmingEnd) {
+            PatienceEndDialog(
+                what = "The game ends here. Anyone else at the table is told you have left.",
+                onEnd = onExit,
+                onKeepPlaying = { confirmingEnd = false },
+            )
+        }
+    }
     val legal by controller.legalMoves.collectAsState()
     val notice by controller.notice.collectAsState()
 
     val current = state
     if (current == null) {
-        ScreenScaffold(title = "Euchre", onBack = onExit) { modifier ->
+        ScreenScaffold(title = "Euchre", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
             Box(modifier, contentAlignment = Alignment.Center) { Text("Dealing…") }
         }
         return
     }
 
-    ScreenScaffold(title = "Euchre", onBack = onExit) { modifier ->
+    ScreenScaffold(title = "Euchre", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
         BoxWithConstraints(modifier = modifier) {
             val compact = maxWidth < 600.dp
             val cardWidth = (minOf(maxWidth, maxHeight) * if (compact) 0.17f else 0.12f)

app/src/main/java/org/prolibertate/games/ui/game/GolfScreen.kt

@@ -69,18 +69,36 @@ fun GolfScreen(
     onExit: () -> Unit,
 ) {
     val state by controller.state.collectAsState()
+    val abandoned by controller.abandoned.collectAsState()
+    var confirmingEnd by remember { mutableStateOf(false) }
+
+    val endGameAction: @Composable () -> Unit = {
+        TextButton(onClick = { confirmingEnd = true }) { Text("End game") }
+    }
+    val dialogs: @Composable () -> Unit = {
+        abandoned?.let { PatienceLeftDialog(it, onExit, controller::dismissAbandoned) }
+        if (confirmingEnd) {
+            PatienceEndDialog(
+                what = "The game ends here. Anyone else at the table is told you have left.",
+                onEnd = onExit,
+                onKeepPlaying = { confirmingEnd = false },
+            )
+        }
+    }
     val legal by controller.legalMoves.collectAsState()
     var mode by remember { mutableStateOf(PlaceMode.SWAP) }
 
     val current = state
     if (current == null) {
-        ScreenScaffold(title = "Golf", onBack = onExit) { modifier ->
+        ScreenScaffold(title = "Golf", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
             Box(modifier, contentAlignment = Alignment.Center) { Text("Dealing…") }
         }
         return
     }
 
-    ScreenScaffold(title = "Golf", onBack = onExit) { modifier ->
+    ScreenScaffold(title = "Golf", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
         BoxWithConstraints(modifier = modifier) {
             val shortest = minOf(maxWidth, maxHeight)
             val ownCard = (shortest * 0.16f).coerceIn(40.dp, 84.dp)

app/src/main/java/org/prolibertate/games/ui/game/HeartsScreen.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -268,7 +269,12 @@ private fun EndHeartsDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
         onDismissRequest = onKeepPlaying,
         title = { Text("End this game?") },
         text = { Text("The game ends here. Anyone else at the table is told you have left.") },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/KaiserScreen.kt

@@ -22,6 +22,7 @@ import androidx.compose.material3.Button
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
@@ -74,18 +75,36 @@ fun KaiserScreen(
     onExit: () -> Unit,
 ) {
     val state by controller.state.collectAsState()
+    val abandoned by controller.abandoned.collectAsState()
+    var confirmingEnd by remember { mutableStateOf(false) }
+
+    val endGameAction: @Composable () -> Unit = {
+        TextButton(onClick = { confirmingEnd = true }) { Text("End game") }
+    }
+    val dialogs: @Composable () -> Unit = {
+        abandoned?.let { PatienceLeftDialog(it, onExit, controller::dismissAbandoned) }
+        if (confirmingEnd) {
+            PatienceEndDialog(
+                what = "The game ends here. Anyone else at the table is told you have left.",
+                onEnd = onExit,
+                onKeepPlaying = { confirmingEnd = false },
+            )
+        }
+    }
     val legal by controller.legalMoves.collectAsState()
     val notice by controller.notice.collectAsState()
 
     val current = state
     if (current == null) {
-        ScreenScaffold(title = "Kaiser", onBack = onExit) { modifier ->
+        ScreenScaffold(title = "Kaiser", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
             Box(modifier, contentAlignment = Alignment.Center) { Text("Dealing…") }
         }
         return
     }
 
-    ScreenScaffold(title = "Kaiser", onBack = onExit) { modifier ->
+    ScreenScaffold(title = "Kaiser", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
         BoxWithConstraints(modifier = modifier) {
             val compact = maxWidth < 600.dp
             val cardWidth = (minOf(maxWidth, maxHeight) * if (compact) 0.15f else 0.11f)

app/src/main/java/org/prolibertate/games/ui/game/KlondikeScreen.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.BorderStroke
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
@@ -342,7 +343,12 @@ private fun EndTableDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
         onDismissRequest = onKeepPlaying,
         title = { Text("End this game?") },
         text = { Text("The deal is left as it stands.") },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/MastermindScreen.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
 import androidx.compose.foundation.clickable
@@ -356,7 +357,12 @@ private fun EndDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
         onDismissRequest = onKeepPlaying,
         title = { Text("End this game?") },
         text = { Text("The game ends here. Anyone else at the table is told you have left.") },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/MeowdokuScreen.kt

@@ -0,0 +1,379 @@
+package org.prolibertate.games.ui.game
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.border
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.BoxWithConstraints
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.foundation.gestures.awaitEachGesture
+import androidx.compose.foundation.gestures.awaitFirstDown
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.Button
+import androidx.compose.material3.FilterChip
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.input.pointer.pointerInput
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import androidx.compose.ui.unit.TextUnit
+import org.prolibertate.games.game.meowdoku.MeowdokuMove
+import org.prolibertate.games.game.meowdoku.MeowdokuState
+import org.prolibertate.games.game.meowdoku.PlaceCat
+import org.prolibertate.games.game.meowdoku.Square
+import org.prolibertate.games.game.meowdoku.TakeHint
+import org.prolibertate.games.game.meowdoku.TogglePencil
+import org.prolibertate.games.net.MatchController
+import org.prolibertate.games.ui.LocalEndGameHandle
+import org.prolibertate.games.ui.ScreenScaffold
+import org.prolibertate.games.ui.theme.CardRed
+import kotlin.math.abs
+import kotlin.math.roundToInt
+
+private const val TITLE = "Meowdoku"
+
+/**
+ * How long the second tap of a double tap may take to arrive.
+ *
+ * 350 ms, the number the original game ships: long enough that a deliberate
+ * one-two still reads as one question, short enough that nobody pairs two
+ * taps they meant for two separate squares.
+ */
+private const val DOUBLE_TAP_WINDOW_MILLIS = 350L
+
+/**
+ * The region colours, one per cat the board can hold.
+ *
+ * The board never needs two regions of one colour — a side-ten board has ten
+ * regions and the palette has ten — so a region's colour is just its id, and
+ * nothing has to be computed to keep neighbours apart. The palette reads as
+ * watercolour on purpose: cats are dark ink on top of it, and a square the
+ * player has crossed over is too.
+ */
+private val RegionColours = listOf(
+    Color(0xFFF2C6C2), // rose
+    Color(0xFFF7E0A6), // butter
+    Color(0xFFCDE8C5), // mint
+    Color(0xFFC5E3F0), // sky
+    Color(0xFFD8CDEB), // lilac
+    Color(0xFFEBC9A0), // apricot
+    Color(0xFFBFE3D0), // spruce
+    Color(0xFFF0D7E3), // blossom
+    Color(0xFFCFCFE8), // periwinkle
+    Color(0xFFE3E7C1), // lime
+)
+
+/**
+ * The puzzle board, tapped the way the original's is.
+ *
+ * One tap crosses a square over; a second tap on the same square within
+ * [DOUBLE_TAP_WINDOW_MILLIS] asks the board whether a cat lives there. Drag
+ * strokes paint or erase crosses along the line the finger takes, which is
+ * how a row gets crossed out in one gesture rather than eight taps. Cats are
+ * permanent: tapping one does nothing, and a stroke skips over it.
+ */
+@Composable
+fun MeowdokuScreen(
+    controller: MatchController<MeowdokuState, MeowdokuMove>,
+    onNewPuzzle: () -> Unit,
+    onExit: () -> Unit,
+) {
+    val state by controller.state.collectAsState()
+    val legal by controller.legalMoves.collectAsState()
+    val abandoned by controller.abandoned.collectAsState()
+
+    var confirmingEnd by remember { mutableStateOf(false) }
+
+    val endGameAction: @Composable () -> Unit = {
+        TextButton(onClick = { confirmingEnd = true }) { Text("End game") }
+    }
+
+    val current = state
+    if (current == null) {
+        ScreenScaffold(title = TITLE, onBack = onExit, actions = endGameAction) { modifier ->
+            Box(modifier, contentAlignment = Alignment.Center) { Text("Setting up…") }
+            abandoned?.let { LeftBoardDialog(it, onExit, controller::dismissAbandoned) }
+            if (confirmingEnd) EndBoardDialog(onExit) { confirmingEnd = false }
+        }
+        return
+    }
+
+    val places = legal.filterIsInstance<PlaceCat>().map { it.square }.toSet()
+    val pencils = legal.filterIsInstance<TogglePencil>().map { it.square }.toSet()
+    val finished by controller.finished.collectAsState()
+
+    ScreenScaffold(title = TITLE, onBack = onExit, actions = endGameAction) { modifier ->
+        Column(
+            modifier = modifier.verticalScroll(rememberScrollState()),
+            verticalArrangement = Arrangement.spacedBy(10.dp),
+        ) {
+            Text(
+                text = when {
+                    current.solved -> "Found every cat" +
+                        if (current.wrongCats == 0) ", not one tap wasted." else ", with ${current.wrongCats} wrong taps."
+                    current.lost -> "Out of hearts, with ${current.side - current.catsFound} cats still hiding."
+                    else -> "${current.catsFound} of ${current.side} cats found. " +
+                        "Tap to cross a square, tap it again for a cat."
+                },
+                fontWeight = FontWeight.Bold,
+            )
+            Text(
+                text = "Hearts " + "♥".repeat(current.heartsLeft) +
+                    " · Hints " + current.hintsLeft,
+                style = MaterialTheme.typography.bodySmall,
+            )
+
+            Board(
+                state = current,
+                // Moves are refused rather than hidden: an attempt or a note
+                // the board would reject (a tap on a cat, mostly) has to die
+                // here, in the gesture, where the player can be doing nothing
+                // else the same instant.
+                onNote = { square -> if (square in pencils) controller.submit(TogglePencil(square)) },
+                onAttempt = { square -> if (square in places) controller.submit(PlaceCat(square)) },
+            )
+
+            if (TakeHint in legal) {
+                FilterChip(
+                    selected = false,
+                    onClick = { controller.submit(TakeHint) },
+                    label = { Text("Hint") },
+                )
+            }
+
+            if (finished) {
+                Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                    Button(onClick = onNewPuzzle) { Text("New puzzle") }
+                    TextButton(onClick = onExit) { Text("Leave") }
+                }
+            }
+
+            current.log.takeLast(2).forEach {
+                Text(it, style = MaterialTheme.typography.bodySmall)
+            }
+        }
+
+        abandoned?.let { LeftBoardDialog(it, onExit, controller::dismissAbandoned) }
+        if (confirmingEnd) EndBoardDialog(onExit) { confirmingEnd = false }
+    }
+}
+
+/**
+ * The board as one gesture surface.
+ *
+ * Cells are drawn by weight inside a square frame, but input is not per-cell:
+ * a stroke is one continuous gesture, so the pointer works in board
+ * coordinates and maps positions to squares itself. The cell list renders
+ * underneath, and the live state is read through [rememberUpdatedState]
+ * because a gesture outlives the recompositions it lands in.
+ */
+@Composable
+private fun Board(
+    state: MeowdokuState,
+    onNote: (Square) -> Unit,
+    onAttempt: (Square) -> Unit,
+) {
+    val side = state.side
+    val current by rememberUpdatedState(state)
+    val note by rememberUpdatedState(onNote)
+    val attempt by rememberUpdatedState(onAttempt)
+
+    BoxWithConstraints(modifier = Modifier.fillMaxWidth()) {
+        // One cell's edge, so a cat is always about half a square whatever
+        // board was dealt.
+        val cell = maxWidth / side
+        Box(
+            modifier = Modifier
+                .aspectRatio(1f)
+                .pointerInput(side) {
+                    val cellPx = size.width.toFloat() / side
+                    var lastTap: Square? = null
+                    var lastTapAt = 0L
+                    awaitEachGesture {
+                        val down = awaitFirstDown(requireUnconsumed = false)
+                        val board = current
+                        val start = squareAt(down.position, cellPx, side)
+                            ?: return@awaitEachGesture
+                        if (start in board.cats) return@awaitEachGesture
+
+                        val now = System.currentTimeMillis()
+                        if (start == lastTap && now - lastTapAt < DOUBLE_TAP_WINDOW_MILLIS) {
+                            // The second tap of a pair: the cat attempt, and
+                            // no note — the cross it lands on was drawn by
+                            // this pair's first tap, and the board replaces it.
+                            lastTap = null
+                            attempt(start)
+                            do {
+                                val event = awaitPointerEvent()
+                                val change = event.changes.firstOrNull { it.id == down.id }
+                                change?.consume()
+                            } while (change != null && change.pressed)
+                            return@awaitEachGesture
+                        }
+
+                        // The first tap: a note, and the stroke that may follow
+                        // paints the same note everywhere it goes.
+                        lastTap = start
+                        lastTapAt = now
+                        val erasing = start in board.marks
+                        note(start)
+                        val marks = board.marks.toMutableSet()
+                        marks.flip(start)
+                        var previous = start
+
+                        while (true) {
+                            val event = awaitPointerEvent()
+                            val change = event.changes.firstOrNull { it.id == down.id }
+                            if (change == null || !change.pressed) break
+                            change.consume()
+                            val here = squareAt(change.position, cellPx, side) ?: continue
+                            if (here == previous) continue
+                            for (square in path(previous, here)) {
+                                if (square in board.cats) continue
+                                // `marks` is the stroke's own mirror: the base
+                                // board plus every note this stroke has
+                                // already submitted. The state flow lags a
+                                // frame behind submissions, and a stroke that
+                                // crosses a square twice must leave it at the
+                                // stroke's target, not flip it back.
+                                //
+                                // Erasing means "flip everything still
+                                // crossed"; painting means "flip everything
+                                // still blank" — which is the same test read
+                                // two ways: flip while marked == erasing.
+                                if ((square in marks) == erasing) {
+                                    note(square)
+                                    marks.flip(square)
+                                }
+                            }
+                            previous = here
+                        }
+                    }
+                }
+        ) {
+            Column(modifier = Modifier.aspectRatio(1f)) {
+                for (row in 0 until side) {
+                    Row(modifier = Modifier.weight(1f)) {
+                        for (col in 0 until side) {
+                            CellView(
+                                square = Square(row, col),
+                                state = current,
+                                glyphSize = (cell.value * 0.55f).sp,
+                                modifier = Modifier.weight(1f),
+                            )
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+/** Which square a pointer position is over, or null if it has left the board. */
+private fun squareAt(position: Offset, cellPx: Float, side: Int): Square? {
+    val col = (position.x / cellPx).toInt()
+    val row = (position.y / cellPx).toInt()
+    if (row !in 0 until side || col !in 0 until side) return null
+    return Square(row, col)
+}
+
+/** Add the square, or drop it if it was already there — the stroke's own toggle. */
+private fun MutableSet<Square>.flip(square: Square) {
+    if (!add(square)) remove(square)
+}
+
+/**
+ * The squares between two consecutive pointer reads, endpoints not repeated.
+ *
+ * A fast stroke publishes fewer positions than it crosses cells, so the line
+ * between two reads is walked in whole-cell steps. [path] returns at most one
+ * square per cell crossed, in order, which is what lets a stroke cross a row
+ * in one drag without missing the squares between two events.
+ */
+private fun path(from: Square, to: Square): List<Square> {
+    val dr = to.row - from.row
+    val dc = to.col - from.col
+    val steps = maxOf(abs(dr), abs(dc))
+    if (steps <= 1) return listOf(to)
+    return (1..steps).map { i ->
+        Square(
+            from.row + (dr * i.toFloat() / steps).roundToInt(),
+            from.col + (dc * i.toFloat() / steps).roundToInt(),
+        )
+    }
+}
+
+@Composable
+private fun CellView(
+    square: Square,
+    state: MeowdokuState,
+    glyphSize: TextUnit,
+    modifier: Modifier,
+) {
+    val isCat = square in state.cats
+    val isMark = square in state.marks
+    val justWrong = state.lastWrong && state.lastSquare == square
+    Box(
+        modifier = modifier
+            .aspectRatio(1f)
+            .border(1.dp, Color(0x33000000))
+            .background(RegionColours[state.regionOf(square) % RegionColours.size])
+            .then(
+                if (justWrong) Modifier.border(3.dp, CardRed) else Modifier
+            ),
+        contentAlignment = Alignment.Center,
+    ) {
+        when {
+            isCat -> Text("🐱", fontSize = glyphSize)
+            isMark -> Text(
+                "✕",
+                color = Color(0xAA1C1B1F),
+                fontWeight = FontWeight.Bold,
+                fontSize = glyphSize,
+            )
+        }
+    }
+}
+
+@Composable
+private fun EndBoardDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
+    AlertDialog(
+        onDismissRequest = onKeepPlaying,
+        title = { Text("End this game?") },
+        text = { Text("The board is left as it stands.") },
+        confirmButton = {
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
+        dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
+    )
+}
+
+@Composable
+private fun LeftBoardDialog(notice: String, onExit: () -> Unit, onStay: () -> Unit) {
+    AlertDialog(
+        onDismissRequest = onStay,
+        title = { Text("The game has ended") },
+        text = { Text(notice) },
+        confirmButton = { TextButton(onClick = onExit) { Text("Leave the game") } },
+        dismissButton = { TextButton(onClick = onStay) { Text("Look at the board") } },
+    )
+}

app/src/main/java/org/prolibertate/games/ui/game/MorrisScreen.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.Canvas
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
@@ -483,7 +484,12 @@ private fun LeaveBoardDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
                     "at the table is told you have left."
             )
         },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/PegSolitaireScreen.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.BorderStroke
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
@@ -242,7 +243,12 @@ private fun EndBoardDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
         onDismissRequest = onKeepPlaying,
         title = { Text("End this game?") },
         text = { Text("The board is left as it stands.") },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/PiratesScreen.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.Canvas
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
@@ -371,7 +372,12 @@ private fun LeaveFieldDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
                     "at the table is told you have left."
             )
         },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/PresidentScreen.kt

@@ -20,11 +20,15 @@ import androidx.compose.foundation.rememberScrollState
 import androidx.compose.material3.Button
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.TextButton
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.key
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.rotate
@@ -66,16 +70,34 @@ fun PresidentScreen(
 ) {
     val state by controller.state.collectAsState()
     val legal by controller.legalMoves.collectAsState()
+    val abandoned by controller.abandoned.collectAsState()
+    var confirmingEnd by remember { mutableStateOf(false) }
+
+    val endGameAction: @Composable () -> Unit = {
+        TextButton(onClick = { confirmingEnd = true }) { Text("End game") }
+    }
+    val dialogs: @Composable () -> Unit = {
+        abandoned?.let { PatienceLeftDialog(it, onExit, controller::dismissAbandoned) }
+        if (confirmingEnd) {
+            PatienceEndDialog(
+                what = "The game ends here. Anyone else at the table is told you have left.",
+                onEnd = onExit,
+                onKeepPlaying = { confirmingEnd = false },
+            )
+        }
+    }
 
     val current = state
     if (current == null) {
-        ScreenScaffold(title = "President", onBack = onExit) { modifier ->
+        ScreenScaffold(title = "President", onBack = onExit, actions = endGameAction) { modifier ->
             Box(modifier, contentAlignment = Alignment.Center) { Text("Dealing…") }
+            dialogs()
         }
         return
     }
 
-    ScreenScaffold(title = "President", onBack = onExit) { modifier ->
+    ScreenScaffold(title = "President", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
         BoxWithConstraints(modifier = modifier) {
             val cardWidth = (minOf(maxWidth, maxHeight) * 0.15f).coerceIn(44.dp, 88.dp)
 

app/src/main/java/org/prolibertate/games/ui/game/SequenceScreen.kt

@@ -18,6 +18,7 @@ import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
@@ -81,12 +82,29 @@ fun SequenceScreen(
     onExit: () -> Unit,
 ) {
     val state by controller.state.collectAsState()
+    val abandoned by controller.abandoned.collectAsState()
+    var confirmingEnd by remember { mutableStateOf(false) }
+
+    val endGameAction: @Composable () -> Unit = {
+        TextButton(onClick = { confirmingEnd = true }) { Text("End game") }
+    }
+    val dialogs: @Composable () -> Unit = {
+        abandoned?.let { PatienceLeftDialog(it, onExit, controller::dismissAbandoned) }
+        if (confirmingEnd) {
+            PatienceEndDialog(
+                what = "The game ends here. Anyone else at the table is told you have left.",
+                onEnd = onExit,
+                onKeepPlaying = { confirmingEnd = false },
+            )
+        }
+    }
     val legal by controller.legalMoves.collectAsState()
     var selected by remember { mutableStateOf<Card?>(null) }
 
     val current = state
     if (current == null) {
-        ScreenScaffold(title = "Sequence", onBack = onExit) { modifier ->
+        ScreenScaffold(title = "Sequence", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
             Box(modifier, contentAlignment = Alignment.Center) { Text("Dealing…") }
         }
         return
@@ -97,7 +115,8 @@ fun SequenceScreen(
     val removals = legal.filterIsInstance<RemoveChip>().filter { it.card == selected }
     val highlighted = (placements.map { it.cell } + removals.map { it.cell }).toSet()
 
-    ScreenScaffold(title = "Sequence", onBack = onExit) { modifier ->
+    ScreenScaffold(title = "Sequence", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
         BoxWithConstraints(modifier = modifier) {
             val wide = maxWidth > maxHeight
             val boardSide = if (wide) {

app/src/main/java/org/prolibertate/games/ui/game/TayuScreen.kt

@@ -1,5 +1,6 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.Canvas
 import androidx.compose.foundation.gestures.detectTapGestures
 import androidx.compose.foundation.layout.Arrangement
@@ -668,7 +669,12 @@ private fun TayuConfirmEndDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
                     "table is told you have left."
             )
         },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/WizardScreen.kt

@@ -75,18 +75,36 @@ fun WizardScreen(
     onExit: () -> Unit,
 ) {
     val state by controller.state.collectAsState()
+    val abandoned by controller.abandoned.collectAsState()
+    var confirmingEnd by remember { mutableStateOf(false) }
+
+    val endGameAction: @Composable () -> Unit = {
+        TextButton(onClick = { confirmingEnd = true }) { Text("End game") }
+    }
+    val dialogs: @Composable () -> Unit = {
+        abandoned?.let { PatienceLeftDialog(it, onExit, controller::dismissAbandoned) }
+        if (confirmingEnd) {
+            PatienceEndDialog(
+                what = "The game ends here. Anyone else at the table is told you have left.",
+                onEnd = onExit,
+                onKeepPlaying = { confirmingEnd = false },
+            )
+        }
+    }
     val legal by controller.legalMoves.collectAsState()
     val notice by controller.notice.collectAsState()
 
     val current = state
     if (current == null) {
-        ScreenScaffold(title = "Wizard", onBack = onExit) { modifier ->
+        ScreenScaffold(title = "Wizard", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
             Box(modifier, contentAlignment = Alignment.Center) { Text("Dealing…") }
         }
         return
     }
 
-    ScreenScaffold(title = "Wizard", onBack = onExit) { modifier ->
+    ScreenScaffold(title = "Wizard", onBack = onExit, actions = endGameAction) { modifier ->
+        dialogs()
         BoxWithConstraints(modifier = modifier) {
             val cardWidth = (minOf(maxWidth, maxHeight) * 0.14f).coerceIn(40.dp, 88.dp)
 

app/src/main/java/org/prolibertate/games/ui/game/YahtzeeScreen.kt

@@ -1,11 +1,16 @@
 package org.prolibertate.games.ui.game
 
+import org.prolibertate.games.ui.LocalEndGameHandle
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.BoxWithConstraints
+import androidx.compose.foundation.horizontalScroll
+import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.Canvas
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
@@ -29,12 +34,17 @@ import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import org.prolibertate.games.game.yahtzee.DICE_COUNT
 import org.prolibertate.games.game.yahtzee.RollDice
 import org.prolibertate.games.game.yahtzee.ScoreIn
 import org.prolibertate.games.game.yahtzee.YahtzeeCategory
+import org.prolibertate.games.game.yahtzee.YahtzeeComparison
+import org.prolibertate.games.game.yahtzee.recordOf
+import org.prolibertate.games.settings.YahtzeeStatsRepository
+import kotlin.math.roundToInt
 import org.prolibertate.games.game.yahtzee.YahtzeeMove
 import org.prolibertate.games.game.yahtzee.YahtzeeSection
 import org.prolibertate.games.game.yahtzee.YahtzeeState
@@ -60,6 +70,7 @@ private const val TITLE = "Yahtzee"
 fun YahtzeeScreen(
     controller: MatchController<YahtzeeState, YahtzeeMove>,
     localSeat: Int,
+    stats: YahtzeeStatsRepository,
     onExit: () -> Unit,
 ) {
     val state by controller.state.collectAsState()
@@ -68,6 +79,11 @@ fun YahtzeeScreen(
 
     val kept = remember { mutableStateListOf<Int>() }
     var confirmingEnd by remember { mutableStateOf(false) }
+    var confirmingZero by remember { mutableStateOf<YahtzeeCategory?>(null) }
+    var comparison by remember { mutableStateOf<YahtzeeComparison?>(null) }
+    // Only a game seen to finish is recorded: reopening a saved game that was
+    // already over must not count it a second time.
+    var sawInProgress by remember { mutableStateOf(false) }
 
     val endGameAction: @Composable () -> Unit = {
         TextButton(onClick = { confirmingEnd = true }) { Text("End game") }
@@ -88,6 +104,15 @@ fun YahtzeeScreen(
     // refused, and the Throw button would look broken again.
     LaunchedEffect(current.turn, current.round) { kept.clear() }
 
+    LaunchedEffect(current.isOver) {
+        if (!current.isOver) {
+            sawInProgress = true
+        } else if (sawInProgress) {
+            sawInProgress = false
+            comparison = stats.finish(recordOf(current, localSeat))
+        }
+    }
+
     val yours = current.turn == localSeat && !current.isOver
     val canRoll = legal.any { it is RollDice }
     val writable = legal.filterIsInstance<ScoreIn>().map { it.category }.toSet()
@@ -137,8 +162,14 @@ fun YahtzeeScreen(
                 localSeat = localSeat,
                 writable = if (yours) writable else emptySet(),
                 onWrite = {
-                    controller.submit(ScoreIn(it))
-                    kept.clear()
+                    // A zero is a box spent for nothing, and one mis-tap on a
+                    // dense card is all it takes, so ask first.
+                    if (scoreOf(it, current.dice) == 0) {
+                        confirmingZero = it
+                    } else {
+                        controller.submit(ScoreIn(it))
+                        kept.clear()
+                    }
                 },
             )
 
@@ -149,9 +180,79 @@ fun YahtzeeScreen(
 
         abandoned?.let { LeftCardDialog(it, onExit, controller::dismissAbandoned) }
         if (confirmingEnd) EndCardDialog(onExit) { confirmingEnd = false }
+        comparison?.let { StatsDialog(it, onExit) { comparison = null } }
+        confirmingZero?.let { category ->
+            ZeroScoreDialog(
+                category = category,
+                onConfirm = {
+                    confirmingZero = null
+                    controller.submit(ScoreIn(category))
+                    kept.clear()
+                },
+                onCancel = { confirmingZero = null },
+            )
+        }
     }
 }
 
+@Composable
+private fun StatsDialog(c: YahtzeeComparison, onLeave: () -> Unit, onClose: () -> Unit) {
+    fun pct(v: Double?) = v?.let { "${(it * 100).roundToInt()}%" } ?: "—"
+    val headline = when {
+        c.previousGames == 0 -> "Your first recorded game."
+        c.rank == 1 -> "A new personal best!"
+        else -> "${ordinal(c.rank)} best of ${c.gamesRanked} games."
+    }
+    AlertDialog(
+        onDismissRequest = onClose,
+        title = { Text("Game over: ${c.current.total} points") },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(6.dp)) {
+                Text(headline, fontWeight = FontWeight.Bold)
+                StatLine("", "This game", "Before")
+                StatLine("Score", "${c.current.total}", c.averageBefore?.let { "avg ${it.roundToInt()}, best ${c.bestBefore}" } ?: "—")
+                StatLine("Upper bonus", if (c.current.gotBonus) "Yes" else "No", pct(c.bonusRateBefore))
+                StatLine("Yahtzees", "${c.current.yahtzees}", "${c.yahtzeesBefore} total")
+                StatLine("Zeroed boxes", "${c.current.zeros}", "")
+                if (c.current.players > 1) {
+                    StatLine("Result", if (c.current.won) "Won" else "Lost", "won ${pct(c.winRateBefore)}")
+                }
+                Text(
+                    "Games before this one: ${c.previousGames}",
+                    style = MaterialTheme.typography.bodySmall,
+                )
+            }
+        },
+        confirmButton = { TextButton(onClick = onLeave) { Text("Leave the game") } },
+        dismissButton = { TextButton(onClick = onClose) { Text("Look at the card") } },
+    )
+}
+
+@Composable
+private fun StatLine(label: String, now: String, before: String) {
+    Row(modifier = Modifier.fillMaxWidth()) {
+        Text(label, modifier = Modifier.weight(1.2f), fontWeight = FontWeight.Bold)
+        Text(now, modifier = Modifier.weight(1f))
+        Text(before, modifier = Modifier.weight(1.6f))
+    }
+}
+
+private fun ordinal(n: Int): String {
+    val suffix = if (n % 100 in 11..13) "th" else when (n % 10) { 1 -> "st"; 2 -> "nd"; 3 -> "rd"; else -> "th" }
+    return "$n$suffix"
+}
+
+@Composable
+private fun ZeroScoreDialog(category: YahtzeeCategory, onConfirm: () -> Unit, onCancel: () -> Unit) {
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text("Score zero?") },
+        text = { Text("These dice are worth 0 in ${category.label}. Write the zero there?") },
+        confirmButton = { TextButton(onClick = onConfirm) { Text("Score 0") } },
+        dismissButton = { TextButton(onClick = onCancel) { Text("Choose another") } },
+    )
+}
+
 @Composable
 private fun DiceRow(
     dice: List<Int>,
@@ -189,12 +290,29 @@ private fun Die(face: Int?, held: Boolean, enabled: Boolean, onClick: () -> Unit
             .clickable(enabled = enabled) { onClick() },
         contentAlignment = Alignment.Center,
     ) {
-        Text(
-            text = face?.toString() ?: "·",
-            style = MaterialTheme.typography.titleLarge,
-            fontWeight = FontWeight.Bold,
-            color = WallaceRed,
-        )
+        if (face != null) {
+            Canvas(modifier = Modifier.size(48.dp)) {
+                val radius = size.minDimension * 0.08f
+                pipPositions(face).forEach { (x, y) ->
+                    drawCircle(WallaceRed, radius, Offset(size.width * x, size.height * y))
+                }
+            }
+        }
+    }
+}
+
+/** Pip centres as fractions of the die face, in the usual casino layout. */
+private fun pipPositions(face: Int): List<Pair<Float, Float>> {
+    val lo = 0.28f
+    val mid = 0.5f
+    val hi = 0.72f
+    return when (face) {
+        1 -> listOf(mid to mid)
+        2 -> listOf(lo to lo, hi to hi)
+        3 -> listOf(lo to lo, mid to mid, hi to hi)
+        4 -> listOf(lo to lo, hi to lo, lo to hi, hi to hi)
+        5 -> listOf(lo to lo, hi to lo, mid to mid, lo to hi, hi to hi)
+        else -> listOf(lo to lo, hi to lo, lo to mid, hi to mid, lo to hi, hi to hi)
     }
 }
 
@@ -205,28 +323,61 @@ private fun ScoreCard(
     writable: Set<YahtzeeCategory>,
     onWrite: (YahtzeeCategory) -> Unit,
 ) {
-    Column(modifier = Modifier.fillMaxWidth()) {
-        Row(modifier = Modifier.fillMaxWidth()) {
-            Text("", modifier = Modifier.weight(2f), style = MaterialTheme.typography.labelSmall)
-            state.cards.indices.forEach { seat ->
-                Text(
-                    text = if (seat == localSeat) "You" else "S$seat",
-                    modifier = Modifier.weight(1f),
-                    style = MaterialTheme.typography.labelSmall,
-                    fontWeight = FontWeight.Bold,
-                )
-            }
-        }
-        YahtzeeSection.entries.forEach { section ->
-            YahtzeeCategory.entries.filter { it.section == section }.forEach { category ->
-                CardRow(state, localSeat, category, writable, onWrite)
-            }
-            if (section == YahtzeeSection.UPPER) {
+    // Upper boxes and bonus on the left, lower boxes and total on the right, so
+    // each half is wide enough for text that can actually be read. Each half
+    // has a floor on its width; if two of them do not fit (many players, large
+    // text) the pair scrolls sideways instead of squeezing.
+    BoxWithConstraints(modifier = Modifier.fillMaxWidth()) {
+        val needed = (CARD_LABEL_WIDTH + CARD_SEAT_WIDTH * state.cards.size).dp
+        val half = maxOf((maxWidth - CARD_GAP.dp) / 2, needed)
+        Row(
+            modifier = Modifier.horizontalScroll(rememberScrollState()),
+            horizontalArrangement = Arrangement.spacedBy(CARD_GAP.dp),
+        ) {
+            Column(modifier = Modifier.width(half)) {
+                CardHeader(state, localSeat)
+                CardSection(YahtzeeSection.UPPER, state, localSeat, writable, onWrite)
                 TotalRow("Bonus at 63", state.cards.map { it.upperBonus })
             }
+            Column(modifier = Modifier.width(half)) {
+                CardHeader(state, localSeat)
+                CardSection(YahtzeeSection.LOWER, state, localSeat, writable, onWrite)
+                Divider()
+                TotalRow("Total", state.cards.indices.map { state.totalFor(it) }, bold = true)
+            }
         }
-        Divider()
-        TotalRow("Total", state.cards.indices.map { state.totalFor(it) }, bold = true)
+    }
+}
+
+private const val CARD_LABEL_WIDTH = 120
+private const val CARD_SEAT_WIDTH = 56
+private const val CARD_GAP = 12
+
+@Composable
+private fun CardHeader(state: YahtzeeState, localSeat: Int) {
+    Row(modifier = Modifier.fillMaxWidth()) {
+        Text("", modifier = Modifier.weight(2f))
+        state.cards.indices.forEach { seat ->
+            Text(
+                text = if (seat == localSeat) "You" else "S$seat",
+                modifier = Modifier.weight(1f),
+                style = MaterialTheme.typography.labelLarge,
+                fontWeight = FontWeight.Bold,
+            )
+        }
+    }
+}
+
+@Composable
+private fun CardSection(
+    section: YahtzeeSection,
+    state: YahtzeeState,
+    localSeat: Int,
+    writable: Set<YahtzeeCategory>,
+    onWrite: (YahtzeeCategory) -> Unit,
+) {
+    YahtzeeCategory.entries.filter { it.section == section }.forEach { category ->
+        CardRow(state, localSeat, category, writable, onWrite)
     }
 }
 
@@ -243,12 +394,12 @@ private fun CardRow(
         modifier = Modifier
             .fillMaxWidth()
             .clickable(enabled = open) { onWrite(category) }
-            .padding(vertical = 2.dp),
+            .padding(vertical = 5.dp),
     ) {
         Text(
             text = category.label,
             modifier = Modifier.weight(2f),
-            style = MaterialTheme.typography.bodySmall,
+            style = MaterialTheme.typography.bodyMedium,
             fontWeight = if (open) FontWeight.Bold else FontWeight.Normal,
         )
         state.cards.forEachIndexed { seat, card ->
@@ -262,7 +413,7 @@ private fun CardRow(
                     else -> "—"
                 },
                 modifier = Modifier.weight(1f),
-                style = MaterialTheme.typography.bodySmall,
+                style = MaterialTheme.typography.bodyMedium,
                 color = if (written == null && open) WallaceRed else MaterialTheme.colorScheme.onSurface,
             )
         }
@@ -271,18 +422,18 @@ private fun CardRow(
 
 @Composable
 private fun TotalRow(label: String, values: List<Int>, bold: Boolean = false) {
-    Row(modifier = Modifier.fillMaxWidth().padding(vertical = 2.dp)) {
+    Row(modifier = Modifier.fillMaxWidth().padding(vertical = 5.dp)) {
         Text(
             text = label,
             modifier = Modifier.weight(2f),
-            style = MaterialTheme.typography.bodySmall,
+            style = MaterialTheme.typography.bodyMedium,
             fontWeight = if (bold) FontWeight.Bold else FontWeight.Normal,
         )
         values.forEach {
             Text(
                 text = "$it",
                 modifier = Modifier.weight(1f),
-                style = MaterialTheme.typography.bodySmall,
+                style = MaterialTheme.typography.bodyMedium,
                 fontWeight = if (bold) FontWeight.Bold else FontWeight.Normal,
             )
         }
@@ -295,7 +446,12 @@ private fun EndCardDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
         onDismissRequest = onKeepPlaying,
         title = { Text("End this game?") },
         text = { Text("The game ends here. Anyone else at the table is told you have left.") },
-        confirmButton = { TextButton(onClick = onEnd) { Text("End the game") } },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
         dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
     )
 }

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanBoardView.kt

@@ -0,0 +1,743 @@
+package org.prolibertate.games.ui.game.catan
+
+import androidx.compose.foundation.Canvas
+import androidx.compose.foundation.gestures.detectTapGestures
+import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.geometry.Size
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.Path
+import androidx.compose.ui.graphics.PathEffect
+import androidx.compose.ui.graphics.StrokeCap
+import androidx.compose.ui.graphics.drawscope.DrawScope
+import androidx.compose.ui.graphics.drawscope.Stroke
+import androidx.compose.ui.input.pointer.pointerInput
+import androidx.compose.ui.layout.onSizeChanged
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.text.TextMeasurer
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.drawText
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.rememberTextMeasurer
+import androidx.compose.ui.unit.IntSize
+import org.prolibertate.games.game.catan.BuildingType
+import org.prolibertate.games.game.catan.CatanBoard
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.NO_PLAYER
+import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.Terrain
+
+/**
+ * The island, drawn and tappable.
+ *
+ * A stateless view: it is handed the state, the parts of the board that are
+ * currently tappable ([targets]) and the one setup settlement that is waiting
+ * for its road ([selectedVertex]), and it reports taps. It knows no rules; what
+ * a tap *means* is decided by [CatanInteraction]. Where things are is decided by
+ * [BoardLayout], and what they look like by [CatanStyle], so this file is only
+ * the glue between the three.
+ *
+ * To change how a piece is drawn, edit the matching `draw…` function below. To
+ * change a colour or a proportion, edit [CatanStyle] instead.
+ */
+@Composable
+fun CatanBoardView(
+    state: CatanState,
+    targets: BoardTargets,
+    selectedVertex: Int?,
+    onVertexTap: (Int) -> Unit,
+    onEdgeTap: (Int) -> Unit,
+    onHexTap: (Int) -> Unit,
+    modifier: Modifier = Modifier,
+    style: CatanStyle = LocalCatanStyle.current,
+    /** Hexes to light up as having produced on the latest roll. */
+    rolledHexes: Set<Int> = emptySet(),
+    /** Cities & Knights: the knight whose menu is open or that is about to move. */
+    selectedKnight: Int? = null,
+    /** A placement lined up but not yet confirmed (or being dragged over): drawn as a solid ghost. */
+    stagedVertex: Int? = null,
+    stagedEdge: Int? = null,
+    /** The seat that will own the staged piece, for its colour. */
+    stagedSeat: Int? = null,
+) {
+    val measurer = rememberTextMeasurer()
+    var size by remember { mutableStateOf(IntSize.Zero) }
+    val topo = state.topo
+    val layout = remember(size, topo) {
+        if (size.width > 0 && size.height > 0) {
+            CatanGeometry.fit(size.width.toFloat(), size.height.toFloat(), topo)
+        } else {
+            null
+        }
+    }
+
+    // Held in State so the gesture detector, which is only restarted when the
+    // layout or targets change, always calls the latest callbacks.
+    val vertexTap by rememberUpdatedState(onVertexTap)
+    val edgeTap by rememberUpdatedState(onEdgeTap)
+    val hexTap by rememberUpdatedState(onHexTap)
+
+    Canvas(
+        modifier = modifier
+            .aspectRatio(CatanGeometry.aspect(topo))
+            .onSizeChanged { size = it }
+            .semantics { contentDescription = "Katan island board" }
+            .pointerInput(layout, targets, style) {
+                detectTapGestures { tap ->
+                    val board = layout ?: return@detectTapGestures
+                    val at = Pt(tap.x, tap.y)
+                    val reach = board.radius * style.tapReach
+                    when {
+                        targets.tappableVertices.isNotEmpty() ->
+                            board.nearestVertex(at, reach, targets.tappableVertices)?.let { vertexTap(it) }
+
+                        targets.edges.isNotEmpty() || targets.ships.isNotEmpty() ->
+                            board.nearestEdge(at, reach, targets.edges + targets.ships)?.let { edgeTap(it) }
+
+                        targets.hexes.isNotEmpty() ->
+                            // A hex is big: accept a tap anywhere near its middle.
+                            board.nearestHex(at, board.radius * 0.95f, targets.hexes)?.let { hexTap(it) }
+                    }
+                }
+            },
+    ) {
+        val board = layout ?: return@Canvas
+        drawRect(color = style.sea)
+        drawPorts(state, board, style, measurer)
+        drawHexes(state, board, style, measurer)
+        drawRolled(rolledHexes, board, style)
+        drawRobber(state, board, style)
+        drawPirate(state, board, style)
+        drawMerchant(state, board, style, measurer)
+        drawRoads(state, board, style)
+        drawShips(state, board, style)
+        drawEdgeTargets(targets, board, style)
+        drawShipTargets(targets, board, style)
+        drawBuildings(state, board, style)
+        drawWalls(state, board, style)
+        drawMetropolises(state, board, style)
+        drawKnights(state, board, style)
+        drawKnightTargets(targets, board, style)
+        drawVertexTargets(targets, selectedVertex ?: selectedKnight, board, style)
+        drawHexTargets(targets, board, style)
+        drawStaged(stagedVertex, stagedEdge, stagedSeat, board, style)
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Terrain and tokens
+// ---------------------------------------------------------------------------
+
+private fun DrawScope.drawHexes(
+    state: CatanState,
+    board: BoardLayout,
+    style: CatanStyle,
+    measurer: TextMeasurer,
+) {
+    for (hex in 0 until state.topo.HEX_COUNT) {
+        val centre = board.hexCenter(hex)
+        val corners = board.hexCorners(hex).map { insetToward(it, centre, style.hexInset) }
+        val path = polygon(corners)
+        if (state.terrains[hex] == Terrain.SEA) {
+            // Open water: only a faint outline, so ships have a grid to sail on.
+            drawPath(path, color = style.hexEdge.copy(alpha = 0.12f), style = Stroke(width = board.radius * 0.02f))
+            continue
+        }
+        drawPath(path, color = style.terrain.getValue(state.terrains[hex]))
+        drawPath(path, color = style.hexEdge, style = Stroke(width = board.radius * 0.03f))
+
+        val number = state.numbers[hex]
+        if (number != 0) drawToken(number, centre, board, style, measurer)
+    }
+}
+
+/** A bright wash and rim on each hex that paid out, drawn over the terrain and under the pieces. */
+private fun DrawScope.drawRolled(hexes: Set<Int>, board: BoardLayout, style: CatanStyle) {
+    for (hex in hexes) {
+        val centre = board.hexCenter(hex)
+        val path = polygon(board.hexCorners(hex).map { insetToward(it, centre, style.hexInset + 0.04f) })
+        drawPath(path, color = style.rolled.copy(alpha = 0.28f))
+        drawPath(path, color = style.pieceOutline, style = Stroke(width = board.radius * 0.13f))
+        drawPath(path, color = style.rolled, style = Stroke(width = board.radius * 0.075f))
+    }
+}
+
+private fun DrawScope.drawToken(
+    number: Int,
+    at: Pt,
+    board: BoardLayout,
+    style: CatanStyle,
+    measurer: TextMeasurer,
+) {
+    val radius = board.radius * style.tokenRadius
+    drawCircle(color = style.token, radius = radius, center = at.offset())
+    drawCircle(
+        color = style.hexEdge,
+        radius = radius,
+        center = at.offset(),
+        style = Stroke(width = board.radius * 0.02f),
+    )
+    val hot = number == 6 || number == 8
+    drawCentered(
+        measurer = measurer,
+        text = number.toString(),
+        at = Pt(at.x, at.y - radius * 0.12f),
+        fontPx = board.radius * style.tokenText,
+        color = if (hot) style.tokenHotInk else style.tokenInk,
+        weight = if (hot) FontWeight.ExtraBold else FontWeight.Bold,
+    )
+    // One pip per thirty-sixth of the odds, so the likelier numbers read at a glance.
+    val pips = CatanBoard.numberOdds(number)
+    val pipRadius = radius * 0.075f
+    val gap = pipRadius * 2.6f
+    val startX = at.x - gap * (pips - 1) / 2f
+    for (i in 0 until pips) {
+        drawCircle(
+            color = if (hot) style.tokenHotInk else style.tokenInk,
+            radius = pipRadius,
+            center = Offset(startX + i * gap, at.y + radius * 0.52f),
+        )
+    }
+}
+
+private fun DrawScope.drawRobber(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    // In Cities & Knights the robber sleeps, drawn faintly, until the barbarians first land.
+    val asleep = state.ck?.attacked == false
+    val tint = if (asleep) style.robber.copy(alpha = 0.3f) else style.robber
+    val rim = Color.White.copy(alpha = if (asleep) 0.25f else 0.7f)
+    val hex = board.hexCenter(state.robber)
+    // Beside the number token rather than on it, so the number stays readable.
+    val x = hex.x + board.radius * 0.5f
+    val y = hex.y + board.radius * 0.3f
+    val s = board.radius * style.robberSize
+    val pawn = Path().apply {
+        moveTo(x - s * 0.55f, y + s * 0.9f)
+        lineTo(x - s * 0.25f, y - s * 0.15f)
+        lineTo(x + s * 0.25f, y - s * 0.15f)
+        lineTo(x + s * 0.55f, y + s * 0.9f)
+        close()
+    }
+    drawPath(pawn, color = tint)
+    drawCircle(color = tint, radius = s * 0.38f, center = Offset(x, y - s * 0.42f))
+    drawPath(pawn, color = rim, style = Stroke(width = s * 0.07f))
+    drawCircle(
+        color = rim,
+        radius = s * 0.38f,
+        center = Offset(x, y - s * 0.42f),
+        style = Stroke(width = s * 0.07f),
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Harbours
+// ---------------------------------------------------------------------------
+
+private fun DrawScope.drawPorts(
+    state: CatanState,
+    board: BoardLayout,
+    style: CatanStyle,
+    measurer: TextMeasurer,
+) {
+    for (port in state.ports) {
+        val anchor = board.portAnchor(port.edge)
+        val (a, b) = board.edgeEnds(port.edge)
+        val tint = port.resource?.let { style.resource.getValue(it) } ?: style.portInk
+        // Two piers from the marker to the vertices that can use the harbour.
+        for (end in listOf(a, b)) {
+            drawLine(
+                color = style.portMarker.copy(alpha = 0.9f),
+                start = anchor.offset(),
+                end = end.offset(),
+                strokeWidth = board.radius * 0.07f,
+                cap = StrokeCap.Round,
+            )
+        }
+        val radius = board.radius * style.portRadius
+        drawCircle(color = style.portMarker, radius = radius, center = anchor.offset())
+        drawCircle(
+            color = tint,
+            radius = radius,
+            center = anchor.offset(),
+            style = Stroke(width = board.radius * 0.07f),
+        )
+        // What the harbour trades: a picture of the resource, or "?" for any.
+        val iconAt = Pt(anchor.x, anchor.y - radius * 0.27f)
+        val iconSize = radius * 0.5f
+        val resource = port.resource
+        if (resource != null) {
+            drawResourceIcon(resource, iconAt, iconSize, tint, style.pieceOutline)
+        } else {
+            drawCentered(
+                measurer = measurer,
+                text = "?",
+                at = iconAt,
+                fontPx = board.radius * style.portText * 1.5f,
+                color = style.portInk,
+                weight = FontWeight.ExtraBold,
+            )
+        }
+        drawCentered(
+            measurer = measurer,
+            text = "${port.ratio}:1",
+            at = Pt(anchor.x, anchor.y + radius * 0.5f),
+            fontPx = board.radius * style.portText,
+            color = style.portInk,
+            weight = FontWeight.Bold,
+        )
+    }
+}
+
+/**
+ * A small pictogram of [resource] centred on [at], about 2·[s] across: a tree,
+ * bricks, a sheep, an ear of wheat or a rock. Drawn with paths so there are no
+ * image assets to ship or scale.
+ */
+private fun DrawScope.drawResourceIcon(resource: Resource, at: Pt, s: Float, fill: Color, line: Color) {
+    val outline = Stroke(width = s * 0.12f)
+    when (resource) {
+        Resource.LUMBER -> {
+            val crown = Path().apply {
+                moveTo(at.x, at.y - s)
+                lineTo(at.x + s * 0.8f, at.y + s * 0.3f)
+                lineTo(at.x - s * 0.8f, at.y + s * 0.3f)
+                close()
+            }
+            drawRect(color = line, topLeft = Offset(at.x - s * 0.14f, at.y + s * 0.3f), size = Size(s * 0.28f, s * 0.6f))
+            drawPath(crown, color = fill)
+            drawPath(crown, color = line, style = outline)
+        }
+
+        Resource.BRICK -> {
+            val w = s * 0.9f
+            val h = s * 0.42f
+            for ((row, shift) in listOf(0f to 0f, 1f to w * 0.5f)) {
+                val top = at.y - h + row * h
+                val left = at.x - w + shift - w * 0.25f
+                for (col in 0..1) {
+                    val x = left + col * w
+                    drawRect(color = fill, topLeft = Offset(x, top), size = Size(w, h))
+                    drawRect(color = line, topLeft = Offset(x, top), size = Size(w, h), style = outline)
+                }
+            }
+        }
+
+        Resource.WOOL -> {
+            for ((dx, dy) in listOf(-0.45f to 0f, 0.1f to -0.25f, 0.5f to 0.05f, 0f to 0.2f)) {
+                drawCircle(color = fill, radius = s * 0.42f, center = Offset(at.x + dx * s, at.y + dy * s))
+            }
+            drawCircle(color = line, radius = s * 0.24f, center = Offset(at.x - s * 0.85f, at.y + s * 0.15f))
+            drawRect(color = line, topLeft = Offset(at.x - s * 0.5f, at.y + s * 0.5f), size = Size(s * 0.14f, s * 0.45f))
+            drawRect(color = line, topLeft = Offset(at.x + s * 0.3f, at.y + s * 0.5f), size = Size(s * 0.14f, s * 0.45f))
+        }
+
+        Resource.GRAIN -> {
+            drawLine(color = line, start = Offset(at.x, at.y + s), end = Offset(at.x, at.y - s * 0.7f), strokeWidth = s * 0.14f)
+            for (i in 0..2) {
+                val y = at.y - s * 0.7f + i * s * 0.5f
+                for (side in listOf(-1f, 1f)) {
+                    val kernel = Path().apply {
+                        moveTo(at.x, y + s * 0.3f)
+                        lineTo(at.x + side * s * 0.6f, y - s * 0.05f)
+                        lineTo(at.x + side * s * 0.15f, y - s * 0.2f)
+                        close()
+                    }
+                    drawPath(kernel, color = fill)
+                    drawPath(kernel, color = line, style = Stroke(width = s * 0.08f))
+                }
+            }
+        }
+
+        Resource.ORE -> {
+            val peak = Path().apply {
+                moveTo(at.x - s, at.y + s * 0.8f)
+                lineTo(at.x - s * 0.3f, at.y - s * 0.6f)
+                lineTo(at.x + s * 0.1f, at.y + s * 0.05f)
+                lineTo(at.x + s * 0.45f, at.y - s * 0.3f)
+                lineTo(at.x + s, at.y + s * 0.8f)
+                close()
+            }
+            drawPath(peak, color = fill)
+            drawPath(peak, color = line, style = outline)
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Pieces
+// ---------------------------------------------------------------------------
+
+private fun DrawScope.drawRoads(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    for (edge in 0 until state.topo.EDGE_COUNT) {
+        val owner = state.roads[edge]
+        if (owner == NO_PLAYER) continue
+        val (a, b) = board.edgeEnds(edge)
+        // Pulled in from the ends so adjacent roads do not fuse into a blob.
+        val from = lerp(a, b, 0.12f)
+        val to = lerp(a, b, 0.88f)
+        val width = board.radius * style.roadWidth
+        drawLine(
+            color = style.pieceOutline,
+            start = from.offset(),
+            end = to.offset(),
+            strokeWidth = width * 1.45f,
+            cap = StrokeCap.Round,
+        )
+        drawLine(
+            color = style.seats[owner % style.seats.size],
+            start = from.offset(),
+            end = to.offset(),
+            strokeWidth = width,
+            cap = StrokeCap.Round,
+        )
+    }
+}
+
+private fun DrawScope.drawBuildings(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    for (vertex in 0 until state.topo.VERTEX_COUNT) {
+        val building = state.buildings[vertex] ?: continue
+        val at = board.vertex(vertex)
+        val fill = style.seats[building.owner % style.seats.size]
+        val path = when (building.type) {
+            BuildingType.SETTLEMENT -> housePath(at, board.radius * style.settlementSize)
+            BuildingType.CITY -> cityPath(at, board.radius * style.citySize * 0.8f)
+        }
+        drawPath(path, color = fill)
+        drawPath(path, color = style.pieceOutline, style = Stroke(width = board.radius * 0.045f))
+    }
+}
+
+/** One gable: a settlement. [s] is its half-width. */
+private fun housePath(at: Pt, s: Float): Path = Path().apply {
+    moveTo(at.x - s, at.y + s * 0.7f)
+    lineTo(at.x - s, at.y - s * 0.1f)
+    lineTo(at.x, at.y - s)
+    lineTo(at.x + s, at.y - s * 0.1f)
+    lineTo(at.x + s, at.y + s * 0.7f)
+    close()
+}
+
+/** Two gables, the taller on the left: a city. [s] is the unit its outline is scaled by. */
+private fun cityPath(at: Pt, s: Float): Path = Path().apply {
+    moveTo(at.x - s, at.y + s * 0.7f)
+    lineTo(at.x - s, at.y - s * 0.5f)
+    lineTo(at.x - s * 0.45f, at.y - s * 1.1f)
+    lineTo(at.x + s * 0.1f, at.y - s * 0.5f)
+    lineTo(at.x + s * 0.1f, at.y - s * 0.1f)
+    lineTo(at.x + s * 0.55f, at.y - s * 0.55f)
+    lineTo(at.x + s * 1.1f, at.y - s * 0.1f)
+    lineTo(at.x + s * 1.1f, at.y + s * 0.7f)
+    close()
+}
+
+// ---------------------------------------------------------------------------
+// Cities & Knights pieces
+// ---------------------------------------------------------------------------
+
+/** A dashed wall round each walled city, crenellated by the dashes. */
+private fun DrawScope.drawWalls(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    val walls = state.ck?.walls ?: return
+    for (vertex in walls) {
+        val at = board.vertex(vertex).offset()
+        val radius = board.radius * style.citySize * 1.25f
+        val dash = PathEffect.dashPathEffect(floatArrayOf(radius * 0.38f, radius * 0.22f))
+        drawCircle(
+            color = style.pieceOutline,
+            radius = radius,
+            center = at,
+            style = Stroke(width = board.radius * 0.13f, pathEffect = dash),
+        )
+        drawCircle(
+            color = style.wall,
+            radius = radius,
+            center = at,
+            style = Stroke(width = board.radius * 0.09f, pathEffect = dash),
+        )
+    }
+}
+
+/** A pennant in the track's colour flying over a city that carries its metropolis. */
+private fun DrawScope.drawMetropolises(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    val metropolises = state.ck?.metropolises ?: return
+    for ((track, at) in metropolises) {
+        val base = board.vertex(at.vertex)
+        val unit = board.radius * style.citySize
+        val poleTop = Pt(base.x + unit * 0.9f, base.y - unit * 2.0f)
+        val poleBottom = Pt(base.x + unit * 0.9f, base.y - unit * 0.4f)
+        drawLine(
+            color = style.pieceOutline,
+            start = poleBottom.offset(),
+            end = poleTop.offset(),
+            strokeWidth = board.radius * 0.05f,
+        )
+        val flag = Path().apply {
+            moveTo(poleTop.x, poleTop.y)
+            lineTo(poleTop.x + unit * 1.1f, poleTop.y + unit * 0.35f)
+            lineTo(poleTop.x, poleTop.y + unit * 0.7f)
+            close()
+        }
+        drawPath(flag, color = style.track.getValue(track))
+        drawPath(flag, color = style.pieceOutline, style = Stroke(width = board.radius * 0.035f))
+    }
+}
+
+/**
+ * Each knight is a shield in its owner's colour, marked with one, two or three
+ * dots for its strength. A sleeping knight is drawn faded; an awake one has a
+ * bright rim.
+ */
+private fun DrawScope.drawKnights(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    val knights = state.ck?.knights ?: return
+    for (knight in knights) {
+        val at = board.vertex(knight.vertex)
+        val s = board.radius * style.knightSize
+        val seat = style.seats[knight.owner % style.seats.size]
+        val path = shieldPath(at, s)
+        if (knight.active) {
+            drawPath(path, color = style.knightReady, style = Stroke(width = s * 0.55f))
+        }
+        drawPath(path, color = if (knight.active) seat else seat.copy(alpha = 0.55f))
+        drawPath(path, color = style.pieceOutline, style = Stroke(width = s * 0.16f))
+        val pip = s * 0.14f
+        val gap = pip * 2.8f
+        val startX = at.x - gap * (knight.level - 1) / 2f
+        for (i in 0 until knight.level) {
+            drawCircle(
+                color = style.pieceOutline,
+                radius = pip,
+                center = Offset(startX + i * gap, at.y - s * 0.05f),
+            )
+        }
+    }
+}
+
+private fun shieldPath(at: Pt, s: Float): Path = Path().apply {
+    moveTo(at.x - s * 0.8f, at.y - s)
+    lineTo(at.x + s * 0.8f, at.y - s)
+    lineTo(at.x + s * 0.8f, at.y + s * 0.1f)
+    quadraticBezierTo(at.x + s * 0.8f, at.y + s * 0.9f, at.x, at.y + s * 1.25f)
+    quadraticBezierTo(at.x - s * 0.8f, at.y + s * 0.9f, at.x - s * 0.8f, at.y + s * 0.1f)
+    close()
+}
+
+/** A ring round each of the player's knights that can do something now. */
+private fun DrawScope.drawKnightTargets(targets: BoardTargets, board: BoardLayout, style: CatanStyle) {
+    for (vertex in targets.knights) {
+        drawCircle(
+            color = style.target,
+            radius = board.radius * style.knightSize * 1.9f,
+            center = board.vertex(vertex).offset(),
+            style = Stroke(width = board.radius * 0.07f),
+        )
+    }
+}
+
+/** The merchant: a coin in its controller's colour, beside the hex it sits on. */
+private fun DrawScope.drawMerchant(
+    state: CatanState,
+    board: BoardLayout,
+    style: CatanStyle,
+    measurer: TextMeasurer,
+) {
+    val merchant = state.ck?.merchant ?: return
+    val hex = board.hexCenter(merchant.hex)
+    val at = Pt(hex.x - board.radius * 0.5f, hex.y + board.radius * 0.3f)
+    val r = board.radius * 0.2f
+    drawCircle(color = style.seats[merchant.seat % style.seats.size], radius = r, center = at.offset())
+    drawCircle(color = style.pieceOutline, radius = r, center = at.offset(), style = Stroke(width = r * 0.3f))
+    drawCentered(
+        measurer = measurer,
+        text = "M",
+        at = at,
+        fontPx = r * 1.3f,
+        color = style.pieceOutline,
+        weight = FontWeight.ExtraBold,
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Tap targets
+// ---------------------------------------------------------------------------
+
+private fun DrawScope.drawVertexTargets(
+    targets: BoardTargets,
+    selected: Int?,
+    board: BoardLayout,
+    style: CatanStyle,
+) {
+    val radius = board.radius * style.targetRadius
+    for (vertex in targets.vertices) {
+        val at = board.vertex(vertex).offset()
+        drawCircle(color = style.target.copy(alpha = 0.85f), radius = radius, center = at)
+        drawCircle(
+            color = style.pieceOutline,
+            radius = radius,
+            center = at,
+            style = Stroke(width = board.radius * 0.04f),
+        )
+    }
+    if (selected != null) {
+        val at = board.vertex(selected).offset()
+        drawCircle(
+            color = style.targetSelected,
+            radius = radius * 1.6f,
+            center = at,
+            style = Stroke(width = board.radius * 0.09f),
+        )
+    }
+}
+
+private fun DrawScope.drawEdgeTargets(targets: BoardTargets, board: BoardLayout, style: CatanStyle) {
+    for (edge in targets.edges) {
+        val (a, b) = board.edgeEnds(edge)
+        val from = lerp(a, b, 0.15f)
+        val to = lerp(a, b, 0.85f)
+        drawLine(
+            color = style.pieceOutline,
+            start = from.offset(),
+            end = to.offset(),
+            strokeWidth = board.radius * style.roadWidth * 1.5f,
+            cap = StrokeCap.Round,
+        )
+        drawLine(
+            color = style.target.copy(alpha = 0.9f),
+            start = from.offset(),
+            end = to.offset(),
+            strokeWidth = board.radius * style.roadWidth,
+            cap = StrokeCap.Round,
+        )
+    }
+}
+
+private fun DrawScope.drawHexTargets(targets: BoardTargets, board: BoardLayout, style: CatanStyle) {
+    for (hex in targets.hexes) {
+        val centre = board.hexCenter(hex)
+        val path = polygon(board.hexCorners(hex).map { insetToward(it, centre, style.hexInset + 0.08f) })
+        drawPath(path, color = style.target.copy(alpha = 0.38f))
+        drawPath(path, color = style.target, style = Stroke(width = board.radius * 0.07f))
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Drawing helpers
+// ---------------------------------------------------------------------------
+
+private fun Pt.offset(): Offset = Offset(x, y)
+
+private fun lerp(a: Pt, b: Pt, t: Float): Pt = Pt(a.x + (b.x - a.x) * t, a.y + (b.y - a.y) * t)
+
+/** [p] moved [fraction] of the way toward [centre]. */
+private fun insetToward(p: Pt, centre: Pt, fraction: Float): Pt = lerp(p, centre, fraction)
+
+private fun polygon(points: List<Pt>): Path = Path().apply {
+    points.forEachIndexed { i, p -> if (i == 0) moveTo(p.x, p.y) else lineTo(p.x, p.y) }
+    close()
+}
+
+private fun DrawScope.drawCentered(
+    measurer: TextMeasurer,
+    text: String,
+    at: Pt,
+    fontPx: Float,
+    color: Color,
+    weight: FontWeight,
+) {
+    val layout = measurer.measure(
+        text = text,
+        style = TextStyle(fontSize = fontPx.toSp(), fontWeight = weight, color = color),
+    )
+    drawText(
+        textLayoutResult = layout,
+        topLeft = Offset(at.x - layout.size.width / 2f, at.y - layout.size.height / 2f),
+    )
+}
+
+/** The ghost of a placement waiting for ✓: a solid piece in the player's colour with a bright ring. */
+private fun DrawScope.drawStaged(vertex: Int?, edge: Int?, seat: Int?, board: BoardLayout, style: CatanStyle) {
+    val colour = seat?.let { style.seats.getOrNull(it) } ?: style.target
+    if (edge != null) {
+        val (a, b) = board.edgeEnds(edge)
+        val from = lerp(a, b, 0.1f)
+        val to = lerp(a, b, 0.9f)
+        drawLine(style.targetSelected, from.offset(), to.offset(), board.radius * style.roadWidth * 2.1f, StrokeCap.Round)
+        drawLine(colour, from.offset(), to.offset(), board.radius * style.roadWidth * 1.3f, StrokeCap.Round)
+    }
+    if (vertex != null) {
+        val at = board.vertex(vertex).offset()
+        val radius = board.radius * style.targetRadius
+        drawCircle(colour, radius * 1.3f, at)
+        drawCircle(style.targetSelected, radius * 1.9f, at, style = Stroke(width = board.radius * 0.1f))
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Seafarers: ships, the pirate
+// ---------------------------------------------------------------------------
+
+/** A ship on each sea edge that has one: a hull along the edge with a sail amidships, in the owner's colour. */
+private fun DrawScope.drawShips(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    val sea = state.sea ?: return
+    for (edge in sea.ships.indices) {
+        val owner = sea.ships[edge]
+        if (owner == NO_PLAYER) continue
+        val (a, b) = board.edgeEnds(edge)
+        val from = lerp(a, b, 0.2f)
+        val to = lerp(a, b, 0.8f)
+        val width = board.radius * style.roadWidth * 1.15f
+        val colour = style.seats[owner % style.seats.size]
+        drawLine(style.pieceOutline, from.offset(), to.offset(), width * 1.5f, StrokeCap.Round)
+        drawLine(colour, from.offset(), to.offset(), width, StrokeCap.Round)
+        // The sail: a small triangle standing off the hull, on the screen's upper side.
+        val mid = lerp(a, b, 0.5f)
+        val s = board.radius * 0.17f
+        val sail = Path().apply {
+            moveTo(mid.x - s * 0.1f, mid.y - s * 1.9f)
+            lineTo(mid.x + s * 1.1f, mid.y - s * 0.2f)
+            lineTo(mid.x - s * 0.1f, mid.y - s * 0.2f)
+            close()
+        }
+        drawPath(sail, style.shipSail)
+        drawPath(sail, style.pieceOutline, style = Stroke(width = board.radius * 0.03f))
+    }
+}
+
+/** A ring round each of the player's ships that can sail, so they read as tappable. */
+private fun DrawScope.drawShipTargets(targets: BoardTargets, board: BoardLayout, style: CatanStyle) {
+    for (edge in targets.ships) {
+        val mid = board.edgeMidpoint(edge).offset()
+        drawCircle(style.target, board.radius * 0.38f, mid, style = Stroke(width = board.radius * 0.07f))
+    }
+}
+
+/** The pirate: a black pawn with a flag, drawn beside the middle of its sea hex like the robber. */
+private fun DrawScope.drawPirate(state: CatanState, board: BoardLayout, style: CatanStyle) {
+    val sea = state.sea ?: return
+    val hex = board.hexCenter(sea.pirate)
+    val x = hex.x
+    val y = hex.y + board.radius * 0.1f
+    val s = board.radius * style.robberSize
+    val hull = Path().apply {
+        moveTo(x - s * 1.0f, y)
+        lineTo(x + s * 1.0f, y)
+        lineTo(x + s * 0.6f, y + s * 0.7f)
+        lineTo(x - s * 0.6f, y + s * 0.7f)
+        close()
+    }
+    drawPath(hull, style.pirate)
+    drawLine(style.pirate, Offset(x, y), Offset(x, y - s * 1.5f), strokeWidth = s * 0.12f)
+    val flag = Path().apply {
+        moveTo(x, y - s * 1.5f)
+        lineTo(x + s * 0.9f, y - s * 1.15f)
+        lineTo(x, y - s * 0.8f)
+        close()
+    }
+    drawPath(flag, style.pirate)
+    drawPath(hull, Color.White.copy(alpha = 0.7f), style = Stroke(width = s * 0.07f))
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanCkDialogs.kt

@@ -0,0 +1,813 @@
+package org.prolibertate.games.ui.game.catan
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.ExperimentalLayoutApi
+import androidx.compose.foundation.layout.FlowRow
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.heightIn
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.Button
+import androidx.compose.material3.FilledTonalButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import org.prolibertate.games.game.catan.AcceptCounter
+import org.prolibertate.games.game.catan.ActivateKnight
+import org.prolibertate.games.game.catan.BuyImprovement
+import org.prolibertate.games.game.catan.CatanCk
+import org.prolibertate.games.game.catan.CatanMove
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.ChaseRobber
+import org.prolibertate.games.game.catan.CounterGoods
+import org.prolibertate.games.game.catan.DropProgress
+import org.prolibertate.games.game.catan.GoodsBankTrade
+import org.prolibertate.games.game.catan.Good
+import org.prolibertate.games.game.catan.GoodsCounter
+import org.prolibertate.games.game.catan.GoodsOffer
+import org.prolibertate.games.game.catan.IMPROVEMENT_MAX
+import org.prolibertate.games.game.catan.MoveKnight
+import org.prolibertate.games.game.catan.OfferGoods
+import org.prolibertate.games.game.catan.PickDeck
+import org.prolibertate.games.game.catan.PlayProgress
+import org.prolibertate.games.game.catan.ProgressCard
+import org.prolibertate.games.game.catan.ProgressType
+import org.prolibertate.games.game.catan.PromoteKnight
+import org.prolibertate.games.game.catan.SpyTake
+import org.prolibertate.games.game.catan.TakeAqueduct
+import org.prolibertate.games.game.catan.Track
+
+/*
+ * The Cities & Knights dialogs. Like the base game's, each is a stateless
+ * composable apart from the choice it is helping the player make, and what is
+ * allowed is always asked of the engine's legal list through CatanInteraction.
+ */
+
+// ---------------------------------------------------------------------------
+// Shared pieces
+// ---------------------------------------------------------------------------
+
+/** A card tile with a minus and a plus, for choosing how many of a good. */
+@Composable
+private fun GoodCounter(good: Good, count: Int, max: Int, onChange: (Int) -> Unit) {
+    Column(horizontalAlignment = Alignment.CenterHorizontally, verticalArrangement = Arrangement.spacedBy(4.dp)) {
+        GoodTile(good, count, enabled = max > 0 || count > 0)
+        Row(horizontalArrangement = Arrangement.spacedBy(4.dp)) {
+            OutlinedButton(
+                onClick = { onChange(count - 1) },
+                enabled = count > 0,
+                contentPadding = PaddingValues(0.dp),
+                modifier = Modifier.width(34.dp).height(32.dp),
+            ) { Text("−") }
+            OutlinedButton(
+                onClick = { onChange(count + 1) },
+                enabled = count < max,
+                contentPadding = PaddingValues(0.dp),
+                modifier = Modifier.width(34.dp).height(32.dp),
+            ) { Text("+") }
+        }
+    }
+}
+
+private fun Map<Good, Int>.asGoods(): List<Good> = Good.entries.flatMap { g -> List(this[g] ?: 0) { g } }
+
+/** A row of the three track colours, used for decks and improvements. */
+@Composable
+private fun TrackChip(track: Track, style: CatanStyle = LocalCatanStyle.current) {
+    Box(
+        modifier = Modifier
+            .size(14.dp)
+            .clip(RoundedCornerShape(3.dp))
+            .background(style.track.getValue(track)),
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Choosing cards to give up
+// ---------------------------------------------------------------------------
+
+/**
+ * Pick exactly [quota] cards out of [held] — to discard on a seven or a saboteur,
+ * or to hand over for a wedding or a commercial harbour. Not dismissable: the
+ * game is waiting on it. [allowed] is the engine's structural check, so the
+ * confirm button only lights when the move would be accepted.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanGoodsPickDialog(
+    title: String,
+    intro: String,
+    held: Map<Good, Int>,
+    quota: Int,
+    confirmLabel: String,
+    selectable: (Good) -> Boolean,
+    allowed: (List<Good>) -> Boolean,
+    onConfirm: (List<Good>) -> Unit,
+) {
+    var picked by remember { mutableStateOf(emptyMap<Good, Int>()) }
+    val selection = picked.asGoods()
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text(title) },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(12.dp)) {
+                Text("$intro (${selection.size} of $quota chosen).")
+                FlowRow(
+                    horizontalArrangement = Arrangement.spacedBy(8.dp),
+                    verticalArrangement = Arrangement.spacedBy(8.dp),
+                ) {
+                    Good.entries.forEach { good ->
+                        val have = held[good] ?: 0
+                        if (have > 0 && selectable(good)) {
+                            GoodCounter(
+                                good = good,
+                                count = picked[good] ?: 0,
+                                max = if (selection.size < quota) have else (picked[good] ?: 0),
+                                onChange = { n -> picked = picked + (good to n.coerceIn(0, have)) },
+                            )
+                        }
+                    }
+                }
+            }
+        },
+        confirmButton = {
+            Button(onClick = { onConfirm(selection) }, enabled = allowed(selection)) { Text(confirmLabel) }
+        },
+    )
+}
+
+// ---------------------------------------------------------------------------
+// City improvements
+// ---------------------------------------------------------------------------
+
+/** The three improvement tracks: where the player stands, what the next level costs, and what it earns. */
+@Composable
+fun CatanImproveDialog(
+    state: CatanState,
+    seat: Int,
+    legal: List<CatanMove>,
+    onBuy: (BuyImprovement) -> Unit,
+    onCancel: () -> Unit,
+) {
+    val ck = state.ck ?: return
+    val buyable = CatanInteraction.improvable(legal)
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text(CatanText.IMPROVE) },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(14.dp),
+            ) {
+                Track.entries.forEach { track ->
+                    val level = CatanCk.improvement(state, seat, track)
+                    val have = ck.commodities[seat][track.commodity] ?: 0
+                    Column(verticalArrangement = Arrangement.spacedBy(4.dp)) {
+                        Row(verticalAlignment = Alignment.CenterVertically, horizontalArrangement = Arrangement.spacedBy(6.dp)) {
+                            TrackChip(track)
+                            Text(CatanText.track(track), fontWeight = FontWeight.Bold)
+                            Text("level $level of $IMPROVEMENT_MAX", style = MaterialTheme.typography.labelMedium)
+                        }
+                        Text(CatanText.trackPower(track), style = MaterialTheme.typography.bodySmall)
+                        if (level >= IMPROVEMENT_MAX) {
+                            Text("Fully built.", style = MaterialTheme.typography.bodySmall)
+                        } else {
+                            val cost = CatanCk.improvementCost(state, seat, track)
+                            Button(onClick = { onBuy(BuyImprovement(track)) }, enabled = track in buyable) {
+                                Text(
+                                    "${CatanCk.improvementName(track, level + 1)}: $cost " +
+                                        "${CatanText.good(Good.of(track.commodity))} (you hold $have)",
+                                )
+                            }
+                            if (level + 1 == org.prolibertate.games.game.catan.METROPOLIS_LEVEL ||
+                                level + 1 == IMPROVEMENT_MAX
+                            ) {
+                                Text(
+                                    if (level + 1 == IMPROVEMENT_MAX) {
+                                        "Level five takes a metropolis from a seat still on four."
+                                    } else {
+                                        "Level four earns the first metropolis in this track: two more points."
+                                    },
+                                    style = MaterialTheme.typography.labelSmall,
+                                )
+                            }
+                        }
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+        dismissButton = { TextButton(onClick = onCancel) { Text("Close") } },
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Progress cards
+// ---------------------------------------------------------------------------
+
+/**
+ * The player's progress cards. A card with nothing to decide plays at once; one
+ * that names a seat, a card or dice asks for it in a second step; one that
+ * needs a tap on the board closes the dialog and arms the board (see [ArmedCard]).
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanProgressDialog(
+    hand: List<ProgressInHand>,
+    seats: CatanSeats,
+    onPlay: (CatanMove) -> Unit,
+    onArm: (ArmedCard) -> Unit,
+    onCancel: () -> Unit,
+) {
+    var chosen by remember { mutableStateOf<ProgressInHand?>(null) }
+    var target by remember { mutableStateOf<Int?>(null) }
+    var yellow by remember { mutableStateOf(1) }
+    var red by remember { mutableStateOf(1) }
+    val entry = chosen
+
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text(entry?.let { CatanText.progress(it.card.kind) } ?: "Progress cards") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 440.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(10.dp),
+            ) {
+                if (entry == null) {
+                    if (hand.isEmpty()) Text("You hold no progress cards.")
+                    hand.forEach { card ->
+                        ProgressRow(card) { picked ->
+                            val kind = picked.card.kind
+                            when {
+                                kind in CatanInteraction.BOARD_CARDS -> onArm(ArmedCard(kind, picked.plays))
+                                picked.plays.size == 1 && picked.plays[0].isBare() -> onPlay(picked.plays[0])
+                                else -> {
+                                    chosen = picked
+                                    target = null
+                                }
+                            }
+                        }
+                    }
+                } else {
+                    Text(CatanText.progressHelp(entry.card.kind), style = MaterialTheme.typography.bodySmall)
+                    val kind = entry.card.kind
+                    val plays = entry.plays
+                    when {
+                        kind == ProgressType.ALCHEMIST -> {
+                            Text("Production die (yellow)", fontWeight = FontWeight.Bold)
+                            DiePicker(yellow) { yellow = it }
+                            Text("Progress die (red)", fontWeight = FontWeight.Bold)
+                            DiePicker(red) { red = it }
+                        }
+
+                        kind == ProgressType.DESERTER || kind == ProgressType.SPY -> {
+                            Text("Choose a player:", fontWeight = FontWeight.Bold)
+                            plays.mapNotNull { it.target }.distinct().forEach { seat ->
+                                OutlinedButton(
+                                    onClick = { plays.firstOrNull { it.target == seat }?.let(onPlay) },
+                                    modifier = Modifier.fillMaxWidth(),
+                                ) { Text(seats.label(seat)) }
+                            }
+                        }
+
+                        kind == ProgressType.MASTER_MERCHANT -> {
+                            Text("Choose a player with more points:", fontWeight = FontWeight.Bold)
+                            Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                                plays.mapNotNull { it.target }.distinct().forEach { seat ->
+                                    if (target == seat) {
+                                        FilledTonalButton(onClick = { target = seat }) { Text(seats.label(seat)) }
+                                    } else {
+                                        OutlinedButton(onClick = { target = seat }) { Text(seats.label(seat)) }
+                                    }
+                                }
+                            }
+                            val seat = target
+                            if (seat != null) {
+                                Text("Take:", fontWeight = FontWeight.Bold)
+                                plays.filter { it.target == seat }.forEach { play ->
+                                    OutlinedButton(
+                                        onClick = { onPlay(play) },
+                                        modifier = Modifier.fillMaxWidth(),
+                                    ) { Text(CatanText.goods(play.goods.orEmpty())) }
+                                }
+                            }
+                        }
+
+                        else -> {
+                            val label = when (kind) {
+                                ProgressType.COMMERCIAL_HARBOR -> "Offer which resource?"
+                                ProgressType.MERCHANT_FLEET -> "Trade which card two for one?"
+                                ProgressType.RESOURCE_MONOPOLY -> "Name a resource:"
+                                else -> "Name a commodity:"
+                            }
+                            Text(label, fontWeight = FontWeight.Bold)
+                            FlowRow(
+                                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                                verticalArrangement = Arrangement.spacedBy(8.dp),
+                            ) {
+                                plays.mapNotNull { it.good }.distinct().forEach { good ->
+                                    GoodTile(
+                                        good = good,
+                                        count = 0,
+                                        onClick = { plays.firstOrNull { it.good == good }?.let(onPlay) },
+                                    )
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        },
+        confirmButton = {
+            if (entry != null && entry.card.kind == ProgressType.ALCHEMIST) {
+                val play = entry.plays.firstOrNull { it.dice == listOf(yellow, red) }
+                Button(onClick = { play?.let(onPlay) }, enabled = play != null) { Text("Play") }
+            }
+        },
+        dismissButton = {
+            TextButton(
+                onClick = {
+                    if (entry == null) {
+                        onCancel()
+                    } else {
+                        chosen = null
+                        target = null
+                    }
+                },
+            ) { Text(if (entry == null) CatanText.CANCEL else "Back") }
+        },
+    )
+}
+
+private fun PlayProgress.isBare(): Boolean =
+    target == null && vertex == null && edge == null && hexA == null && hexB == null &&
+        good == null && dice == null && goods == null
+
+@Composable
+private fun DiePicker(selected: Int, onPick: (Int) -> Unit) {
+    Row(horizontalArrangement = Arrangement.spacedBy(6.dp)) {
+        (1..6).forEach { n ->
+            if (n == selected) {
+                FilledTonalButton(
+                    onClick = { onPick(n) },
+                    contentPadding = PaddingValues(0.dp),
+                    modifier = Modifier.size(40.dp),
+                ) { Text("$n") }
+            } else {
+                OutlinedButton(
+                    onClick = { onPick(n) },
+                    contentPadding = PaddingValues(0.dp),
+                    modifier = Modifier.size(40.dp),
+                ) { Text("$n") }
+            }
+        }
+    }
+}
+
+@Composable
+private fun ProgressRow(entry: ProgressInHand, onChoose: (ProgressInHand) -> Unit) {
+    val kind = entry.card.kind
+    Row(
+        modifier = Modifier.fillMaxWidth(),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        TrackChip(kind.track)
+        Column(modifier = Modifier.weight(1f)) {
+            Text(CatanText.progress(kind), fontWeight = FontWeight.Bold)
+            Text(CatanText.progressHelp(kind), style = MaterialTheme.typography.bodySmall)
+        }
+        if (entry.playable) {
+            Button(onClick = { onChoose(entry) }) { Text("Play") }
+        } else {
+            Text("Not now", style = MaterialTheme.typography.labelSmall)
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Knights
+// ---------------------------------------------------------------------------
+
+/** What the knight on one crossing can do: wake, promote, move, chase the robber. */
+@Composable
+fun CatanKnightDialog(
+    state: CatanState,
+    vertex: Int,
+    actions: List<CatanMove>,
+    onDo: (CatanMove) -> Unit,
+    onMove: (Int) -> Unit,
+    onCancel: () -> Unit,
+) {
+    val knight = state.ck?.knights?.firstOrNull { it.vertex == vertex }
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text(knight?.let { CatanText.knightName(it.level) } ?: "Knight") },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                if (knight != null) {
+                    val mood = when {
+                        !knight.active -> "Asleep. Waking it costs ${CatanText.ACTIVATE_COST}."
+                        knight.activatedTurn == state.turnNumber -> "Awake, but it woke this turn and cannot act yet."
+                        else -> "Awake and ready. It counts against the barbarians."
+                    }
+                    Text(mood, style = MaterialTheme.typography.bodySmall)
+                }
+                actions.forEach { move ->
+                    when (move) {
+                        is ActivateKnight ->
+                            Button(onClick = { onDo(move) }, modifier = Modifier.fillMaxWidth()) {
+                                Text("Wake (${CatanText.ACTIVATE_COST})")
+                            }
+
+                        is PromoteKnight ->
+                            Button(onClick = { onDo(move) }, modifier = Modifier.fillMaxWidth()) {
+                                Text("Promote (${CatanText.KNIGHT_COST})")
+                            }
+
+                        is MoveKnight ->
+                            OutlinedButton(onClick = { onMove(move.from) }, modifier = Modifier.fillMaxWidth()) {
+                                Text("Move along your roads")
+                            }
+
+                        is ChaseRobber ->
+                            OutlinedButton(onClick = { onDo(move) }, modifier = Modifier.fillMaxWidth()) {
+                                Text("Chase away the robber")
+                            }
+
+                        else -> Unit
+                    }
+                }
+                if (actions.isEmpty()) Text("Nothing to do with it right now.")
+            }
+        },
+        confirmButton = {},
+        dismissButton = { TextButton(onClick = onCancel) { Text("Close") } },
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Chores that are answered in a dialog
+// ---------------------------------------------------------------------------
+
+/** Choose a colour of progress deck to draw from. */
+@Composable
+fun CatanPickDeckDialog(legal: List<CatanMove>, onPick: (PickDeck) -> Unit) {
+    val open = legal.filterIsInstance<PickDeck>()
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Draw a progress card") },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                Text("Catan held. You tied for the strongest defence, so choose any deck.")
+                open.forEach { pick ->
+                    Button(onClick = { onPick(pick) }, modifier = Modifier.fillMaxWidth()) {
+                        TrackChip(pick.track)
+                        Text("  ${CatanText.track(pick.track)}")
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+    )
+}
+
+/** The hand is over its limit: give one progress card back. */
+@Composable
+fun CatanDropProgressDialog(hand: List<ProgressCard>, onDrop: (DropProgress) -> Unit) {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Too many progress cards") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 380.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                Text("You may keep four. Choose one to give back.")
+                hand.forEach { card ->
+                    OutlinedButton(onClick = { onDrop(DropProgress(card.id)) }, modifier = Modifier.fillMaxWidth()) {
+                        TrackChip(card.kind.track)
+                        Text("  ${CatanText.progress(card.kind)}")
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+    )
+}
+
+/** The aqueduct pays: take any one resource. */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanAqueductDialog(legal: List<CatanMove>, onTake: (TakeAqueduct) -> Unit) {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Aqueduct") },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(12.dp)) {
+                Text("The dice paid you nothing. Take any resource.")
+                FlowRow(
+                    horizontalArrangement = Arrangement.spacedBy(8.dp),
+                    verticalArrangement = Arrangement.spacedBy(8.dp),
+                ) {
+                    legal.filterIsInstance<TakeAqueduct>().forEach { take ->
+                        ResourceTile(resource = take.resource, count = 1, onClick = { onTake(take) })
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+    )
+}
+
+/** A spy: these are the progress cards the other player holds; take one. */
+@Composable
+fun CatanSpyDialog(cards: List<ProgressCard>, legal: List<CatanMove>, onTake: (SpyTake) -> Unit) {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Spy") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 380.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                Text("Choose a card to take.")
+                cards.forEach { card ->
+                    val take = SpyTake(card.id)
+                    OutlinedButton(
+                        onClick = { onTake(take) },
+                        enabled = take in legal,
+                        modifier = Modifier.fillMaxWidth(),
+                    ) {
+                        TrackChip(card.kind.track)
+                        Text("  ${CatanText.progress(card.kind)}")
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Trading in goods
+// ---------------------------------------------------------------------------
+
+private enum class GoodsTab { BANK, PLAYER }
+
+/**
+ * Trade with the bank at the best ratio each card has, or offer cards —
+ * commodities included — to one other player.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanGoodsTradeDialog(
+    state: CatanState,
+    seat: Int,
+    seats: CatanSeats,
+    legal: List<CatanMove>,
+    onBank: (GoodsBankTrade) -> Unit,
+    onOffer: (OfferGoods) -> Unit,
+    onCancel: () -> Unit,
+) {
+    var tab by remember { mutableStateOf(GoodsTab.BANK) }
+    var bankGive by remember { mutableStateOf<Good?>(null) }
+    var everyone by remember { mutableStateOf(true) }
+    var partner by remember { mutableStateOf<Int?>(null) }
+    var give by remember { mutableStateOf(emptyMap<Good, Int>()) }
+    var get by remember { mutableStateOf(emptyMap<Good, Int>()) }
+    val held = CatanCk.goodsOf(state, seat)
+
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text(CatanText.TRADE) },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(12.dp),
+            ) {
+                Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                    GoodsTabButton(CatanText.TRADE_WITH_BANK, tab == GoodsTab.BANK) { tab = GoodsTab.BANK }
+                    GoodsTabButton(CatanText.TRADE_WITH_PLAYER, tab == GoodsTab.PLAYER) { tab = GoodsTab.PLAYER }
+                }
+                if (tab == GoodsTab.BANK) {
+                    val trades = CatanInteraction.goodsBankTrades(legal)
+                    if (trades.isEmpty()) {
+                        Text("You do not hold enough of any one card to trade with the bank.")
+                    } else {
+                        Text("Give:", fontWeight = FontWeight.Bold)
+                        FlowRow(
+                            horizontalArrangement = Arrangement.spacedBy(8.dp),
+                            verticalArrangement = Arrangement.spacedBy(8.dp),
+                        ) {
+                            trades.keys.forEach { good ->
+                                val ratio = CatanCk.bankRatio(state, seat, good)
+                                Column(horizontalAlignment = Alignment.CenterHorizontally) {
+                                    GoodTile(good, ratio, selected = bankGive == good, onClick = { bankGive = good })
+                                    Text("$ratio : 1", style = MaterialTheme.typography.labelSmall)
+                                }
+                            }
+                        }
+                        val chosen = bankGive
+                        if (chosen != null && chosen in trades) {
+                            Text("Get one:", fontWeight = FontWeight.Bold)
+                            FlowRow(
+                                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                                verticalArrangement = Arrangement.spacedBy(8.dp),
+                            ) {
+                                trades.getValue(chosen).forEach { good ->
+                                    GoodTile(good, 1, onClick = { onBank(GoodsBankTrade(chosen, good)) })
+                                }
+                            }
+                        }
+                    }
+                } else {
+                    Text("Offer to:", fontWeight = FontWeight.Bold)
+                    FlowRow(
+                        horizontalArrangement = Arrangement.spacedBy(8.dp),
+                        verticalArrangement = Arrangement.spacedBy(8.dp),
+                    ) {
+                        GoodsTabButton(CatanText.EVERYONE, everyone) {
+                            everyone = true
+                            partner = null
+                        }
+                        (0 until state.playerCount).filter { it != seat }.forEach { other ->
+                            GoodsTabButton(seats.label(other), !everyone && partner == other) {
+                                everyone = false
+                                partner = other
+                            }
+                        }
+                    }
+                    Text(CatanText.YOU_GIVE, fontWeight = FontWeight.Bold)
+                    GoodCounters(give, { held[it] ?: 0 }) { give = it }
+                    Text(CatanText.YOU_GET, fontWeight = FontWeight.Bold)
+                    GoodCounters(get, { 9 }) { get = it }
+                }
+            }
+        },
+        confirmButton = {
+            if (tab == GoodsTab.PLAYER) {
+                val to = if (everyone) null else partner
+                val giveCards = give.asGoods()
+                val getCards = get.asGoods()
+                val allowed = (everyone || partner != null) &&
+                    CatanInteraction.goodsOfferAllowed(state, seat, to, giveCards, getCards)
+                Button(
+                    onClick = { onOffer(OfferGoods(to, giveCards, getCards)) },
+                    enabled = allowed,
+                ) { Text(CatanText.SEND_OFFER) }
+            }
+        },
+        dismissButton = { TextButton(onClick = onCancel) { Text(CatanText.CANCEL) } },
+    )
+}
+
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+private fun GoodCounters(counts: Map<Good, Int>, limit: (Good) -> Int, onChange: (Map<Good, Int>) -> Unit) {
+    FlowRow(
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+        verticalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        Good.entries.forEach { good ->
+            GoodCounter(
+                good = good,
+                count = counts[good] ?: 0,
+                max = limit(good),
+                onChange = { n -> onChange(counts + (good to n.coerceIn(0, limit(good)))) },
+            )
+        }
+    }
+}
+
+@Composable
+private fun GoodsTabButton(label: String, selected: Boolean, onClick: () -> Unit) {
+    if (selected) {
+        FilledTonalButton(onClick = onClick) { Text(label) }
+    } else {
+        OutlinedButton(onClick = onClick) { Text(label) }
+    }
+}
+
+/**
+ * A goods offer has reached the local player: accept it, decline it, or answer
+ * with different terms. The counter's two sides start as the offer turned around.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanGoodsTradeResponseDialog(
+    state: CatanState,
+    seat: Int,
+    offer: GoodsOffer,
+    seats: CatanSeats,
+    canAccept: Boolean,
+    onAccept: () -> Unit,
+    onDecline: () -> Unit,
+    onCounter: (CounterGoods) -> Unit,
+) {
+    var countering by remember(offer) { mutableStateOf(false) }
+    var give by remember(offer) { mutableStateOf(offer.get.groupingBy { it }.eachCount()) }
+    var get by remember(offer) { mutableStateOf(offer.give.groupingBy { it }.eachCount()) }
+
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text(if (countering) "Counter-offer" else "Trade offer") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                Text(
+                    "${seats.label(offer.by)} offers ${CatanText.goods(offer.give)} to " +
+                        "${if (offer.to == null) "the table" else "you"} for ${CatanText.goods(offer.get)}",
+                )
+                if (countering) {
+                    Text(CatanText.YOU_GIVE, fontWeight = FontWeight.Bold)
+                    GoodCounters(give, { CatanCk.goodsOf(state, seat)[it] ?: 0 }) { give = it }
+                    Text(CatanText.YOU_GET, fontWeight = FontWeight.Bold)
+                    GoodCounters(get, { CatanCk.goodsOf(state, offer.by)[it] ?: 0 }) { get = it }
+                } else if (!canAccept) {
+                    Text(
+                        "You cannot accept this: one side no longer holds the cards.",
+                        style = MaterialTheme.typography.bodySmall,
+                    )
+                }
+            }
+        },
+        confirmButton = {
+            if (countering) {
+                val move = CounterGoods(give.asGoods(), get.asGoods())
+                Button(
+                    onClick = { onCounter(move) },
+                    enabled = CatanInteraction.goodsCounterAllowed(state, seat, move.give, move.get),
+                ) { Text(CatanText.SEND_COUNTER) }
+            } else {
+                Button(onClick = onAccept, enabled = canAccept) { Text(CatanText.ACCEPT) }
+            }
+        },
+        dismissButton = {
+            Row(horizontalArrangement = Arrangement.spacedBy(4.dp)) {
+                if (countering) {
+                    TextButton(onClick = { countering = false }) { Text(CatanText.CANCEL) }
+                } else {
+                    TextButton(onClick = { countering = true }) { Text(CatanText.COUNTER) }
+                }
+                TextButton(onClick = onDecline) { Text(CatanText.DECLINE) }
+            }
+        },
+    )
+}
+
+/** The offerer's choice once nobody accepted a goods offer: take a counter-offer, or none. */
+@Composable
+fun CatanGoodsCounterChoiceDialog(
+    counters: List<GoodsCounter>,
+    seats: CatanSeats,
+    onTake: (AcceptCounter) -> Unit,
+    onNoDeal: () -> Unit,
+) {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Counter-offers") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                if (counters.isEmpty()) Text("None of the counter-offers can be met any more.")
+                counters.forEach { counter ->
+                    Column(verticalArrangement = Arrangement.spacedBy(4.dp)) {
+                        Text(
+                            "${seats.label(counter.by)} would give ${CatanText.goods(counter.give)} " +
+                                "for ${CatanText.goods(counter.get)}",
+                        )
+                        Button(onClick = { onTake(AcceptCounter(counter.by)) }) { Text(CatanText.ACCEPT) }
+                    }
+                }
+            }
+        },
+        confirmButton = { TextButton(onClick = onNoDeal) { Text(CatanText.NO_DEAL) } },
+    )
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanDialogs.kt

@@ -0,0 +1,675 @@
+package org.prolibertate.games.ui.game.catan
+
+import org.prolibertate.games.ui.LocalEndGameHandle
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.ExperimentalLayoutApi
+import androidx.compose.foundation.layout.FlowRow
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.heightIn
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.Button
+import androidx.compose.material3.FilledTonalButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import org.prolibertate.games.game.catan.CatanMove
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.DevCardType
+import org.prolibertate.games.game.catan.Discard
+import org.prolibertate.games.game.catan.MaritimeTrade
+import org.prolibertate.games.game.catan.OfferTrade
+import org.prolibertate.games.game.catan.TradeCounter
+import org.prolibertate.games.game.catan.CounterTrade
+import org.prolibertate.games.game.catan.AcceptCounter
+import org.prolibertate.games.game.catan.PlayKnight
+import org.prolibertate.games.game.catan.PlayRoadBuilding
+import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.TradeOffer
+
+/*
+ * Every Katan dialog. Each is a stateless composable apart from the selection it
+ * is helping the player make (cards picked, a partner chosen); the move it ends
+ * in is reported through a lambda and sent by the screen. What is *allowed* is
+ * always asked of [CatanInteraction], never decided here.
+ */
+
+// ---------------------------------------------------------------------------
+// Shared pieces
+// ---------------------------------------------------------------------------
+
+/** A resource tile with a minus and a plus, for choosing how many cards. */
+@Composable
+private fun ResourceCounter(
+    resource: Resource,
+    count: Int,
+    max: Int,
+    onChange: (Int) -> Unit,
+) {
+    Column(horizontalAlignment = Alignment.CenterHorizontally, verticalArrangement = Arrangement.spacedBy(4.dp)) {
+        ResourceTile(resource, count, enabled = max > 0 || count > 0)
+        Row(horizontalArrangement = Arrangement.spacedBy(4.dp)) {
+            OutlinedButton(
+                onClick = { onChange(count - 1) },
+                enabled = count > 0,
+                contentPadding = PaddingValues(0.dp),
+                modifier = Modifier.width(34.dp).height(32.dp),
+            ) { Text("−") }
+            OutlinedButton(
+                onClick = { onChange(count + 1) },
+                enabled = count < max,
+                contentPadding = PaddingValues(0.dp),
+                modifier = Modifier.width(34.dp).height(32.dp),
+            ) { Text("+") }
+        }
+    }
+}
+
+private fun Map<Resource, Int>.asCards(): List<Resource> =
+    Resource.entries.flatMap { r -> List(this[r] ?: 0) { r } }
+
+// ---------------------------------------------------------------------------
+// Discarding on a seven
+// ---------------------------------------------------------------------------
+
+/**
+ * A seven was rolled and this player holds more than seven cards: choose which
+ * half to give up. Not dismissable — the game is waiting on it.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanDiscardDialog(
+    held: Map<Resource, Int>,
+    quota: Int,
+    legal: List<CatanMove>,
+    onSubmit: (Discard) -> Unit,
+) {
+    var picked by remember { mutableStateOf(emptyMap<Resource, Int>()) }
+    val selection = picked.asCards()
+    val move = CatanInteraction.discardMove(legal, selection)
+
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Discard $quota cards") },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(12.dp)) {
+                Text(
+                    "A seven was rolled. Choose $quota cards to give up " +
+                        "(${selection.size} of $quota chosen).",
+                )
+                FlowRow(
+                    horizontalArrangement = Arrangement.spacedBy(8.dp),
+                    verticalArrangement = Arrangement.spacedBy(8.dp),
+                ) {
+                    Resource.entries.forEach { resource ->
+                        val have = held[resource] ?: 0
+                        if (have > 0) {
+                            ResourceCounter(
+                                resource = resource,
+                                count = picked[resource] ?: 0,
+                                max = if (selection.size < quota) have else (picked[resource] ?: 0),
+                                onChange = { n -> picked = picked + (resource to n.coerceIn(0, have)) },
+                            )
+                        }
+                    }
+                }
+            }
+        },
+        confirmButton = {
+            Button(onClick = { move?.let(onSubmit) }, enabled = move != null) { Text("Discard") }
+        },
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Gold (Seafarers)
+// ---------------------------------------------------------------------------
+
+/**
+ * A gold field paid out: choose the resource cards it gives. Not dismissable: the game
+ * is waiting. The engine's list says which resources the bank can still pay.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanGoldDialog(
+    legal: List<CatanMove>,
+    onSubmit: (org.prolibertate.games.game.catan.PickGold) -> Unit,
+) {
+    val count = CatanInteraction.goldCount(legal)
+    var picked by remember { mutableStateOf(emptyMap<Resource, Int>()) }
+    val selection = picked.asCards()
+    val move = CatanInteraction.goldMove(legal, selection)
+    // A resource is on offer if some legal pick names it.
+    val offered = legal.filterIsInstance<org.prolibertate.games.game.catan.PickGold>()
+        .flatMap { it.cards }.toSet()
+
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text(CatanText.GOLD_TITLE) },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(12.dp)) {
+                Text("Gold! Choose $count resource cards (${selection.size} of $count chosen).")
+                FlowRow(
+                    horizontalArrangement = Arrangement.spacedBy(8.dp),
+                    verticalArrangement = Arrangement.spacedBy(8.dp),
+                ) {
+                    Resource.entries.filter { it in offered }.forEach { resource ->
+                        ResourceCounter(
+                            resource = resource,
+                            count = picked[resource] ?: 0,
+                            max = if (selection.size < count) count else (picked[resource] ?: 0),
+                            onChange = { n -> picked = picked + (resource to n.coerceIn(0, count)) },
+                        )
+                    }
+                }
+            }
+        },
+        confirmButton = {
+            Button(onClick = { move?.let(onSubmit) }, enabled = move != null) { Text(CatanText.GOLD_TAKE) }
+        },
+    )
+}
+
+// ---------------------------------------------------------------------------
+// The robber
+// ---------------------------------------------------------------------------
+
+/** More than one player can be robbed from this hex: choose whom. */
+@Composable
+fun CatanVictimDialog(
+    victims: List<Int>,
+    seats: CatanSeats,
+    onPick: (Int) -> Unit,
+    onCancel: () -> Unit,
+) {
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text("Steal from…") },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                victims.forEach { seat ->
+                    OutlinedButton(onClick = { onPick(seat) }, modifier = Modifier.fillMaxWidth()) {
+                        Text(seats.label(seat))
+                    }
+                }
+            }
+        },
+        confirmButton = {},
+        dismissButton = { TextButton(onClick = onCancel) { Text(CatanText.CANCEL) } },
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Development cards
+// ---------------------------------------------------------------------------
+
+/**
+ * The player's development cards. A Knight or Road Building plays at once; a
+ * Monopoly or Year of Plenty asks for its resource choice in a second step.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanPlayCardDialog(
+    hand: List<DevCardInHand>,
+    onPlay: (CatanMove) -> Unit,
+    onCancel: () -> Unit,
+) {
+    var chosen by remember { mutableStateOf<DevCardInHand?>(null) }
+    var picked by remember { mutableStateOf(emptyList<Resource>()) }
+    val card = chosen
+
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text(card?.let { CatanText.devCard(it.card.type) } ?: "Development cards") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 420.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(10.dp),
+            ) {
+                when {
+                    card == null -> {
+                        if (hand.isEmpty()) Text("You have no development cards.")
+                        hand.forEach { entry -> DevCardRow(entry, onPlay) { chosen = it } }
+                    }
+
+                    card.card.type == DevCardType.MONOPOLY -> {
+                        Text("Name a resource. Every other player hands over all of it.")
+                        val choices = CatanInteraction.monopolyChoices(card.plays)
+                        FlowRow(
+                            horizontalArrangement = Arrangement.spacedBy(8.dp),
+                            verticalArrangement = Arrangement.spacedBy(8.dp),
+                        ) {
+                            Resource.entries.forEach { resource ->
+                                val move = choices[resource]
+                                ResourceTile(
+                                    resource = resource,
+                                    count = 0,
+                                    enabled = move != null,
+                                    onClick = { move?.let(onPlay) },
+                                )
+                            }
+                        }
+                    }
+
+                    card.card.type == DevCardType.YEAR_OF_PLENTY -> {
+                        Text("Take two resource cards from the bank (${picked.size} of 2 chosen).")
+                        val available = CatanInteraction.plentyAvailable(card.plays, picked)
+                        FlowRow(
+                            horizontalArrangement = Arrangement.spacedBy(8.dp),
+                            verticalArrangement = Arrangement.spacedBy(8.dp),
+                        ) {
+                            Resource.entries.forEach { resource ->
+                                ResourceTile(
+                                    resource = resource,
+                                    count = picked.count { it == resource },
+                                    selected = resource in picked,
+                                    enabled = resource in available,
+                                    onClick = { picked = picked + resource },
+                                )
+                            }
+                        }
+                        if (picked.isNotEmpty()) {
+                            TextButton(onClick = { picked = emptyList() }) { Text("Clear") }
+                        }
+                    }
+                }
+            }
+        },
+        confirmButton = {
+            if (card != null && card.card.type == DevCardType.YEAR_OF_PLENTY) {
+                val move = CatanInteraction.plentyMove(card.plays, picked)
+                Button(onClick = { move?.let(onPlay) }, enabled = move != null) { Text("Take") }
+            }
+        },
+        dismissButton = {
+            TextButton(
+                onClick = {
+                    if (card == null) {
+                        onCancel()
+                    } else {
+                        chosen = null
+                        picked = emptyList()
+                    }
+                },
+            ) { Text(if (card == null) CatanText.CANCEL else "Back") }
+        },
+    )
+}
+
+@Composable
+private fun DevCardRow(
+    entry: DevCardInHand,
+    onPlay: (CatanMove) -> Unit,
+    onChoose: (DevCardInHand) -> Unit,
+) {
+    val type = entry.card.type
+    Row(
+        modifier = Modifier.fillMaxWidth(),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        Column(modifier = Modifier.weight(1f)) {
+            Text(CatanText.devCard(type), fontWeight = FontWeight.Bold)
+            Text(CatanText.devCardHelp(type), style = MaterialTheme.typography.bodySmall)
+        }
+        when {
+            type == DevCardType.VICTORY_POINT -> Text("Hidden", style = MaterialTheme.typography.labelSmall)
+            !entry.playable -> Text("Not now", style = MaterialTheme.typography.labelSmall)
+            entry.plays.size == 1 && (entry.plays[0] is PlayKnight || entry.plays[0] is PlayRoadBuilding) ->
+                Button(onClick = { onPlay(entry.plays[0]) }) { Text("Play") }
+
+            else -> Button(onClick = { onChoose(entry) }) { Text("Play…") }
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Trading
+// ---------------------------------------------------------------------------
+
+private enum class TradeTab { BANK, PLAYER }
+
+/**
+ * Trade with the bank at the best ratio the player has, or offer cards to one
+ * other player. Offers are free-form, so they are checked with the engine's
+ * structural rule ([CatanInteraction.offerAllowed]) rather than looked up in
+ * the legal list.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanTradeDialog(
+    state: CatanState,
+    seat: Int,
+    seats: CatanSeats,
+    legal: List<CatanMove>,
+    onBank: (MaritimeTrade) -> Unit,
+    onOffer: (OfferTrade) -> Unit,
+    onCancel: () -> Unit,
+) {
+    var tab by remember { mutableStateOf(TradeTab.BANK) }
+    var bankGive by remember { mutableStateOf<Resource?>(null) }
+    var everyone by remember { mutableStateOf(true) }
+    var partner by remember { mutableStateOf<Int?>(null) }
+    var give by remember { mutableStateOf(emptyMap<Resource, Int>()) }
+    var get by remember { mutableStateOf(emptyMap<Resource, Int>()) }
+
+    AlertDialog(
+        onDismissRequest = onCancel,
+        title = { Text(CatanText.TRADE) },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(12.dp),
+            ) {
+                Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                    TabButton(CatanText.TRADE_WITH_BANK, tab == TradeTab.BANK) { tab = TradeTab.BANK }
+                    TabButton(CatanText.TRADE_WITH_PLAYER, tab == TradeTab.PLAYER) { tab = TradeTab.PLAYER }
+                }
+
+                if (tab == TradeTab.BANK) {
+                    val trades = CatanInteraction.bankTrades(legal)
+                    if (trades.isEmpty()) {
+                        Text("You do not hold enough of any one resource to trade with the bank.")
+                    } else {
+                        Text("Give:", fontWeight = FontWeight.Bold)
+                        FlowRow(
+                            horizontalArrangement = Arrangement.spacedBy(8.dp),
+                            verticalArrangement = Arrangement.spacedBy(8.dp),
+                        ) {
+                            trades.keys.forEach { resource ->
+                                val ratio = CatanInteraction.bankRatio(state, seat, resource)
+                                Column(horizontalAlignment = Alignment.CenterHorizontally) {
+                                    ResourceTile(
+                                        resource = resource,
+                                        count = ratio,
+                                        selected = bankGive == resource,
+                                        onClick = { bankGive = resource },
+                                    )
+                                    Text("$ratio : 1", style = MaterialTheme.typography.labelSmall)
+                                }
+                            }
+                        }
+                        val chosen = bankGive
+                        if (chosen != null && chosen in trades) {
+                            Text("Get one:", fontWeight = FontWeight.Bold)
+                            FlowRow(
+                                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                                verticalArrangement = Arrangement.spacedBy(8.dp),
+                            ) {
+                                trades.getValue(chosen).forEach { resource ->
+                                    ResourceTile(
+                                        resource = resource,
+                                        count = 1,
+                                        onClick = { onBank(MaritimeTrade(chosen, resource)) },
+                                    )
+                                }
+                            }
+                        }
+                    }
+                } else {
+                    Text("Offer to:", fontWeight = FontWeight.Bold)
+                    FlowRow(
+                        horizontalArrangement = Arrangement.spacedBy(8.dp),
+                        verticalArrangement = Arrangement.spacedBy(8.dp),
+                    ) {
+                        TabButton(CatanText.EVERYONE, everyone) { everyone = true; partner = null }
+                        (0 until state.playerCount).filter { it != seat }.forEach { other ->
+                            TabButton(seats.label(other), !everyone && partner == other) {
+                                everyone = false
+                                partner = other
+                            }
+                        }
+                    }
+                    Text(CatanText.YOU_GIVE, fontWeight = FontWeight.Bold)
+                    CounterRow(
+                        counts = give,
+                        limit = { state.resources[seat][it] ?: 0 },
+                        onChange = { give = it },
+                    )
+                    Text(CatanText.YOU_GET, fontWeight = FontWeight.Bold)
+                    CounterRow(counts = get, limit = { 9 }, onChange = { get = it })
+                }
+            }
+        },
+        confirmButton = {
+            if (tab == TradeTab.PLAYER) {
+                val to = if (everyone) null else partner
+                val giveCards = give.asCards()
+                val getCards = get.asCards()
+                val allowed = (everyone || partner != null) &&
+                    CatanInteraction.offerAllowed(state, seat, to, giveCards, getCards)
+                Button(
+                    onClick = { onOffer(OfferTrade(to, giveCards, getCards)) },
+                    enabled = allowed,
+                ) { Text(CatanText.SEND_OFFER) }
+            }
+        },
+        dismissButton = { TextButton(onClick = onCancel) { Text(CatanText.CANCEL) } },
+    )
+}
+
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+private fun CounterRow(
+    counts: Map<Resource, Int>,
+    limit: (Resource) -> Int,
+    onChange: (Map<Resource, Int>) -> Unit,
+) {
+    FlowRow(
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+        verticalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        Resource.entries.forEach { resource ->
+            ResourceCounter(
+                resource = resource,
+                count = counts[resource] ?: 0,
+                max = limit(resource),
+                onChange = { n -> onChange(counts + (resource to n.coerceIn(0, limit(resource)))) },
+            )
+        }
+    }
+}
+
+@Composable
+private fun TabButton(label: String, selected: Boolean, onClick: () -> Unit) {
+    if (selected) {
+        FilledTonalButton(onClick = onClick) { Text(label) }
+    } else {
+        OutlinedButton(onClick = onClick) { Text(label) }
+    }
+}
+
+/**
+ * Another player has put an offer to the local player (alone, or as one of the
+ * table). Accept, decline, or — via a second step — answer with different terms.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanTradeResponseDialog(
+    state: CatanState,
+    seat: Int,
+    offer: TradeOffer,
+    seats: CatanSeats,
+    canAccept: Boolean,
+    onAccept: () -> Unit,
+    onDecline: () -> Unit,
+    onCounter: (CounterTrade) -> Unit,
+) {
+    var countering by remember(offer) { mutableStateOf(false) }
+    // What we would give the offerer, and what we would ask of them.
+    var give by remember(offer) { mutableStateOf(offer.get.groupingBy { it }.eachCount()) }
+    var get by remember(offer) { mutableStateOf(offer.give.groupingBy { it }.eachCount()) }
+
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text(if (countering) "Counter-offer" else "Trade offer") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                Text(
+                    CatanText.tradeSummary(
+                        by = seats.label(offer.by),
+                        to = if (offer.to == null) "the table" else "you",
+                        give = offer.give,
+                        get = offer.get,
+                    ),
+                )
+                if (countering) {
+                    Text(CatanText.YOU_GIVE, fontWeight = FontWeight.Bold)
+                    CounterRow(
+                        counts = give,
+                        limit = { state.resources[seat][it] ?: 0 },
+                        onChange = { give = it },
+                    )
+                    Text(CatanText.YOU_GET, fontWeight = FontWeight.Bold)
+                    CounterRow(
+                        counts = get,
+                        limit = { state.resources[offer.by][it] ?: 0 },
+                        onChange = { get = it },
+                    )
+                } else if (!canAccept) {
+                    Text(
+                        "You cannot accept this: one side no longer holds the cards.",
+                        style = MaterialTheme.typography.bodySmall,
+                    )
+                }
+            }
+        },
+        confirmButton = {
+            if (countering) {
+                val move = CounterTrade(give.asCards(), get.asCards())
+                Button(
+                    onClick = { onCounter(move) },
+                    enabled = CatanInteraction.counterAllowed(state, seat, move.give, move.get),
+                ) { Text(CatanText.SEND_COUNTER) }
+            } else {
+                Button(onClick = onAccept, enabled = canAccept) { Text(CatanText.ACCEPT) }
+            }
+        },
+        dismissButton = {
+            Row(horizontalArrangement = Arrangement.spacedBy(4.dp)) {
+                if (countering) {
+                    TextButton(onClick = { countering = false }) { Text(CatanText.CANCEL) }
+                } else {
+                    TextButton(onClick = { countering = true }) { Text(CatanText.COUNTER) }
+                }
+                TextButton(onClick = onDecline) { Text(CatanText.DECLINE) }
+            }
+        },
+    )
+}
+
+/** The offerer's choice once nobody accepted: take a counter-offer, or none. */
+@Composable
+fun CatanCounterChoiceDialog(
+    counters: List<TradeCounter>,
+    seats: CatanSeats,
+    onTake: (AcceptCounter) -> Unit,
+    onNoDeal: () -> Unit,
+) {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Counter-offers") },
+        text = {
+            Column(
+                modifier = Modifier.heightIn(max = 460.dp).verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                if (counters.isEmpty()) {
+                    Text("None of the counter-offers can be met any more.")
+                }
+                counters.forEach { counter ->
+                    Column(verticalArrangement = Arrangement.spacedBy(4.dp)) {
+                        Text(CatanText.counterSummary(seats.label(counter.by), counter.give, counter.get))
+                        Button(onClick = { onTake(AcceptCounter(counter.by)) }) { Text(CatanText.ACCEPT) }
+                    }
+                }
+            }
+        },
+        confirmButton = { TextButton(onClick = onNoDeal) { Text(CatanText.NO_DEAL) } },
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Ending
+// ---------------------------------------------------------------------------
+
+/** The game is over: who won, and what everyone finished with. */
+@Composable
+fun CatanGameOverDialog(
+    state: CatanState,
+    seats: CatanSeats,
+    onExit: () -> Unit,
+    onLook: () -> Unit,
+) {
+    val points = (0 until state.playerCount).map { seat ->
+        // The winner's hidden victory-point cards are revealed by winning; the
+        // host's copy of the state has them, a client's has only its own.
+        seat to if (seat == seats.me) CatanRules.victoryPoints(state, seat)
+        else CatanRules.publicVictoryPoints(state)[seat]
+    }
+    AlertDialog(
+        onDismissRequest = onLook,
+        title = { Text(CatanText.winnerHeadline(state, seats)) },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(4.dp)) {
+                points.sortedByDescending { it.second }.forEach { (seat, vp) ->
+                    Text("${seats.label(seat)}: $vp points")
+                }
+            }
+        },
+        confirmButton = { TextButton(onClick = onExit) { Text(CatanText.LEAVE_GAME) } },
+        dismissButton = { TextButton(onClick = onLook) { Text(CatanText.LOOK_AT_BOARD) } },
+    )
+}
+
+@Composable
+fun CatanEndGameDialog(onEnd: () -> Unit, onKeepPlaying: () -> Unit) {
+    AlertDialog(
+        onDismissRequest = onKeepPlaying,
+        title = { Text("End this game?") },
+        text = {
+            Text(
+                "This game ends here and the position is not saved. Anyone else " +
+                    "at the table is told you have left.",
+            )
+        },
+        confirmButton = {
+            // Ending a game on purpose also forgets the saved position: only
+            // leaving the table keeps it to be picked up again.
+            val handle = LocalEndGameHandle.current
+            TextButton(onClick = { handle.end(); onEnd() }) { Text("End the game") }
+        },
+        dismissButton = { TextButton(onClick = onKeepPlaying) { Text("Keep playing") } },
+    )
+}
+
+@Composable
+fun CatanAbandonedDialog(notice: String, onExit: () -> Unit, onStay: () -> Unit) {
+    AlertDialog(
+        onDismissRequest = onStay,
+        title = { Text("The game has ended") },
+        text = { Text("$notice There are no more moves to play.") },
+        confirmButton = { TextButton(onClick = onExit) { Text(CatanText.LEAVE_GAME) } },
+        dismissButton = { TextButton(onClick = onStay) { Text(CatanText.LOOK_AT_BOARD) } },
+    )
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanGeometry.kt

@@ -0,0 +1,143 @@
+package org.prolibertate.games.ui.game.catan
+
+import org.prolibertate.games.game.catan.CatanBoard
+import org.prolibertate.games.game.catan.Topology
+import kotlin.math.sqrt
+
+/** A point in board pixels. Plain floats, so this file needs no Compose types. */
+data class Pt(val x: Float, val y: Float)
+
+/**
+ * Where the island sits on screen: the one place the engine's integer lattice
+ * (see [CatanBoard]) becomes pixels, and pixels become "which vertex / edge /
+ * hex did the player tap".
+ *
+ * Pure and Android-free, so it is unit-tested (`CatanGeometryTest`). The drawing
+ * code ([CatanBoardView]) and the tap handling both go through this, which is
+ * what keeps what is drawn and what is tappable from ever disagreeing.
+ *
+ * Lattice to pixel: a hex of circumradius `R` is pointy-top, so one lattice x-unit
+ * is `R·√3/2` and one lattice y-unit is `R/2`, and lattice +Y points up the board
+ * while pixel +y points down.
+ */
+class BoardLayout(
+    val width: Float,
+    val height: Float,
+    /** Circumradius of one hex, in pixels. */
+    val radius: Float,
+    /** The board this layout draws: the standard island unless the game is Seafarers. */
+    val topo: Topology = CatanBoard.base,
+) {
+    private val centreX = width / 2f
+    private val centreY = height / 2f
+    private val unitX = radius * SQRT3 / 2f
+    private val unitY = radius / 2f
+
+    /** The lattice point drawn at the middle of the box: the middle of the frame. */
+    private val midX = (topo.lattice[0] + topo.lattice[1]) / 2f
+    private val midY = (topo.lattice[2] + topo.lattice[3]) / 2f
+
+    fun point(latticeX: Int, latticeY: Int): Pt =
+        Pt(centreX + (latticeX - midX) * unitX, centreY - (latticeY - midY) * unitY)
+
+    fun hexCenter(hex: Int): Pt {
+        val (lx, ly) = topo.hexCenter(hex)
+        return point(lx, ly)
+    }
+
+    fun vertex(vertex: Int): Pt {
+        val (lx, ly) = topo.VERTEX_POS[vertex]
+        return point(lx, ly)
+    }
+
+    fun hexCorners(hex: Int): List<Pt> = topo.HEX_CORNERS[hex].map { vertex(it) }
+
+    fun edgeEnds(edge: Int): Pair<Pt, Pt> {
+        val (a, b) = topo.EDGE_VERTICES[edge]
+        return vertex(a) to vertex(b)
+    }
+
+    fun edgeMidpoint(edge: Int): Pt {
+        val (a, b) = edgeEnds(edge)
+        return Pt((a.x + b.x) / 2f, (a.y + b.y) / 2f)
+    }
+
+    /**
+     * Where a harbour's marker is drawn: just off the coast, straight out from
+     * the middle of its edge. The marker is joined to the edge's two vertices by
+     * the board view, which is what shows which settlements can use it.
+     */
+    fun portAnchor(edge: Int): Pt {
+        val mid = edgeMidpoint(edge)
+        // Straight out from the middle of the island on the standard board; on a map of
+        // islands, straight out from the land hex the harbour sits on.
+        val from = if (topo.EDGE_HEXES[edge].size == 1) {
+            Pt(centreX, centreY)
+        } else {
+            topo.EDGE_HEXES[edge].firstOrNull { topo.land[it] }?.let { hexCenter(it) } ?: Pt(centreX, centreY)
+        }
+        val dx = mid.x - from.x
+        val dy = mid.y - from.y
+        val length = sqrt(dx * dx + dy * dy).coerceAtLeast(1f)
+        return Pt(mid.x + dx / length * radius * PORT_OFFSET, mid.y + dy / length * radius * PORT_OFFSET)
+    }
+
+    /** The nearest of [among] within [reach] pixels of [at], or null. */
+    fun nearestVertex(at: Pt, reach: Float, among: Collection<Int>): Int? =
+        nearest(at, reach, among) { vertex(it) }
+
+    fun nearestEdge(at: Pt, reach: Float, among: Collection<Int>): Int? =
+        nearest(at, reach, among) { edgeMidpoint(it) }
+
+    fun nearestHex(at: Pt, reach: Float, among: Collection<Int>): Int? =
+        nearest(at, reach, among) { hexCenter(it) }
+
+    private fun nearest(at: Pt, reach: Float, among: Collection<Int>, position: (Int) -> Pt): Int? {
+        var best: Int? = null
+        var bestDistance = reach * reach
+        for (candidate in among) {
+            val p = position(candidate)
+            val dx = p.x - at.x
+            val dy = p.y - at.y
+            val d = dx * dx + dy * dy
+            if (d <= bestDistance) {
+                best = candidate
+                bestDistance = d
+            }
+        }
+        return best
+    }
+}
+
+object CatanGeometry {
+
+    /** Empty space round the island, in hex radii, for the sea and the harbours. */
+    const val MARGIN = 1.75f
+
+    /** A Seafarers frame already ends in a ring of sea, so it needs almost none. */
+    private const val FRAME_MARGIN = 0.3f
+
+    private fun margin(topo: Topology) = if (topo.land.all { it }) MARGIN else FRAME_MARGIN
+
+    private fun widthInRadii(topo: Topology) =
+        (topo.lattice[1] - topo.lattice[0]) * SQRT3 / 2f + 2 * margin(topo)
+
+    private fun heightInRadii(topo: Topology) =
+        (topo.lattice[3] - topo.lattice[2]) / 2f + 2 * margin(topo)
+
+    /** Width ÷ height of the board including its margin, for sizing its box. */
+    val ASPECT: Float = widthInRadii(CatanBoard.base) / heightInRadii(CatanBoard.base)
+
+    fun aspect(topo: Topology): Float = widthInRadii(topo) / heightInRadii(topo)
+
+    /** The largest layout that fits [width] × [height] pixels. */
+    fun fit(width: Float, height: Float, topo: Topology = CatanBoard.base): BoardLayout {
+        val radius = minOf(width / widthInRadii(topo), height / heightInRadii(topo))
+        return BoardLayout(width, height, radius, topo)
+    }
+}
+
+private const val SQRT3 = 1.7320508f
+
+/** How far past the coast a harbour marker sits, in hex radii. Far enough that its piers are clearly visible. */
+internal const val PORT_OFFSET = 1.0f

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanHud.kt

@@ -0,0 +1,474 @@
+package org.prolibertate.games.ui.game.catan
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.border
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.gestures.detectDragGestures
+import androidx.compose.foundation.gestures.detectTransformGestures
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.horizontalScroll
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.material3.Surface
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableFloatStateOf
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.input.pointer.pointerInput
+import androidx.compose.ui.layout.LayoutCoordinates
+import androidx.compose.ui.layout.onGloballyPositioned
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+
+/*
+ * The heads-up display pieces of the landscape Katan screen: the controls the
+ * Catan Universe match screen uses (see docs/RE-catan-universe.md), redrawn in
+ * 2D. Stateless, like everything in CatanPanels.kt: values in, lambdas out.
+ */
+
+/** A round HUD button: a glyph or short word, optionally with a one-word caption. */
+@Composable
+fun HudRoundButton(
+    glyph: String,
+    modifier: Modifier = Modifier,
+    caption: String? = null,
+    enabled: Boolean = true,
+    primary: Boolean = false,
+    tint: Color = Color.Unspecified,
+    diameter: Dp = 56.dp,
+    onClick: () -> Unit,
+) {
+    val container = when {
+        tint != Color.Unspecified -> tint
+        primary -> MaterialTheme.colorScheme.primary
+        else -> MaterialTheme.colorScheme.secondaryContainer
+    }
+    val ink = if (primary || tint != Color.Unspecified) Color.White else MaterialTheme.colorScheme.onSecondaryContainer
+    Column(modifier, horizontalAlignment = Alignment.CenterHorizontally) {
+        Box(
+            modifier = Modifier
+                .size(diameter)
+                .clip(CircleShape)
+                .background(container.copy(alpha = if (enabled) 1f else 0.35f))
+                .border(2.dp, Color(0x55000000), CircleShape)
+                .then(if (enabled) Modifier.clickable(onClick = onClick) else Modifier),
+            contentAlignment = Alignment.Center,
+        ) {
+            Text(glyph, color = ink.copy(alpha = if (enabled) 1f else 0.6f), fontSize = 18.sp, fontWeight = FontWeight.Bold)
+        }
+        // Always laid out, so the button column never changes height.
+        Text(caption ?: " ", fontSize = 10.sp, maxLines = 1)
+    }
+}
+
+/**
+ * The left-hand build column: one icon per piece. **Drag one onto the board** and
+ * release over a lit spot to stage it; or tap to arm the board and tap a spot. The
+ * column reports pointer positions in window coordinates so the screen can find the
+ * spot under the finger whatever the board's zoom and pan.
+ */
+@Composable
+fun HudBuildColumn(
+    kinds: List<BuildKind>,
+    canBuild: Set<BuildKind>,
+    armed: BuildKind?,
+    modifier: Modifier = Modifier,
+    onTap: (BuildKind) -> Unit,
+    onDragStart: (BuildKind, Offset) -> Unit,
+    onDrag: (Offset) -> Unit,
+    onDragEnd: () -> Unit,
+) {
+    Column(modifier, verticalArrangement = Arrangement.spacedBy(3.dp), horizontalAlignment = Alignment.CenterHorizontally) {
+        kinds.forEach { kind ->
+            BuildChip(kind, enabled = kind in canBuild, armed = armed == kind, onTap, onDragStart, onDrag, onDragEnd)
+        }
+    }
+}
+
+@Composable
+private fun BuildChip(
+    kind: BuildKind,
+    enabled: Boolean,
+    armed: Boolean,
+    onTap: (BuildKind) -> Unit,
+    onDragStart: (BuildKind, Offset) -> Unit,
+    onDrag: (Offset) -> Unit,
+    onDragEnd: () -> Unit,
+) {
+    var coords by remember { mutableStateOf<LayoutCoordinates?>(null) }
+    val start by rememberUpdatedState(onDragStart)
+    val move by rememberUpdatedState(onDrag)
+    val end by rememberUpdatedState(onDragEnd)
+    val tap by rememberUpdatedState(onTap)
+    val shape = RoundedCornerShape(12.dp)
+    Column(horizontalAlignment = Alignment.CenterHorizontally) {
+        Box(
+            modifier = Modifier
+                .size(46.dp)
+                .clip(shape)
+                .background(
+                    when {
+                        armed -> MaterialTheme.colorScheme.primary
+                        else -> MaterialTheme.colorScheme.secondaryContainer.copy(alpha = if (enabled) 1f else 0.35f)
+                    },
+                )
+                .border(2.dp, Color(0x55000000), shape)
+                .onGloballyPositioned { coords = it }
+                .pointerInput(enabled, kind) {
+                    if (!enabled) return@pointerInput
+                    detectDragGestures(
+                        onDragStart = { local ->
+                            coords?.localToWindow(local)?.let { start(kind, it) }
+                        },
+                        onDrag = { change, _ ->
+                            change.consume()
+                            coords?.localToWindow(change.position)?.let { move(it) }
+                        },
+                        onDragEnd = { end() },
+                        onDragCancel = { end() },
+                    )
+                }
+                .then(if (enabled) Modifier.clickable { tap(kind) } else Modifier),
+            contentAlignment = Alignment.Center,
+        ) {
+            Text(
+                CatanHudGlyphs.of(kind),
+                fontSize = 22.sp,
+                color = if (armed) Color.White else MaterialTheme.colorScheme.onSecondaryContainer,
+            )
+        }
+        Text(CatanHudGlyphs.label(kind), fontSize = 10.sp, maxLines = 1)
+    }
+}
+
+/** Glyphs and captions of the build column. Kept apart so the art can be swapped for drawables. */
+object CatanHudGlyphs {
+    fun of(kind: BuildKind): String = when (kind) {
+        BuildKind.ROAD -> "━"
+        BuildKind.SETTLEMENT -> "⌂"
+        BuildKind.CITY -> "▲"
+        BuildKind.WALL -> "▦"
+        BuildKind.KNIGHT -> "♞"
+        BuildKind.SHIP -> "⛵"
+    }
+
+    fun label(kind: BuildKind): String = when (kind) {
+        BuildKind.ROAD -> CatanText.ROAD
+        BuildKind.SETTLEMENT -> CatanText.SETTLEMENT
+        BuildKind.CITY -> CatanText.CITY
+        BuildKind.WALL -> CatanText.WALL
+        BuildKind.KNIGHT -> CatanText.KNIGHT
+        BuildKind.SHIP -> CatanText.SHIP
+    }
+}
+
+/** ✓ beside ✗: confirm or cancel a staged placement. Always laid out; enabled only while something is staged. */
+@Composable
+fun HudConfirmButtons(
+    staged: Boolean,
+    modifier: Modifier = Modifier,
+    onConfirm: () -> Unit,
+    onCancel: () -> Unit,
+) {
+    Row(modifier, horizontalArrangement = Arrangement.spacedBy(6.dp), verticalAlignment = Alignment.Bottom) {
+        HudRoundButton("✓", caption = CatanText.CONFIRM_BUILD, enabled = staged, tint = Color(0xFF2E7D32), diameter = 48.dp, onClick = onConfirm)
+        HudRoundButton("✕", caption = CatanText.CANCEL_BUILD, enabled = staged, tint = Color(0xFFC62828), diameter = 48.dp, onClick = onCancel)
+    }
+}
+
+/**
+ * Pan with one finger, pinch to zoom, like the Universe board camera. The content
+ * is drawn through a graphics layer, so taps inside it arrive already in the
+ * content's own coordinates and the board's hit-testing needs no changes.
+ */
+@Composable
+fun ZoomPanBox(
+    modifier: Modifier = Modifier,
+    minScale: Float = 1f,
+    maxScale: Float = 3f,
+    content: @Composable () -> Unit,
+) {
+    var scale by remember { mutableFloatStateOf(1f) }
+    var offset by remember { mutableStateOf(Offset.Zero) }
+    Box(
+        modifier = modifier
+            .clip(RoundedCornerShape(0.dp))
+            .pointerInput(Unit) {
+                detectTransformGestures { centroid, pan, zoom, _ ->
+                    val newScale = (scale * zoom).coerceIn(minScale, maxScale)
+                    val centre = Offset(size.width / 2f, size.height / 2f)
+                    // The content point under the fingers stays under them while zooming; then pan.
+                    val world = (centroid - centre - offset) / scale
+                    val next = centroid - centre - world * newScale + pan
+                    val maxX = size.width * (newScale - 1f) / 2f
+                    val maxY = size.height * (newScale - 1f) / 2f
+                    offset = Offset(next.x.coerceIn(-maxX, maxX), next.y.coerceIn(-maxY, maxY))
+                    scale = newScale
+                }
+            },
+    ) {
+        Box(
+            Modifier
+                .fillMaxSize()
+                .graphicsLayer {
+                    scaleX = scale
+                    scaleY = scale
+                    translationX = offset.x
+                    translationY = offset.y
+                },
+            contentAlignment = Alignment.Center,
+        ) { content() }
+    }
+}
+
+/** A small caption pill, for the drag hint and the staged-move text. */
+@Composable
+fun HudPill(text: String, modifier: Modifier = Modifier) {
+    Text(
+        text,
+        color = Color.White,
+        fontSize = 12.sp,
+        maxLines = 1,
+        modifier = modifier
+            .clip(RoundedCornerShape(50))
+            .background(Color(0xCC000000))
+            .padding(horizontal = 12.dp, vertical = 4.dp),
+    )
+}
+
+/**
+ * The landscape screen, laid out like the Catan Universe match view:
+ *
+ * ```
+ * ┌ player strip ───────────────────────────────────────────────┐
+ * │ prompt + dice                                               │
+ * │ [build]            the island (pinch / pan)        [✓] [✕]  │
+ * │ [column]                                                    │
+ * │ [log]       ┌ your cards ┐                  [buy][play] [⇄][●]│
+ * └─────────────┴────────────┴───────────────────────────────────┘
+ * ```
+ *
+ * Everything here is wiring around the existing panels; the island is handed in as [board].
+ */
+@Composable
+fun CatanHud(
+    state: org.prolibertate.games.game.catan.CatanState,
+    seats: CatanSeats,
+    style: CatanStyle,
+    actions: CatanActions,
+    prompt: String,
+    notice: String?,
+    legal: List<org.prolibertate.games.game.catan.CatanMove>,
+    localSeat: Int,
+    targets: BoardTargets,
+    pointsOf: (Int) -> Int,
+    staged: org.prolibertate.games.game.catan.CatanMove?,
+    dragKind: BuildKind?,
+    dragAt: Offset?,
+    showLog: Boolean,
+    boardCoords: LayoutCoordinates?,
+    building: BuildKind?,
+    onBoardCoords: (LayoutCoordinates) -> Unit,
+    onToggleLog: () -> Unit,
+    onArm: (BuildKind) -> Unit,
+    onDragStart: (BuildKind, Offset) -> Unit,
+    onDrag: (Offset) -> Unit,
+    onDragEnd: () -> Unit,
+    onConfirm: () -> Unit,
+    onCancelStaged: () -> Unit,
+    onRoll: () -> Unit,
+    onEndTurn: () -> Unit,
+    onEndFreeRoads: () -> Unit,
+    onEndSmith: () -> Unit,
+    onRepickSetup: () -> Unit,
+    onBuyCard: () -> Unit,
+    onPlayCard: () -> Unit,
+    onTrade: () -> Unit,
+    onImprove: () -> Unit,
+    onProgress: () -> Unit,
+    board: @Composable (Modifier) -> Unit,
+) {
+    Column(Modifier.fillMaxSize(), verticalArrangement = Arrangement.spacedBy(2.dp)) {
+        HudPlayerStrip(state, seats, pointsOf, style)
+        // Cities & Knights: the ship and the improvement levels are as much part
+        // of the game as the scores, so they sit with them rather than in a panel
+        // this layout does not have room for.
+        if (state.isCk) CatanBarbarians(state, Modifier.padding(horizontal = 8.dp), style)
+        Box(Modifier.weight(1f).fillMaxWidth()) {
+            // The island fills the whole area; controls float over its sea margin.
+            ZoomPanBox(Modifier.fillMaxSize().padding(start = 64.dp, end = 64.dp, top = 30.dp, bottom = 44.dp)) {
+                board(Modifier.onGloballyPositioned(onBoardCoords))
+            }
+
+            // What is going on, and the dice. Two lines, always.
+            Row(
+                Modifier.align(Alignment.TopCenter).padding(horizontal = 64.dp)
+                    .clip(RoundedCornerShape(10.dp))
+                    .background(MaterialTheme.colorScheme.surface.copy(alpha = 0.8f))
+                    .padding(horizontal = 8.dp, vertical = 1.dp),
+                verticalAlignment = Alignment.CenterVertically,
+                horizontalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                Text(
+                    text = notice ?: prompt,
+                    style = MaterialTheme.typography.bodySmall,
+                    color = if (notice != null) MaterialTheme.colorScheme.error else Color.Unspecified,
+                    minLines = 2,
+                    maxLines = 2,
+                    modifier = Modifier.weight(1f),
+                )
+                CatanDice(state.lastDice, ck = state.isCk, event = state.ck?.eventDie)
+            }
+
+            // Left: pieces to drag onto the island.
+            HudBuildColumn(
+                kinds = actions.buildKinds,
+                canBuild = actions.canBuild,
+                armed = building,
+                modifier = Modifier.align(Alignment.CenterStart).padding(start = 6.dp),
+                onTap = onArm,
+                onDragStart = onDragStart,
+                onDrag = onDrag,
+                onDragEnd = onDragEnd,
+            )
+
+            // Right, middle: the card actions.
+            Column(
+                Modifier.align(Alignment.CenterEnd).padding(end = 6.dp),
+                verticalArrangement = Arrangement.spacedBy(4.dp),
+                horizontalAlignment = Alignment.CenterHorizontally,
+            ) {
+                if (actions.ck) {
+                    HudRoundButton("⬆", caption = CatanText.IMPROVE, enabled = actions.canImprove, diameter = 44.dp, onClick = onImprove)
+                    HudRoundButton("🂠", caption = CatanText.CARDS_SHORT, enabled = actions.canPlayProgress, diameter = 44.dp, onClick = onProgress)
+                } else {
+                    HudRoundButton("＋", caption = CatanText.BUY_SHORT, enabled = actions.canBuyCard, diameter = 44.dp, onClick = onBuyCard)
+                    HudRoundButton("🂠", caption = CatanText.CARDS_SHORT, enabled = actions.canPlayCard, diameter = 44.dp, onClick = onPlayCard)
+                }
+            }
+
+            // Bottom centre: your cards.
+            Box(
+                Modifier.align(Alignment.BottomCenter).padding(bottom = 4.dp, start = 80.dp, end = 270.dp)
+                    .clip(RoundedCornerShape(12.dp))
+                    .background(MaterialTheme.colorScheme.surface.copy(alpha = 0.85f))
+                    .horizontalScroll(rememberScrollState())
+                    .padding(6.dp),
+            ) { CatanHand(state, localSeat) }
+
+            // Bottom left: the log.
+            Column(Modifier.align(Alignment.BottomStart).padding(start = 6.dp, bottom = 4.dp)) {
+                if (showLog) {
+                    Surface(
+                        modifier = Modifier.padding(bottom = 6.dp),
+                        shape = RoundedCornerShape(12.dp),
+                        color = MaterialTheme.colorScheme.surface.copy(alpha = 0.92f),
+                        tonalElevation = 4.dp,
+                    ) {
+                        CatanLog(state, Modifier.padding(8.dp).height(150.dp).width(260.dp))
+                    }
+                }
+                HudRoundButton("☰", caption = CatanText.LOG_BUTTON, diameter = 40.dp, onClick = onToggleLog)
+            }
+
+            // Bottom right: place / cancel a lined-up piece, trade, and the turn button.
+            Row(
+                Modifier.align(Alignment.BottomEnd).padding(end = 6.dp, bottom = 4.dp),
+                horizontalArrangement = Arrangement.spacedBy(6.dp),
+                verticalAlignment = Alignment.Bottom,
+            ) {
+                HudConfirmButtons(staged = staged != null, onConfirm = onConfirm, onCancel = onCancelStaged)
+                HudRoundButton("⇄", caption = CatanText.TRADE, enabled = actions.canTrade, diameter = 48.dp, onClick = onTrade)
+                PrimaryTurnButton(actions, onRoll, onEndTurn, onEndFreeRoads, onEndSmith, onRepickSetup)
+            }
+
+            if (dragKind != null && dragAt == null) HudPill(CatanText.DRAG_HINT, Modifier.align(Alignment.TopCenter))
+        }
+    }
+}
+
+/** The one big button: roll, end the turn, finish roads, or step back from a setup choice. */
+@Composable
+private fun PrimaryTurnButton(
+    actions: CatanActions,
+    onRoll: () -> Unit,
+    onEndTurn: () -> Unit,
+    onEndFreeRoads: () -> Unit,
+    onEndSmith: () -> Unit,
+    onRepickSetup: () -> Unit,
+) {
+    val (glyph, caption, enabled, click) = when {
+        actions.canRoll -> Quad("🎲", CatanText.ROLL_SHORT, true, onRoll)
+        actions.canEndFreeRoads -> Quad("✔", CatanText.DONE_SHORT, true, onEndFreeRoads)
+        actions.canEndSmith -> Quad("✔", CatanText.DONE_SHORT, true, onEndSmith)
+        actions.canRepickSetup -> Quad("↺", CatanText.CANCEL, true, onRepickSetup)
+        else -> Quad("➜", CatanText.END_SHORT, actions.canEndTurn, onEndTurn)
+    }
+    HudRoundButton(glyph, caption = caption, enabled = enabled, primary = true, diameter = 72.dp, onClick = click)
+}
+
+private data class Quad(val glyph: String, val caption: String, val enabled: Boolean, val click: () -> Unit)
+
+/** Everyone's colour, name, points and card count in one thin row across the top. */
+@Composable
+private fun HudPlayerStrip(
+    state: org.prolibertate.games.game.catan.CatanState,
+    seats: CatanSeats,
+    pointsOf: (Int) -> Int,
+    style: CatanStyle,
+) {
+    Row(Modifier.fillMaxWidth().padding(horizontal = 6.dp, vertical = 2.dp), horizontalArrangement = Arrangement.spacedBy(6.dp)) {
+        (0 until state.playerCount).forEach { seat ->
+            val onTurn = seat == state.turn
+            val shape = RoundedCornerShape(10.dp)
+            Row(
+                Modifier.weight(1f)
+                    .clip(shape)
+                    .background(MaterialTheme.colorScheme.surfaceVariant)
+                    .border(if (onTurn) 2.dp else 1.dp, if (onTurn) MaterialTheme.colorScheme.primary else Color(0x33000000), shape)
+                    .padding(horizontal = 8.dp, vertical = 4.dp),
+                verticalAlignment = Alignment.CenterVertically,
+                horizontalArrangement = Arrangement.spacedBy(6.dp),
+            ) {
+                Box(
+                    Modifier.size(14.dp).clip(CircleShape).background(style.seats[seat]).border(1.dp, style.pieceOutline, CircleShape),
+                )
+                Text(seats.label(seat), fontSize = 12.sp, fontWeight = FontWeight.Bold, maxLines = 1, modifier = Modifier.weight(1f))
+                // Trade, politics, science: the three improvement levels.
+                if (state.isCk) {
+                    Text(
+                        text = org.prolibertate.games.game.catan.Track.entries.joinToString(" ") {
+                            "${it.name.first()}${org.prolibertate.games.game.catan.CatanCk.improvement(state, seat, it)}"
+                        },
+                        fontSize = 12.sp,
+                        maxLines = 1,
+                    )
+                }
+                Text("${pointsOf(seat)} VP · ${state.resourceCount(seat)}🂠", fontSize = 12.sp, maxLines = 1)
+            }
+        }
+    }
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanInteraction.kt

@@ -0,0 +1,691 @@
+package org.prolibertate.games.ui.game.catan
+
+import org.prolibertate.games.game.catan.AcceptCounter
+import org.prolibertate.games.game.catan.AcceptTrade
+import org.prolibertate.games.game.catan.ActivateKnight
+import org.prolibertate.games.game.catan.BuildCity
+import org.prolibertate.games.game.catan.BuildRoad
+import org.prolibertate.games.game.catan.BuildShip
+import org.prolibertate.games.game.catan.MovePirate
+import org.prolibertate.games.game.catan.MoveShip
+import org.prolibertate.games.game.catan.Topology
+import org.prolibertate.games.game.catan.BuildSettlement
+import org.prolibertate.games.game.catan.BuildWall
+import org.prolibertate.games.game.catan.BuyDevCard
+import org.prolibertate.games.game.catan.BuyImprovement
+import org.prolibertate.games.game.catan.CatanBoard
+import org.prolibertate.games.game.catan.CatanMove
+import org.prolibertate.games.game.catan.CatanPhase
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.ChaseRobber
+import org.prolibertate.games.game.catan.Chore
+import org.prolibertate.games.game.catan.CounterTrade
+import org.prolibertate.games.game.catan.DeclineTrade
+import org.prolibertate.games.game.catan.DevCard
+import org.prolibertate.games.game.catan.DevCardType
+import org.prolibertate.games.game.catan.Discard
+import org.prolibertate.games.game.catan.EndFreeRoads
+import org.prolibertate.games.game.catan.EndSmith
+import org.prolibertate.games.game.catan.EndTurn
+import org.prolibertate.games.game.catan.CounterGoods
+import org.prolibertate.games.game.catan.GoodsBankTrade
+import org.prolibertate.games.game.catan.GoodsCounter
+import org.prolibertate.games.game.catan.Good
+import org.prolibertate.games.game.catan.HexCoord
+import org.prolibertate.games.game.catan.HireKnight
+import org.prolibertate.games.game.catan.MaritimeTrade
+import org.prolibertate.games.game.catan.MoveKnight
+import org.prolibertate.games.game.catan.MoveRobber
+import org.prolibertate.games.game.catan.OfferGoods
+import org.prolibertate.games.game.catan.OfferTrade
+import org.prolibertate.games.game.catan.PickGold
+import org.prolibertate.games.game.catan.PillageCity
+import org.prolibertate.games.game.catan.PlaceKnight
+import org.prolibertate.games.game.catan.PlaceMetropolis
+import org.prolibertate.games.game.catan.TradeCounter
+import org.prolibertate.games.game.catan.PlayKnight
+import org.prolibertate.games.game.catan.PlayMonopoly
+import org.prolibertate.games.game.catan.PlayProgress
+import org.prolibertate.games.game.catan.PlayRoadBuilding
+import org.prolibertate.games.game.catan.PlayYearOfPlenty
+import org.prolibertate.games.game.catan.ProgressCard
+import org.prolibertate.games.game.catan.ProgressType
+import org.prolibertate.games.game.catan.PromoteKnight
+import org.prolibertate.games.game.catan.RelocateKnight
+import org.prolibertate.games.game.catan.RemoveKnight
+import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.RollDice
+import org.prolibertate.games.game.catan.SetupPlace
+import org.prolibertate.games.game.catan.Track
+
+/**
+ * What a player can ask to build by tapping the board. Wall and Knight exist
+ * only in Cities & Knights; the base game's build menu lists the first three.
+ */
+enum class BuildKind {
+    ROAD, SETTLEMENT, CITY, WALL, KNIGHT,
+
+    /** Seafarers: a ship, laid on a sea edge. */
+    SHIP;
+
+    companion object {
+        val BASE: List<BuildKind> = listOf(ROAD, SETTLEMENT, CITY)
+
+        /** Seafarers adds the ship, listed after the road it sails beside. */
+        val SEAFARERS: List<BuildKind> = listOf(ROAD, SHIP, SETTLEMENT, CITY)
+    }
+}
+
+/**
+ * The parts of the board the player may tap right now. Everything else is inert.
+ * [knights] are crossings holding one of the player's own knights that can do
+ * something this turn: tapping one opens its menu.
+ */
+data class BoardTargets(
+    val vertices: Set<Int> = emptySet(),
+    val edges: Set<Int> = emptySet(),
+    val hexes: Set<Int> = emptySet(),
+    val knights: Set<Int> = emptySet(),
+    /** Seafarers: the player's ships that can sail this turn, tapped to pick one up. */
+    val ships: Set<Int> = emptySet(),
+    /** The player's other knights: tappable for their menu, but with nothing to do, so not ringed. */
+    val idleKnights: Set<Int> = emptySet(),
+) {
+    val isEmpty: Boolean
+        get() = vertices.isEmpty() && edges.isEmpty() && hexes.isEmpty() && knights.isEmpty() &&
+            idleKnights.isEmpty() && ships.isEmpty()
+
+    /** Every crossing a tap can land on. */
+    val tappableVertices: Set<Int> get() = vertices + knights + idleKnights
+}
+
+/**
+ * A progress card that is waiting for a tap on the board: [plays] are every play
+ * of it the engine accepts, and the player's tap picks one. [firstHex] is the
+ * first of the two hexes an Inventor swaps, once tapped.
+ */
+data class ArmedCard(val kind: ProgressType, val plays: List<PlayProgress>, val firstHex: Int? = null)
+
+/** One progress card in the local player's hand, and the plays the engine allows for it. */
+data class ProgressInHand(val card: ProgressCard, val plays: List<PlayProgress>) {
+    val playable: Boolean get() = plays.isNotEmpty()
+}
+
+/** What a tap on the board amounts to. */
+sealed interface TapOutcome {
+    /** Nothing: the tap landed somewhere that is not a legal target. */
+    data object Ignored : TapOutcome
+
+    /** Send this move to the table. */
+    data class Submit(val move: CatanMove) : TapOutcome
+
+    /** Setup: remember this settlement; the road that goes with it is tapped next. */
+    data class PickSetupVertex(val vertex: Int) : TapOutcome
+
+    /** The robber's (or the pirate's) hex has more than one possible victim: ask which. */
+    data class PickRobberVictim(val hex: HexCoord, val victims: List<Int>, val pirate: Boolean = false) : TapOutcome
+
+    /** Seafarers: one of the player's ships was tapped; its destination is tapped next. */
+    data class PickShip(val edge: Int) : TapOutcome
+
+    /** One of the player's own knights was tapped: open its menu. */
+    data class PickKnight(val vertex: Int) : TapOutcome
+
+    /** An Inventor's first hex was tapped; the second completes the swap. */
+    data class PickFirstHex(val hex: Int) : TapOutcome
+}
+
+/**
+ * One development card in the local player's hand, and what can be done with it
+ * right now. [plays] is empty when it cannot be played this turn (bought this
+ * turn, a card has already been played, a victory-point card, or it is not the
+ * player's turn).
+ */
+data class DevCardInHand(val card: DevCard, val plays: List<CatanMove>) {
+    val playable: Boolean get() = plays.isNotEmpty()
+}
+
+/**
+ * The rules of *tapping*: given the game state, the moves the engine says are
+ * legal, and what the player has selected, what can be tapped and what a tap does.
+ *
+ * Pure functions with no Android and no Compose, so the whole interaction model is
+ * unit-tested (`CatanInteractionTest`). The screen holds the two bits of UI state
+ * ([BuildKind] and the chosen setup settlement) and passes them in; it contains no
+ * game rules of its own. **Anything that decides whether a tap is allowed belongs
+ * here, never in a composable** — the engine's [legal] list is the single source
+ * of truth, so the UI can never offer a move the rules would refuse.
+ */
+object CatanInteraction {
+
+    // --- Staged placements and drag-to-build ------------------------------------
+
+    /** A place on the board a dragged piece is over: one crossing or one edge. */
+    data class Spot(val vertex: Int? = null, val edge: Int? = null)
+
+    /**
+     * The spot a finger at [at] (board pixels) is nearest to, among [targets]. [reach] is
+     * generous (fingers cover what they point at), and edges are only offered when no
+     * crossing is lit, matching what a tap would do.
+     */
+    fun snap(layout: BoardLayout, targets: BoardTargets, at: Pt, reach: Float): Spot? = when {
+        targets.tappableVertices.isNotEmpty() ->
+            layout.nearestVertex(at, reach, targets.tappableVertices)?.let { Spot(vertex = it) }
+
+        targets.edges.isNotEmpty() -> layout.nearestEdge(at, reach, targets.edges)?.let { Spot(edge = it) }
+        else -> null
+    }
+
+    /** The move a build tap or drop would make, if it is a placement that waits for ✓. */
+    fun stageable(outcome: TapOutcome, building: BuildKind?): CatanMove? {
+        if (building == null || outcome !is TapOutcome.Submit) return null
+        return outcome.move.takeIf {
+            it is BuildRoad || it is BuildShip || it is BuildSettlement || it is BuildCity || it is BuildWall || it is HireKnight
+        }
+    }
+
+    /** Where a staged move sits on the board, for drawing its ghost. */
+    fun spotOf(move: CatanMove?): Spot = when (move) {
+        is BuildRoad -> Spot(edge = move.edge)
+        is BuildShip -> Spot(edge = move.edge)
+        is BuildSettlement -> Spot(vertex = move.vertex)
+        is BuildCity -> Spot(vertex = move.vertex)
+        is BuildWall -> Spot(vertex = move.vertex)
+        is HireKnight -> Spot(vertex = move.vertex)
+        else -> Spot()
+    }
+
+    // --- Board ---------------------------------------------------------------
+
+    fun targets(
+        state: CatanState,
+        legal: List<CatanMove>,
+        building: BuildKind?,
+        setupVertex: Int?,
+        movingKnight: Int? = null,
+        armed: ArmedCard? = null,
+        /** The local seat, so its sleeping knights can be tapped for their menu too. */
+        localSeat: Int? = null,
+        /** Seafarers: the ship that has been picked up and is waiting for a destination. */
+        movingShip: Int? = null,
+    ): BoardTargets {
+        val setup = legal.filterIsInstance<SetupPlace>()
+        if (setup.isNotEmpty()) {
+            return if (setupVertex == null) {
+                BoardTargets(vertices = setup.map { it.vertex }.toSet())
+            } else {
+                BoardTargets(edges = setup.filter { it.vertex == setupVertex }.map { it.edge }.toSet())
+            }
+        }
+
+        val robber = legal.filterIsInstance<MoveRobber>()
+        val pirate = legal.filterIsInstance<MovePirate>()
+        if (robber.isNotEmpty() || pirate.isNotEmpty()) {
+            return BoardTargets(
+                hexes = (robber.map { it.hex } + pirate.map { it.hex }).mapNotNull { state.topo.hexIndex[it] }.toSet(),
+            )
+        }
+
+        // Cities & Knights: answers to a queued chore are taps on the board.
+        val chore = choreVertices(legal)
+        if (chore.isNotEmpty()) return BoardTargets(vertices = chore)
+
+        val roads = legal.filterIsInstance<BuildRoad>().map { it.edge }.toSet()
+        val ships = legal.filterIsInstance<BuildShip>().map { it.edge }.toSet()
+        if (state.phase == CatanPhase.FREE_ROADS) return BoardTargets(edges = roads + ships)
+
+        if (movingShip != null) {
+            return BoardTargets(
+                edges = legal.filterIsInstance<MoveShip>().filter { it.from == movingShip }.map { it.to }.toSet(),
+            )
+        }
+
+        if (armed != null) return armedTargets(armed)
+
+        if (movingKnight != null) {
+            return BoardTargets(
+                vertices = legal.filterIsInstance<MoveKnight>().filter { it.from == movingKnight }.map { it.to }.toSet(),
+            )
+        }
+
+        return when (building) {
+            BuildKind.ROAD -> BoardTargets(edges = roads)
+            BuildKind.SHIP -> BoardTargets(edges = ships)
+            BuildKind.SETTLEMENT ->
+                BoardTargets(vertices = legal.filterIsInstance<BuildSettlement>().map { it.vertex }.toSet())
+
+            BuildKind.CITY ->
+                BoardTargets(vertices = legal.filterIsInstance<BuildCity>().map { it.vertex }.toSet())
+
+            BuildKind.WALL ->
+                BoardTargets(vertices = legal.filterIsInstance<BuildWall>().map { it.vertex }.toSet())
+
+            BuildKind.KNIGHT ->
+                BoardTargets(vertices = legal.filterIsInstance<HireKnight>().map { it.vertex }.toSet())
+
+            null -> {
+                val ready = knightsWithActions(legal)
+                val mine = if (localSeat != null && legal.isNotEmpty()) {
+                    state.ck?.knights?.filter { it.owner == localSeat }?.map { it.vertex }?.toSet().orEmpty()
+                } else {
+                    emptySet()
+                }
+                BoardTargets(
+                    knights = ready,
+                    idleKnights = mine - ready,
+                    ships = legal.filterIsInstance<MoveShip>().map { it.from }.toSet(),
+                )
+            }
+        }
+    }
+
+    /** The crossings a queued chore is asking the player to tap, from the legal list. */
+    private fun choreVertices(legal: List<CatanMove>): Set<Int> = buildSet {
+        legal.forEach { move ->
+            when (move) {
+                is PillageCity -> add(move.vertex)
+                is PlaceMetropolis -> add(move.vertex)
+                is RelocateKnight -> add(move.to)
+                is RemoveKnight -> add(move.vertex)
+                is PlaceKnight -> add(move.vertex)
+                else -> Unit
+            }
+        }
+        // A Smith's promotions are knights to tap, while the chore is open.
+        if (legal.any { it is EndSmith }) {
+            legal.filterIsInstance<PromoteKnight>().forEach { add(it.vertex) }
+        }
+    }
+
+    private fun choreMove(legal: List<CatanMove>, vertex: Int): CatanMove? = legal.firstOrNull { move ->
+        when (move) {
+            is PillageCity -> move.vertex == vertex
+            is PlaceMetropolis -> move.vertex == vertex
+            is RelocateKnight -> move.to == vertex
+            is RemoveKnight -> move.vertex == vertex
+            is PlaceKnight -> move.vertex == vertex
+            is PromoteKnight -> legal.any { it is EndSmith } && move.vertex == vertex
+            else -> false
+        }
+    }
+
+    // --- Cities & Knights: knights ---------------------------------------------
+
+    /** Crossings of the player's knights that have an action available. */
+    fun knightsWithActions(legal: List<CatanMove>): Set<Int> = buildSet {
+        legal.forEach { move ->
+            when (move) {
+                is ActivateKnight -> add(move.vertex)
+                is MoveKnight -> add(move.from)
+                is ChaseRobber -> add(move.vertex)
+                is PromoteKnight -> if (legal.none { it is EndSmith }) add(move.vertex)
+                else -> Unit
+            }
+        }
+    }
+
+    /** What the knight on [vertex] can do right now, in the order its menu lists them. */
+    fun knightActions(legal: List<CatanMove>, vertex: Int): List<CatanMove> =
+        legal.filter { move ->
+            when (move) {
+                is ActivateKnight -> move.vertex == vertex
+                is PromoteKnight -> move.vertex == vertex && legal.none { it is EndSmith }
+                is ChaseRobber -> move.vertex == vertex
+                else -> false
+            }
+        } + listOfNotNull(legal.firstOrNull { it is MoveKnight && it.from == vertex })
+
+    fun canEndSmith(legal: List<CatanMove>): Boolean = legal.any { it is EndSmith }
+
+    // --- Cities & Knights: progress cards --------------------------------------
+
+    /** [seat]'s progress cards, each with the plays the engine currently allows. */
+    fun progressHand(state: CatanState, seat: Int, legal: List<CatanMove>): List<ProgressInHand> =
+        state.ck?.progressHands?.getOrNull(seat).orEmpty().map { card ->
+            ProgressInHand(card, legal.filterIsInstance<PlayProgress>().filter { it.card == card.id })
+        }.sortedWith(compareBy({ it.card.kind.track.ordinal }, { it.card.kind.ordinal }, { it.card.id }))
+
+    /** The cards that are played by tapping the board, not by choosing in a dialog. */
+    val BOARD_CARDS: Set<ProgressType> = setOf(
+        ProgressType.ENGINEER, ProgressType.MEDICINE, ProgressType.MERCHANT,
+        ProgressType.DIPLOMAT, ProgressType.INTRIGUE, ProgressType.INVENTOR,
+    )
+
+    private fun armedTargets(armed: ArmedCard): BoardTargets = when (armed.kind) {
+        ProgressType.ENGINEER, ProgressType.MEDICINE, ProgressType.INTRIGUE ->
+            BoardTargets(vertices = armed.plays.mapNotNull { it.vertex }.toSet())
+
+        ProgressType.DIPLOMAT -> BoardTargets(edges = armed.plays.mapNotNull { it.edge }.toSet())
+
+        ProgressType.MERCHANT -> BoardTargets(hexes = armed.plays.mapNotNull { it.hexA }.toSet())
+
+        ProgressType.INVENTOR -> {
+            val first = armed.firstHex
+            val all = armed.plays.flatMap { listOfNotNull(it.hexA, it.hexB) }.toSet()
+            if (first == null) {
+                BoardTargets(hexes = all)
+            } else {
+                BoardTargets(
+                    hexes = armed.plays
+                        .filter { it.hexA == first || it.hexB == first }
+                        .flatMap { listOfNotNull(it.hexA, it.hexB) }
+                        .filter { it != first }
+                        .toSet(),
+                )
+            }
+        }
+
+        else -> BoardTargets()
+    }
+
+    /** The improvement tracks the player can buy a level of right now. */
+    fun improvable(legal: List<CatanMove>): Set<Track> =
+        legal.filterIsInstance<BuyImprovement>().map { it.track }.toSet()
+
+    // --- Cities & Knights: goods ----------------------------------------------
+
+    /** The gold pick that names exactly [selection], if the engine allows it. */
+    fun goldMove(legal: List<CatanMove>, selection: List<Resource>): PickGold? {
+        val want = selection.groupingBy { it }.eachCount()
+        return legal.filterIsInstance<PickGold>().firstOrNull { it.cards.groupingBy { c -> c }.eachCount() == want }
+    }
+
+    /** How many cards the gold pick on offer must name. */
+    fun goldCount(legal: List<CatanMove>): Int = legal.filterIsInstance<PickGold>().firstOrNull()?.cards?.size ?: 0
+
+    /** Bank trades on offer in Cities & Knights: what can be given, and for what. */
+    fun goodsBankTrades(legal: List<CatanMove>): Map<Good, List<Good>> =
+        legal.filterIsInstance<GoodsBankTrade>()
+            .groupBy({ it.give }, { it.get })
+            .mapValues { (_, gets) -> gets.sortedBy { it.ordinal } }
+            .toSortedMap(compareBy<Good> { it.ordinal })
+
+    fun goodsOfferAllowed(
+        state: CatanState,
+        seat: Int,
+        to: Int?,
+        give: List<Good>,
+        get: List<Good>,
+    ): Boolean = give.isNotEmpty() && get.isNotEmpty() &&
+        CatanRules.isLegalMove(state, seat, OfferGoods(to, give, get))
+
+    /** Whether [seat] may answer the goods offer on the table with [give] for [get]. */
+    fun goodsCounterAllowed(state: CatanState, seat: Int, give: List<Good>, get: List<Good>): Boolean =
+        give.isNotEmpty() && get.isNotEmpty() &&
+            CatanRules.isLegalMove(state, seat, CounterGoods(give, get))
+
+    /** The goods counter-offers the offerer may take right now, in the order they came in. */
+    fun goodsCounterChoices(state: CatanState, legal: List<CatanMove>): List<GoodsCounter> {
+        val takeable = legal.filterIsInstance<AcceptCounter>().map { it.seat }.toSet()
+        return state.ck?.goodsOffer?.counters.orEmpty().filter { it.by in takeable }
+    }
+
+    /** The chore at the front of the queue, if the table is waiting on one. */
+    fun chore(state: CatanState): Chore? =
+        if (state.phase == CatanPhase.CHORE) state.ck?.chores?.firstOrNull() else null
+
+    fun onVertexTap(
+        vertex: Int,
+        legal: List<CatanMove>,
+        building: BuildKind?,
+        setupVertex: Int?,
+        movingKnight: Int? = null,
+        armed: ArmedCard? = null,
+        /** The local player's knights, which can be tapped for their menu even with nothing to do. */
+        ownKnights: Set<Int> = emptySet(),
+    ): TapOutcome {
+        val setup = legal.filterIsInstance<SetupPlace>()
+        if (setup.isNotEmpty()) {
+            // Re-picking is allowed until the road is chosen, so a misplaced
+            // tap does not commit the settlement.
+            return if (setup.any { it.vertex == vertex }) {
+                TapOutcome.PickSetupVertex(vertex)
+            } else {
+                TapOutcome.Ignored
+            }
+        }
+        choreMove(legal, vertex)?.let { return TapOutcome.Submit(it) }
+
+        if (armed != null) {
+            val play = armed.plays.firstOrNull { it.vertex == vertex } ?: return TapOutcome.Ignored
+            return if (play in legal) TapOutcome.Submit(play) else TapOutcome.Ignored
+        }
+        if (movingKnight != null) {
+            val move = MoveKnight(movingKnight, vertex)
+            return if (move in legal) TapOutcome.Submit(move) else TapOutcome.Ignored
+        }
+
+        val move: CatanMove = when (building) {
+            BuildKind.SETTLEMENT -> BuildSettlement(vertex)
+            BuildKind.CITY -> BuildCity(vertex)
+            BuildKind.WALL -> BuildWall(vertex)
+            BuildKind.KNIGHT -> HireKnight(vertex)
+            else -> return if (building == null && (vertex in knightsWithActions(legal) || vertex in ownKnights)) {
+                TapOutcome.PickKnight(vertex)
+            } else {
+                TapOutcome.Ignored
+            }
+        }
+        return if (move in legal) TapOutcome.Submit(move) else TapOutcome.Ignored
+    }
+
+    fun onEdgeTap(
+        edge: Int,
+        legal: List<CatanMove>,
+        building: BuildKind?,
+        setupVertex: Int?,
+        armed: ArmedCard? = null,
+        /** Seafarers: the ship picked up and waiting for a destination. */
+        movingShip: Int? = null,
+    ): TapOutcome {
+        if (legal.any { it is SetupPlace }) {
+            if (setupVertex == null) return TapOutcome.Ignored
+            val move = SetupPlace(setupVertex, edge)
+            return if (move in legal) TapOutcome.Submit(move) else TapOutcome.Ignored
+        }
+        if (armed != null) {
+            val play = armed.plays.firstOrNull { it.edge == edge } ?: return TapOutcome.Ignored
+            return if (play in legal) TapOutcome.Submit(play) else TapOutcome.Ignored
+        }
+        if (movingShip != null) {
+            val move = MoveShip(movingShip, edge)
+            return if (move in legal) TapOutcome.Submit(move) else TapOutcome.Ignored
+        }
+        // Free roads (and free ships) need no build mode; a paid one does.
+        val free = legal.any { it is EndFreeRoads }
+        if (building == BuildKind.SHIP || (free && BuildShip(edge) in legal)) {
+            val move = BuildShip(edge)
+            return if (move in legal) TapOutcome.Submit(move) else TapOutcome.Ignored
+        }
+        if (building == null && !free) {
+            // Nothing armed: tapping one of your own ships that can sail picks it up.
+            return if (legal.any { it is MoveShip && it.from == edge }) TapOutcome.PickShip(edge) else TapOutcome.Ignored
+        }
+        val canBuild = building == BuildKind.ROAD || free
+        if (!canBuild) return TapOutcome.Ignored
+        val move = BuildRoad(edge)
+        return if (move in legal) TapOutcome.Submit(move) else TapOutcome.Ignored
+    }
+
+    fun onHexTap(
+        hex: Int,
+        legal: List<CatanMove>,
+        armed: ArmedCard? = null,
+        /** The board the hex index belongs to (the standard island unless the game is Seafarers). */
+        topo: Topology = CatanBoard.base,
+    ): TapOutcome {
+        if (armed != null) return onArmedHexTap(hex, legal, armed)
+        val coord = topo.HEXES.getOrNull(hex) ?: return TapOutcome.Ignored
+        val moves = legal.filterIsInstance<MoveRobber>().filter { it.hex == coord }
+        val pirates = legal.filterIsInstance<MovePirate>().filter { it.hex == coord }
+        return when {
+            moves.isNotEmpty() -> if (moves.size == 1) {
+                TapOutcome.Submit(moves.first())
+            } else {
+                TapOutcome.PickRobberVictim(coord, moves.mapNotNull { it.victim })
+            }
+
+            pirates.isNotEmpty() -> if (pirates.size == 1) {
+                TapOutcome.Submit(pirates.first())
+            } else {
+                TapOutcome.PickRobberVictim(coord, pirates.mapNotNull { it.victim }, pirate = true)
+            }
+
+            else -> TapOutcome.Ignored
+        }
+    }
+
+    private fun onArmedHexTap(hex: Int, legal: List<CatanMove>, armed: ArmedCard): TapOutcome {
+        if (armed.kind == ProgressType.INVENTOR) {
+            val first = armed.firstHex ?: return if (hex in armedTargets(armed).hexes) {
+                TapOutcome.PickFirstHex(hex)
+            } else {
+                TapOutcome.Ignored
+            }
+            val play = armed.plays.firstOrNull {
+                (it.hexA == first && it.hexB == hex) || (it.hexA == hex && it.hexB == first)
+            } ?: return TapOutcome.Ignored
+            return if (play in legal) TapOutcome.Submit(play) else TapOutcome.Ignored
+        }
+        val play = armed.plays.firstOrNull { it.hexA == hex } ?: return TapOutcome.Ignored
+        return if (play in legal) TapOutcome.Submit(play) else TapOutcome.Ignored
+    }
+
+    // --- Action bar ------------------------------------------------------------
+
+    fun canRoll(legal: List<CatanMove>): Boolean = legal.any { it is RollDice }
+
+    /**
+     * The hexes that paid out for this turn's roll, so the board can light them.
+     * Empty until the turn's roll has happened (the dice left over from the last
+     * turn are not this turn's), on a seven, and for the hex the robber sits on.
+     */
+    fun rolledHexes(state: CatanState): Set<Int> {
+        if (state.lastDice.size != 2) return emptySet()
+        if (state.phase == CatanPhase.AWAIT_ROLL || state.phase == CatanPhase.SETUP_FIRST ||
+            state.phase == CatanPhase.SETUP_SECOND
+        ) {
+            return emptySet()
+        }
+        val total = state.lastDice.sum()
+        if (total == 7) return emptySet()
+        return (0 until state.topo.HEX_COUNT)
+            .filter { state.numbers[it] == total && it != state.robber }
+            .toSet()
+    }
+
+    fun canEndTurn(legal: List<CatanMove>): Boolean = legal.any { it is EndTurn }
+
+    fun canEndFreeRoads(legal: List<CatanMove>): Boolean = legal.any { it is EndFreeRoads }
+
+    fun canBuyDevCard(legal: List<CatanMove>): Boolean = legal.any { it is BuyDevCard }
+
+    fun canBuild(legal: List<CatanMove>): Set<BuildKind> = buildSet {
+        if (legal.any { it is BuildRoad }) add(BuildKind.ROAD)
+        if (legal.any { it is BuildShip }) add(BuildKind.SHIP)
+        if (legal.any { it is BuildSettlement }) add(BuildKind.SETTLEMENT)
+        if (legal.any { it is BuildCity }) add(BuildKind.CITY)
+        if (legal.any { it is BuildWall }) add(BuildKind.WALL)
+        if (legal.any { it is HireKnight }) add(BuildKind.KNIGHT)
+    }
+
+    fun tradeResponses(legal: List<CatanMove>): Pair<Boolean, Boolean> =
+        legal.any { it is AcceptTrade } to legal.any { it is DeclineTrade }
+
+    // --- Development cards -----------------------------------------------------
+
+    /** [seat]'s development cards, each with the plays the engine currently allows. */
+    fun devHand(state: CatanState, seat: Int, legal: List<CatanMove>): List<DevCardInHand> =
+        state.devHands.getOrNull(seat).orEmpty().map { card ->
+            DevCardInHand(card, legal.filter { playOf(it) == card.id })
+        }.sortedWith(compareBy({ it.card.type.ordinal }, { it.card.id }))
+
+    private fun playOf(move: CatanMove): Int? = when (move) {
+        is PlayKnight -> move.card
+        is PlayRoadBuilding -> move.card
+        is PlayMonopoly -> move.card
+        is PlayYearOfPlenty -> move.card
+        else -> null
+    }
+
+    /** The Monopoly moves for one card, by the resource each would name. */
+    fun monopolyChoices(plays: List<CatanMove>): Map<Resource, PlayMonopoly> =
+        plays.filterIsInstance<PlayMonopoly>().associateBy { it.resource }
+
+    /** The Year of Plenty move that takes exactly [take], if the engine allows it. */
+    fun plentyMove(plays: List<CatanMove>, take: List<Resource>): PlayYearOfPlenty? {
+        val want = take.groupingBy { it }.eachCount()
+        return plays.filterIsInstance<PlayYearOfPlenty>().firstOrNull {
+            it.take.groupingBy { r -> r }.eachCount() == want
+        }
+    }
+
+    /**
+     * Resources a Year of Plenty can still be asked for, given what is already
+     * [picked]: those that complete some take the engine allows. Empty once the
+     * two cards are chosen.
+     */
+    fun plentyAvailable(plays: List<CatanMove>, picked: List<Resource>): Set<Resource> {
+        val chosen = picked.groupingBy { it }.eachCount()
+        val available = mutableSetOf<Resource>()
+        for (play in plays.filterIsInstance<PlayYearOfPlenty>()) {
+            if (!chosen.all { (resource, n) -> play.take.count { it == resource } >= n }) continue
+            val remaining = play.take.toMutableList()
+            picked.forEach { remaining.remove(it) }
+            available += remaining
+        }
+        return available
+    }
+
+    // --- Discarding -----------------------------------------------------------
+
+    /** How many cards a player holding [held] must discard on a seven. */
+    fun discardQuota(held: Int): Int = held / 2
+
+    /** The discard move that gives up exactly [selection], if the engine allows it. */
+    fun discardMove(legal: List<CatanMove>, selection: List<Resource>): Discard? {
+        val want = selection.groupingBy { it }.eachCount()
+        return legal.filterIsInstance<Discard>().firstOrNull {
+            it.cards.groupingBy { r -> r }.eachCount() == want
+        }
+    }
+
+    // --- Trading ---------------------------------------------------------------
+
+    /** Bank trades on offer: what can be given, and for what. */
+    fun bankTrades(legal: List<CatanMove>): Map<Resource, List<Resource>> =
+        legal.filterIsInstance<MaritimeTrade>()
+            .groupBy({ it.give }, { it.get })
+            .mapValues { (_, gets) -> gets.sortedBy { it.ordinal } }
+            .toSortedMap(compareBy<Resource> { it.ordinal })
+
+    /** What it costs [seat] to give one [resource] to the bank: 4, 3 or 2 cards. */
+    fun bankRatio(state: CatanState, seat: Int, resource: Resource): Int =
+        CatanRules.bestPortRatio(state, seat, resource)
+
+    /**
+     * Whether [seat] can offer [give] for [get] to [to] right now. Uses the
+     * engine's own structural check, since offers are not in the enumerated
+     * move list.
+     */
+    fun offerAllowed(
+        state: CatanState,
+        seat: Int,
+        to: Int?,
+        give: List<Resource>,
+        get: List<Resource>,
+    ): Boolean = give.isNotEmpty() && get.isNotEmpty() &&
+        CatanRules.isLegalMove(state, seat, OfferTrade(to, give, get))
+
+    /** Whether [seat] may answer the offer on the table with [give] for [get]. */
+    fun counterAllowed(state: CatanState, seat: Int, give: List<Resource>, get: List<Resource>): Boolean =
+        give.isNotEmpty() && get.isNotEmpty() &&
+            CatanRules.isLegalMove(state, seat, CounterTrade(give, get))
+
+    /** The counter-offers the offerer may take right now, in the order they came in. */
+    fun counterChoices(state: CatanState, legal: List<CatanMove>): List<TradeCounter> {
+        val takeable = legal.filterIsInstance<AcceptCounter>().map { it.seat }.toSet()
+        return state.pendingTrade?.counters.orEmpty().filter { it.by in takeable }
+    }
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanPanels.kt

@@ -0,0 +1,636 @@
+package org.prolibertate.games.ui.game.catan
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.border
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.ExperimentalLayoutApi
+import androidx.compose.foundation.layout.FlowRow
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.defaultMinSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.Button
+import androidx.compose.material3.DropdownMenu
+import androidx.compose.material3.DropdownMenuItem
+import androidx.compose.material3.FilledTonalButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import org.prolibertate.games.game.catan.BuildingType
+import org.prolibertate.games.game.catan.CatanCk
+import org.prolibertate.games.game.catan.CatanPhase
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.EventFace
+import org.prolibertate.games.game.catan.Good
+import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.Track
+
+/*
+ * Stateless building blocks for the Katan screen.
+ *
+ * Every composable here takes plain values and reports events through lambdas;
+ * none of them holds game state or touches the controller, so each can be
+ * restyled, re-laid-out or replaced on its own. Colours and proportions come
+ * from [CatanStyle] and wording from [CatanText].
+ */
+
+// ---------------------------------------------------------------------------
+// Resource tile
+// ---------------------------------------------------------------------------
+
+/**
+ * One resource as a coloured tile with its count. The hand, the discard picker
+ * and the trade pickers all use this, so a resource looks the same everywhere.
+ */
+@Composable
+fun ResourceTile(
+    resource: Resource,
+    count: Int,
+    modifier: Modifier = Modifier,
+    selected: Boolean = false,
+    enabled: Boolean = true,
+    style: CatanStyle = LocalCatanStyle.current,
+    onClick: (() -> Unit)? = null,
+) {
+    val shape = RoundedCornerShape(10.dp)
+    Column(
+        modifier = modifier
+            .defaultMinSize(minWidth = 56.dp)
+            .clip(shape)
+            .background(style.resource.getValue(resource).copy(alpha = if (enabled) 1f else 0.4f))
+            .border(
+                width = if (selected) 3.dp else 1.dp,
+                color = if (selected) Color.White else Color(0x33000000),
+                shape = shape,
+            )
+            .then(if (onClick != null && enabled) Modifier.clickable { onClick() } else Modifier)
+            .padding(horizontal = 6.dp, vertical = 6.dp),
+        horizontalAlignment = Alignment.CenterHorizontally,
+    ) {
+        Text(
+            text = count.toString(),
+            color = style.resourceInk,
+            fontWeight = FontWeight.Bold,
+            fontSize = 20.sp,
+        )
+        Text(
+            text = CatanText.resource(resource),
+            color = style.resourceInk,
+            fontSize = 11.sp,
+            maxLines = 1,
+        )
+    }
+}
+
+/**
+ * One card type — a resource or a commodity — as a coloured tile with its count.
+ * Cities & Knights hands, discards and trades use this so commodities look the
+ * same everywhere.
+ */
+@Composable
+fun GoodTile(
+    good: Good,
+    count: Int,
+    modifier: Modifier = Modifier,
+    selected: Boolean = false,
+    enabled: Boolean = true,
+    style: CatanStyle = LocalCatanStyle.current,
+    onClick: (() -> Unit)? = null,
+) {
+    val resource = good.resource
+    if (resource != null) {
+        ResourceTile(resource, count, modifier, selected, enabled, style, onClick)
+        return
+    }
+    val commodity = good.commodity!!
+    val shape = RoundedCornerShape(10.dp)
+    val ink = style.commodityInk.getValue(commodity)
+    Column(
+        modifier = modifier
+            .defaultMinSize(minWidth = 56.dp)
+            .clip(shape)
+            .background(style.commodity.getValue(commodity).copy(alpha = if (enabled) 1f else 0.4f))
+            .border(
+                width = if (selected) 3.dp else 1.dp,
+                color = if (selected) Color.White else Color(0x33000000),
+                shape = shape,
+            )
+            .then(if (onClick != null && enabled) Modifier.clickable { onClick() } else Modifier)
+            .padding(horizontal = 6.dp, vertical = 6.dp),
+        horizontalAlignment = Alignment.CenterHorizontally,
+    ) {
+        Text(text = count.toString(), color = ink, fontWeight = FontWeight.Bold, fontSize = 20.sp)
+        Text(text = CatanText.good(good), color = ink, fontSize = 11.sp, maxLines = 1)
+    }
+}
+
+/**
+ * The local player's cards: one tile per resource, and in Cities & Knights one
+ * per commodity as well, in a row that wraps.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanHand(
+    state: CatanState,
+    seat: Int,
+    modifier: Modifier = Modifier,
+) {
+    FlowRow(
+        modifier = modifier,
+        horizontalArrangement = Arrangement.spacedBy(6.dp),
+        verticalArrangement = Arrangement.spacedBy(6.dp),
+    ) {
+        if (state.isCk) {
+            val held = CatanCk.goodsOf(state, seat)
+            Good.entries.forEach { good -> GoodTile(good, held[good] ?: 0) }
+        } else {
+            Resource.entries.forEach { resource ->
+                ResourceTile(resource, state.resources[seat][resource] ?: 0)
+            }
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Players
+// ---------------------------------------------------------------------------
+
+/**
+ * One player's public standing: colour, name, points, how many cards they hold
+ * (not which), and — in the roomier layout — development cards, knights and
+ * their longest road.
+ *
+ * **Fixed height.** Every line is always present (blank when there is nothing to
+ * say) and never wraps, so the card is the same height whatever the game is
+ * doing. The board is given whatever room is left, so anything that made this
+ * card taller or shorter would rescale the island under the player's thumb.
+ *
+ * [points] is passed in rather than computed here because the local player's
+ * own count includes hidden victory-point cards and everyone else's does not;
+ * the screen decides which. [compact] is the narrow portrait strip (four cards
+ * across a phone); the default has room for the detail lines.
+ */
+@Composable
+fun CatanPlayerCard(
+    state: CatanState,
+    seat: Int,
+    seats: CatanSeats,
+    points: Int,
+    modifier: Modifier = Modifier,
+    style: CatanStyle = LocalCatanStyle.current,
+    compact: Boolean = false,
+) {
+    val onTurn = state.turn == seat && state.phase != CatanPhase.GAME_OVER
+    val shape = RoundedCornerShape(12.dp)
+    Column(
+        modifier = modifier
+            .clip(shape)
+            .background(MaterialTheme.colorScheme.surfaceVariant)
+            .border(
+                width = if (onTurn) 3.dp else 1.dp,
+                color = if (onTurn) MaterialTheme.colorScheme.primary else Color(0x22000000),
+                shape = shape,
+            )
+            .padding(8.dp),
+        verticalArrangement = Arrangement.spacedBy(2.dp),
+    ) {
+        Row(verticalAlignment = Alignment.CenterVertically, horizontalArrangement = Arrangement.spacedBy(6.dp)) {
+            Box(
+                modifier = Modifier
+                    .size(14.dp)
+                    .clip(CircleShape)
+                    .background(style.seats[seat % style.seats.size])
+                    .border(1.dp, style.pieceOutline, CircleShape),
+            )
+            CardLine(seats.label(seat), MaterialTheme.typography.labelLarge, FontWeight.Bold)
+        }
+        CardLine("$points VP", MaterialTheme.typography.titleMedium, FontWeight.Bold)
+        val ck = state.ck
+        if (ck != null) {
+            val cards = CatanCk.goodsCount(state, seat)
+            val strength = CatanCk.strength(state, seat)
+            if (compact) {
+                CardLine("$cards cards · ⚔$strength", MaterialTheme.typography.bodySmall)
+            } else {
+                CardLine("$cards cards · ${ck.progressCounts[seat]} progress", MaterialTheme.typography.bodySmall)
+                CardLine(
+                    "⚔ ${CatanCk.knightsOf(state, seat).size} · str $strength · " +
+                        "Road ${CatanRules.longestRoadFor(state, seat)}",
+                    MaterialTheme.typography.bodySmall,
+                )
+            }
+            // Trade, politics, science: the three improvement levels.
+            CardLine(
+                Track.entries.joinToString(" ") { "${it.name.first()}${CatanCk.improvement(state, seat, it)}" },
+                MaterialTheme.typography.bodySmall,
+                color = Color.Unspecified,
+            )
+            val ckAwards = buildList {
+                if (state.longestRoadOwner == seat) add(if (compact) "Road" else "Longest road")
+                ck.metropolises.forEach { (track, at) ->
+                    if (at.seat == seat) add(if (compact) track.name.first().toString() else "${CatanText.track(track)} metropolis")
+                }
+                if (ck.merchant?.seat == seat) add("Merchant")
+            }
+            CardLine(
+                text = ckAwards.joinToString(" · ").ifEmpty { BLANK },
+                style = MaterialTheme.typography.labelSmall,
+                weight = FontWeight.Bold,
+                color = MaterialTheme.colorScheme.primary,
+            )
+            return@Column
+        }
+        if (compact) {
+            CardLine("${state.resourceCount(seat)} cards", MaterialTheme.typography.bodySmall)
+        } else {
+            CardLine(
+                "${state.resourceCount(seat)} cards · ${state.devHandCounts[seat]} dev",
+                MaterialTheme.typography.bodySmall,
+            )
+            CardLine(
+                "Knights ${state.knightsPlayed[seat]} · Road ${CatanRules.longestRoadFor(state, seat)}",
+                MaterialTheme.typography.bodySmall,
+            )
+        }
+        val awards = buildList {
+            if (state.longestRoadOwner == seat) add(if (compact) "Road" else "Longest road")
+            if (state.largestArmyOwner == seat) add(if (compact) "Army" else "Largest army")
+        }
+        // Always drawn, so the card does not grow when somebody takes an award.
+        CardLine(
+            text = awards.joinToString(" · ").ifEmpty { BLANK },
+            style = MaterialTheme.typography.labelSmall,
+            weight = FontWeight.Bold,
+            color = MaterialTheme.colorScheme.primary,
+        )
+    }
+}
+
+/** A non-breaking space: a line of text with nothing in it, still one line tall. */
+private const val BLANK = "\u00A0"
+
+/** One line of a player card: never wraps, so the card's height cannot change. */
+@Composable
+private fun CardLine(
+    text: String,
+    style: TextStyle,
+    weight: FontWeight? = null,
+    color: Color = Color.Unspecified,
+) {
+    Text(
+        text = text,
+        style = style,
+        fontWeight = weight,
+        color = color,
+        maxLines = 1,
+        overflow = TextOverflow.Ellipsis,
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Dice
+// ---------------------------------------------------------------------------
+
+/**
+ * The two dice as last rolled, with their total. Blank until the first roll. In
+ * Cities & Knights the dice are yellow and red (the red one decides progress
+ * cards) and a third, the event die, shows a ship or a coloured city gate.
+ */
+@Composable
+fun CatanDice(
+    dice: List<Int>,
+    modifier: Modifier = Modifier,
+    ck: Boolean = false,
+    event: EventFace? = null,
+    style: CatanStyle = LocalCatanStyle.current,
+) {
+    Row(
+        modifier = modifier,
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(6.dp),
+    ) {
+        val shown = if (dice.size == 2) dice else listOf(null, null)
+        shown.forEachIndexed { index, value ->
+            val face = when {
+                !ck -> Color.White
+                index == 0 -> Color(0xFFFFF176)
+                else -> Color(0xFFEF9A9A)
+            }
+            Box(
+                modifier = Modifier
+                    .size(36.dp)
+                    .clip(RoundedCornerShape(8.dp))
+                    .background(face)
+                    .border(1.dp, Color(0x55000000), RoundedCornerShape(8.dp)),
+                contentAlignment = Alignment.Center,
+            ) {
+                Text(
+                    text = value?.toString() ?: "–",
+                    color = Color(0xFF1C1B1F),
+                    fontWeight = FontWeight.Bold,
+                    fontSize = 20.sp,
+                    textAlign = TextAlign.Center,
+                )
+            }
+        }
+        if (ck) {
+            val gate = when (event) {
+                EventFace.TRADE -> style.track.getValue(Track.TRADE)
+                EventFace.POLITICS -> style.track.getValue(Track.POLITICS)
+                EventFace.SCIENCE -> style.track.getValue(Track.SCIENCE)
+                EventFace.SHIP -> style.barbarian
+                null -> Color(0x33000000)
+            }
+            Box(
+                modifier = Modifier
+                    .size(width = 52.dp, height = 36.dp)
+                    .clip(RoundedCornerShape(8.dp))
+                    .background(gate)
+                    .border(1.dp, Color(0x55000000), RoundedCornerShape(8.dp)),
+                contentAlignment = Alignment.Center,
+            ) {
+                Text(
+                    text = if (event == EventFace.SHIP) "⛵ Ship" else CatanText.event(event),
+                    color = if (event == EventFace.TRADE) Color(0xFF1C1B1F) else Color.White,
+                    fontWeight = FontWeight.Bold,
+                    fontSize = 11.sp,
+                    maxLines = 1,
+                )
+            }
+        }
+        // Always drawn ("= –" before the first roll) so the row never changes width.
+        Text(
+            text = if (dice.size == 2) "= ${dice.sum()}" else "= –",
+            style = MaterialTheme.typography.titleMedium,
+            fontWeight = FontWeight.Bold,
+        )
+    }
+}
+
+/**
+ * Cities & Knights: how close the barbarians are, and how the cities on the
+ * island compare with the knights standing ready. **Fixed height**, like every
+ * other strip around the board.
+ */
+@Composable
+fun CatanBarbarians(state: CatanState, modifier: Modifier = Modifier, style: CatanStyle = LocalCatanStyle.current) {
+    val ck = state.ck ?: return
+    val cities = state.buildings.count { it?.type == BuildingType.CITY }
+    val defence = (0 until state.playerCount).sumOf { CatanCk.strength(state, it) }
+    Row(
+        modifier = modifier.fillMaxWidth().height(24.dp),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(6.dp),
+    ) {
+        Text("⛵", fontSize = 14.sp)
+        Row(horizontalArrangement = Arrangement.spacedBy(2.dp), modifier = Modifier.weight(1f)) {
+            // The ship starts seven steps out and lands when the last box fills.
+            val sailed = BARBARIAN_STEPS_DISPLAY - ck.barbarians
+            for (i in 0 until BARBARIAN_STEPS_DISPLAY) {
+                Box(
+                    modifier = Modifier
+                        .weight(1f)
+                        .height(10.dp)
+                        .clip(RoundedCornerShape(3.dp))
+                        .background(if (i < sailed) style.barbarian else Color(0x33000000)),
+                )
+            }
+        }
+        val verdict = if (defence >= cities) "holds" else "falls"
+        Text(
+            text = "${CatanText.barbarianSteps(ck.barbarians)} · knights $defence v. $cities cities ($verdict)",
+            style = MaterialTheme.typography.labelSmall,
+            maxLines = 1,
+            overflow = TextOverflow.Ellipsis,
+        )
+    }
+}
+
+/** Steps shown on the barbarian strip: the engine's seven. */
+private const val BARBARIAN_STEPS_DISPLAY = org.prolibertate.games.game.catan.BARBARIAN_STEPS
+
+// ---------------------------------------------------------------------------
+// Actions
+// ---------------------------------------------------------------------------
+
+/** What the action bar offers right now. Built by the screen from [CatanInteraction]. */
+data class CatanActions(
+    val canRoll: Boolean = false,
+    val canBuild: Set<BuildKind> = emptySet(),
+    val building: BuildKind? = null,
+    val canBuyCard: Boolean = false,
+    val canPlayCard: Boolean = false,
+    val canTrade: Boolean = false,
+    val canEndTurn: Boolean = false,
+    val canEndFreeRoads: Boolean = false,
+    /** A setup settlement is chosen and a different one may still be picked. */
+    val canRepickSetup: Boolean = false,
+    /** Which kinds the Build menu lists: three in the base game, five in Cities & Knights. */
+    val buildKinds: List<BuildKind> = BuildKind.BASE,
+    /** Cities & Knights: the table plays the expansion, so the bar shows its buttons instead. */
+    val ck: Boolean = false,
+    val canImprove: Boolean = false,
+    val canPlayProgress: Boolean = false,
+    val progressCount: Int = 0,
+    val canEndSmith: Boolean = false,
+)
+
+/**
+ * The buttons for whatever the player can do now. Pure display: every press is a lambda.
+ *
+ * **The bar never changes size.** The top row holds the one "primary" action
+ * (roll, end turn, done with roads, cancel) and keeps its height when it is
+ * empty; the second row is always all six buttons, greyed out when they do not
+ * apply. Buttons appearing and disappearing used to resize this area and, with
+ * it, the board above — so nothing here may be conditionally *present*, only
+ * conditionally *enabled*.
+ */
+@OptIn(ExperimentalLayoutApi::class)
+@Composable
+fun CatanActionBar(
+    actions: CatanActions,
+    onRoll: () -> Unit,
+    onBuild: (BuildKind?) -> Unit,
+    onBuyCard: () -> Unit,
+    onPlayCard: () -> Unit,
+    onTrade: () -> Unit,
+    onEndTurn: () -> Unit,
+    onEndFreeRoads: () -> Unit,
+    onRepickSetup: () -> Unit,
+    modifier: Modifier = Modifier,
+    /** Small screens: fold Road / Settlement / City into one "Build" button with a menu. */
+    compact: Boolean = false,
+    onImprove: () -> Unit = {},
+    onProgress: () -> Unit = {},
+    onEndSmith: () -> Unit = {},
+) {
+    Column(modifier = modifier.fillMaxWidth(), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        Row(
+            modifier = Modifier.fillMaxWidth().height(PRIMARY_ROW_HEIGHT),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.spacedBy(8.dp),
+        ) {
+            if (actions.canRoll) Button(onClick = onRoll) { Text(CatanText.ROLL) }
+            if (actions.canRepickSetup) OutlinedButton(onClick = onRepickSetup) { Text(CatanText.CANCEL) }
+            if (actions.canEndFreeRoads) Button(onClick = onEndFreeRoads) { Text(CatanText.STOP_ROADS) }
+            if (actions.canEndSmith) Button(onClick = onEndSmith) { Text(CatanText.STOP_SMITH) }
+            if (actions.canEndTurn) Button(onClick = onEndTurn) { Text(CatanText.END_TURN) }
+        }
+
+        FlowRow(
+            modifier = Modifier.fillMaxWidth(),
+            horizontalArrangement = Arrangement.spacedBy(8.dp),
+            verticalArrangement = Arrangement.spacedBy(8.dp),
+        ) {
+            if (compact || actions.ck) {
+                BuildMenuButton(actions, onBuild)
+            } else {
+                BuildButton(BuildKind.ROAD, CatanText.ROAD, CatanText.ROAD_COST, actions, onBuild)
+                BuildButton(BuildKind.SETTLEMENT, CatanText.SETTLEMENT, CatanText.SETTLEMENT_COST, actions, onBuild)
+                BuildButton(BuildKind.CITY, CatanText.CITY, CatanText.CITY_COST, actions, onBuild)
+            }
+            if (actions.ck) {
+                OutlinedButton(onClick = onImprove, enabled = actions.canImprove) {
+                    LabelWithCost(CatanText.IMPROVE, CatanText.NO_COST)
+                }
+                OutlinedButton(onClick = onProgress, enabled = actions.canPlayProgress) {
+                    LabelWithCost(CatanText.CARDS_BUTTON, "${actions.progressCount} held")
+                }
+            } else {
+                OutlinedButton(onClick = onBuyCard, enabled = actions.canBuyCard) {
+                    LabelWithCost(CatanText.BUY_CARD, CatanText.DEV_COST)
+                }
+                OutlinedButton(onClick = onPlayCard, enabled = actions.canPlayCard) {
+                    LabelWithCost(CatanText.PLAY_CARD, CatanText.NO_COST)
+                }
+            }
+            OutlinedButton(onClick = onTrade, enabled = actions.canTrade) {
+                LabelWithCost(CatanText.TRADE, CatanText.NO_COST)
+            }
+        }
+    }
+}
+
+/** Room for one button, held whether or not there is one to show. */
+private val PRIMARY_ROW_HEIGHT = 48.dp
+
+@Composable
+private fun BuildButton(
+    kind: BuildKind,
+    label: String,
+    cost: String,
+    actions: CatanActions,
+    onBuild: (BuildKind?) -> Unit,
+) {
+    val enabled = kind in actions.canBuild
+    val active = actions.building == kind
+    val onClick = { onBuild(if (active) null else kind) }
+    if (active) {
+        FilledTonalButton(onClick = onClick, enabled = enabled) { LabelWithCost(label, cost) }
+    } else {
+        OutlinedButton(onClick = onClick, enabled = enabled) { LabelWithCost(label, cost) }
+    }
+}
+
+/**
+ * The small-screen stand-in for the three build buttons: one "Build" button
+ * whose menu lists Road, Settlement and City with their costs. While a build
+ * mode is armed the button shows which, and choosing that entry again cancels it.
+ */
+@Composable
+private fun BuildMenuButton(actions: CatanActions, onBuild: (BuildKind?) -> Unit) {
+    var open by remember { mutableStateOf(false) }
+    val armed = actions.building
+    val anyEnabled = actions.canBuild.isNotEmpty() || armed != null
+    val label: @Composable () -> Unit = {
+        LabelWithCost(CatanText.BUILD, armed?.let { buildLabel(it) } ?: CatanText.NO_COST)
+    }
+    Box {
+        if (armed != null) {
+            FilledTonalButton(onClick = { open = true }, enabled = anyEnabled) { label() }
+        } else {
+            OutlinedButton(onClick = { open = true }, enabled = anyEnabled) { label() }
+        }
+        DropdownMenu(expanded = open, onDismissRequest = { open = false }) {
+            for (kind in actions.buildKinds) {
+                DropdownMenuItem(
+                    text = { LabelWithCost(buildLabel(kind), buildCost(kind)) },
+                    enabled = kind in actions.canBuild,
+                    onClick = {
+                        open = false
+                        onBuild(if (armed == kind) null else kind)
+                    },
+                )
+            }
+        }
+    }
+}
+
+private fun buildLabel(kind: BuildKind): String = when (kind) {
+    BuildKind.ROAD -> CatanText.ROAD
+    BuildKind.SETTLEMENT -> CatanText.SETTLEMENT
+    BuildKind.CITY -> CatanText.CITY
+    BuildKind.WALL -> CatanText.WALL
+    BuildKind.KNIGHT -> CatanText.KNIGHT
+    BuildKind.SHIP -> CatanText.SHIP
+}
+
+private fun buildCost(kind: BuildKind): String = when (kind) {
+    BuildKind.ROAD -> CatanText.ROAD_COST
+    BuildKind.SETTLEMENT -> CatanText.SETTLEMENT_COST
+    BuildKind.CITY -> CatanText.CITY_COST
+    BuildKind.WALL -> CatanText.WALL_COST
+    BuildKind.KNIGHT -> CatanText.KNIGHT_COST
+    BuildKind.SHIP -> CatanText.SHIP_COST_TEXT
+}
+
+@Composable
+private fun LabelWithCost(label: String, cost: String) {
+    Column(horizontalAlignment = Alignment.CenterHorizontally) {
+        Text(label)
+        Text(cost, fontSize = 9.sp, maxLines = 1)
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Log
+// ---------------------------------------------------------------------------
+
+/** The most recent happenings, newest last. Scrolls. */
+@Composable
+fun CatanLog(state: CatanState, modifier: Modifier = Modifier) {
+    if (state.log.isEmpty()) {
+        Text(CatanText.NO_LOG, style = MaterialTheme.typography.bodySmall, modifier = modifier)
+        return
+    }
+    Column(modifier = modifier.verticalScroll(rememberScrollState())) {
+        state.log.takeLast(40).forEach {
+            Text(text = it, style = MaterialTheme.typography.bodySmall)
+        }
+    }
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanPreviews.kt

@@ -0,0 +1,132 @@
+package org.prolibertate.games.ui.game.catan
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.dp
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.prolibertate.games.game.GameCatalog
+import org.prolibertate.games.game.catan.CatanAi
+import org.prolibertate.games.game.catan.CatanOptions
+import org.prolibertate.games.game.catan.CatanPhase
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+/*
+ * Android Studio previews for the Katan UI. They exist so the look can be
+ * iterated on without starting a match: open this file, open the Preview pane,
+ * and edit CatanStyle / CatanText / the panels. Each preview draws a real
+ * position (the computer plays itself for a while), not a mock.
+ *
+ * Nothing here ships in a behaviour sense: previews are only compiled for tooling.
+ */
+
+private val previewJson = Json { encodeDefaults = true }
+
+/** A real game, played forward by the computer for [moves] moves, for previewing. */
+private fun sampleState(players: Int = 4, moves: Int = 90, seed: Long = 11L): CatanState {
+    val config = TableConfig(
+        gameId = GameCatalog.CATAN,
+        seats = (0 until players).map { PlayerSlot(it, "P$it", PlayerKind.AI, it) },
+        optionsJson = previewJson.encodeToString(CatanOptions(playerCount = players)),
+        seed = seed,
+    )
+    val ai = CatanAi()
+    var state = CatanRules.initialState(config)
+    repeat(moves) {
+        if (state.phase == CatanPhase.GAME_OVER) return state
+        val seat = CatanRules.currentSeat(state) ?: return state
+        val legal = CatanRules.legalMoves(state, seat)
+        if (legal.isEmpty()) return state
+        state = CatanRules.applyMove(state, seat, ai.chooseMove(state, seat, legal))
+    }
+    return state
+}
+
+@Preview(showBackground = true, widthDp = 360, heightDp = 360)
+@Composable
+private fun BoardPreview() {
+    val state = remember { sampleState() }
+    CompositionLocalProvider(LocalCatanStyle provides catanStyle(dark = false)) {
+        CatanBoardView(
+            state = state,
+            targets = BoardTargets(),
+            selectedVertex = null,
+            onVertexTap = {},
+            onEdgeTap = {},
+            onHexTap = {},
+        )
+    }
+}
+
+@Preview(showBackground = true, widthDp = 360, heightDp = 360)
+@Composable
+private fun BoardDarkPreview() {
+    val state = remember { sampleState() }
+    CompositionLocalProvider(LocalCatanStyle provides catanStyle(dark = true)) {
+        CatanBoardView(
+            state = state,
+            targets = BoardTargets(),
+            selectedVertex = null,
+            onVertexTap = {},
+            onEdgeTap = {},
+            onHexTap = {},
+        )
+    }
+}
+
+@Preview(showBackground = true, widthDp = 360, heightDp = 360)
+@Composable
+private fun BoardWithTargetsPreview() {
+    val state = remember { sampleState(moves = 6) }
+    val legal = remember(state) { CatanRules.currentSeat(state)?.let { CatanRules.legalMoves(state, it) }.orEmpty() }
+    CompositionLocalProvider(LocalCatanStyle provides catanStyle(dark = false)) {
+        CatanBoardView(
+            state = state,
+            targets = CatanInteraction.targets(state, legal, building = null, setupVertex = null),
+            selectedVertex = null,
+            onVertexTap = {},
+            onEdgeTap = {},
+            onHexTap = {},
+        )
+    }
+}
+
+@Preview(showBackground = true, widthDp = 360, heightDp = 560)
+@Composable
+private fun PanelsPreview() {
+    val state = remember { sampleState() }
+    val seats = CatanSeats(me = 0, names = listOf("You", "Ann", "Bo", "Cy"))
+    val points = remember(state) { CatanRules.publicVictoryPoints(state) }
+    Column(Modifier.padding(8.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.spacedBy(6.dp)) {
+            (0 until state.playerCount).forEach { seat ->
+                CatanPlayerCard(state, seat, seats, points[seat], Modifier.weight(1f), compact = true)
+            }
+        }
+        CatanHand(state, seat = 0)
+        CatanDice(state.lastDice)
+        CatanActionBar(
+            actions = CatanActions(
+                canBuild = setOf(BuildKind.ROAD, BuildKind.CITY),
+                building = BuildKind.ROAD,
+                canBuyCard = true,
+                canTrade = true,
+                canEndTurn = true,
+            ),
+            onRoll = {}, onBuild = {}, onBuyCard = {}, onPlayCard = {}, onTrade = {},
+            onEndTurn = {}, onEndFreeRoads = {}, onRepickSetup = {},
+        )
+    }
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanScreen.kt

@@ -0,0 +1,731 @@
+package org.prolibertate.games.ui.game.catan
+
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.BoxWithConstraints
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.horizontalScroll
+import androidx.compose.foundation.background
+import androidx.compose.material3.Surface
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.layout.LayoutCoordinates
+import androidx.compose.ui.layout.onGloballyPositioned
+import androidx.compose.ui.unit.IntSize
+import org.prolibertate.games.game.catan.BuildRoad
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.platform.LocalConfiguration
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import org.prolibertate.games.game.catan.AcceptTrade
+import org.prolibertate.games.game.catan.AqueductChore
+import org.prolibertate.games.game.catan.BuyDevCard
+import org.prolibertate.games.game.catan.CatanCk
+import org.prolibertate.games.game.catan.CatanMove
+import org.prolibertate.games.game.catan.CatanPhase
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.DeclineTrade
+import org.prolibertate.games.game.catan.DiscardChore
+import org.prolibertate.games.game.catan.DiscardGoods
+import org.prolibertate.games.game.catan.DropProgress
+import org.prolibertate.games.game.catan.DropProgressChore
+import org.prolibertate.games.game.catan.DismissCounters
+import org.prolibertate.games.game.catan.EndFreeRoads
+import org.prolibertate.games.game.catan.EndSmith
+import org.prolibertate.games.game.catan.EndTurn
+import org.prolibertate.games.game.catan.GiveChore
+import org.prolibertate.games.game.catan.GiveGoods
+import org.prolibertate.games.game.catan.MoveKnight
+import org.prolibertate.games.game.catan.MoveShip
+import org.prolibertate.games.game.catan.MoveRobber
+import org.prolibertate.games.game.catan.PickDeckChore
+import org.prolibertate.games.game.catan.RollDice
+import org.prolibertate.games.game.catan.SetupPlace
+import org.prolibertate.games.game.catan.SpyChore
+import org.prolibertate.games.net.MatchController
+import org.prolibertate.games.ui.ScreenScaffold
+
+/**
+ * Katan, on the island.
+ *
+ * This composable is only wiring. It reads the match from the controller, holds
+ * the handful of purely visual choices (which build mode is armed, which setup
+ * settlement is waiting for its road, which dialog is open), and hands
+ * everything else to single-purpose pieces:
+ *
+ * | Concern                        | Where it lives             |
+ * | ------------------------------ | -------------------------- |
+ * | Colours, sizes, shapes         | [CatanStyle]               |
+ * | Every word on screen           | [CatanText]                |
+ * | Island → pixels, taps → hexes  | [CatanGeometry]            |
+ * | What is tappable, what a tap does | [CatanInteraction]      |
+ * | Drawing the island             | [CatanBoardView]           |
+ * | Cards, players, dice, buttons  | `CatanPanels.kt`           |
+ * | Every dialog                   | `CatanDialogs.kt`          |
+ *
+ * There are no game rules here: the engine's legal-move list is the only source
+ * of what the player may do, so the screen cannot offer a move the rules refuse.
+ * See `docs/UI-catan.md` for how to adapt the look and feel.
+ */
+@Composable
+fun CatanScreen(
+    controller: MatchController<CatanState, CatanMove>,
+    localSeat: Int,
+    onExit: () -> Unit,
+    seatNames: List<String> = emptyList(),
+) {
+    val state by controller.state.collectAsState()
+    val legal by controller.legalMoves.collectAsState()
+    val abandoned by controller.abandoned.collectAsState()
+    val notice by controller.notice.collectAsState()
+
+    // Purely visual state. Anything that affects the game goes through submit().
+    var building by remember { mutableStateOf<BuildKind?>(null) }
+    var setupVertex by remember { mutableStateOf<Int?>(null) }
+    var victimChoice by remember { mutableStateOf<TapOutcome.PickRobberVictim?>(null) }
+    var showCards by remember { mutableStateOf(false) }
+    var showTrade by remember { mutableStateOf(false) }
+    var confirmingEnd by remember { mutableStateOf(false) }
+    var resultDismissed by remember { mutableStateOf(false) }
+    // Cities & Knights: the knight whose menu is open, the one about to move,
+    // a progress card waiting for a tap on the board, and the two list dialogs.
+    var knightMenu by remember { mutableStateOf<Int?>(null) }
+    var movingKnight by remember { mutableStateOf<Int?>(null) }
+    var armed by remember { mutableStateOf<ArmedCard?>(null) }
+    // Seafarers: the ship that has been picked up and is waiting for somewhere to sail.
+    var movingShip by remember { mutableStateOf<Int?>(null) }
+    var showImprove by remember { mutableStateOf(false) }
+    var showProgress by remember { mutableStateOf(false) }
+    // The landscape HUD: a placement waiting for its ✓, the piece being dragged from the
+    // build column (and where the finger is, in window pixels), the log popup, and the board.
+    var staged by remember { mutableStateOf<CatanMove?>(null) }
+    var dragKind by remember { mutableStateOf<BuildKind?>(null) }
+    var dragAt by remember { mutableStateOf<Offset?>(null) }
+    var showLog by remember { mutableStateOf(false) }
+    var boardCoords by remember { mutableStateOf<LayoutCoordinates?>(null) }
+
+    val config = LocalConfiguration.current
+    // Landscape gets the heads-up display; portrait keeps the stacked layout.
+    val wide = config.screenWidthDp > config.screenHeightDp * 1.1f
+    val staging = wide
+
+    val dark = isSystemInDarkTheme()
+    val style = remember(dark) { catanStyle(dark) }
+    val seats = remember(localSeat, seatNames) { CatanSeats(localSeat, seatNames) }
+
+    // The engine's list changes after every move; drop any selection it no
+    // longer supports (a build mode the player can no longer afford, a setup
+    // settlement that is no longer pending).
+    LaunchedEffect(legal) {
+        if (building != null && building !in CatanInteraction.canBuild(legal)) building = null
+        if (staged != null && staged !in legal) staged = null
+        if (setupVertex != null && legal.none { it is SetupPlace && it.vertex == setupVertex }) {
+            setupVertex = null
+        }
+        if (movingKnight != null && legal.none { it is MoveKnight && it.from == movingKnight }) movingKnight = null
+        if (movingShip != null && legal.none { it is MoveShip && it.from == movingShip }) movingShip = null
+        armed?.let { card -> if (card.plays.none { it in legal }) armed = null }
+        if (legal.isEmpty()) {
+            showCards = false
+            showTrade = false
+            victimChoice = null
+            showImprove = false
+            showProgress = false
+            knightMenu = null
+            movingKnight = null
+            armed = null
+            staged = null
+        }
+    }
+
+    val submit: (CatanMove) -> Unit = { move ->
+        controller.submit(move)
+        building = null
+        setupVertex = null
+        victimChoice = null
+        showCards = false
+        showTrade = false
+        showImprove = false
+        showProgress = false
+        knightMenu = null
+        movingKnight = null
+        movingShip = null
+        armed = null
+        staged = null
+        dragKind = null
+        dragAt = null
+    }
+
+    val endGameAction: @Composable () -> Unit = {
+        TextButton(onClick = { confirmingEnd = true }) { Text(CatanText.END_GAME) }
+    }
+
+    val current = state
+    if (current == null) {
+        ScreenScaffold(title = CatanText.TITLE, onBack = onExit, actions = endGameAction) { modifier ->
+            Box(modifier, contentAlignment = Alignment.Center) { Text("Setting up…") }
+            abandoned?.let { CatanAbandonedDialog(it, onExit, controller::dismissAbandoned) }
+            if (confirmingEnd) CatanEndGameDialog(onExit) { confirmingEnd = false }
+        }
+        return
+    }
+
+    val targets = CatanInteraction.targets(current, legal, building, setupVertex, movingKnight, armed, localSeat, movingShip)
+    val ownKnights = current.ck?.knights?.filter { it.owner == localSeat }?.map { it.vertex }?.toSet().orEmpty()
+    val devHand = CatanInteraction.devHand(current, localSeat, legal)
+    val progressHand = CatanInteraction.progressHand(current, localSeat, legal)
+    val playing = current.phase == CatanPhase.PLAYING && legal.isNotEmpty()
+    val actions = CatanActions(
+        buildKinds = when {
+            current.isCk -> BuildKind.entries.filter { it != BuildKind.SHIP }
+            current.isSea -> BuildKind.SEAFARERS
+            else -> BuildKind.BASE
+        },
+        ck = current.isCk,
+        canImprove = CatanInteraction.improvable(legal).isNotEmpty(),
+        canPlayProgress = progressHand.any { it.playable },
+        progressCount = progressHand.size,
+        canEndSmith = CatanInteraction.canEndSmith(legal),
+        canRoll = CatanInteraction.canRoll(legal),
+        canBuild = CatanInteraction.canBuild(legal),
+        building = building,
+        canBuyCard = CatanInteraction.canBuyDevCard(legal),
+        canPlayCard = devHand.any { it.playable },
+        canTrade = playing,
+        canEndTurn = CatanInteraction.canEndTurn(legal),
+        canEndFreeRoads = CatanInteraction.canEndFreeRoads(legal),
+        canRepickSetup = setupVertex != null,
+    )
+    val rolledHexes = CatanInteraction.rolledHexes(current)
+    val prompt = CatanText.prompt(
+        current,
+        seats,
+        setupVertexChosen = setupVertex != null,
+        building = building,
+        movingKnight = movingKnight != null,
+        armed = armed?.kind,
+        movingShip = movingShip != null,
+    )
+
+    val handle: (TapOutcome) -> Unit = { outcome ->
+        val wait = if (staging) CatanInteraction.stageable(outcome, building) else null
+        when {
+            wait != null -> staged = wait
+            else -> when (outcome) {
+            TapOutcome.Ignored -> Unit
+            is TapOutcome.Submit -> submit(outcome.move)
+            is TapOutcome.PickSetupVertex -> setupVertex = outcome.vertex
+            is TapOutcome.PickRobberVictim -> victimChoice = outcome
+            is TapOutcome.PickKnight -> knightMenu = outcome.vertex
+            is TapOutcome.PickShip -> movingShip = outcome.edge
+            is TapOutcome.PickFirstHex -> armed = armed?.copy(firstHex = outcome.hex)
+            }
+        }
+    }
+
+    val publicPoints = CatanRules.publicVictoryPoints(current)
+    val pointsOf: (Int) -> Int = { seat ->
+        if (seat == localSeat) CatanRules.victoryPoints(current, seat) else publicPoints[seat]
+    }
+
+    CompositionLocalProvider(LocalCatanStyle provides style) {
+        ScreenScaffold(title = CatanText.TITLE, onBack = onExit, actions = endGameAction) { modifier ->
+            BoxWithConstraints(modifier = modifier) {
+                // Phones (either way up) get the one-button build menu.
+                val compactBuild = !wide || maxWidth < 600.dp
+
+                val hoverSpot = if (dragKind != null) dragSpot(boardCoords, dragAt, targets) else null
+                val stagedSpot = CatanInteraction.spotOf(staged)
+                val ghostVertex = hoverSpot?.vertex ?: stagedSpot.vertex
+                val ghostEdge = hoverSpot?.edge ?: stagedSpot.edge
+
+                val board: @Composable (Modifier) -> Unit = { boardModifier ->
+                    CatanBoardView(
+                        state = current,
+                        targets = targets,
+                        selectedVertex = setupVertex,
+                        onVertexTap = {
+                            handle(
+                                CatanInteraction.onVertexTap(
+                                    it, legal, building, setupVertex, movingKnight, armed,
+                                    ownKnights = if (legal.isNotEmpty()) ownKnights else emptySet(),
+                                ),
+                            )
+                        },
+                        onEdgeTap = { handle(CatanInteraction.onEdgeTap(it, legal, building, setupVertex, armed, movingShip)) },
+                        onHexTap = { handle(CatanInteraction.onHexTap(it, legal, armed, current.topo)) },
+                        modifier = boardModifier,
+                        style = style,
+                        rolledHexes = rolledHexes,
+                        selectedKnight = movingKnight ?: knightMenu,
+                        stagedVertex = ghostVertex,
+                        stagedEdge = ghostEdge,
+                        stagedSeat = localSeat,
+                    )
+                }
+                val players: @Composable (Boolean) -> Unit = { grid ->
+                    PlayerCards(current, seats, pointsOf, style, twoPerRow = grid)
+                }
+                val promptRow: @Composable () -> Unit = {
+                    PromptRow(prompt, notice, current)
+                }
+                val handAndActions: @Composable () -> Unit = {
+                    Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                        CatanHand(current, localSeat)
+                        CatanActionBar(
+                            actions = actions,
+                            onRoll = { submit(RollDice()) },
+                            onBuild = { building = it },
+                            onBuyCard = { legal.firstOrNull { m -> m is BuyDevCard }?.let(submit) },
+                            onPlayCard = { showCards = true },
+                            onTrade = { showTrade = true },
+                            onEndTurn = { legal.firstOrNull { m -> m is EndTurn }?.let(submit) },
+                            onEndFreeRoads = {
+                                legal.firstOrNull { m -> m is EndFreeRoads }?.let(submit)
+                            },
+                            onRepickSetup = { setupVertex = null },
+                            compact = compactBuild,
+                            onImprove = { showImprove = true },
+                            onProgress = { showProgress = true },
+                            onEndSmith = { legal.firstOrNull { m -> m is EndSmith }?.let(submit) },
+                        )
+                    }
+                }
+
+                if (wide) {
+                    CatanHud(
+                        state = current,
+                        seats = seats,
+                        style = style,
+                        actions = actions,
+                        prompt = prompt,
+                        notice = notice,
+                        legal = legal,
+                        localSeat = localSeat,
+                        targets = targets,
+                        pointsOf = pointsOf,
+                        staged = staged,
+                        dragKind = dragKind,
+                        dragAt = dragAt,
+                        showLog = showLog,
+                        boardCoords = boardCoords,
+                        building = building,
+                        onBoardCoords = { boardCoords = it },
+                        onToggleLog = { showLog = !showLog },
+                        onArm = { kind -> building = if (building == kind) null else kind; staged = null },
+                        onDragStart = { kind, at ->
+                            building = kind
+                            staged = null
+                            dragKind = kind
+                            dragAt = at
+                        },
+                        onDrag = { dragAt = it },
+                        onDragEnd = {
+                            val spot = dragSpot(boardCoords, dragAt, targets)
+                            dragKind = null
+                            dragAt = null
+                            val outcome = when {
+                                spot?.vertex != null -> CatanInteraction.onVertexTap(
+                                    spot.vertex, legal, building, setupVertex,
+                                    ownKnights = if (legal.isNotEmpty()) ownKnights else emptySet(),
+                                )
+                                spot?.edge != null -> CatanInteraction.onEdgeTap(spot.edge, legal, building, setupVertex, armed, movingShip)
+                                else -> TapOutcome.Ignored
+                            }
+                            handle(outcome)
+                        },
+                        onConfirm = { staged?.let(submit) },
+                        onCancelStaged = { staged = null; building = null },
+                        onRoll = { submit(RollDice()) },
+                        onEndTurn = { legal.firstOrNull { m -> m is EndTurn }?.let(submit) },
+                        onEndFreeRoads = { legal.firstOrNull { m -> m is EndFreeRoads }?.let(submit) },
+                        onEndSmith = { legal.firstOrNull { m -> m is EndSmith }?.let(submit) },
+                        onRepickSetup = { setupVertex = null },
+                        onBuyCard = { legal.firstOrNull { m -> m is BuyDevCard }?.let(submit) },
+                        onPlayCard = { showCards = true },
+                        onTrade = { showTrade = true },
+                        onImprove = { showImprove = true },
+                        onProgress = { showProgress = true },
+                        board = { m -> board(m) },
+                    )
+                } else {
+                    Column(Modifier.fillMaxSize(), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                        players(false)
+                        if (current.isCk) CatanBarbarians(current, style = style)
+                        promptRow()
+                        Box(Modifier.weight(1f).fillMaxWidth(), contentAlignment = Alignment.Center) {
+                            board(Modifier)
+                        }
+                        handAndActions()
+                    }
+                }
+
+                // The trade board slides up over the bottom of the island (base game; Cities &
+                // Knights trades goods and still uses its dialogs).
+                val offerToMe = current.pendingTrade?.takeIf {
+                    current.phase == CatanPhase.TRADE_PENDING && it.asking == localSeat && !current.isCk
+                }
+                val boardsAllowed = abandoned == null && !confirmingEnd && current.phase != CatanPhase.GAME_OVER
+                if (boardsAllowed && offerToMe != null) {
+                    CatanTradeReplyBoard(
+                        state = current,
+                        seat = localSeat,
+                        offer = offerToMe,
+                        seats = seats,
+                        canAccept = CatanInteraction.tradeResponses(legal).first,
+                        onAccept = { submit(AcceptTrade) },
+                        onDecline = { submit(DeclineTrade) },
+                        onCounter = submit,
+                        modifier = Modifier.align(Alignment.BottomCenter),
+                        style = style,
+                    )
+                } else if (boardsAllowed && showTrade && !current.isCk) {
+                    CatanTradeBoard(
+                        state = current,
+                        seat = localSeat,
+                        seats = seats,
+                        legal = legal,
+                        onBank = submit,
+                        onOffer = submit,
+                        onClose = { showTrade = false },
+                        modifier = Modifier.align(Alignment.BottomCenter),
+                        style = style,
+                    )
+                }
+            }
+
+            CatanDialogHost(
+                state = current,
+                seats = seats,
+                localSeat = localSeat,
+                legal = legal,
+                abandoned = abandoned,
+                confirmingEnd = confirmingEnd,
+                resultDismissed = resultDismissed,
+                victimChoice = victimChoice,
+                showCards = showCards,
+                showTrade = showTrade,
+                devHand = devHand,
+                knightMenu = knightMenu,
+                showImprove = showImprove,
+                showProgress = showProgress,
+                progressHand = progressHand,
+                onMoveKnight = { from ->
+                    knightMenu = null
+                    movingKnight = from
+                },
+                onArmCard = { card ->
+                    showProgress = false
+                    armed = card
+                },
+                onCancelKnight = { knightMenu = null },
+                onCancelImprove = { showImprove = false },
+                onCancelProgress = { showProgress = false },
+                onExit = onExit,
+                onSubmit = submit,
+                onStay = controller::dismissAbandoned,
+                onKeepPlaying = { confirmingEnd = false },
+                onDismissResult = { resultDismissed = true },
+                onCancelVictim = { victimChoice = null },
+                onCancelCards = { showCards = false },
+                onCancelTrade = { showTrade = false },
+            )
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Layout pieces
+// ---------------------------------------------------------------------------
+
+@Composable
+private fun PlayerCards(
+    state: CatanState,
+    seats: CatanSeats,
+    pointsOf: (Int) -> Int,
+    style: CatanStyle,
+    twoPerRow: Boolean,
+) {
+    val order = (0 until state.playerCount).toList()
+    val rows = if (twoPerRow) order.chunked(2) else listOf(order)
+    Column(verticalArrangement = Arrangement.spacedBy(6.dp)) {
+        rows.forEach { row ->
+            Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.spacedBy(6.dp)) {
+                row.forEach { seat ->
+                    CatanPlayerCard(
+                        state = state,
+                        seat = seat,
+                        seats = seats,
+                        points = pointsOf(seat),
+                        modifier = Modifier.weight(1f),
+                        style = style,
+                        compact = !twoPerRow,
+                    )
+                }
+                // Keep an odd last row's card the same width as the others.
+                if (twoPerRow && row.size == 1) Box(Modifier.weight(1f))
+            }
+        }
+    }
+}
+
+/**
+ * The one line telling the player what is going on, and the dice.
+ *
+ * **Fixed height.** The text always occupies exactly two lines (padded when it is
+ * shorter, clipped when it is longer) and a refused move replaces the prompt
+ * rather than adding to it, so this row is the same height whatever is said and
+ * the board below it never moves.
+ */
+@Composable
+private fun PromptRow(prompt: String, notice: String?, state: CatanState) {
+    Row(
+        modifier = Modifier.fillMaxWidth(),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        Text(
+            text = notice ?: prompt,
+            style = MaterialTheme.typography.bodyMedium,
+            color = if (notice != null) MaterialTheme.colorScheme.error else Color.Unspecified,
+            minLines = 2,
+            maxLines = 2,
+            overflow = TextOverflow.Ellipsis,
+            modifier = Modifier.weight(1f),
+        )
+        CatanDice(state.lastDice, ck = state.isCk, event = state.ck?.eventDie)
+    }
+}
+
+/**
+ * Chooses which dialog, if any, is showing. Pulled out of [CatanScreen] so the
+ * priority order — an ended table beats a result beats a forced discard beats
+ * an optional picker — is in one readable place.
+ */
+@Composable
+private fun CatanDialogHost(
+    state: CatanState,
+    seats: CatanSeats,
+    localSeat: Int,
+    legal: List<CatanMove>,
+    abandoned: String?,
+    confirmingEnd: Boolean,
+    resultDismissed: Boolean,
+    victimChoice: TapOutcome.PickRobberVictim?,
+    showCards: Boolean,
+    showTrade: Boolean,
+    devHand: List<DevCardInHand>,
+    knightMenu: Int?,
+    showImprove: Boolean,
+    showProgress: Boolean,
+    progressHand: List<ProgressInHand>,
+    onMoveKnight: (Int) -> Unit,
+    onArmCard: (ArmedCard) -> Unit,
+    onCancelKnight: () -> Unit,
+    onCancelImprove: () -> Unit,
+    onCancelProgress: () -> Unit,
+    onExit: () -> Unit,
+    onSubmit: (CatanMove) -> Unit,
+    onStay: () -> Unit,
+    onKeepPlaying: () -> Unit,
+    onDismissResult: () -> Unit,
+    onCancelVictim: () -> Unit,
+    onCancelCards: () -> Unit,
+    onCancelTrade: () -> Unit,
+) {
+    val goodsOffer = state.ck?.goodsOffer
+    when {
+        abandoned != null -> CatanAbandonedDialog(abandoned, onExit, onStay)
+
+        confirmingEnd -> CatanEndGameDialog(onEnd = onExit, onKeepPlaying = onKeepPlaying)
+
+        state.phase == CatanPhase.GAME_OVER ->
+            if (!resultDismissed) CatanGameOverDialog(state, seats, onExit, onDismissResult)
+
+        state.phase == CatanPhase.DISCARDING && state.discardSeat == localSeat ->
+            CatanDiscardDialog(
+                held = state.resources[localSeat],
+                quota = CatanInteraction.discardQuota(state.resourceCount(localSeat)),
+                legal = legal,
+                onSubmit = onSubmit,
+            )
+
+        state.phase == CatanPhase.GOLD && CatanRules.currentSeat(state) == localSeat && legal.isNotEmpty() ->
+            CatanGoldDialog(legal, onSubmit)
+
+        state.phase == CatanPhase.CHORE && CatanRules.currentSeat(state) == localSeat ->
+            ChoreDialog(state, localSeat, legal, onSubmit)
+
+        state.phase == CatanPhase.TRADE_PENDING && goodsOffer != null && goodsOffer.asking == localSeat ->
+            CatanGoodsTradeResponseDialog(
+                state = state,
+                seat = localSeat,
+                offer = goodsOffer,
+                seats = seats,
+                canAccept = CatanInteraction.tradeResponses(legal).first,
+                onAccept = { onSubmit(AcceptTrade) },
+                onDecline = { onSubmit(DeclineTrade) },
+                onCounter = onSubmit,
+            )
+
+        state.phase == CatanPhase.TRADE_COUNTERS && goodsOffer != null && state.turn == localSeat && legal.isNotEmpty() ->
+            CatanGoodsCounterChoiceDialog(
+                counters = CatanInteraction.goodsCounterChoices(state, legal),
+                seats = seats,
+                onTake = onSubmit,
+                onNoDeal = { onSubmit(DismissCounters) },
+            )
+
+        state.phase == CatanPhase.TRADE_COUNTERS && state.turn == localSeat && legal.isNotEmpty() ->
+            CatanCounterChoiceDialog(
+                counters = CatanInteraction.counterChoices(state, legal),
+                seats = seats,
+                onTake = onSubmit,
+                onNoDeal = { onSubmit(DismissCounters) },
+            )
+
+        victimChoice != null ->
+            CatanVictimDialog(
+                victims = victimChoice.victims,
+                seats = seats,
+                onPick = { victim ->
+                    onSubmit(
+                        if (victimChoice.pirate) {
+                            org.prolibertate.games.game.catan.MovePirate(victimChoice.hex, victim)
+                        } else {
+                            MoveRobber(victimChoice.hex, victim)
+                        },
+                    )
+                },
+                onCancel = onCancelVictim,
+            )
+
+        knightMenu != null ->
+            CatanKnightDialog(
+                state = state,
+                vertex = knightMenu,
+                actions = CatanInteraction.knightActions(legal, knightMenu),
+                onDo = onSubmit,
+                onMove = onMoveKnight,
+                onCancel = onCancelKnight,
+            )
+
+        showImprove ->
+            CatanImproveDialog(
+                state = state,
+                seat = localSeat,
+                legal = legal,
+                onBuy = onSubmit,
+                onCancel = onCancelImprove,
+            )
+
+        showProgress ->
+            CatanProgressDialog(
+                hand = progressHand,
+                seats = seats,
+                onPlay = onSubmit,
+                onArm = onArmCard,
+                onCancel = onCancelProgress,
+            )
+
+        showCards -> CatanPlayCardDialog(devHand, onPlay = onSubmit, onCancel = onCancelCards)
+
+        showTrade && state.isCk ->
+            CatanGoodsTradeDialog(
+                state = state,
+                seat = localSeat,
+                seats = seats,
+                legal = legal,
+                onBank = onSubmit,
+                onOffer = onSubmit,
+                onCancel = onCancelTrade,
+            )
+    }
+}
+
+/**
+ * The dialog for the chore at the front of the queue, when it is the local
+ * player's. Chores that are answered by tapping the board (a city to lose, a
+ * metropolis site, a knight to place) have no dialog: the prompt line tells the
+ * player what to tap.
+ */
+@Composable
+private fun ChoreDialog(
+    state: CatanState,
+    localSeat: Int,
+    legal: List<CatanMove>,
+    onSubmit: (CatanMove) -> Unit,
+) {
+    val ck = state.ck ?: return
+    val check: (List<org.prolibertate.games.game.catan.Good>, (List<org.prolibertate.games.game.catan.Good>) -> CatanMove) -> Boolean =
+        { cards, make -> CatanRules.isLegalMove(state, localSeat, make(cards)) }
+    when (val chore = ck.chores.firstOrNull()) {
+        is DiscardChore -> {
+            val quota = minOf(chore.count, CatanCk.goodsCount(state, localSeat))
+            CatanGoodsPickDialog(
+                title = "Discard $quota cards",
+                intro = "Choose $quota cards to give up",
+                held = CatanCk.goodsOf(state, localSeat),
+                quota = quota,
+                confirmLabel = "Discard",
+                selectable = { true },
+                allowed = { check(it, ::DiscardGoods) },
+                onConfirm = { onSubmit(DiscardGoods(it)) },
+            )
+        }
+
+        is GiveChore -> {
+            val pool = CatanCk.goodsOf(state, localSeat).filterKeys { !chore.commoditiesOnly || it.isCommodity }
+            val quota = minOf(chore.count, pool.values.sum())
+            CatanGoodsPickDialog(
+                title = "Hand over $quota ${if (quota == 1) "card" else "cards"}",
+                intro = if (chore.commoditiesOnly) "Choose a commodity to give" else "Choose which cards to give",
+                held = pool,
+                quota = quota,
+                confirmLabel = "Give",
+                selectable = { !chore.commoditiesOnly || it.isCommodity },
+                allowed = { check(it, ::GiveGoods) },
+                onConfirm = { onSubmit(GiveGoods(it)) },
+            )
+        }
+
+        is PickDeckChore -> CatanPickDeckDialog(legal) { onSubmit(it) }
+
+        is DropProgressChore -> CatanDropProgressDialog(ck.progressHands[localSeat]) { onSubmit(it) }
+
+        is AqueductChore -> CatanAqueductDialog(legal) { onSubmit(it) }
+
+        is SpyChore -> CatanSpyDialog(ck.progressHands[chore.target], legal) { onSubmit(it) }
+
+        else -> Unit
+    }
+}
+
+/** The board spot under a dragged finger ([at], in window pixels), or null off the board. */
+private fun dragSpot(coords: LayoutCoordinates?, at: Offset?, targets: BoardTargets): CatanInteraction.Spot? {
+    if (coords == null || at == null || !coords.isAttached) return null
+    val local = coords.windowToLocal(at)
+    val layout = CatanGeometry.fit(coords.size.width.toFloat(), coords.size.height.toFloat())
+    return CatanInteraction.snap(layout, targets, Pt(local.x, local.y), layout.radius * 1.2f)
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanStyle.kt

@@ -0,0 +1,173 @@
+package org.prolibertate.games.ui.game.catan
+
+import androidx.compose.runtime.Immutable
+import androidx.compose.runtime.staticCompositionLocalOf
+import androidx.compose.ui.graphics.Color
+import org.prolibertate.games.game.catan.Commodity
+import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.Terrain
+import org.prolibertate.games.game.catan.Track
+
+/**
+ * Every visual decision for the Katan screen, in one place.
+ *
+ * **To restyle Katan, edit this file.** Nothing else in `ui/game/catan/` hard-
+ * codes a colour or a proportion: the board, the hand, the player strip and the
+ * dialogs all read a [CatanStyle] from [LocalCatanStyle]. A different art
+ * direction is a different [CatanStyle] value (see [catanStyle]); a new theme
+ * can be supplied at the screen's root with
+ * `CompositionLocalProvider(LocalCatanStyle provides myStyle)`.
+ *
+ * Wording is the same story in [CatanText]; geometry is in [CatanGeometry].
+ *
+ * Proportions are fractions of the *hex radius* (centre of a hex to one of its
+ * corners), so they scale with the board whatever the screen size.
+ */
+@Immutable
+data class CatanStyle(
+    // --- Board surfaces -----------------------------------------------------
+    /** The water around the island. */
+    val sea: Color,
+    /** Fill of each hex by terrain. */
+    val terrain: Map<Terrain, Color>,
+    /** Outline between hexes. */
+    val hexEdge: Color,
+    /** The number-token disc, and the ink for ordinary and hot (6 / 8) numbers. */
+    val token: Color,
+    val tokenInk: Color,
+    val tokenHotInk: Color,
+    /** The robber's pawn. */
+    val robber: Color,
+    /** Outline and wash on hexes that produced for the latest dice roll. */
+    val rolled: Color,
+    /** Harbour marker disc and its ink. */
+    val portMarker: Color,
+    val portInk: Color,
+
+    // --- Resources (hand tiles, trade pickers, harbour markers) -------------
+    val resource: Map<Resource, Color>,
+    val resourceInk: Color,
+
+    // --- Cities & Knights ---------------------------------------------------
+    /** Commodity cards: cloth, coin and paper. */
+    val commodity: Map<Commodity, Color> = LightCommodities,
+    /** Ink on a commodity tile (paper is pale, so it is not white). */
+    val commodityInk: Map<Commodity, Color> = LightCommodityInk,
+    /** The colour of each improvement track, its city gate, its deck and its metropolis. */
+    val track: Map<Track, Color> = LightTracks,
+    /** Wall round a city, and the barbarian strip. */
+    val wall: Color = Color(0xFF5D4037),
+    val barbarian: Color = Color(0xFFB71C1C),
+    /** The halo round a knight that is awake. White, so it is not mistaken for the yellow tap ring. */
+    val knightReady: Color = Color(0xFFFFFFFF),
+
+    // --- Players ------------------------------------------------------------
+    /** One colour per seat, in seat order. Roads, settlements, cities, player strip. */
+    val seats: List<Color>,
+    /** Outline drawn round every piece so any seat colour reads on any terrain. */
+    val pieceOutline: Color,
+
+    // --- Interaction feedback ----------------------------------------------
+    /** Marks where the player may build or move right now. */
+    val target: Color,
+    /** The setup settlement that has been chosen and is waiting for its road. */
+    val targetSelected: Color,
+
+    // --- Metrics (fractions of the hex radius) ------------------------------
+    /** How far each tile polygon is pulled in from its corners, leaving a gap. */
+    val hexInset: Float = 0.04f,
+    val roadWidth: Float = 0.20f,
+    val settlementSize: Float = 0.30f,
+    val citySize: Float = 0.42f,
+    val tokenRadius: Float = 0.36f,
+    val robberSize: Float = 0.34f,
+    /** Seafarers: the pirate's flag, and the hull and sail of a ship. */
+    val pirate: Color = Color(0xFF000000),
+    val shipSail: Color = Color(0xFFFFFFFF),
+    val portRadius: Float = 0.46f,
+    val targetRadius: Float = 0.20f,
+    /** How close a tap must land to a vertex / edge / hex centre to count. */
+    val tapReach: Float = 0.55f,
+    val tokenText: Float = 0.34f,
+    val portText: Float = 0.27f,
+    val knightSize: Float = 0.30f,
+)
+
+private val LightCommodities = mapOf(
+    Commodity.CLOTH to Color(0xFF7E57C2),
+    Commodity.COIN to Color(0xFFF9A825),
+    Commodity.PAPER to Color(0xFFECEFF1),
+)
+
+private val LightCommodityInk = mapOf(
+    Commodity.CLOTH to Color(0xFFFFFFFF),
+    Commodity.COIN to Color(0xFF3E2723),
+    Commodity.PAPER to Color(0xFF263238),
+)
+
+private val LightTracks = mapOf(
+    Track.TRADE to Color(0xFFF2C300),
+    Track.POLITICS to Color(0xFF1E6FD9),
+    Track.SCIENCE to Color(0xFF2E9E4F),
+)
+
+/** The light palette, which is also the reference for the dark one. */
+private val LightStyle = CatanStyle(
+    sea = Color(0xFF3A7CA5),
+    terrain = mapOf(
+        Terrain.FOREST to Color(0xFF2F6B3A),
+        Terrain.PASTURE to Color(0xFF9CCC65),
+        Terrain.FIELDS to Color(0xFFE8C84A),
+        Terrain.HILLS to Color(0xFFB4532F),
+        Terrain.MOUNTAINS to Color(0xFF7C8794),
+        Terrain.DESERT to Color(0xFFE6D3A0),
+        // Seafarers. Sea hexes are drawn as a faint wash over the water; gold is a rich yellow.
+        Terrain.SEA to Color(0xFF3A7CA5),
+        Terrain.GOLD to Color(0xFFF2B01E),
+    ),
+    hexEdge = Color(0x55000000),
+    token = Color(0xFFF7EFD9),
+    tokenInk = Color(0xFF2B2B2B),
+    tokenHotInk = Color(0xFFC62828),
+    robber = Color(0xFF263238),
+    rolled = Color(0xFFFFFFFF),
+    portMarker = Color(0xFFFFF8E1),
+    portInk = Color(0xFF2B2B2B),
+    resource = mapOf(
+        Resource.LUMBER to Color(0xFF2F6B3A),
+        Resource.BRICK to Color(0xFFB4532F),
+        Resource.WOOL to Color(0xFF8BC34A),
+        Resource.GRAIN to Color(0xFFE0B020),
+        Resource.ORE to Color(0xFF6B7684),
+    ),
+    resourceInk = Color(0xFFFFFFFF),
+    seats = listOf(
+        Color(0xFF1565C0), // blue
+        Color(0xFFEF6C00), // orange
+        Color(0xFFF5F5F5), // white
+        Color(0xFF8E24AA), // purple
+    ),
+    pieceOutline = Color(0xFF1B1B1B),
+    target = Color(0xFFFFEB3B),
+    targetSelected = Color(0xFF00E5FF),
+)
+
+/** Deeper sea and slightly dimmer land so the board is not a glare at night. */
+private val DarkStyle = LightStyle.copy(
+    sea = Color(0xFF14354D),
+    terrain = LightStyle.terrain.mapValues { (_, c) -> c.dim(0.82f) },
+    token = Color(0xFFE9DFC4),
+)
+
+/** The style for the current light / dark setting. */
+fun catanStyle(dark: Boolean): CatanStyle = if (dark) DarkStyle else LightStyle
+
+/**
+ * What the Katan composables read their look from. Defaults to the light style
+ * so a preview or a test with no provider still draws something sensible;
+ * [CatanScreen] provides the right one for the current theme.
+ */
+val LocalCatanStyle = staticCompositionLocalOf { LightStyle }
+
+private fun Color.dim(factor: Float): Color =
+    Color(red * factor, green * factor, blue * factor, alpha)

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanText.kt

@@ -0,0 +1,521 @@
+package org.prolibertate.games.ui.game.catan
+
+import org.prolibertate.games.game.catan.AqueductChore
+import org.prolibertate.games.game.catan.CatanCk
+import org.prolibertate.games.game.catan.CatanPhase
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.DevCardType
+import org.prolibertate.games.game.catan.DiscardChore
+import org.prolibertate.games.game.catan.DropProgressChore
+import org.prolibertate.games.game.catan.EventFace
+import org.prolibertate.games.game.catan.GiveChore
+import org.prolibertate.games.game.catan.Good
+import org.prolibertate.games.game.catan.MetropolisChore
+import org.prolibertate.games.game.catan.PickDeckChore
+import org.prolibertate.games.game.catan.PillageChore
+import org.prolibertate.games.game.catan.PlaceKnightChore
+import org.prolibertate.games.game.catan.Port
+import org.prolibertate.games.game.catan.ProgressType
+import org.prolibertate.games.game.catan.RelocateChore
+import org.prolibertate.games.game.catan.RemoveKnightChore
+import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.SmithChore
+import org.prolibertate.games.game.catan.SpyChore
+import org.prolibertate.games.game.catan.Terrain
+import org.prolibertate.games.game.catan.Track
+
+/**
+ * Who is who at the table, for wording. [names] may be empty or short — a
+ * client device does not always know everyone's name — and the rest fall back
+ * to "Seat N".
+ */
+class CatanSeats(val me: Int, private val names: List<String> = emptyList()) {
+    fun label(seat: Int): String = when {
+        seat == me -> "You"
+        else -> names.getOrNull(seat)?.takeIf { it.isNotBlank() } ?: "Seat ${seat + 1}"
+    }
+
+    /** For mid-sentence use: "you" rather than "You". */
+    fun lower(seat: Int): String = if (seat == me) "you" else label(seat)
+}
+
+/**
+ * Every word the Katan screen shows, in one place.
+ *
+ * **To change copy, or to localise, edit this file.** The composables never
+ * build a sentence themselves; they ask for it here. Keeping the sentences as
+ * plain functions of state also means they are unit-tested (`CatanTextTest`)
+ * without a device.
+ *
+ * "Katan" is this app's name for the game (see `docs/RULES-catan.md`); the
+ * resources are lumber, brick, wool, grain and ore.
+ */
+object CatanText {
+
+    const val TITLE = "Katan"
+
+    // --- Names ---------------------------------------------------------------
+
+    fun resource(resource: Resource): String = when (resource) {
+        Resource.LUMBER -> "Lumber"
+        Resource.BRICK -> "Brick"
+        Resource.WOOL -> "Wool"
+        Resource.GRAIN -> "Grain"
+        Resource.ORE -> "Ore"
+    }
+
+    fun terrain(terrain: Terrain): String = when (terrain) {
+        Terrain.FOREST -> "Forest"
+        Terrain.PASTURE -> "Pasture"
+        Terrain.FIELDS -> "Fields"
+        Terrain.HILLS -> "Hills"
+        Terrain.MOUNTAINS -> "Mountains"
+        Terrain.DESERT -> "Desert"
+        Terrain.SEA -> "Sea"
+        Terrain.GOLD -> "Gold field"
+    }
+
+    fun devCard(type: DevCardType): String = when (type) {
+        DevCardType.KNIGHT -> "Knight"
+        DevCardType.ROAD_BUILDING -> "Road building"
+        DevCardType.MONOPOLY -> "Monopoly"
+        DevCardType.YEAR_OF_PLENTY -> "Year of plenty"
+        DevCardType.VICTORY_POINT -> "Victory point"
+    }
+
+    fun devCardHelp(type: DevCardType): String = when (type) {
+        DevCardType.KNIGHT -> "Move the robber and steal a card. Three played knights take Largest Army."
+        DevCardType.ROAD_BUILDING -> "Build two roads for free."
+        DevCardType.MONOPOLY -> "Name a resource and take every card of it from the other players."
+        DevCardType.YEAR_OF_PLENTY -> "Take any two resource cards from the bank."
+        DevCardType.VICTORY_POINT -> "One victory point. Kept hidden until you win."
+    }
+
+    /** "3:1" for a generic harbour, "2:1" for a resource one. */
+    fun portRatio(port: Port): String = "${port.ratio}:1"
+
+    fun portName(port: Port): String =
+        port.resource?.let { "${portRatio(port)} ${resource(it).lowercase()}" } ?: "3:1 any"
+
+    // --- Costs ---------------------------------------------------------------
+
+    fun cost(cost: Map<Resource, Int>): String =
+        cost.entries.joinToString(" + ") { (r, n) -> "$n ${resource(r).lowercase()}" }
+
+    val ROAD_COST: String get() = cost(CatanRules.ROAD_COST)
+    val SETTLEMENT_COST: String get() = cost(CatanRules.SETTLEMENT_COST)
+    val CITY_COST: String get() = cost(CatanRules.CITY_COST)
+    val DEV_COST: String get() = cost(CatanRules.DEV_COST)
+
+    // --- Buttons and headings --------------------------------------------------
+
+    const val SEA_ROBBER = "Move the robber (tap a land hex) or the pirate (tap a sea hex)."
+    const val SHIP = "Ship"
+    const val SHIP_COST_TEXT = "1 lumber + 1 wool"
+    const val GOLD_TITLE = "Gold field"
+    const val GOLD_TAKE = "Take"
+    const val ROLL = "Roll dice"
+    const val END_TURN = "End turn"
+    const val ROAD = "Road"
+    const val SETTLEMENT = "Settlement"
+    const val CITY = "City"
+    const val BUY_CARD = "Buy card"
+    const val PLAY_CARD = "Play card"
+    const val TRADE = "Trade"
+    const val CANCEL = "Cancel"
+    const val CONFIRM = "Confirm"
+    const val STOP_ROADS = "Done with roads"
+    const val BUILD = "Build"
+    const val COUNTER = "Counter…"
+    const val SEND_COUNTER = "Send counter"
+    const val EVERYONE = "Everyone"
+    const val NO_DEAL = "No deal"
+
+    /**
+     * The empty second line of a button that has no cost, so every button in the
+     * action bar is the same height. A non-breaking space: blank, but a line.
+     */
+    const val NO_COST = "\u00A0"
+    const val YOUR_HAND = "Your hand"
+    const val CARDS = "cards"
+    const val ACCEPT = "Accept"
+    const val DECLINE = "Decline"
+    const val TRADE_WITH_PLAYER = "Offer to a player"
+    const val TRADE_WITH_BANK = "Trade with the bank"
+    const val YOU_GIVE = "You give"
+    const val YOU_GET = "You get"
+    const val SEND_OFFER = "Send offer"
+
+    // --- Trade board and HUD -----------------------------------------------------
+    const val TAB_PLAYER = "Player"
+    const val TAB_BANK = "Bank"
+    const val YOU_RECEIVE_ROW = "You get"
+    const val YOU_GIVE_ROW = "You give"
+    const val TRADE_HINT_PLAYER = "Tap cards to build an offer. Tap a player to address it to them alone."
+    const val TRADE_HINT_BANK = "Tap what you give, then what you want."
+    const val TRADE_HINT_BANK_EMPTY = "You do not hold enough of any one resource to trade with the bank."
+    const val TRADE_HINT_COUNTER = "Change the terms, then send them back."
+    const val HIDE = "Hide"
+    const val DENY = "Deny"
+    const val CONFIRM_BUILD = "Place"
+    const val CANCEL_BUILD = "Cancel"
+    const val DRAG_HINT = "Drag a piece onto the board"
+    const val LOG_BUTTON = "Log"
+    const val CARDS_SHORT = "Cards"
+    const val BUY_SHORT = "Buy"
+    const val ROLL_SHORT = "Roll"
+    const val END_SHORT = "End"
+    const val DONE_SHORT = "Done"
+    const val LOG_TITLE = "Table log"
+    const val NO_LOG = "Nothing has happened yet."
+    const val END_GAME = "End game"
+    const val LOOK_AT_BOARD = "Look at the board"
+    const val LEAVE_GAME = "Leave the game"
+
+    // --- The prompt line ------------------------------------------------------
+
+    /**
+     * The one line that tells the player what is going on and what to do.
+     *
+     * [setupVertexChosen] is the setup settlement already picked and waiting
+     * for its road; [building] is the build mode the player has entered, if any.
+     */
+    fun prompt(
+        state: CatanState,
+        seats: CatanSeats,
+        setupVertexChosen: Boolean,
+        building: BuildKind?,
+        /** Cities & Knights: a knight has been picked to move, and its destination is awaited. */
+        movingKnight: Boolean = false,
+        /** Cities & Knights: a progress card is waiting for a tap on the board. */
+        armed: ProgressType? = null,
+        /** Seafarers: a ship has been picked to sail, and its destination is awaited. */
+        movingShip: Boolean = false,
+    ): String {
+        if (state.isCk) return ckPrompt(state, seats, setupVertexChosen, building, movingKnight, armed)
+        val me = seats.me
+        val onClock = CatanRules.currentSeat(state)
+        val mine = onClock == me
+        val turn = seats.label(state.turn)
+
+        return when (state.phase) {
+            CatanPhase.GAME_OVER -> {
+                val winner = state.winner
+                if (winner == null) "The game is over." else "${seats.label(winner)} won the game."
+            }
+
+            CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND -> when {
+                !mine -> "${seats.label(onClock ?: state.turn)} is placing a settlement and a road…"
+                setupVertexChosen -> "Now tap the road to place beside that settlement."
+                state.phase == CatanPhase.SETUP_SECOND ->
+                    "Place your second settlement. It earns resources from the hexes around it."
+
+                else -> "Place a settlement, then a road."
+            }
+
+            CatanPhase.AWAIT_ROLL ->
+                if (mine) "Your turn. Roll the dice." else "$turn is rolling…"
+
+            CatanPhase.DISCARDING -> {
+                val discarder = state.discardSeat
+                when {
+                    discarder == me -> "A seven! You hold ${state.resourceCount(me)} cards; " +
+                        "discard ${state.resourceCount(me) / 2}."
+
+                    discarder != null -> "A seven! ${seats.label(discarder)} must discard half."
+                    else -> "A seven! Discarding…"
+                }
+            }
+
+            CatanPhase.ROBBER ->
+                if (mine) {
+                    if (state.isSea) SEA_ROBBER else "Move the robber. Tap a hex."
+                } else {
+                    "$turn is moving the robber…"
+                }
+
+            CatanPhase.GOLD ->
+                if (mine) {
+                    "Gold! Choose ${state.sea?.gold?.firstOrNull()?.count ?: 1} resource cards."
+                } else {
+                    "${seats.label(onClock ?: state.turn)} is choosing from the gold…"
+                }
+
+            CatanPhase.PLAYING -> when {
+                !mine -> "$turn is playing…"
+                movingShip -> "Tap the sea edge to sail the ship to."
+                building == BuildKind.SHIP -> "Tap a sea edge beside your fleet or a harbour town to launch a ship."
+                building == BuildKind.ROAD -> "Tap an edge to build a road."
+                building == BuildKind.SETTLEMENT -> "Tap an empty crossing to build a settlement."
+                building == BuildKind.CITY -> "Tap one of your settlements to upgrade it."
+                else -> "Your turn. Build, trade, or end the turn."
+            }
+
+            CatanPhase.FREE_ROADS ->
+                if (mine) {
+                    "Road building: place ${state.pendingFreeRoads} more " +
+                        if (state.pendingFreeRoads == 1) "road." else "roads."
+                } else {
+                    "$turn is placing free roads…"
+                }
+
+            CatanPhase.CHORE -> "Waiting for ${seats.label(onClock ?: state.turn)}…"
+
+            CatanPhase.TRADE_PENDING -> {
+                val offer = state.pendingTrade
+                when {
+                    offer == null -> "Waiting for a reply…"
+                    offer.asking == me -> if (offer.to == null) {
+                        "${seats.label(offer.by)} offers the table a trade. Accept, decline or counter."
+                    } else {
+                        "${seats.label(offer.by)} offers you a trade. Accept, decline or counter."
+                    }
+
+                    offer.by == me -> "Waiting for ${seats.label(offer.asking)} to answer your offer…"
+                    else -> "${seats.label(offer.by)}'s offer is with ${seats.label(offer.asking)}."
+                }
+            }
+
+            CatanPhase.TRADE_COUNTERS ->
+                if (mine) {
+                    "Nobody accepted, but there are counter-offers. Take one or turn them down."
+                } else {
+                    "$turn is weighing counter-offers…"
+                }
+        }
+    }
+
+    /** "3 Lumber + 1 Brick" for a flat list of cards. */
+    fun cards(cards: List<Resource>): String =
+        cards.groupingBy { it }.eachCount().entries
+            .sortedBy { it.key.ordinal }
+            .joinToString(" + ") { (r, n) -> "$n ${resource(r)}" }
+            .ifEmpty { "nothing" }
+
+    fun tradeSummary(by: String, to: String, give: List<Resource>, get: List<Resource>): String =
+        "$by offers ${cards(give)} to $to for ${cards(get)}"
+
+    /** One counter-offer as the offerer sees it: what that seat gives and wants. */
+    fun counterSummary(by: String, give: List<Resource>, get: List<Resource>): String =
+        "$by gives ${cards(give)} for your ${cards(get)}"
+
+    fun winnerHeadline(state: CatanState, seats: CatanSeats): String {
+        val winner = state.winner ?: return "Game over"
+        return if (winner == seats.me) "You won!" else "${seats.label(winner)} won"
+    }
+
+    // --- Cities & Knights ----------------------------------------------------
+
+    fun good(good: Good): String = when (good) {
+        Good.LUMBER -> "Lumber"
+        Good.BRICK -> "Brick"
+        Good.WOOL -> "Wool"
+        Good.GRAIN -> "Grain"
+        Good.ORE -> "Ore"
+        Good.CLOTH -> "Cloth"
+        Good.COIN -> "Coin"
+        Good.PAPER -> "Paper"
+    }
+
+    /** "2 Lumber + 1 Cloth" for a flat list of goods. */
+    fun goods(cards: List<Good>): String =
+        cards.groupingBy { it }.eachCount().entries
+            .sortedBy { it.key.ordinal }
+            .joinToString(" + ") { (g, n) -> "$n ${good(g)}" }
+            .ifEmpty { "nothing" }
+
+    fun track(track: Track): String = when (track) {
+        Track.TRADE -> "Trade"
+        Track.POLITICS -> "Politics"
+        Track.SCIENCE -> "Science"
+    }
+
+    /** What the third level of a track gives, for the improvement dialog. */
+    fun trackPower(track: Track): String = when (track) {
+        Track.TRADE -> "From level 3, trade commodities with the bank two for one."
+        Track.POLITICS -> "From level 3, knights can be promoted to mighty."
+        Track.SCIENCE -> "From level 3, when the dice pay you nothing, take any resource."
+    }
+
+    fun knightName(level: Int): String = when (level) {
+        1 -> "Basic knight"
+        2 -> "Strong knight"
+        else -> "Mighty knight"
+    }
+
+    fun event(face: EventFace?): String = when (face) {
+        null -> "–"
+        EventFace.SHIP -> "Ship"
+        EventFace.TRADE -> "Trade"
+        EventFace.POLITICS -> "Politics"
+        EventFace.SCIENCE -> "Science"
+    }
+
+    fun progress(kind: ProgressType): String = CatanCk.progressName(kind)
+
+    fun progressHelp(kind: ProgressType): String = when (kind) {
+        ProgressType.ALCHEMIST -> "Before rolling, choose what the two number dice show."
+        ProgressType.CRANE -> "Your next city improvement costs one commodity less."
+        ProgressType.ENGINEER -> "Raise a wall round one of your cities for free."
+        ProgressType.INVENTOR -> "Swap two number tokens (not 2, 6, 8 or 12)."
+        ProgressType.IRRIGATION -> "Take 2 grain for each fields hex beside your settlements and cities."
+        ProgressType.MEDICINE -> "Upgrade a settlement to a city for 2 ore and 1 grain."
+        ProgressType.MINING -> "Take 2 ore for each mountains hex beside your settlements and cities."
+        ProgressType.PRINTER -> "One victory point."
+        ProgressType.ROAD_BUILDING -> "Build two roads for free."
+        ProgressType.SMITH -> "Promote up to two of your knights one level for free."
+        ProgressType.BISHOP -> "Move the robber and take a card from every player beside its new hex."
+        ProgressType.CONSTITUTION -> "One victory point."
+        ProgressType.DESERTER -> "Another player removes a knight; you place a free one of the same strength."
+        ProgressType.DIPLOMAT -> "Remove an open road. If it was yours, build it again anywhere for free."
+        ProgressType.INTRIGUE -> "Drive an opponent's knight off a crossing beside one of your roads."
+        ProgressType.SABOTEUR -> "Every player with as many points as you or more discards half their cards."
+        ProgressType.SPY -> "Look at another player's progress cards and take one."
+        ProgressType.WARLORD -> "Wake all your knights without paying grain."
+        ProgressType.WEDDING -> "Every player with more points gives you 2 cards."
+        ProgressType.COMMERCIAL_HARBOR -> "Offer a resource to each player; each swaps it for a commodity."
+        ProgressType.MASTER_MERCHANT -> "Take 2 cards from a player with more points."
+        ProgressType.MERCHANT -> "Put the merchant beside your settlement: trade that resource 2:1 and score a point."
+        ProgressType.MERCHANT_FLEET -> "This turn, trade one chosen card type with the bank two for one."
+        ProgressType.RESOURCE_MONOPOLY -> "Name a resource. Every other player gives you 2 of it."
+        ProgressType.TRADE_MONOPOLY -> "Name a commodity. Every other player gives you 1 of it."
+    }
+
+    const val IMPROVE = "Improve"
+    const val KNIGHTS = "Knights"
+    const val CARDS_BUTTON = "Progress"
+    const val WALL = "Wall"
+    const val KNIGHT = "Knight"
+    const val STOP_SMITH = "Done promoting"
+
+    val KNIGHT_COST: String get() = cost(CatanCk.KNIGHT_COST)
+    val ACTIVATE_COST: String get() = cost(CatanCk.ACTIVATE_COST)
+    val WALL_COST: String get() = cost(CatanCk.WALL_COST)
+
+    private fun ckPrompt(
+        state: CatanState,
+        seats: CatanSeats,
+        setupVertexChosen: Boolean,
+        building: BuildKind?,
+        movingKnight: Boolean,
+        armed: ProgressType?,
+    ): String {
+        val me = seats.me
+        val onClock = CatanRules.currentSeat(state)
+        val mine = onClock == me
+        val turn = seats.label(state.turn)
+        val ck = state.ck!!
+
+        return when (state.phase) {
+            CatanPhase.GOLD -> ""
+
+            CatanPhase.GAME_OVER -> {
+                val winner = state.winner
+                if (winner == null) "The game is over." else "${seats.label(winner)} won the game."
+            }
+
+            CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND -> when {
+                !mine -> "${seats.label(onClock ?: state.turn)} is placing a settlement and a road…"
+                setupVertexChosen -> "Now tap the road to place beside that settlement."
+                state.phase == CatanPhase.SETUP_SECOND ->
+                    "Place your second piece: it is a city, and earns resources from the hexes around it."
+
+                else -> "Place a settlement, then a road."
+            }
+
+            CatanPhase.AWAIT_ROLL -> when {
+                !mine -> "$turn is rolling…"
+                armed != null -> armedPrompt(armed)
+                movingKnight -> "Tap where the knight should go."
+                else -> "Your turn. Roll the dice, or wake knights and play progress cards first."
+            }
+
+            CatanPhase.ROBBER -> when {
+                !mine -> "$turn is moving the robber…"
+                ck.bishop -> "The bishop: tap a hex. Everyone beside it pays you a card."
+                else -> "Move the robber. Tap a hex."
+            }
+
+            CatanPhase.PLAYING -> when {
+                !mine -> "$turn is playing…"
+                armed != null -> armedPrompt(armed)
+                movingKnight -> "Tap where the knight should go."
+                building == BuildKind.ROAD -> "Tap an edge to build a road."
+                building == BuildKind.SETTLEMENT -> "Tap an empty crossing to build a settlement."
+                building == BuildKind.CITY -> "Tap one of your settlements to upgrade it."
+                building == BuildKind.WALL -> "Tap one of your cities to raise a wall."
+                building == BuildKind.KNIGHT -> "Tap an empty crossing at the end of your road to hire a knight."
+                else -> "Your turn. Build, improve, trade, or end the turn. Tap a knight to use it."
+            }
+
+            CatanPhase.FREE_ROADS ->
+                if (mine) {
+                    "Place ${state.pendingFreeRoads} free " +
+                        if (state.pendingFreeRoads == 1) "road." else "roads."
+                } else {
+                    "$turn is placing free roads…"
+                }
+
+            CatanPhase.TRADE_PENDING -> {
+                val offer = ck.goodsOffer
+                val asking = offer?.asking?.takeIf { it >= 0 }
+                when {
+                    offer == null || asking == null -> "Waiting for a reply…"
+                    asking == me -> "${seats.label(offer.by)} offers you a trade."
+                    offer.by == me -> "Waiting for ${seats.label(asking)} to answer your offer…"
+                    else -> "${seats.label(offer.by)} has offered ${seats.label(asking)} a trade."
+                }
+            }
+
+            CatanPhase.TRADE_COUNTERS ->
+                if (mine) {
+                    "Nobody accepted, but there are counter-offers. Take one or turn them down."
+                } else {
+                    "$turn is weighing counter-offers…"
+                }
+
+            CatanPhase.DISCARDING -> "Discarding…"
+
+            CatanPhase.CHORE -> {
+                val chore = ck.chores.firstOrNull()
+                val who = seats.label(chore?.seat ?: state.turn)
+                if (chore == null || chore.seat != me) {
+                    when (chore) {
+                        is PillageChore -> "The barbarians have landed. $who must give up a city."
+                        is DiscardChore -> "$who must discard ${chore.count} cards."
+                        else -> "Waiting for $who…"
+                    }
+                } else {
+                    when (chore) {
+                        is DiscardChore -> "Discard ${chore.count} cards."
+                        is GiveChore -> "Give ${chore.count} card${if (chore.count == 1) "" else "s"} to ${seats.lower(chore.to)}."
+                        is PillageChore -> "The barbarians won. Tap a city of yours to give up."
+                        is PickDeckChore -> "Choose a progress deck to draw from."
+                        is DropProgressChore -> "You hold too many progress cards. Give one back."
+                        is MetropolisChore -> "Tap the city that will bear the ${track(chore.track).lowercase()} metropolis."
+                        is AqueductChore -> "Your aqueduct pays. Take any resource."
+                        is RelocateChore -> "Your knight was driven off. Tap where it goes."
+                        is RemoveKnightChore -> "Tap one of your knights to remove."
+                        is PlaceKnightChore -> "Tap where your free ${knightName(chore.level).lowercase()} stands."
+                        is SpyChore -> "Choose a progress card to take."
+                        is SmithChore -> "Tap a knight to promote (${chore.left} left), or stop."
+                    }
+                }
+            }
+        }
+    }
+
+    private fun armedPrompt(kind: ProgressType): String = when (kind) {
+        ProgressType.ENGINEER -> "Engineer: tap a city to wall."
+        ProgressType.MEDICINE -> "Medicine: tap a settlement to upgrade."
+        ProgressType.MERCHANT -> "Merchant: tap a hex beside one of your buildings."
+        ProgressType.DIPLOMAT -> "Diplomat: tap an open road to remove."
+        ProgressType.INTRIGUE -> "Intrigue: tap an enemy knight beside your road."
+        ProgressType.INVENTOR -> "Inventor: tap two hexes to swap their tokens."
+        else -> "Tap the board."
+    }
+
+    /** "6 steps away", "1 step away" for the barbarian ship. */
+    fun barbarianSteps(steps: Int): String = "$steps ${if (steps == 1) "step" else "steps"} away"
+}

app/src/main/java/org/prolibertate/games/ui/game/catan/CatanTradeBoard.kt

@@ -0,0 +1,415 @@
+package org.prolibertate.games.ui.game.catan
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.border
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.horizontalScroll
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.heightIn
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.alpha
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import org.prolibertate.games.game.catan.CatanMove
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.CounterTrade
+import org.prolibertate.games.game.catan.MaritimeTrade
+import org.prolibertate.games.game.catan.OfferTrade
+import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.TradeOffer
+
+/*
+ * The trade board: the 2D version of Catan Universe's trade panel (see
+ * docs/RE-catan-universe.md). One panel slides up over the bottom of the board:
+ *
+ *   header   [Player | Bank]   hint                          rival buttons
+ *   top row    the cards you GET, tinted with the other side's colour
+ *   arrows
+ *   bottom row the cards you GIVE, tinted with your colour
+ *   right      ▾ hide     ✕ deny     ✓ accept
+ *
+ * Like every Katan panel it decides nothing: what may be offered is asked of
+ * [CatanInteraction], and what a bank trade costs comes from the engine's legal list.
+ */
+
+private enum class TradeMode { PLAYER, BANK }
+
+private fun Map<Resource, Int>.cards(): List<Resource> =
+    Resource.entries.flatMap { r -> List(this[r] ?: 0) { r } }
+
+/** The panel for starting a trade: with the bank, or an offer to one rival or everyone. */
+@Composable
+fun CatanTradeBoard(
+    state: CatanState,
+    seat: Int,
+    seats: CatanSeats,
+    legal: List<CatanMove>,
+    onBank: (MaritimeTrade) -> Unit,
+    onOffer: (OfferTrade) -> Unit,
+    onClose: () -> Unit,
+    modifier: Modifier = Modifier,
+    style: CatanStyle = LocalCatanStyle.current,
+) {
+    var mode by remember { mutableStateOf(TradeMode.BANK) }
+    var to by remember { mutableStateOf<Int?>(null) }
+    var give by remember { mutableStateOf(emptyMap<Resource, Int>()) }
+    var get by remember { mutableStateOf(emptyMap<Resource, Int>()) }
+    var bankGive by remember { mutableStateOf<Resource?>(null) }
+    var bankGet by remember { mutableStateOf<Resource?>(null) }
+
+    val bank = CatanInteraction.bankTrades(legal)
+    val giveCards = give.cards()
+    val getCards = get.cards()
+    val canSend = CatanInteraction.offerAllowed(state, seat, to, giveCards, getCards)
+    val bankMove = bankGive?.let { g -> bankGet?.takeIf { it in bank[g].orEmpty() }?.let { MaritimeTrade(g, it) } }
+
+    val rivals = (0 until state.playerCount).filter { it != seat }
+    val headerRight: @Composable () -> Unit = {
+        if (mode == TradeMode.PLAYER) {
+            RivalButtons(rivals, to, style, seats) { to = if (to == it) null else it }
+        }
+    }
+
+    TradeBoardFrame(
+        modifier = modifier,
+        topTint = if (mode == TradeMode.PLAYER && to != null) style.seats[to!!] else Color.Gray,
+        bottomTint = style.seats[seat],
+        header = {
+            TradeTab(CatanText.TAB_BANK, mode == TradeMode.BANK) { mode = TradeMode.BANK }
+            TradeTab(CatanText.TAB_PLAYER, mode == TradeMode.PLAYER) { mode = TradeMode.PLAYER }
+        },
+        headline = when {
+            mode == TradeMode.PLAYER -> CatanText.TRADE_HINT_PLAYER
+            bank.isEmpty() -> CatanText.TRADE_HINT_BANK_EMPTY
+            else -> CatanText.TRADE_HINT_BANK
+        },
+        headerRight = headerRight,
+        topLabel = CatanText.YOU_RECEIVE_ROW,
+        bottomLabel = CatanText.YOU_GIVE_ROW,
+        topRow = {
+            if (mode == TradeMode.PLAYER) {
+                TradeCardRow(
+                    counts = get,
+                    limit = { 9 },
+                    onChange = { get = it },
+                )
+            } else {
+                val choices = bankGive?.let { bank[it] }.orEmpty().toSet()
+                TradeCardRow(
+                    counts = bankGet?.let { mapOf(it to 1) } ?: emptyMap(),
+                    limit = { if (it in choices) 1 else 0 },
+                    enabledOf = { it in choices },
+                    onChange = {},
+                    pick = { bankGet = if (bankGet == it) null else it },
+                )
+            }
+        },
+        bottomRow = {
+            if (mode == TradeMode.PLAYER) {
+                TradeCardRow(
+                    counts = give,
+                    limit = { state.resources[seat][it] ?: 0 },
+                    onChange = { give = it },
+                )
+            } else {
+                TradeCardRow(
+                    counts = bank.keys.associateWith { CatanInteraction.bankRatio(state, seat, it) },
+                    limit = { 0 },
+                    enabledOf = { it in bank },
+                    selected = bankGive,
+                    caption = { r -> if (r in bank) "${CatanInteraction.bankRatio(state, seat, r)} : 1" else " " },
+                    onChange = {},
+                    pick = { r ->
+                        bankGive = if (bankGive == r) null else r
+                        bankGet = null
+                    },
+                )
+            }
+        },
+        acceptEnabled = if (mode == TradeMode.PLAYER) canSend else bankMove != null,
+        onAccept = {
+            if (mode == TradeMode.PLAYER) {
+                onOffer(OfferTrade(to, giveCards, getCards))
+            } else {
+                bankMove?.let(onBank)
+            }
+        },
+        denyEnabled = true,
+        onDeny = {
+            give = emptyMap()
+            get = emptyMap()
+            bankGive = null
+            bankGet = null
+            to = null
+        },
+        onHide = onClose,
+    )
+}
+
+/**
+ * The panel for an offer made to the local player: the same layout, read-only. ✓ accepts,
+ * ✕ declines, and *Counter…* turns the rows editable, pre-filled with the mirror of the offer.
+ */
+@Composable
+fun CatanTradeReplyBoard(
+    state: CatanState,
+    seat: Int,
+    offer: TradeOffer,
+    seats: CatanSeats,
+    canAccept: Boolean,
+    onAccept: () -> Unit,
+    onDecline: () -> Unit,
+    onCounter: (CounterTrade) -> Unit,
+    modifier: Modifier = Modifier,
+    style: CatanStyle = LocalCatanStyle.current,
+) {
+    var countering by remember(offer) { mutableStateOf(false) }
+    var give by remember(offer) { mutableStateOf(offer.get.groupingBy { it }.eachCount()) }
+    var get by remember(offer) { mutableStateOf(offer.give.groupingBy { it }.eachCount()) }
+    val counter = CounterTrade(give.cards(), get.cards())
+
+    TradeBoardFrame(
+        modifier = modifier,
+        topTint = style.seats[offer.by],
+        bottomTint = style.seats[seat],
+        header = {
+            TradeTab(CatanText.COUNTER, countering) { countering = !countering }
+        },
+        headline = if (countering) {
+            CatanText.TRADE_HINT_COUNTER
+        } else {
+            CatanText.tradeSummary(
+                by = seats.label(offer.by),
+                to = if (offer.to == null) "the table" else "you",
+                give = offer.give,
+                get = offer.get,
+            )
+        },
+        headerRight = {},
+        topLabel = CatanText.YOU_RECEIVE_ROW,
+        bottomLabel = CatanText.YOU_GIVE_ROW,
+        topRow = {
+            if (countering) {
+                TradeCardRow(get, limit = { state.resources[offer.by][it] ?: 0 }, onChange = { get = it })
+            } else {
+                TradeCardRow(offer.give.groupingBy { it }.eachCount(), limit = { 0 }, onChange = {})
+            }
+        },
+        bottomRow = {
+            if (countering) {
+                TradeCardRow(give, limit = { state.resources[seat][it] ?: 0 }, onChange = { give = it })
+            } else {
+                TradeCardRow(offer.get.groupingBy { it }.eachCount(), limit = { 0 }, onChange = {})
+            }
+        },
+        acceptEnabled = if (countering) {
+            CatanInteraction.counterAllowed(state, seat, counter.give, counter.get)
+        } else {
+            canAccept
+        },
+        onAccept = { if (countering) onCounter(counter) else onAccept() },
+        denyEnabled = true,
+        onDeny = onDecline,
+        onHide = null,
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Pieces
+// ---------------------------------------------------------------------------
+
+@Composable
+private fun TradeBoardFrame(
+    topTint: Color,
+    bottomTint: Color,
+    header: @Composable () -> Unit,
+    headline: String,
+    headerRight: @Composable () -> Unit,
+    topLabel: String,
+    bottomLabel: String,
+    topRow: @Composable () -> Unit,
+    bottomRow: @Composable () -> Unit,
+    acceptEnabled: Boolean,
+    onAccept: () -> Unit,
+    denyEnabled: Boolean,
+    onDeny: () -> Unit,
+    onHide: (() -> Unit)?,
+    modifier: Modifier = Modifier,
+) {
+    Surface(
+        modifier = modifier.fillMaxWidth(),
+        shape = RoundedCornerShape(topStart = 18.dp, topEnd = 18.dp),
+        color = MaterialTheme.colorScheme.surface.copy(alpha = 0.97f),
+        tonalElevation = 6.dp,
+        shadowElevation = 12.dp,
+    ) {
+        Row(Modifier.padding(horizontal = 12.dp, vertical = 8.dp)) {
+            Column(Modifier.weight(1f), verticalArrangement = Arrangement.spacedBy(6.dp)) {
+                Row(verticalAlignment = Alignment.CenterVertically, horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                    header()
+                    Text(
+                        headline,
+                        style = MaterialTheme.typography.bodySmall,
+                        // Two lines, always: the panel keeps its height whatever is said.
+                        minLines = 2,
+                        maxLines = 2,
+                        modifier = Modifier.weight(1f),
+                    )
+                    headerRight()
+                }
+                HorizontalDivider()
+                TintedRow(topTint, topLabel, topRow)
+                Text("⇣   ⇣   ⇣", modifier = Modifier.align(Alignment.CenterHorizontally), fontSize = 14.sp)
+                TintedRow(bottomTint, bottomLabel, bottomRow)
+            }
+            Column(
+                modifier = Modifier.padding(start = 10.dp).width(72.dp),
+                verticalArrangement = Arrangement.spacedBy(6.dp, Alignment.CenterVertically),
+                horizontalAlignment = Alignment.CenterHorizontally,
+            ) {
+                // Always three slots, so the column does not shift when there is nothing to hide.
+                if (onHide != null) {
+                    HudRoundButton("▾", caption = CatanText.HIDE, diameter = 48.dp, onClick = onHide)
+                } else {
+                    Box(Modifier.size(48.dp))
+                }
+                HudRoundButton("✕", caption = CatanText.DENY, enabled = denyEnabled, tint = Color(0xFFC62828), diameter = 52.dp, onClick = onDeny)
+                HudRoundButton("✓", caption = CatanText.ACCEPT, enabled = acceptEnabled, tint = Color(0xFF2E7D32), diameter = 60.dp, onClick = onAccept)
+            }
+        }
+    }
+}
+
+@Composable
+private fun TintedRow(tint: Color, label: String, content: @Composable () -> Unit) {
+    val shape = RoundedCornerShape(12.dp)
+    Column(
+        Modifier
+            .fillMaxWidth()
+            .clip(shape)
+            .background(tint.copy(alpha = 0.18f))
+            .border(1.dp, tint.copy(alpha = 0.5f), shape)
+            .padding(horizontal = 8.dp, vertical = 4.dp),
+    ) {
+        Text(label, fontSize = 10.sp, fontWeight = FontWeight.Bold)
+        Box(Modifier.horizontalScroll(rememberScrollState())) { content() }
+    }
+}
+
+/**
+ * Five resource cards in a row. Tapping a card adds one (up to [limit]); the "−" under it
+ * takes one back. A bank row passes [pick] instead, and a tap selects the card.
+ */
+@Composable
+private fun TradeCardRow(
+    counts: Map<Resource, Int>,
+    limit: (Resource) -> Int,
+    onChange: (Map<Resource, Int>) -> Unit,
+    enabledOf: (Resource) -> Boolean = { true },
+    selected: Resource? = null,
+    caption: ((Resource) -> String)? = null,
+    pick: ((Resource) -> Unit)? = null,
+) {
+    Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+        Resource.entries.forEach { resource ->
+            val n = counts[resource] ?: 0
+            Column(horizontalAlignment = Alignment.CenterHorizontally) {
+                ResourceTile(
+                    resource = resource,
+                    count = n,
+                    selected = selected == resource,
+                    enabled = enabledOf(resource) && (pick != null || n > 0 || limit(resource) > 0),
+                    onClick = {
+                        if (pick != null) {
+                            pick(resource)
+                        } else if (n < limit(resource)) {
+                            onChange(counts + (resource to n + 1))
+                        }
+                    },
+                )
+                if (caption != null) {
+                    Text(caption(resource), fontSize = 11.sp, fontWeight = FontWeight.Bold)
+                } else {
+                    // Always laid out so the row never changes height.
+                    Text(
+                        "−",
+                        fontSize = 20.sp,
+                        fontWeight = FontWeight.Bold,
+                        modifier = Modifier
+                            .alpha(if (n > 0 && pick == null && limit(resource) >= 0) 1f else 0f)
+                            .clickable(enabled = n > 0 && pick == null) {
+                                onChange(counts + (resource to n - 1))
+                            }
+                            .padding(horizontal = 14.dp),
+                    )
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun TradeTab(label: String, selected: Boolean, onClick: () -> Unit) {
+    val shape = RoundedCornerShape(50)
+    Text(
+        label,
+        fontSize = 13.sp,
+        fontWeight = FontWeight.Bold,
+        color = if (selected) MaterialTheme.colorScheme.onPrimary else MaterialTheme.colorScheme.onSurface,
+        modifier = Modifier
+            .clip(shape)
+            .background(if (selected) MaterialTheme.colorScheme.primary else MaterialTheme.colorScheme.surfaceVariant)
+            .clickable(onClick = onClick)
+            .padding(horizontal = 14.dp, vertical = 8.dp),
+    )
+}
+
+/** One round button per rival: tap to address the offer to them alone, tap again for everyone. */
+@Composable
+private fun RivalButtons(
+    rivals: List<Int>,
+    chosen: Int?,
+    style: CatanStyle,
+    seats: CatanSeats,
+    onTap: (Int) -> Unit,
+) {
+    Row(horizontalArrangement = Arrangement.spacedBy(6.dp)) {
+        rivals.forEach { rival ->
+            val picked = chosen == rival
+            Box(
+                Modifier
+                    .size(40.dp)
+                    .clip(CircleShape)
+                    .background(style.seats[rival])
+                    .border(if (picked) 4.dp else 1.dp, if (picked) Color.White else Color(0x55000000), CircleShape)
+                    .clickable { onTap(rival) },
+                contentAlignment = Alignment.Center,
+            ) {
+                Text(seats.label(rival).take(1).uppercase(), color = Color.White, fontWeight = FontWeight.Bold, fontSize = 14.sp)
+            }
+        }
+    }
+}

app/src/main/java/org/prolibertate/games/update/UpdatePolicy.kt

@@ -1,19 +1,17 @@
 package org.prolibertate.games.update
 
-import java.net.URI
-
 /**
  * Which line of builds an APK belongs to.
  *
  * This is a property of the build, never a preference. The two channels are
  * published by different workflows and have entirely separate version
- * sequences — a dev build's versionCode is its CI build number, a production
- * build's is its release build number, and the two are unrelated. There is no
+ * sequences — a dev build's versionCode is its CI run number, a production
+ * build's is its release run number, and the two are unrelated. There is no
  * meaning to be had from comparing across them, so nothing does.
  *
  * They also carry different applicationIds — a dev build installs as
- * `…prolibertategames.dev` — so both can sit on one device, each updating
- * itself down its own line and leaving the other alone.
+ * `…games.dev` — so both can sit on one device, each updating itself down its
+ * own line and leaving the other alone.
  */
 enum class UpdateChannel(val label: String, val blurb: String) {
     PRODUCTION("Production", "Stable builds released from main"),
@@ -23,7 +21,7 @@ enum class UpdateChannel(val label: String, val blurb: String) {
 /** Marks a tag or a version name as belonging to the dev channel. */
 const val DEV_SUFFIX = "-dev"
 
-/** One published build, as read off a repository release. */
+/** One published build, as read off a channel's `latest.json`. */
 data class Release(
     val tag: String,
     val versionCode: Int,
@@ -51,14 +49,14 @@ fun channelOfVersionName(versionName: String): UpdateChannel =
  * The channel a release belongs to.
  *
  * Two independent marks, and either is enough: the `-dev` suffix the workflow
- * puts on the tag, and the release's own prerelease flag. A release would have
- * to lose both to be mistaken for the other channel.
+ * puts on the tag, and GitHub's own prerelease flag. A release would have to
+ * lose both to be mistaken for the other channel.
  */
 fun channelOfTag(tag: String, prerelease: Boolean): UpdateChannel =
     if (tag.endsWith(DEV_SUFFIX) || prerelease) UpdateChannel.DEV else UpdateChannel.PRODUCTION
 
 /**
- * The build number out of a `v<series>.<n>` tag, which is what an APK's
+ * The run number out of a `v<series>.<n>` tag, which is what an APK's
  * versionCode is.
  *
  * Only the trailing number is read. The series is a name for people, and
@@ -67,37 +65,15 @@ fun channelOfTag(tag: String, prerelease: Boolean): UpdateChannel =
 fun versionCodeOfTag(tag: String): Int? =
     tag.substringAfterLast('.').removeSuffix(DEV_SUFFIX).toIntOrNull()
 
-/**
- * Rewrites a download URL onto [host], keeping its scheme, path and query.
- *
- * A release server can answer for more than one host name, and it hands out
- * asset URLs on whichever one it treats as canonical — which need not be the
- * one the app was told to talk to. Fetching the release list from one host and
- * the APK from another is a single DNS change away from a channel that half
- * works, so the app stays on the host it decided to trust and takes only the
- * path from what the server reported.
- *
- * Anything that cannot be parsed is returned unchanged: a broken URL fails
- * loudly at download time, while a swallowed one would fail as a silent
- * "something went wrong".
- */
-fun onReportedHost(url: String, host: String): String = try {
-    val reported = URI(url)
-    val scheme = reported.scheme ?: "https"
-    URI(scheme, null, host, -1, reported.path, reported.query, null).toString()
-} catch (e: Exception) {
-    url
-}
-
 /**
  * The build a check on launch should interrupt somebody for, or null to say
  * nothing at all.
  *
  * Only an actual update is worth a word. Opening the app is not asking a
- * question, so a check that finds nothing — or that cannot reach the release
- * server at all — stays quiet; a phone on a train would otherwise be told off
- * for it every single launch. The button in Settings *is* asking a question, and
- * reports every answer including those two.
+ * question, so a check that finds nothing — or that cannot reach the update server at all
+ * — stays quiet; a phone on a train would otherwise be told off for it every
+ * single launch. The button in Settings *is* asking a question, and reports
+ * every answer including those two.
  */
 fun launchOffer(verdict: UpdateVerdict): Release? =
     (verdict as? UpdateVerdict.Install)?.release

app/src/main/java/org/prolibertate/games/update/Updater.kt

@@ -8,36 +8,17 @@ import android.provider.Settings
 import androidx.core.content.FileProvider
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
-import org.json.JSONArray
 import org.json.JSONObject
-import org.prolibertate.games.BuildConfig
 import java.io.File
 import java.net.HttpURLConnection
 import java.net.URL
 
 /**
- * Over-the-air updates from the repository's releases.
+ * Over-the-air updates from plg.wallacenet.ca (Cloudflare Pages).
  *
- * The channel is the Gitea instance this app ships from
- * (`git.wallacenet.ca`), not GitHub. Gitea's release API answers with the
- * same shape the updater reads — `tag_name`, `prerelease`, `draft`, and
- * assets carrying `browser_download_url` — so this is the same code the
- * upstream ran, pointed at `/api/v1/repos/...` routes instead of
- * `api.github.com`, with `limit` where GitHub says `per_page`.
- *
- * Release tags are v<series>.<n>, where **n is the stamped build number the
- * APK's versionCode was built from** (the CI run number plus the fixed
- * `plgVersionRunOffset` — see docs/CI.md), so comparing the two is enough to
- * tell whether a newer build exists.
- *
- * The repository and its releases are public: no token is embedded in the
- * app, and every download is anonymous by design. If the repo were ever made
- * private, every check would simply start failing rather than leaking
- * anything.
- *
- * `BuildConfig.OTA_ENABLED` is a kill switch, not a channel decision — it is
- * true in this build; setting it false makes every check report that and
- * fetch nothing.
+ * Release tags are v<series>.<run-number> and the APK's versionCode is that same run
+ * number, so comparing the two is enough to tell whether a newer build exists.
+ * Everything there is public — no token is embedded in the app.
  *
  * There is nothing to choose here. The channel comes from the running APK, so
  * a dev install looks only at dev builds and a production install only at
@@ -52,11 +33,6 @@ class Updater(private val activity: Activity) {
      * this phone is on, and the phone already knows.
      */
     suspend fun check(): UpdateVerdict = withContext(Dispatchers.IO) {
-        if (!BuildConfig.OTA_ENABLED) {
-            return@withContext UpdateVerdict.Refused(
-                "In-app updates are not enabled for this build yet."
-            )
-        }
         try {
             val channel = installedChannel()
             verdictFor(
@@ -70,70 +46,37 @@ class Updater(private val activity: Activity) {
     }
 
     /**
-     * Production reads the "latest release", which by definition skips
-     * prereleases — Gitea implements it as the most recent non-prerelease,
-     * non-draft release, so the rule holds on this instance too.
-     *
-     * Dev walks the release list for the newest prerelease, which is what the
-     * CI pipeline publishes from the dev branch. The list is taken as the
-     * highest versionCode among the dev releases rather than the first one
-     * returned, so the answer does not depend on how the server chose to
-     * order the page.
+     * Each channel publishes a `latest.json` next to its APK on Cloudflare
+     * Pages: `/prod/latest.json` and `/dev/latest.json`. The two live in one
+     * site but separate paths, so a build can only ever look down its own line.
      */
-    private fun fetchLatestRelease(channel: UpdateChannel): Release? = when (channel) {
-        UpdateChannel.PRODUCTION ->
-            getJsonObject("$API/releases/latest")
-                ?.let { toRelease(it) }
-
-        UpdateChannel.DEV ->
-            getJsonArray("$API/releases?limit=30")
-                ?.let { releases ->
-                    (0 until releases.length())
-                        .mapNotNull { toRelease(releases.getJSONObject(it)) }
-                        .filter { it.channel == UpdateChannel.DEV }
-                        .maxByOrNull { it.versionCode }
-                }
+    private fun fetchLatestRelease(channel: UpdateChannel): Release? {
+        val path = if (channel == UpdateChannel.DEV) "dev" else "prod"
+        return getJsonObject("$BASE_URL/$path/latest.json")?.let { toRelease(it) }
     }
 
     private fun toRelease(json: JSONObject): Release? {
-        val tag = json.optString("tag_name").ifBlank { return null }
+        val tag = json.optString("tag").ifBlank { return null }
         val versionCode = versionCodeOfTag(tag) ?: return null
-        val channel = channelOfTag(tag, json.optBoolean("prerelease"))
-
-        val assets = json.optJSONArray("assets") ?: return null
-        val apks = (0 until assets.length())
-            .map { assets.getJSONObject(it) }
-            .filter { it.optString("name").endsWith(".apk") }
-
-        // A production release may carry the same build twice: once named for
-        // its version, and once under a fixed name so a permanent download link
-        // exists. Pick the versioned one explicitly rather than whichever was
-        // uploaded first, so what gets installed is traceable to its tag.
-        val chosen = apks.firstOrNull { it.optString("name").contains(tag) }
-            ?: apks.firstOrNull()
-            ?: return null
-
+        val apkUrl = json.optString("apkUrl").ifBlank { return null }
         return Release(
             tag = tag,
             versionCode = versionCode,
-            apkUrl = onReportedHost(chosen.getString("browser_download_url"), SERVER_HOST),
-            apkName = chosen.optString("name"),
-            channel = channel,
+            apkUrl = apkUrl,
+            apkName = json.optString("apkName"),
+            channel = channelOfTag(tag, prerelease = false),
         )
     }
 
-    private fun openConnection(url: String): HttpURLConnection =
-        (URL(url).openConnection() as HttpURLConnection).apply {
+    private fun getJsonObject(url: String): JSONObject? {
+        val connection = (URL(url).openConnection() as HttpURLConnection).apply {
             requestMethod = "GET"
-            setRequestProperty("Accept", "application/json")
             setRequestProperty("User-Agent", "ProLibertateGames-Updater")
             connectTimeout = 15_000
             readTimeout = 15_000
         }
-
-    private fun getJsonObject(url: String): JSONObject? {
-        val connection = openConnection(url)
         try {
+            // 404 means the channel has nothing published yet.
             if (connection.responseCode != 200) return null
             return JSONObject(connection.inputStream.bufferedReader().use { it.readText() })
         } finally {
@@ -141,16 +84,6 @@ class Updater(private val activity: Activity) {
         }
     }
 
-    private fun getJsonArray(url: String): JSONArray? {
-        val connection = openConnection(url)
-        try {
-            if (connection.responseCode != 200) return null
-            return JSONArray(connection.inputStream.bufferedReader().use { it.readText() })
-        } finally {
-            connection.disconnect()
-        }
-    }
-
     /** Read back from the installed APK's own version name. */
     fun installedChannel(): UpdateChannel = channelOfVersionName(installedVersionName())
 
@@ -202,13 +135,6 @@ class Updater(private val activity: Activity) {
         activity.packageManager.getPackageInfo(activity.packageName, 0).versionName ?: "unknown"
 
     private companion object {
-        /** The Gitea instance that publishes this app's releases. */
-        const val SERVER = "https://git.wallacenet.ca"
-        const val SERVER_HOST = "git.wallacenet.ca"
-        const val OWNER = "devadmin"
-        const val REPO = "ProLibertateGames"
-
-        /** Release routes, Gitea's `/api/v1` spelling of GitHub's API. */
-        const val API = "$SERVER/api/v1/repos/$OWNER/$REPO"
+        const val BASE_URL = "https://plg.wallacenet.ca"
     }
 }

app/src/test/java/org/prolibertate/games/game/CatalogTest.kt

@@ -106,19 +106,36 @@ class CatalogTest {
     }
 
     @Test
-    fun `every reference game in the catalogue can be played`() {
-        // Every game the app ships is playable. The one exception is Katan,
-        // listed so the slot exists and marked *Coming soon* until its engine
-        // and screen land — `available = false` is what keeps an unfinished
-        // game out of a production build while leaving it visible on a dev one.
-        assertEquals(
-            listOf(GameCatalog.CATAN),
-            GameCatalog.all.filterNot { it.available }.map { it.id },
-        )
-        // It is also the only difference the two channels see in a menu.
-        val hiddenFromProduction = GameCatalog.inMenu(GameMenu.BOARD, includeComingSoon = true) -
-            GameCatalog.inMenu(GameMenu.BOARD, includeComingSoon = false)
-        assertEquals(listOf(GameCatalog.byId(GameCatalog.CATAN)!!), hiddenFromProduction)
+    fun `every game in the catalogue can be played`() {
+        // `available` is the release gate. Nothing is held back at the moment,
+        // so a production menu lists every game; a game parked behind the gate
+        // belongs in `devPreview`, and must say so rather than being quietly
+        // unavailable everywhere.
+        GameCatalog.all.filterNot { it.available }.forEach { game ->
+            assertTrue("${game.id} is unavailable but not a dev preview", game.devPreview)
+        }
+        GameMenu.entries.forEach { menu ->
+            val held = GameCatalog.inMenu(menu, includeComingSoon = true) -
+                GameCatalog.inMenu(menu, includeComingSoon = false).toSet()
+            held.forEach { assertTrue("${it.id} hidden from production without a preview flag", it.devPreview) }
+        }
+    }
+
+    @Test
+    fun `a preview game opens on a dev build and nowhere else`() {
+        GameCatalog.all.filter { it.devPreview }.forEach { game ->
+            assertFalse("${game.id}: preview is for games that are not yet available", game.available)
+            assertTrue("${game.id} should open on a dev build", game.playableIn(devBuild = true))
+            assertFalse("${game.id} must not open in production", game.playableIn(devBuild = false))
+        }
+        // The two games that were once previews now open everywhere.
+        listOf(GameCatalog.CATAN, GameCatalog.MEOWDOKU).forEach { id ->
+            val game = GameCatalog.byId(id)!!
+            assertTrue("$id should open in production", game.playableIn(devBuild = false))
+        }
+        // An ordinary finished game opens everywhere.
+        val chess = GameCatalog.byId(GameCatalog.CHESS)!!
+        assertTrue(chess.playableIn(devBuild = true) && chess.playableIn(devBuild = false))
     }
 
     @Test
@@ -160,6 +177,8 @@ class CatalogTest {
                 GameCatalog.MASTERMIND,
                 GameCatalog.BACKGAMMON,
                 GameCatalog.PIRATES,
+                GameCatalog.CATAN,
+                GameCatalog.MEOWDOKU,
             ),
             GameCatalog.playable.map { it.id }.toSet(),
         )

app/src/test/java/org/prolibertate/games/game/backgammon/BackgammonAiProfileTest.kt

@@ -0,0 +1,43 @@
+package org.prolibertate.games.game.backgammon
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+
+class BackgammonAiProfileTest {
+
+    private fun playout(ai: BackgammonAi, seed: Long, steps: Int): List<BackgammonMove> {
+        var state = BackgammonRules.initialState(BackgammonOptions(), seed)
+        val chosen = mutableListOf<BackgammonMove>()
+        repeat(steps) {
+            if (BackgammonRules.isFinished(state)) return chosen
+            val seat = BackgammonRules.currentSeat(state) ?: return chosen
+            val legal = BackgammonRules.legalMoves(state, seat)
+            if (legal.isEmpty()) return chosen
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move", move in legal)
+            chosen += move
+            state = BackgammonRules.applyMove(state, seat, move)
+        }
+        return chosen
+    }
+
+    @Test
+    fun everyLevelAndStyleReturnsLegalMoves() {
+        for (difficulty in listOf(AiDifficulty.EASY, AiDifficulty.MEDIUM, AiDifficulty.HARD, AiDifficulty.MIXED)) {
+            for (seed in 0L..5L) {
+                val moves = playout(BackgammonAi(AiProfiles(difficulty, seed)), seed, 14)
+                assertTrue(moves.isNotEmpty())
+            }
+        }
+    }
+
+    @Test
+    fun defaultProfilePlaysAsBefore() {
+        val plain = playout(BackgammonAi(), 3L, 20)
+        val medium = playout(BackgammonAi(AiProfiles(AiDifficulty.MEDIUM, 77L)), 3L, 20)
+        assertEquals(plain, medium)
+    }
+}

app/src/test/java/org/prolibertate/games/game/catan/CatanAiProfilesTest.kt

@@ -0,0 +1,105 @@
+package org.prolibertate.games.game.catan
+
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.GameCatalog
+import org.prolibertate.games.game.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.AiStyle
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+/** Computer seats at every level and style play legal, forward-moving games in each Katan rule set. */
+class CatanAiProfilesTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(options: CatanOptions, seed: Long) = TableConfig(
+        gameId = GameCatalog.CATAN,
+        seats = (0 until options.playerCount).map {
+            PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it)
+        },
+        optionsJson = json.encodeToString(options),
+        seed = seed,
+    )
+
+    /** Plays up to [cap] moves, checking every one; returns the last state. */
+    private fun play(options: CatanOptions, seed: Long, profiles: AiProfiles, cap: Int): CatanState {
+        val ai = CatanAi(profiles)
+        var state = CatanRules.initialState(config(options, seed))
+        var moves = 0
+        while (!CatanRules.isFinished(state) && moves++ < cap) {
+            val seat = CatanRules.currentSeat(state)
+                ?: error("seed $seed: nobody on the clock in ${state.phase}; log tail: ${state.log.takeLast(8)}")
+            val legal = CatanRules.legalMoves(state, seat)
+            assertTrue("seed $seed: seat $seat has no legal move in ${state.phase}", legal.isNotEmpty())
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("seed $seed: chose $move outside the legal list in ${state.phase}", move in legal || CatanRules.isLegalMove(state, seat, move))
+            assertTrue(
+                "seed $seed: seat $seat chose the illegal move $move in ${state.phase}",
+                CatanRules.isLegalMove(state, seat, move),
+            )
+            state = CatanRules.applyMove(state, seat, move)
+        }
+        return state
+    }
+
+    /** A table seed on which some seat among the first three has [style] at [difficulty]. */
+    private fun tableSeedFor(difficulty: AiDifficulty, style: AiStyle): Long =
+        (1L..2_000L).first { s ->
+            val p = AiProfiles(difficulty, s)
+            (0 until 3).any { p.of(it).style == style }
+        }
+
+    private fun forEveryProfile(rules: Set<CatanExpansion>, cap: Int) {
+        val options = CatanOptions(
+            playerCount = 3,
+            pointsToWin = when {
+                CatanExpansion.CITIES_AND_KNIGHTS in rules -> 13
+                CatanExpansion.SEAFARERS in rules -> 12
+                else -> 10
+            },
+            expansions = rules,
+        )
+        for (difficulty in listOf(AiDifficulty.EASY, AiDifficulty.HARD)) {
+            for (style in AiStyle.entries) {
+                val tableSeed = tableSeedFor(difficulty, style)
+                val state = play(options, 40L + style.ordinal, AiProfiles(difficulty, tableSeed), cap)
+                assertTrue(
+                    "$rules $difficulty $style: the game never got past setup",
+                    state.turnNumber > 3 || CatanRules.isFinished(state),
+                )
+            }
+        }
+    }
+
+    @Test
+    fun `easy and hard seats of every style play the base game`() = forEveryProfile(emptySet(), 1_500)
+
+    @Test
+    fun `easy and hard seats of every style play Cities and Knights`() =
+        forEveryProfile(setOf(CatanExpansion.CITIES_AND_KNIGHTS), 1_500)
+
+    @Test
+    fun `easy and hard seats of every style play Seafarers`() = forEveryProfile(setOf(CatanExpansion.SEAFARERS), 1_500)
+
+    @Test
+    fun `a mixed table of four finishes a base game`() {
+        val state = play(CatanOptions(playerCount = 4), 77L, AiProfiles(AiDifficulty.MIXED, 5L), 12_000)
+        assertEquals(CatanPhase.GAME_OVER, state.phase)
+    }
+
+    @Test
+    fun `the default profile plays exactly as an explicit medium table does`() {
+        for (rules in listOf(emptySet(), setOf(CatanExpansion.CITIES_AND_KNIGHTS))) {
+            val options = CatanOptions(playerCount = 3, pointsToWin = 10, expansions = rules)
+            val plain = play(options, 9L, AiProfiles.DEFAULT, 600)
+            val medium = play(options, 9L, AiProfiles(AiDifficulty.MEDIUM, 1234L), 600)
+            assertEquals("$rules", plain, medium)
+        }
+    }
+}

app/src/test/java/org/prolibertate/games/game/catan/CatanAiTest.kt

@@ -0,0 +1,191 @@
+package org.prolibertate.games.game.catan
+
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.GameCatalog
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class CatanAiTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(options: CatanOptions, seed: Long) = TableConfig(
+        gameId = GameCatalog.CATAN,
+        seats = (0 until options.playerCount).map {
+            PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it)
+        },
+        optionsJson = json.encodeToString(options),
+        seed = seed,
+    )
+
+    /** Plays one table of engines out to a result, refusing every illegal move. */
+    private fun playOut(options: CatanOptions, seed: Long, cap: Int = 4_000): CatanState {
+        val ai = CatanAi()
+        var state = CatanRules.initialState(config(options, seed))
+        var moves = 0
+        while (!CatanRules.isFinished(state)) {
+            assertTrue("seed $seed ran past $cap moves", moves++ < cap)
+            val seat = CatanRules.currentSeat(state) ?: break
+            val move = ai.chooseMove(state, seat, CatanRules.legalMoves(state, seat))
+            assertTrue(
+                "seed $seed: seat $seat chose the illegal move $move",
+                CatanRules.isLegalMove(state, seat, move),
+            )
+            state = CatanRules.applyMove(state, seat, move)
+        }
+        return state
+    }
+
+    @Test
+    fun `three engines finish a game at ten points`() {
+        listOf(11L, 22L, 33L).forEach { seed ->
+            val state = playOut(CatanOptions(), seed)
+            assertEquals("seed $seed", CatanPhase.GAME_OVER, state.phase)
+            val winner = state.winner
+            assertTrue("seed $seed finished without a winner", winner != null)
+            assertTrue(
+                "seed $seed: the winner fell short of the target",
+                CatanRules.victoryPoints(state, winner!!) >= state.options.pointsToWin,
+            )
+        }
+    }
+
+    @Test
+    fun `four engines finish a game at ten points`() {
+        listOf(44L, 55L).forEach { seed ->
+            val state = playOut(CatanOptions(playerCount = 4), seed)
+            assertEquals("seed $seed", CatanPhase.GAME_OVER, state.phase)
+            val winner = state.winner
+            assertTrue("seed $seed finished without a winner", winner != null)
+            assertTrue(
+                "seed $seed: the winner fell short of the target",
+                CatanRules.victoryPoints(state, winner!!) >= state.options.pointsToWin,
+            )
+        }
+    }
+
+    /** A mid-game state on seat 0's turn, one card short of a settlement. */
+    private fun offeringState(): CatanState =
+        CatanRules.initialState(config(CatanOptions(), seed = 7L))
+            .copy(
+                phase = CatanPhase.PLAYING,
+                turn = 0,
+                turnNumber = 1,
+                // Lumber to spare, brick missing, and a neighbour visibly
+                // holding brick. No roads or buildings, so no build is legal
+                // and no port is open — the offer is the only move forward.
+                resources = listOf(
+                    hand(Resource.LUMBER to 4, Resource.WOOL to 1, Resource.GRAIN to 1),
+                    hand(Resource.BRICK to 2),
+                    hand(),
+                ),
+            )
+
+    private fun hand(vararg cards: Pair<Resource, Int>): Map<Resource, Int> =
+        Resource.entries.associateWith { cards.toMap()[it] ?: 0 }
+
+    @Test
+    fun `the AI offers the trade that closes its build`() {
+        val state = offeringState()
+        val move = CatanAi().chooseMove(state, 0, CatanRules.legalMoves(state, 0))
+        assertEquals(
+            OfferTrade(to = 1, give = listOf(Resource.LUMBER, Resource.LUMBER), get = listOf(Resource.BRICK)),
+            move,
+        )
+    }
+
+    @Test
+    fun `the AI offers at most one trade a turn`() {
+        // The same table, but the offer was already made and refused once.
+        val state = offeringState().copy(
+            log = listOf(
+                "Seat 0 rolls 3 + 2.",
+                "Seat 0 offers 2 lumber for a brick to seat 1.",
+                "Seat 1 declines the offer.",
+            ),
+        )
+        val move = CatanAi().chooseMove(state, 0, CatanRules.legalMoves(state, 0))
+        assertTrue("the AI re-offered within one turn: $move", move !is OfferTrade)
+        assertEquals(EndTurn, move)
+    }
+
+    @Test
+    fun `the AI answers a pending offer with accept or decline`() {
+        val state = CatanRules.initialState(config(CatanOptions(), seed = 7L))
+            .copy(
+                phase = CatanPhase.TRADE_PENDING,
+                turn = 0,
+                turnNumber = 1,
+                pendingTrade = TradeOffer(
+                    by = 0, to = 1,
+                    give = listOf(Resource.LUMBER, Resource.LUMBER),
+                    get = listOf(Resource.BRICK),
+                ),
+                resources = listOf(
+                    hand(Resource.LUMBER to 3),
+                    hand(Resource.BRICK to 2, Resource.WOOL to 1),
+                    hand(),
+                ),
+            )
+        val legal = CatanRules.legalMoves(state, 1)
+        val move = CatanAi().chooseMove(state, 1, legal)
+        assertTrue("neither accept nor decline: $move", move == AcceptTrade || move == DeclineTrade)
+        assertTrue(move in legal)
+
+        val after = CatanRules.applyMove(state, 1, move)
+        assertEquals(CatanPhase.PLAYING, after.phase)
+        assertNull(after.pendingTrade)
+    }
+
+    private fun tradeTable(offer: TradeOffer, vararg hands: Map<Resource, Int>): CatanState =
+        CatanRules.initialState(config(CatanOptions(), seed = 7L)).copy(
+            phase = CatanPhase.TRADE_PENDING,
+            turn = 0,
+            turnNumber = 1,
+            pendingTrade = offer,
+            resources = hands.toList(),
+        )
+
+    @Test
+    fun `the AI accepts an offer that gives it more than it costs, and declines the reverse`() {
+        val generous = tradeTable(
+            TradeOffer(by = 0, to = null, give = listOf(Resource.ORE, Resource.ORE), get = listOf(Resource.WOOL), asking = 1),
+            hand(Resource.ORE to 2), hand(Resource.WOOL to 2), hand(),
+        )
+        assertEquals(AcceptTrade, CatanAi().chooseMove(generous, 1, CatanRules.legalMoves(generous, 1)))
+
+        val stingy = tradeTable(
+            TradeOffer(by = 0, to = null, give = listOf(Resource.WOOL), get = listOf(Resource.ORE), asking = 1),
+            hand(Resource.WOOL to 1), hand(Resource.ORE to 2), hand(),
+        )
+        assertEquals(DeclineTrade, CatanAi().chooseMove(stingy, 1, CatanRules.legalMoves(stingy, 1)))
+    }
+
+    @Test
+    fun `an AI offerer takes the best counter and refuses a losing one`() {
+        val counters = listOf(
+            TradeCounter(by = 1, give = listOf(Resource.ORE), get = listOf(Resource.LUMBER)),
+            TradeCounter(by = 2, give = listOf(Resource.ORE, Resource.GRAIN), get = listOf(Resource.WOOL)),
+        )
+        val state = tradeTable(
+            TradeOffer(by = 0, to = null, give = listOf(Resource.WOOL), get = listOf(Resource.ORE), asking = -1, counters = counters),
+            hand(Resource.LUMBER to 1, Resource.WOOL to 1), hand(Resource.ORE to 1), hand(Resource.ORE to 1, Resource.GRAIN to 1),
+        ).copy(phase = CatanPhase.TRADE_COUNTERS)
+        val legal = CatanRules.legalMoves(state, 0)
+        assertEquals(AcceptCounter(2), CatanAi().chooseMove(state, 0, legal))
+
+        val bad = state.copy(
+            pendingTrade = state.pendingTrade!!.copy(
+                counters = listOf(TradeCounter(by = 1, give = listOf(Resource.WOOL), get = listOf(Resource.LUMBER))),
+            ),
+            resources = listOf(hand(Resource.LUMBER to 1), hand(Resource.WOOL to 1), hand()),
+        )
+        assertEquals(DismissCounters, CatanAi().chooseMove(bad, 0, CatanRules.legalMoves(bad, 0)))
+    }
+}