Merge dev into Seafarers

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01S8evMuUxrft6TQj6NdAoqQ

.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
+      - name: Build debug APK
         run: ./gradlew assembleDebug --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}.${stamp}"
+          # Same arithmetic as build.gradle.kts, so the tag names the APK's own number.
+          version="v${series}.$(( ${{ github.run_number }} + offset ))"
           src="app/build/outputs/apk/debug/app-debug.apk"
           dest="ProLibertateGames-${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 rule
+sets chosen at setup: 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 {

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/catan/CatanAi.kt

@@ -0,0 +1,395 @@
+package org.prolibertate.games.game.catan
+
+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.
+ */
+class CatanAi : GameAi<CatanState, CatanMove> {
+
+    /** Plays the Cities & Knights tables; this class keeps the base game. */
+    private val ck = CatanCkAi(this)
+
+    override fun chooseMove(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+        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>())
+
+            CatanPhase.AWAIT_ROLL -> legal.first { it is RollDice }
+
+            // Gold: take what the seat wants most.
+            CatanPhase.GOLD -> legal.filterIsInstance<PickGold>().maxByOrNull { pick ->
+                pick.cards.sumOf { want(it) }
+            } ?: legal.first()
+
+            CatanPhase.DISCARDING -> chooseDiscard(state, seat, legal.filterIsInstance<Discard>())
+
+            CatanPhase.ROBBER -> chooseRobber(state, seat, legal.filterIsInstance<MoveRobber>())
+
+            CatanPhase.FREE_ROADS -> chooseFreeRoad(state, seat, legal)
+
+            CatanPhase.TRADE_PENDING -> chooseResponse(state, seat, legal)
+
+            CatanPhase.TRADE_COUNTERS -> chooseCounter(state, legal)
+
+            CatanPhase.PLAYING -> choosePlaying(state, seat, legal)
+
+            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>): SetupPlace {
+        require(places.isNotEmpty()) { "No legal settlement placement" }
+        return places.maxByOrNull { place ->
+            spotValue(state, place.vertex) +
+                0.25 * placeDirection(state, place)
+        } ?: places.first()
+    }
+
+    /**
+     * 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>): 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 discards.minByOrNull { discard ->
+            discard.cards.sumOf { want(it) }
+        } ?: discards.first()
+    }
+
+    private fun chooseRobber(state: CatanState, seat: Int, moves: List<MoveRobber>): MoveRobber {
+        require(moves.isNotEmpty()) { "No legal robber move" }
+        val points = CatanRules.publicVictoryPoints(state)
+        return moves.maxByOrNull { move ->
+            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
+                if (building.owner == seat) continue
+                val worth = if (building.type == BuildingType.CITY) 2 else 1
+                score += worth * CatanBoard.numberOdds(state.numbers[hex]) / 36.0
+            }
+            if (move.victim != null) {
+                score += 0.15 * state.resourceCount(move.victim) +
+                    0.3 * points[move.victim]
+            }
+            score
+        } ?: moves.first()
+    }
+
+    // -----------------------------------------------------------------------
+    // The main phase
+    // -----------------------------------------------------------------------
+
+    private fun choosePlaying(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+        // A city doubles the best production the seat already owns.
+        legal.filterIsInstance<BuildCity>().maxByOrNull {
+            spotValue(state, it.vertex)
+        }?.let { return it }
+
+        legal.filterIsInstance<BuildSettlement>().maxByOrNull {
+            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.
+        legal.filterIsInstance<PlayKnight>().firstOrNull()?.let { return it }
+
+        yearOfPlenty(state, legal)?.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()
+        }
+
+        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) > 0.1 }
+            .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 }
+
+        offer(state, seat)?.let { return it }
+
+        return legal.lastOrNull { it is EndTurn } ?: legal.first()
+    }
+
+    /** Year of Plenty: two of whatever the nearest build is shortest of. */
+    private fun yearOfPlenty(state: CatanState, legal: List<CatanMove>): PlayYearOfPlenty? {
+        val takes = legal.filterIsInstance<PlayYearOfPlenty>()
+        if (takes.isEmpty()) return null
+        val shortage = shortage(state) ?: return null
+        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): 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 target = (0 until state.playerCount)
+                .filter { it != seat }
+                .filter { (state.resources[it][need] ?: 0) > 0 }
+                .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>): CatanMove {
+        val roads = legal.filterIsInstance<BuildRoad>()
+            .filter { roadValue(state, it) > 0.05 }
+            .maxByOrNull { roadValue(state, it) }
+        return roads ?: legal.firstOrNull { it is EndFreeRoads }
+            ?: legal.filterIsInstance<BuildRoad>().firstOrNull()
+            ?: legal.first()
+    }
+
+    private fun chooseResponse(state: CatanState, seat: Int, legal: List<CatanMove>): 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 { want(it) }
+        val outgoing = offer.get.sumOf { want(it) }
+        return if (incoming > outgoing) 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, legal: List<CatanMove>): CatanMove {
+        val offer = state.pendingTrade ?: return legal.first()
+        val best = legal.filterIsInstance<AcceptCounter>()
+            .map { choice -> choice to offer.counters.first { it.by == choice.seat } }
+            .maxByOrNull { (_, c) -> c.give.sumOf { want(it) } - c.get.sumOf { want(it) } }
+        if (best != null) {
+            val (choice, c) = best
+            if (c.give.sumOf { want(it) } > c.get.sumOf { want(it) }) 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 && island != sea.home && 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
+    }
+}

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 +1,345 @@
+package org.prolibertate.games.game.catan
+
+/**
+ * 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.
+ */
+internal class CatanCkAi(private val ai: CatanAi) {
+
+    fun choose(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove = when (state.phase) {
+        CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND ->
+            ai.chooseSetup(state, seat, legal.filterIsInstance<SetupPlace>())
+
+        CatanPhase.AWAIT_ROLL -> legal.first { it is RollDice }
+
+        CatanPhase.CHORE -> chooseChore(state, seat, legal)
+
+        CatanPhase.ROBBER -> chooseRobber(state, seat, legal.filterIsInstance<MoveRobber>())
+
+        CatanPhase.FREE_ROADS -> chooseFreeRoad(state, seat, legal)
+
+        CatanPhase.TRADE_PENDING -> chooseResponse(state, seat, legal)
+
+        CatanPhase.TRADE_COUNTERS -> chooseCounter(state, legal)
+
+        CatanPhase.PLAYING -> choosePlaying(state, seat, legal)
+
+        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>): CatanMove {
+        val ck = state.ck!!
+        return when (val chore = ck.chores.first()) {
+            is DiscardChore -> {
+                val n = minOf(chore.count, CatanCk.goodsCount(state, seat))
+                DiscardGoods(CatanCk.goodsList(state, seat).sortedBy { worth(state, seat, it) }.take(n))
+            }
+
+            is GiveChore -> {
+                val pool = CatanCk.goodsList(state, seat)
+                    .filter { !chore.commoditiesOnly || it.isCommodity }
+                    .sortedBy { worth(state, seat, it) }
+                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>): MoveRobber {
+        require(moves.isNotEmpty()) { "No legal robber move" }
+        val points = CatanRules.publicVictoryPoints(state)
+        return moves.maxByOrNull { move ->
+            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 else worth * odds
+            }
+            if (move.victim != null) {
+                score += 0.15 * CatanCk.goodsCount(state, move.victim) + 0.3 * points[move.victim]
+            }
+            score
+        } ?: moves.first()
+    }
+
+    // -----------------------------------------------------------------------
+    // The main phase
+    // -----------------------------------------------------------------------
+
+    private fun choosePlaying(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+        val ck = state.ck!!
+        val soon = ck.barbarians <= 3
+
+        // 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 }
+
+        legal.filterIsInstance<BuildCity>().maxByOrNull { production(state, it.vertex) }
+            ?.let { return it }
+
+        legal.filterIsInstance<BuildSettlement>().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.
+        defence(state, seat, legal, soon)?.let { return it }
+
+        progress(state, seat, legal)?.let { return it }
+
+        legal.filterIsInstance<BuildWall>().firstOrNull()?.let {
+            if (CatanCk.goodsCount(state, seat) >= 7) return it
+        }
+
+        legal.filterIsInstance<BuildRoad>()
+            .filter { ai.roadValue(state, it) > 0.1 }
+            .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 }
+
+        return legal.lastOrNull { it is 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): CatanMove? {
+        val mine = CatanCk.knightsOf(state, seat)
+        val grainLeft = state.resources[seat][Resource.GRAIN] ?: 0
+
+        if (soon) {
+            legal.filterIsInstance<ActivateKnight>().firstOrNull()?.let { return it }
+        }
+        val want = if (soon) 4 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>): CatanMove =
+        legal.filterIsInstance<BuildRoad>()
+            .filter { ai.roadValue(state, it) > 0.05 }
+            .maxByOrNull { ai.roadValue(state, it) }
+            ?: legal.firstOrNull { it is EndFreeRoads }
+            ?: legal.first()
+
+    private fun chooseResponse(state: CatanState, seat: Int, legal: List<CatanMove>): 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) }
+            val outgoing = offer.get.sumOf { worth(state, seat, it) }
+            return if (incoming > outgoing) 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) 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): Double =
+        good.resource?.let { ai.want(it) } ?: when (good) {
+            Good.PAPER -> 0.95
+            Good.COIN -> 0.9
+            else -> 0.85
+        }
+
+    /** 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 +1,444 @@
+package org.prolibertate.games.game.catan
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+/** 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,
+}
+
+/** Which rules a table plays. The expansion is a whole rule set, not a toggle. */
+@Serializable
+enum class CatanRuleSet {
+    /** The base game: development cards, Largest Army, a robber from the start. */
+    BASE,
+
+    /** 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,
+}
+
+@Serializable
+data class CatanOptions(
+    val playerCount: Int = 3,
+    val pointsToWin: Int = 10,
+    val ruleSet: CatanRuleSet = CatanRuleSet.BASE,
+) {
+    init {
+        require(playerCount in 3..4) { "The island seats three or four players" }
+        require(pointsToWin >= 2) { "pointsToWin must be at least 2" }
+    }
+}
+
+/**
+ * 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,
+    /** 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 the players start on. */
+    val home: Int,
+    /** Gold owed after a roll, front first: each seat chooses [GoldOwed.count] cards. */
+    val gold: List<GoldOwed> = emptyList(),
+)
+
+@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 +1,144 @@
+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) {
+    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.",
+    ),
+}
+
+/**
+ * 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 fun rows(scenario: SeaScenario): List<String> = when (scenario) {
+        SeaScenario.NEW_SHORES -> NEW_SHORES_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,
+    )
+
+    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()
+
+        return Generated(terrains, numbers.toList(), desert, pirate, ports, home)
+    }
+}

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 || island == sea.home || 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/engine/Engine.kt

@@ -64,6 +64,21 @@ 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/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/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/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 +51,14 @@ 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.SavedGameStore
+import org.prolibertate.games.game.engine.SavedMatch
 
 /** Everything the screens need, assembled once by the activity. */
 class AppEnv(
@@ -60,6 +69,9 @@ 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,
 )
 
 /**
@@ -83,6 +95,8 @@ sealed interface Route {
         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 +143,14 @@ 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 +188,10 @@ private fun AppContent(
             // Dev builds show the games that are not finished yet; production
             // releases list only what can actually be played.
             showComingSoon = showComingSoon,
+            saved = savedGames(env, stack),
+            onResume = { saved ->
+                push(Route.Play(saved.gameId, saved.config, true, saved.localSeat, saved.stateJson))
+            },
             onPickSection = { push(Route.Section(it)) },
             onJoinGame = { push(Route.Lobby(gameId = "", optionsJson = "{}", hosting = false)) },
             onScorekeeper = { push(Route.Scorekeeper) },
@@ -194,15 +219,30 @@ 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 ->
+                    push(Route.Lobby(route.gameId, optionsJson, hosting = true))
+                },
+                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 +271,8 @@ private fun AppContent(
 @Composable
 fun MainMenuScreen(
     showComingSoon: Boolean,
+    saved: List<SavedMatch>,
+    onResume: (SavedMatch) -> Unit,
     onPickSection: (GameMenu) -> Unit,
     onJoinGame: () -> Unit,
     onScorekeeper: () -> Unit,
@@ -280,6 +322,23 @@ fun MainMenuScreen(
                     )
                 }
 
+                // Games left half-played, most recent first, above everything
+                // else: coming back to the app is mostly coming back to one.
+                if (saved.isNotEmpty()) {
+                    Text(
+                        "Continue",
+                        style = MaterialTheme.typography.labelLarge,
+                        modifier = Modifier.fillMaxWidth(),
+                    )
+                    val now = System.currentTimeMillis()
+                    saved.forEach { match ->
+                        val title = GameCatalog.byId(match.gameId)?.title ?: match.gameId
+                        Button(onClick = { onResume(match) }, modifier = Modifier.fillMaxWidth()) {
+                            Text(savedLine(title, match, now))
+                        }
+                    }
+                }
+
                 // Below the games, and full width like them, so the column
                 // stays one column all the way down.
                 OutlinedButton(
@@ -364,7 +423,11 @@ fun SectionScreen(
                 }
             }
             items(games) { game ->
-                GameTile(game = game, onClick = { onPickGame(game) })
+                GameTile(
+                    game = game,
+                    playable = game.playableIn(devBuild = showComingSoon),
+                    onClick = { onPickGame(game) },
+                )
             }
         }
     }
@@ -403,12 +466,12 @@ 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 +490,18 @@ 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 +549,17 @@ 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
@@ -29,6 +32,7 @@ import org.prolibertate.games.game.GameCatalog
 import org.prolibertate.games.game.GameDescriptor
 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
@@ -46,6 +50,8 @@ 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
@@ -57,6 +63,8 @@ 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.CatanRuleSet
 import org.prolibertate.games.game.sequence.SequenceOptions
 import org.prolibertate.games.game.tayu.TayuLevel
 import org.prolibertate.games.game.tayu.TayuOptions
@@ -81,6 +89,10 @@ fun GameSetupScreen(
     onBack: () -> Unit,
     onPlayOffline: (TableConfig, Int) -> Unit,
     onHostOnline: (String) -> 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()) }
@@ -99,11 +111,13 @@ 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) }
@@ -129,11 +143,13 @@ 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 +161,10 @@ 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 +209,8 @@ 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 +221,8 @@ fun GameSetupScreen(
 
                 GameCatalog.PYRAMID -> PyramidOptionsEditor(pyramid) { pyramid = it }
 
+                GameCatalog.CATAN -> CatanOptionsEditor(catan) { catan = it }
+
                 else -> Text("No options yet for this game.")
             }
 
@@ -227,6 +251,12 @@ 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),
@@ -303,6 +333,9 @@ 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 +359,79 @@ fun teamForSeat(gameId: String, seat: Int, seatCount: Int): Int = when (gameId)
     else -> seat
 }
 
+/** The targets the setup screen offers for a Katan rule set. */
+internal fun catanPointsChoices(ruleSet: CatanRuleSet): List<Int> = when (ruleSet) {
+    // Five is a short game for trying things out; ten is the published target.
+    CatanRuleSet.BASE -> listOf(5, 8, 10, 12)
+    // Cities & Knights is played to thirteen, which is also why it runs longer.
+    CatanRuleSet.CITIES_AND_KNIGHTS -> listOf(8, 10, 13, 15)
+    // Seafarers adds two points for each new island, so the target is higher.
+    CatanRuleSet.SEAFARERS -> listOf(8, 10, 12, 14)
+}
+
+/** The published target for a rule set. */
+internal fun catanDefaultPoints(ruleSet: CatanRuleSet): Int = when (ruleSet) {
+    CatanRuleSet.BASE -> 10
+    CatanRuleSet.CITIES_AND_KNIGHTS -> 13
+    CatanRuleSet.SEAFARERS -> 12
+}
+
+/**
+ * [options] switched to [ruleSet]. The target moves to the new rule set's own
+ * default unless the one already chosen is on its menu too.
+ */
+internal fun catanSwitchRules(options: CatanOptions, ruleSet: CatanRuleSet): CatanOptions =
+    options.copy(
+        ruleSet = ruleSet,
+        pointsToWin = options.pointsToWin.takeIf { it in catanPointsChoices(ruleSet) && it != catanDefaultPoints(options.ruleSet) }
+            ?: catanDefaultPoints(ruleSet),
+    )
+
+private fun catanRuleSetName(ruleSet: CatanRuleSet): String = when (ruleSet) {
+    CatanRuleSet.BASE -> "Base game"
+    CatanRuleSet.CITIES_AND_KNIGHTS -> "Cities & Knights"
+    CatanRuleSet.SEAFARERS -> "Seafarers"
+}
+
+private fun catanRuleSetBlurb(ruleSet: CatanRuleSet): String = when (ruleSet) {
+    CatanRuleSet.BASE ->
+        "Settle the island, trade, and play development cards. Longest Road and Largest Army score."
+    CatanRuleSet.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."
+    CatanRuleSet.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)) {
+        ChipRow(
+            label = "Rules",
+            values = CatanRuleSet.entries,
+            selected = options.ruleSet,
+            display = ::catanRuleSetName,
+            onSelect = { onChange(catanSwitchRules(options, it)) },
+        )
+        Text(catanRuleSetBlurb(options.ruleSet), style = MaterialTheme.typography.bodySmall)
+        ChipRow(
+            label = "Players",
+            values = listOf(3, 4),
+            selected = options.playerCount,
+            display = { "$it players" },
+            onSelect = { onChange(options.copy(playerCount = it)) },
+        )
+        ChipRow(
+            label = "Game to",
+            values = catanPointsChoices(options.ruleSet),
+            selected = options.pointsToWin,
+            display = { "$it points" },
+            onSelect = { onChange(options.copy(pointsToWin = it)) },
+        )
+    }
+}
+
 @Composable
 private fun EuchreOptionsEditor(options: EuchreOptions, onChange: (EuchreOptions) -> Unit) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
@@ -1041,6 +1147,36 @@ 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 +1277,30 @@ 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/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/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/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/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/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 +1,460 @@
+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)
+        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))
+                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/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)))
+    }
+}

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

@@ -0,0 +1,192 @@
+package org.prolibertate.games.game.catan
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class CatanBoardTest {
+
+    // -- Geometry -----------------------------------------------------------
+
+    @Test
+    fun `the island has 19 hexes, 54 vertices, 72 edges and 30 coastal edges`() {
+        assertEquals(19, CatanBoard.HEX_COUNT)
+        assertEquals(54, CatanBoard.VERTEX_COUNT)
+        assertEquals(72, CatanBoard.EDGE_COUNT)
+        assertEquals("the coast is one ring of 30 edges", 30, CatanBoard.COASTAL.size)
+        assertEquals("nine harbour positions", 9, CatanBoard.PORT_POSITIONS.size)
+    }
+
+    @Test
+    fun `every hex has six distinct corners and every edge two distinct ends`() {
+        for (h in 0 until CatanBoard.HEX_COUNT) {
+            assertEquals("hex $h", 6, CatanBoard.HEX_CORNERS[h].size)
+            assertEquals("hex $h repeats a corner", 6, CatanBoard.HEX_CORNERS[h].distinct().size)
+        }
+        CatanBoard.EDGE_VERTICES.forEach { (a, b) -> assertTrue("edge loops on itself", a != b) }
+    }
+
+    @Test
+    fun `two vertices never share a lattice position`() {
+        assertEquals(CatanBoard.VERTEX_COUNT, CatanBoard.VERTEX_POS.distinct().size)
+        assertEquals(CatanBoard.HEX_COUNT, (0 until CatanBoard.HEX_COUNT)
+            .map { CatanBoard.hexCenter(it) }
+            .distinct().size)
+    }
+
+    @Test
+    fun `adjacent hexes share exactly two vertices and one edge`() {
+        for (h in 0 until CatanBoard.HEX_COUNT) {
+            for (n in CatanBoard.HEX_NEIGHBORS[h]) {
+                val shared = CatanBoard.HEX_CORNERS[h].toSet()
+                    .intersect(CatanBoard.HEX_CORNERS[n].toSet())
+                assertEquals("hexes $h and $n", 2, shared.size)
+                val sharedEdge = CatanBoard.EDGE_HEXES.indices.count { e ->
+                    CatanBoard.EDGE_HEXES[e].containsAll(listOf(h, n))
+                }
+                assertEquals("hexes $h and $n", 1, sharedEdge)
+            }
+        }
+    }
+
+    @Test
+    fun `vertices have two or three edges, each to a distinct neighbour`() {
+        for (v in 0 until CatanBoard.VERTEX_COUNT) {
+            assertTrue("vertex $v", CatanBoard.VERTEX_EDGES[v].size in 2..3)
+            assertEquals("vertex $v", CatanBoard.VERTEX_EDGES[v].size, CatanBoard.VERTEX_NEIGHBORS[v].size)
+            CatanBoard.VERTEX_NEIGHBORS[v].forEach { n ->
+                assertTrue(
+                    "vertices $v and $n are not joined by an edge",
+                    CatanBoard.VERTEX_EDGES[v].any { CatanBoard.otherEnd(it, v) == n },
+                )
+            }
+        }
+    }
+
+    @Test
+    fun `interior edges touch two hexes and coastal edges one`() {
+        CatanBoard.EDGE_HEXES.forEach { hexes -> assertTrue(hexes.size in 1..2) }
+        // Nineteen hexes times six edges each, counted per side: 114.
+        assertEquals(114, CatanBoard.EDGE_HEXES.sumOf { it.size })
+        val coastal = CatanBoard.EDGE_HEXES.indices.filter { CatanBoard.EDGE_HEXES[it].size == 1 }
+        assertEquals(CatanBoard.COASTAL.toSet(), coastal.toSet())
+    }
+
+    @Test
+    fun `the coast is one closed ring and the harbours are spread along it`() {
+        CatanBoard.COASTAL.forEachIndexed { i, e ->
+            val next = CatanBoard.COASTAL[(i + 1) % CatanBoard.COASTAL.size]
+            val shared = ends(e).intersect(ends(next))
+            assertTrue("coastal edges $e and $next are not consecutive", shared.isNotEmpty())
+        }
+
+        assertEquals(9, CatanBoard.PORT_POSITIONS.distinct().size)
+        assertTrue(CatanBoard.PORT_POSITIONS.all { it in CatanBoard.COASTAL })
+        val ringSpots = CatanBoard.PORT_POSITIONS.map { CatanBoard.COASTAL.indexOf(it) }.sorted()
+        val gaps = ringSpots.zipWithNext { a, b -> b - a } +
+            (CatanBoard.COASTAL.size - ringSpots.last() + ringSpots.first())
+        assertTrue("harbours sit closer than three edges apart: $gaps", gaps.all { it >= 3 })
+    }
+
+    @Test
+    fun `token odds follow the dice`() {
+        assertEquals(5, CatanBoard.numberOdds(6))
+        assertEquals(5, CatanBoard.numberOdds(8))
+        assertEquals(1, CatanBoard.numberOdds(2))
+        assertEquals(1, CatanBoard.numberOdds(12))
+        assertEquals(36, (2..12).sumOf { CatanBoard.numberOdds(it) })
+    }
+
+    // -- Island generation --------------------------------------------------
+
+    private val terrainCounts = mapOf(
+        Terrain.FOREST to 4,
+        Terrain.PASTURE to 4,
+        Terrain.FIELDS to 4,
+        Terrain.HILLS to 3,
+        Terrain.MOUNTAINS to 3,
+        Terrain.DESERT to 1,
+    )
+
+    /** The 18 number tokens dealt to the land, the seven withheld. */
+    private val tokens = listOf(6, 6, 8, 8, 2, 3, 3, 4, 4, 5, 5, 9, 9, 10, 10, 11, 11, 12)
+
+    @Test
+    fun `every seed deals the fixed terrain mix`() {
+        for (seed in 1L..500L) {
+            val island = CatanBoard.generate(seed)
+            assertEquals("seed $seed", 19, island.terrains.size)
+            terrainCounts.forEach { (terrain, n) ->
+                assertEquals("seed $seed $terrain", n, island.terrains.count { it == terrain })
+            }
+        }
+    }
+
+    @Test
+    fun `every seed deals the full token set and the desert stays bare`() {
+        for (seed in 1L..500L) {
+            val island = CatanBoard.generate(seed)
+            val dealt = island.numbers.filter { it > 0 }
+            assertEquals("seed $seed", 18, dealt.size)
+            assertEquals("seed $seed", tokens.sorted(), dealt.sorted())
+            assertEquals("seed $seed: the desert bears no token", 0, island.numbers[island.robber])
+            assertEquals(
+                "seed $seed: the robber does not start on the desert",
+                island.terrains.indexOf(Terrain.DESERT),
+                island.robber,
+            )
+        }
+    }
+
+    @Test
+    fun `no seed puts two red tokens on adjacent hexes`() {
+        for (seed in 1L..500L) {
+            val island = CatanBoard.generate(seed)
+            val red = island.numbers.withIndex()
+                .filter { it.value == 6 || it.value == 8 }
+                .map { it.index }
+            assertEquals("seed $seed", 4, red.size)
+            for (i in red.indices) {
+                for (j in i + 1 until red.size) {
+                    assertTrue(
+                        "seed $seed: red hexes ${red[i]} and ${red[j]} touch",
+                        !CatanBoard.hexesAdjacent(red[i], red[j]),
+                    )
+                }
+            }
+        }
+    }
+
+    @Test
+    fun `every seed spreads nine harbours, five special and four generic`() {
+        for (seed in 1L..500L) {
+            val island = CatanBoard.generate(seed)
+            assertEquals("seed $seed", 9, island.ports.size)
+            assertEquals("seed $seed", 5, island.ports.count { it.resource != null })
+            assertEquals("seed $seed", 4, island.ports.count { it.resource == null })
+            assertTrue("seed $seed", island.ports.all { port ->
+                port.ratio == if (port.resource == null) 3 else 2
+            })
+            assertEquals(
+                "seed $seed: every resource has its own harbour",
+                Resource.entries,
+                island.ports.mapNotNull { it.resource }.sorted(),
+            )
+            assertEquals("seed $seed", 9, island.ports.map { it.edge }.distinct().size)
+            assertTrue("seed $seed", island.ports.all { it.edge in CatanBoard.COASTAL })
+        }
+    }
+
+    @Test
+    fun `the same seed builds the same island`() {
+        for (seed in listOf(0L, 7L, 42L, 99L, -1L)) {
+            assertEquals("seed $seed", CatanBoard.generate(seed), CatanBoard.generate(seed))
+        }
+    }
+
+    /** The two vertices of [edge], as a set. */
+    private fun ends(edge: Int): Set<Int> {
+        val (a, b) = CatanBoard.EDGE_VERTICES[edge]
+        return setOf(a, b)
+    }
+}

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

@@ -0,0 +1,182 @@
+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.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+/**
+ * Engines playing Cities & Knights against each other. These are the
+ * playtests: every move is checked for legality, the state is round-tripped
+ * through its wire format as it goes, nothing may leave a seat without a move,
+ * and the game has to reach a result.
+ */
+class CatanCkSelfPlayTest {
+
+    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,
+    )
+
+    /** What one game looked like, for the summary printed at the end. */
+    private data class Report(
+        val seed: Long,
+        val moves: Int,
+        val turns: Int,
+        val attacks: Int,
+        val progressPlayed: Int,
+        val metropolises: Int,
+        val winner: Int?,
+        val points: List<Int>,
+    )
+
+    private fun playOut(options: CatanOptions, seed: Long, cap: Int = 30_000): Pair<CatanState, Report> {
+        val ai = CatanAi()
+        var state = CatanRules.initialState(config(options, seed))
+        var moves = 0
+        var attacks = 0
+        var progress = 0
+        while (!CatanRules.isFinished(state)) {
+            assertTrue("seed $seed ran past $cap moves; log tail: ${state.log.takeLast(8)}", 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: seat $seat chose the illegal move $move in ${state.phase}; " +
+                    "log tail: ${state.log.takeLast(5)}",
+                CatanRules.isLegalMove(state, seat, move),
+            )
+            val before = state.ck!!.attacked
+            val wasAttacks = state.log.count { it.contains("The barbarians land") }
+            state = CatanRules.applyMove(state, seat, move)
+            attacks += state.log.count { it.contains("The barbarians land") } - wasAttacks
+            if (move is PlayProgress) progress++
+            if (!before && state.ck!!.attacked) Unit
+
+            if (moves % 97 == 0) {
+                val back = CatanRules.decodeState(CatanRules.encodeState(state))
+                assertEquals("seed $seed: the state did not survive its wire format", state, back)
+                // A seat's view never carries another seat's progress cards or the decks.
+                for (viewer in 0 until options.playerCount) {
+                    val view = CatanRules.viewFor(state, viewer)
+                    assertTrue(view.ck!!.decks.values.all { it.isEmpty() })
+                    for (other in 0 until options.playerCount) {
+                        if (other != viewer) {
+                            val spied = (state.ck!!.chores.firstOrNull() as? SpyChore)
+                            val allowed = spied != null && spied.seat == viewer && spied.target == other
+                            if (!allowed) assertTrue(view.ck!!.progressHands[other].isEmpty())
+                        }
+                    }
+                }
+            }
+            checkInvariants(state, seed)
+        }
+        val ck = state.ck!!
+        return state to Report(
+            seed = seed,
+            moves = moves,
+            turns = state.turnNumber,
+            attacks = attacks,
+            progressPlayed = progress,
+            metropolises = ck.metropolises.size,
+            winner = state.winner,
+            points = CatanRules.publicVictoryPoints(state),
+        )
+    }
+
+    /** Things that must hold in every state of every game. */
+    private fun checkInvariants(state: CatanState, seed: Long) {
+        val ck = state.ck!!
+        val tag = "seed $seed turn ${state.turnNumber}"
+        // Cards are conserved: no good is held in more copies than the bank started with.
+        for (good in Good.entries) {
+            val held = (0 until state.playerCount).sumOf { CatanCk.goodsOf(state, it)[good] ?: 0 }
+            val cap = if (good.isCommodity) BANK_PER_COMMODITY else BANK_PER_RESOURCE
+            assertTrue("$tag: $held ${good} cards exist, the bank only had $cap", held in 0..cap)
+        }
+        for (seat in 0 until state.playerCount) {
+            assertTrue(
+                "$tag: seat $seat holds negative cards",
+                CatanCk.goodsOf(state, seat).values.all { it >= 0 },
+            )
+            for (level in 1..3) {
+                assertTrue(
+                    "$tag: seat $seat has more than two level-$level knights",
+                    ck.knights.count { it.owner == seat && it.level == level } <= KNIGHTS_PER_LEVEL,
+                )
+            }
+            assertTrue("$tag: too many progress cards in seat $seat's hand", ck.progressHands[seat].size <= PROGRESS_HAND_MAX + 1)
+            assertTrue("$tag: seat $seat has more than three walls", CatanCk.wallsOf(state, seat) <= MAX_WALLS)
+            assertTrue(
+                "$tag: seat $seat has more than five settlements",
+                state.buildings.count { it == CatanBuilding(BuildingType.SETTLEMENT, seat) } <= MAX_SETTLEMENTS,
+            )
+            assertTrue(
+                "$tag: seat $seat has more than four cities",
+                state.buildings.count { it == CatanBuilding(BuildingType.CITY, seat) } <= MAX_CITIES,
+            )
+        }
+        // A knight stands on a crossing nothing else stands on, and no two share one.
+        assertEquals("$tag: two knights share a crossing", ck.knights.size, ck.knights.map { it.vertex }.toSet().size)
+        for (k in ck.knights) {
+            assertTrue("$tag: a knight stands on a building at ${k.vertex}", state.buildings[k.vertex] == null)
+        }
+        // Metropolises stand on cities of their owners.
+        for ((_, m) in ck.metropolises) {
+            assertEquals(
+                "$tag: a metropolis is not on its owner's city",
+                CatanBuilding(BuildingType.CITY, m.seat),
+                state.buildings[m.vertex],
+            )
+        }
+        // Every progress card exists exactly once, in a deck or a hand, or was played face up.
+        val cards = ck.decks.values.sumOf { it.size } + ck.progressHands.sumOf { it.size } + ck.progressVp.sum()
+        assertEquals("$tag: progress cards were lost or duplicated", 54, cards)
+        assertTrue("$tag: barbarians out of range", ck.barbarians in 1..BARBARIAN_STEPS)
+    }
+
+    @Test
+    fun `three engines play Cities and Knights to a finish`() {
+        val reports = (1L..12L).map { seed ->
+            val (state, report) = playOut(
+                CatanOptions(playerCount = 3, pointsToWin = 13, ruleSet = CatanRuleSet.CITIES_AND_KNIGHTS),
+                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!!) >= 13,
+            )
+            report
+        }
+        reports.forEach { println("CK3 $it") }
+    }
+
+    @Test
+    fun `four engines play Cities and Knights to a finish`() {
+        val reports = (101L..108L).map { seed ->
+            val (state, report) = playOut(
+                CatanOptions(playerCount = 4, pointsToWin = 13, ruleSet = CatanRuleSet.CITIES_AND_KNIGHTS),
+                seed,
+            )
+            assertEquals("seed $seed", CatanPhase.GAME_OVER, state.phase)
+            report
+        }
+        reports.forEach { println("CK4 $it") }
+    }
+}

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

@@ -0,0 +1,325 @@
+package org.prolibertate.games.game.catan
+
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNotEquals
+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 CatanSeafarersTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun options(players: Int = 3) =
+        CatanOptions(playerCount = players, pointsToWin = 12, ruleSet = CatanRuleSet.SEAFARERS)
+
+    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,
+    )
+
+    private fun start(players: Int = 3, seed: Long = 7L): CatanState =
+        CatanRules.initialState(config(options(players), seed))
+
+    /** A mid-game table on seat 0's turn with plenty of cards. */
+    private fun playing(seed: Long = 7L, adjust: CatanState.() -> CatanState = { this }): CatanState =
+        start(seed = seed).copy(
+            phase = CatanPhase.PLAYING,
+            turn = 0,
+            turnNumber = 1,
+            resources = List(3) { Resource.entries.associateWith { 5 } },
+        ).adjust()
+
+    private fun CatanState.settle(vertex: Int, seat: Int, type: BuildingType = BuildingType.SETTLEMENT) =
+        copy(buildings = buildings.toMutableList().also { it[vertex] = CatanBuilding(type, seat) })
+
+    private fun CatanState.withShip(edge: Int, seat: Int) =
+        copy(sea = sea!!.let { it.copy(ships = it.ships.toMutableList().also { l -> l[edge] = seat }) })
+
+    private fun CatanState.withRoad(edge: Int, seat: Int) =
+        copy(roads = roads.toMutableList().also { it[edge] = seat })
+
+    /** A home-island vertex that touches open water, with a sea edge leaving it. */
+    private fun CatanState.coastVertex(): Int {
+        val topo = topo
+        return (0 until topo.VERTEX_COUNT).first { v ->
+            topo.vertexIsland[v] == sea!!.home &&
+                topo.VERTEX_EDGES[v].any { topo.edgeSea[it] && !topo.edgeLand[it] }
+        }
+    }
+
+    // --- The map -------------------------------------------------------------
+
+    @Test
+    fun `the new shores map is a big home island and three small ones`() {
+        val topo = SeaBoards.topology(SeaScenario.NEW_SHORES)
+        assertEquals(4, topo.islandCount)
+        val sizes = (0 until topo.islandCount).map { i -> topo.islandOf.count { it == i } }.sorted()
+        assertEquals(listOf(2, 3, 3, 21), sizes)
+        // Every coast is closed: nothing on land touches the edge of the frame.
+        for (e in 0 until topo.EDGE_COUNT) {
+            if (topo.EDGE_HEXES[e].size == 1) assertFalse("land on the frame edge at $e", topo.land[topo.EDGE_HEXES[e][0]])
+        }
+    }
+
+    @Test
+    fun `a new game has gold, a desert, numbers on every other land hex, a pirate at sea and nine harbours`() {
+        repeat(5) { i ->
+            val s = start(seed = 100L + i)
+            val topo = s.topo
+            assertEquals(2, s.terrains.count { it == Terrain.GOLD })
+            assertEquals(1, s.terrains.count { it == Terrain.DESERT })
+            for (h in 0 until topo.HEX_COUNT) {
+                val land = s.terrains[h] != Terrain.SEA
+                assertEquals("hex $h", topo.land[h], land)
+                assertEquals("hex $h", land && s.terrains[h] != Terrain.DESERT, s.numbers[h] != 0)
+            }
+            assertEquals(Terrain.SEA, s.terrains[s.sea!!.pirate])
+            assertTrue(s.terrains[s.robber] == Terrain.DESERT)
+            assertEquals(9, s.ports.size)
+            // The red numbers are never neighbours.
+            val reds = (0 until topo.HEX_COUNT).filter { s.numbers[it] == 6 || s.numbers[it] == 8 }
+            for (a in reds) for (b in reds) if (a < b) assertFalse(topo.hexesAdjacent(a, b))
+        }
+    }
+
+    @Test
+    fun `setup places both settlements on the home island, with roads rather than ships`() {
+        val s = start()
+        val moves = CatanRules.legalMoves(s, 0).filterIsInstance<SetupPlace>()
+        assertTrue(moves.isNotEmpty())
+        assertTrue(moves.all { s.topo.vertexIsland[it.vertex] == s.sea!!.home })
+        assertTrue(moves.all { s.topo.edgeLand[it.edge] })
+    }
+
+    @Test
+    fun `the state survives its wire format`() {
+        val s = playing().let { it.settle(it.coastVertex(), 0) }
+        assertEquals(s, CatanRules.decodeState(CatanRules.encodeState(s)))
+    }
+
+    // --- Ships ---------------------------------------------------------------
+
+    @Test
+    fun `a ship launches from a harbour town onto a sea edge and costs a lumber and a wool`() {
+        val s = playing().let { it.settle(it.coastVertex(), 0) }
+        val ships = CatanRules.legalMoves(s, 0).filterIsInstance<BuildShip>()
+        assertTrue(ships.isNotEmpty())
+        assertTrue(ships.all { s.topo.edgeSea[it.edge] })
+        val after = CatanRules.applyMove(s, 0, ships.first())
+        assertEquals(0, after.sea!!.ships.indexOfFirst { it == 0 }.let { if (it == ships.first().edge) 0 else 1 })
+        assertEquals(4, after.resources[0].getValue(Resource.LUMBER))
+        assertEquals(4, after.resources[0].getValue(Resource.WOOL))
+        assertEquals(5, after.resources[0].getValue(Resource.BRICK))
+    }
+
+    @Test
+    fun `no ship without the cards, and none sails out of nothing`() {
+        val bare = playing().let { it.settle(it.coastVertex(), 0) }
+            .let { it.copy(resources = it.resources.toMutableList().also { r -> r[0] = Resource.entries.associateWith { 0 } }) }
+        assertTrue(CatanRules.legalMoves(bare, 0).none { it is BuildShip })
+        // Nobody has a town or a fleet: there is nowhere to start from.
+        val nothing = playing()
+        assertTrue(CatanRules.legalMoves(nothing, 0).none { it is BuildShip })
+    }
+
+    @Test
+    fun `the pirate keeps ships off the edges round its hex`() {
+        val s = playing().let { it.settle(it.coastVertex(), 0) }
+        val ship = CatanRules.legalMoves(s, 0).filterIsInstance<BuildShip>().first()
+        val seaHex = s.topo.EDGE_HEXES[ship.edge].first { !s.topo.land[it] }
+        val blocked = s.copy(sea = s.sea!!.copy(pirate = seaHex))
+        assertTrue(CatanRules.legalMoves(blocked, 0).filterIsInstance<BuildShip>().none { seaHex in s.topo.EDGE_HEXES[it.edge] })
+    }
+
+    @Test
+    fun `a ship cannot sail the turn it is built, but can the next, from the open end only`() {
+        val s0 = playing().let { it.settle(it.coastVertex(), 0) }
+        val first = CatanRules.legalMoves(s0, 0).filterIsInstance<BuildShip>().first()
+        val s1 = CatanRules.applyMove(s0, 0, first)
+        assertTrue(CatanRules.legalMoves(s1, 0).none { it is MoveShip })
+
+        // Next turn (after the others pass), the lone ship is at an open end and can sail.
+        val s2 = s1.copy(sea = s1.sea!!.copy(builtThisTurn = emptyList(), shipMoved = false))
+        val sails = CatanRules.legalMoves(s2, 0).filterIsInstance<MoveShip>()
+        assertTrue(sails.isNotEmpty())
+        assertTrue(sails.all { it.from == first.edge && it.to != first.edge })
+
+        // Sailing uses the turn's one move.
+        val s3 = CatanRules.applyMove(s2, 0, sails.first())
+        assertTrue(s3.sea!!.shipMoved)
+        assertEquals(NO_PLAYER, s3.sea!!.ships[first.edge])
+        assertEquals(0, s3.sea!!.ships[sails.first().to])
+        assertTrue(CatanRules.legalMoves(s3, 0).none { it is MoveShip })
+    }
+
+    @Test
+    fun `a ship in the middle of a route is stuck`() {
+        // Town - ship A - ship B: A has the town at one end and B at the other, so only B is at an open end.
+        val s0 = playing().let { it.settle(it.coastVertex(), 0) }
+        val a = CatanRules.legalMoves(s0, 0).filterIsInstance<BuildShip>().first().edge
+        var s = s0.withShip(a, 0)
+        val far = s.topo.EDGE_VERTICES[a].toList().first { s.buildings[it] == null }
+        val b = s.topo.VERTEX_EDGES[far].first { it != a && s.topo.edgeSea[it] && s.roads[it] == NO_PLAYER }
+        s = s.withShip(b, 0)
+        val movers = CatanRules.legalMoves(s, 0).filterIsInstance<MoveShip>().map { it.from }.toSet()
+        assertEquals(setOf(b), movers)
+    }
+
+    @Test
+    fun `a settlement can rise at the end of a ship route, and the first on a new island scores the bonus`() {
+        val base = playing()
+        val topo = base.topo
+        val sea = base.sea!!
+        // A vertex on a small island, and a ship chain reaching it is too long to build by hand,
+        // so give the player the ship on the edge beside that vertex.
+        val vertex = (0 until topo.VERTEX_COUNT).first { v ->
+            val island = topo.vertexIsland[v]
+            island != -1 && island != sea.home &&
+                topo.VERTEX_EDGES[v].any { topo.edgeSea[it] }
+        }
+        val edge = topo.VERTEX_EDGES[vertex].first { topo.edgeSea[it] }
+        var s = base.withShip(edge, 0)
+        assertTrue(CatanRules.legalMoves(s, 0).any { it == BuildSettlement(vertex) })
+
+        val before = CatanRules.publicVictoryPoints(s)[0]
+        s = CatanRules.applyMove(s, 0, BuildSettlement(vertex))
+        assertEquals(before + 1 + SeaRules.ISLAND_BONUS, CatanRules.publicVictoryPoints(s)[0])
+        assertEquals(0, s.sea!!.islandBonus[topo.vertexIsland[vertex]])
+
+        // A second settlement on that island scores no second bonus.
+        val again = SeaRules.claimIsland(s, 1, vertex)
+        assertEquals(0, again.sea!!.islandBonus[topo.vertexIsland[vertex]])
+    }
+
+    @Test
+    fun `a road and a ship join a route only at a town of your own`() {
+        val base = playing()
+        val topo = base.topo
+        val v = base.coastVertex()
+        val road = topo.VERTEX_EDGES[v].first { topo.edgeLand[it] }
+        val ship = topo.VERTEX_EDGES[v].first { topo.edgeSea[it] && !topo.edgeLand[it] }
+
+        // With a town at the junction, road + ship is one route of two.
+        val withTown = base.settle(v, 0).withRoad(road, 0).withShip(ship, 0)
+        assertEquals(2, SeaRules.longestRouteFor(withTown, 0))
+
+        // Without it, they are two separate pieces.
+        val noTown = base.withRoad(road, 0).withShip(ship, 0)
+        assertEquals(1, SeaRules.longestRouteFor(noTown, 0))
+    }
+
+    // --- Pirate --------------------------------------------------------------
+
+    @Test
+    fun `on a seven the roller may move the robber to land or the pirate to sea, and the pirate robs a ship's owner`() {
+        val s0 = playing().let { it.settle(it.coastVertex(), 1) }
+        val ship = SeaRules.buildShipMoves(s0, 1).first().edge
+        val s = s0.withShip(ship, 1).copy(phase = CatanPhase.ROBBER)
+        val moves = CatanRules.legalMoves(s, 0)
+        assertTrue(moves.any { it is MoveRobber })
+        assertTrue(moves.any { it is MovePirate })
+        // Robber moves are on land only.
+        assertTrue(moves.filterIsInstance<MoveRobber>().all { s.topo.land[s.topo.hexIndex.getValue(it.hex)] })
+        assertTrue(moves.filterIsInstance<MovePirate>().all { !s.topo.land[s.topo.hexIndex.getValue(it.hex)] })
+
+        val robbery = moves.filterIsInstance<MovePirate>().first { it.victim == 1 }
+        val after = CatanRules.applyMove(s, 0, robbery)
+        assertEquals(CatanPhase.PLAYING, after.phase)
+        assertEquals(s.topo.hexIndex.getValue(robbery.hex), after.sea!!.pirate)
+        assertEquals(s.resourceCount(0) + 1, after.resourceCount(0))
+        assertEquals(s.resourceCount(1) - 1, after.resourceCount(1))
+    }
+
+    // --- Gold ----------------------------------------------------------------
+
+    @Test
+    fun `gold pays a resource of the owner's choice`() {
+        val base = playing()
+        val topo = base.topo
+        val goldHex = base.terrains.indexOf(Terrain.GOLD)
+        val number = base.numbers[goldHex]
+        val v = topo.HEX_CORNERS[goldHex].first { topo.vertexLand[it] }
+        // Seat 0's town beside the gold field; nothing else of theirs produces on that number.
+        val s = base.settle(v, 0).copy(
+            robber = (0 until topo.HEX_COUNT).first { topo.land[it] && it != goldHex && v !in topo.HEX_CORNERS[it] },
+            resources = List(3) { Resource.entries.associateWith { 0 } },
+            phase = CatanPhase.AWAIT_ROLL,
+        )
+        val dice = if (number <= 7) listOf(number - 1, 1) else listOf(6, number - 6)
+        val rolled = CatanRules.applyMove(s, 0, RollDice(forced = dice))
+        assertEquals(CatanPhase.GOLD, rolled.phase)
+        assertEquals(0, CatanRules.currentSeat(rolled))
+        val picks = CatanRules.legalMoves(rolled, 0)
+        assertEquals(Resource.entries.size, picks.size)
+        val after = CatanRules.applyMove(rolled, 0, PickGold(listOf(Resource.ORE)))
+        assertEquals(CatanPhase.PLAYING, after.phase)
+        assertEquals(1, after.resources[0].getValue(Resource.ORE))
+    }
+
+    // --- Whole games ---------------------------------------------------------
+
+    private data class Report(val seed: Long, val moves: Int, val ships: Int, val islandsTaken: Int, val points: List<Int>)
+
+    private fun playOut(options: CatanOptions, seed: Long, cap: Int = 20_000): Pair<CatanState, Report> {
+        val ai = CatanAi()
+        var state = CatanRules.initialState(config(options, seed))
+        var moves = 0
+        while (!CatanRules.isFinished(state)) {
+            assertTrue("seed $seed ran past $cap moves; log tail: ${state.log.takeLast(8)}", 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: seat $seat chose the illegal move $move in ${state.phase}; log tail: ${state.log.takeLast(5)}",
+                CatanRules.isLegalMove(state, seat, move),
+            )
+            val next = CatanRules.applyMove(state, seat, move)
+            // The wire format must carry everything, every step.
+            if (moves % 25 == 0) assertEquals(next, CatanRules.decodeState(CatanRules.encodeState(next)))
+            state = next
+        }
+        val sea = state.sea!!
+        return state to Report(
+            seed, moves,
+            ships = sea.ships.count { it != NO_PLAYER },
+            islandsTaken = sea.islandBonus.count { it != NO_PLAYER },
+            points = CatanRules.publicVictoryPoints(state),
+        )
+    }
+
+    @Test
+    fun `engines finish Seafarers games at three and four players`() {
+        val reports = mutableListOf<Report>()
+        for ((players, seeds) in listOf(3 to listOf(1L, 2L, 3L, 4L), 4 to listOf(5L, 6L, 7L))) {
+            for (seed in seeds) {
+                val (state, report) = playOut(options(players), 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,
+                )
+                reports += report
+            }
+        }
+        println("Seafarers self-play: " + reports.joinToString("; ") {
+            "seed ${it.seed}: ${it.moves} moves, ${it.ships} ships, ${it.islandsTaken} islands, points ${it.points}"
+        })
+        // The engines must actually go to sea in at least some of the games.
+        assertNotEquals("no engine ever built a ship", 0, reports.sumOf { it.ships })
+    }
+}

app/src/test/java/org/prolibertate/games/game/engine/SavedGameStoreTest.kt

@@ -0,0 +1,119 @@
+package org.prolibertate.games.game.engine
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Rule
+import org.junit.Test
+import org.junit.rules.TemporaryFolder
+import java.io.File
+
+class SavedGameStoreTest {
+
+    @get:Rule
+    val folder = TemporaryFolder()
+
+    private fun store() = SavedGameStore(File(folder.root, "saves"))
+
+    private fun match(gameId: String = "chess", state: String = "{\"turn\":1}", at: Long = 1_000L) = SavedMatch(
+        gameId = gameId,
+        config = TableConfig(
+            gameId = gameId,
+            seats = listOf(
+                PlayerSlot(0, "You", PlayerKind.HUMAN_LOCAL, 0),
+                PlayerSlot(1, "Computer", PlayerKind.AI, 1),
+            ),
+            optionsJson = "{}",
+            seed = 42L,
+        ),
+        localSeat = 0,
+        stateJson = state,
+        savedAtMillis = at,
+        summary = "White to move",
+    )
+
+    @Test
+    fun `a saved game comes back exactly as it went in`() {
+        val s = store()
+        s.save(match())
+        assertEquals(match(), s.load("chess"))
+    }
+
+    @Test
+    fun `there is nothing to load before anything is saved`() {
+        assertNull(store().load("chess"))
+        assertTrue(store().all().isEmpty())
+    }
+
+    @Test
+    fun `a game keeps one slot, and saving again replaces it`() {
+        val s = store()
+        s.save(match(state = "one", at = 1))
+        s.save(match(state = "two", at = 2))
+        assertEquals("two", s.load("chess")!!.stateJson)
+        assertEquals(1, s.all().size)
+    }
+
+    @Test
+    fun `clearing forgets the game and leaves the others`() {
+        val s = store()
+        s.save(match("chess"))
+        s.save(match("golf"))
+        s.clear("chess")
+        assertNull(s.load("chess"))
+        assertEquals("golf", s.load("golf")!!.gameId)
+        s.clear("chess") // clearing nothing is fine
+    }
+
+    @Test
+    fun `the most recently played game is listed first`() {
+        val s = store()
+        s.save(match("chess", at = 10))
+        s.save(match("golf", at = 30))
+        s.save(match("catan", at = 20))
+        assertEquals(listOf("golf", "catan", "chess"), s.all().map { it.gameId })
+    }
+
+    @Test
+    fun `a file that cannot be read is dropped rather than thrown`() {
+        val s = store()
+        s.save(match())
+        File(folder.root, "saves/chess.json").writeText("{ this is not json")
+        assertNull(s.load("chess"))
+        assertFalse(File(folder.root, "saves/chess.json").exists())
+    }
+
+    @Test
+    fun `a file holding another game is not served as this one`() {
+        val s = store()
+        s.save(match("golf"))
+        File(folder.root, "saves/golf.json").copyTo(File(folder.root, "saves/chess.json"))
+        assertNull(s.load("chess"))
+    }
+
+    @Test
+    fun `a save that was cut off half way leaves the previous position`() {
+        val s = store()
+        s.save(match(state = "good"))
+        // What a kill mid-write leaves behind: a stray temporary file.
+        File(folder.root, "saves/chess.json.tmp").writeText("{ half a wri")
+        assertEquals("good", s.load("chess")!!.stateJson)
+        assertEquals(1, s.all().size)
+    }
+
+    @Test
+    fun `a game id cannot climb out of the folder`() {
+        val bad = runCatching { store().load("../secret") }
+        assertTrue(bad.isFailure)
+    }
+
+    @Test
+    fun `an unknown field from a newer build does not stop a save loading`() {
+        val s = store()
+        s.save(match())
+        val file = File(folder.root, "saves/chess.json")
+        file.writeText(file.readText().replaceFirst("{", "{\"addedLater\":true,"))
+        assertEquals("chess", s.load("chess")!!.gameId)
+    }
+}

app/src/test/java/org/prolibertate/games/game/meowdoku/MeowdokuRulesTest.kt

@@ -0,0 +1,343 @@
+package org.prolibertate.games.game.meowdoku
+
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertThrows
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+/**
+ * The puzzle, the generator, and the referee.
+ *
+ * The generator is where a wrong board would hurt most — a second answer makes
+ * the deduction unfair and the hearts a lottery — so the generation tests run
+ * over seeds rather than one lucky one.
+ */
+class MeowdokuRulesTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun soloConfig(options: MeowdokuOptions, seed: Long = 7L) = TableConfig(
+        gameId = "meowdoku",
+        seats = listOf(PlayerSlot(seat = 0, name = "P0", kind = PlayerKind.HUMAN_LOCAL, team = 0)),
+        optionsJson = json.encodeToString(options),
+        seed = seed,
+    )
+
+    private fun dealt(side: Int, seed: Long = 7L) =
+        MeowdokuRules.initialState(soloConfig(MeowdokuOptions(side = side), seed))
+
+    /**
+     * A puzzle that must exist, named so the assertions below read as facts
+     * rather than as unwrapping.
+     */
+    private fun <T> required(value: T?, message: String): T {
+        assertNotNull(message, value)
+        @Suppress("UNCHECKED_CAST")
+        return value as T
+    }
+
+    // ---- generator ---------------------------------------------------------
+
+    @Test
+    fun `every dealt board has exactly one answer`() {
+        for (side in 4..8) {
+            for (seed in 1L..6L) {
+                val puzzle = required(
+                    MeowdokuGenerator.generate(side, seed),
+                    "no puzzle for side $side seed $seed",
+                )
+                assertEquals(
+                    "the $side board dealt from seed $seed has more than one answer",
+                    1,
+                    MeowdokuGenerator.countSolutions(side, puzzle.regions),
+                )
+            }
+        }
+    }
+
+    @Test
+    fun `the same seed deals the same board`() {
+        val a = MeowdokuGenerator.generate(6, 12345L)
+        val b = MeowdokuGenerator.generate(6, 12345L)
+        assertEquals(a, b)
+    }
+
+    @Test
+    fun `the answer satisfies the cats' own rules`() {
+        for (seed in 0L..20L) {
+            val puzzle = required(MeowdokuGenerator.generate(7, seed), "no puzzle for seed $seed")
+            val cats = puzzle.solutionSquares()
+            assertEquals(7, cats.size)
+            assertEquals(7, cats.map { it.first }.distinct().size)
+            assertEquals(7, cats.map { it.second }.distinct().size)
+            for (i in cats.indices) {
+                for (j in i + 1 until cats.size) {
+                    val (r1, c1) = cats[i]
+                    val (r2, c2) = cats[j]
+                    val touches = kotlin.math.abs(r1 - r2) <= 1 && kotlin.math.abs(c1 - c2) <= 1
+                    assertFalse("cats $cats touch", touches)
+                    assertFalse("two cats share a colour", puzzle.regionOf(r1, c1) == puzzle.regionOf(r2, c2))
+                }
+            }
+        }
+    }
+
+    @Test
+    fun `every colour owns exactly one cat and is contiguous`() {
+        val puzzle = required(MeowdokuGenerator.generate(6, 99L), "no puzzle for seed 99")
+        val cells = (0 until 6).flatMap { r -> (0 until 6).map { c -> r to c } }
+
+        val owned = (0 until 6).map { region ->
+            cells.filter { (r, c) -> puzzle.regionOf(r, c) == region }
+        }
+        owned.forEach { cellsOfRegion ->
+            assertTrue("an empty colour", cellsOfRegion.isNotEmpty())
+            val cats = cellsOfRegion.count { (r, c) -> puzzle.catCols[r] == c }
+            assertEquals("a colour with ${cats}cats", 1, cats)
+
+            // Contiguous: a breadth-first walk from the first cell reaches all.
+            val rest = cellsOfRegion.toMutableSet()
+            val queue = ArrayDeque(listOf(rest.first()))
+            val reached = mutableSetOf(queue.first())
+            while (queue.isNotEmpty()) {
+                val (r, c) = queue.removeFirst()
+                for ((dr, dc) in listOf(0 to 1, 0 to -1, 1 to 0, -1 to 0)) {
+                    val next = (r + dr) to (c + dc)
+                    if (next in rest && reached.add(next)) queue.add(next)
+                }
+            }
+            assertEquals("a colour in two pieces", rest.size, reached.size)
+        }
+    }
+
+    @Test
+    fun `the cats can always be settled`() {
+        // A four board is the smallest deal, and its answer is the point where
+        // no-touch and one-per-line first stop contradicting each other.
+        val rng = SeededRng(42)
+        val cols = MeowdokuGenerator.placeCats(4, rng)
+        assertEquals(4, cols.size)
+        // The placement the generator returns is internally consistent.
+        for (row in 0 until 4) {
+            for (earlier in 0 until row) {
+                assertFalse(MeowdokuGenerator.catFitsHere(row, cols[earlier], cols))
+            }
+        }
+    }
+
+    // ---- the referee -------------------------------------------------------
+
+    @Test
+    fun `the board opens empty and seated for one`() {
+        val state = dealt(6)
+        assertTrue(state.cats.isEmpty())
+        assertTrue(state.marks.isEmpty())
+        assertEquals(6, state.side)
+        assertEquals(3, state.heartsLeft)
+        assertEquals(0, state.catsFound)
+        assertEquals(0, MeowdokuRules.currentSeat(state))
+        assertFalse(MeowdokuRules.isFinished(state))
+        assertTrue(MeowdokuRules.legalMoves(state, 1).isEmpty())
+    }
+
+    @Test
+    fun `a correct tap lands a cat and a wrong tap costs a heart`() {
+        val state = dealt(6)
+        val square = Square(0, state.catCols[0])
+        val found = MeowdokuRules.applyMove(state, 0, PlaceCat(square))
+        assertTrue(square in found.cats)
+        assertEquals(3, found.heartsLeft)
+
+        val wrongRow = (0 until state.side).first { it != square.row }
+        val wrong = Square(wrongRow, if (state.catCols[wrongRow] == 0) 1 else 0)
+        val missed = MeowdokuRules.applyMove(found, 0, PlaceCat(wrong))
+        assertTrue(wrong in missed.marks)
+        assertFalse(wrong in missed.cats)
+        assertEquals(2, missed.heartsLeft)
+        assertEquals(1, missed.wrongCats)
+    }
+
+    @Test
+    fun `a board is solved by finding every cat`() {
+        var state = dealt(5)
+        for (row in 0 until 5) {
+            state = MeowdokuRules.applyMove(state, 0, PlaceCat(Square(row, state.catCols[row])))
+        }
+        assertTrue(state.solved)
+        assertTrue(MeowdokuRules.isFinished(state))
+        assertNull(MeowdokuRules.currentSeat(state))
+        assertTrue(MeowdokuRules.legalMoves(state, 0).isEmpty())
+        assertTrue(MeowdokuRules.summary(state).startsWith("Solved"))
+    }
+
+    @Test
+    fun `running out of hearts loses the board`() {
+        val state = dealt(8, seed = 3L)
+        var lost = state
+        var row = 0
+        while (lost.heartsLeft > 0) {
+            // A wrong square: not the answer's column, in a row with no cat.
+            val wrongCol = if (state.catCols[row] == 0) 1 else 0
+            val before = lost.catsFound
+            lost = MeowdokuRules.applyMove(lost, 0, PlaceCat(Square(row, wrongCol)))
+            assertEquals(before, lost.catsFound)
+            row = (row + 1) % state.side
+        }
+        assertTrue(lost.lost)
+        assertTrue(MeowdokuRules.isFinished(lost))
+        assertEquals(0, lost.catsFound)
+        assertTrue(MeowdokuRules.summary(lost).startsWith("Lost"))
+    }
+
+    @Test
+    fun `a crossed square still takes a cat attempt`() {
+        // The double tap is one gesture pair: the first tap crosses the square
+        // and the second asks it. The cross the pair drew cannot veto the
+        // question that follows it.
+        val state = dealt(6)
+        val truth = Square(0, state.catCols[0])
+        val crossed = MeowdokuRules.applyMove(state, 0, TogglePencil(truth))
+        assertTrue(truth in crossed.marks)
+        assertTrue(
+            "the attempt is offered over its own cross",
+            PlaceCat(truth) in MeowdokuRules.legalMoves(crossed, 0),
+        )
+
+        val placed = MeowdokuRules.applyMove(crossed, 0, PlaceCat(truth))
+        assertTrue(truth in placed.cats)
+        assertFalse("the cat replaces the cross", truth in placed.marks)
+        assertEquals(3, placed.heartsLeft)
+        assertEquals(0, placed.wrongCats)
+    }
+
+    @Test
+    fun `a wrong pair keeps its cross and spends a heart`() {
+        val state = dealt(6)
+        val wrongCol = if (state.catCols[1] == 0) 1 else 0
+        val wrong = Square(1, wrongCol)
+        val crossed = MeowdokuRules.applyMove(state, 0, TogglePencil(wrong))
+        val judged = MeowdokuRules.applyMove(crossed, 0, PlaceCat(wrong))
+        assertTrue(wrong in judged.marks)
+        assertFalse(wrong in judged.cats)
+        assertEquals(2, judged.heartsLeft)
+        assertEquals(1, judged.wrongCats)
+    }
+
+    @Test
+    fun `pencil marks are free notes`() {
+        val state = dealt(6)
+        val square = Square(2, if (state.catCols[2] == 5) 4 else 5)
+        val marked = MeowdokuRules.applyMove(state, 0, TogglePencil(square))
+        assertTrue(square in marked.marks)
+        assertEquals(3, marked.heartsLeft)
+        assertEquals(0, marked.wrongCats)
+
+        val erased = MeowdokuRules.applyMove(marked, 0, TogglePencil(square))
+        assertTrue(erased.marks.isEmpty())
+    }
+
+    @Test
+    fun `a cat square is never a pencil square`() {
+        val state = dealt(6)
+        val cat = Square(0, state.catCols[0])
+        val found = MeowdokuRules.applyMove(state, 0, PlaceCat(cat))
+        assertFalse(
+            "legal moves offer pencil on a cat",
+            MeowdokuRules.legalMoves(found, 0).any {
+                it is TogglePencil && it.square == cat
+            },
+        )
+    }
+
+    @Test
+    fun `a hint shows a missing cat and costs one token`() {
+        val state = dealt(6)
+        val hinted = MeowdokuRules.applyMove(state, 0, TakeHint)
+        assertEquals(1, hinted.catsFound)
+        assertEquals(2, hinted.hintsLeft)
+
+        // Out of hints the move stops being offered.
+        var drained = MeowdokuRules.applyMove(
+            MeowdokuRules.applyMove(hinted, 0, TakeHint),
+            0,
+            TakeHint,
+        )
+        assertEquals(0, drained.hintsLeft)
+        // A note on a square that is not a cat, so the pencil move is legal.
+        val note = Square(0, if (state.catCols[0] == 0) 1 else 0)
+        drained = MeowdokuRules.applyMove(drained, 0, TogglePencil(note))
+        assertFalse(TakeHint in MeowdokuRules.legalMoves(drained, 0))
+    }
+
+    @Test
+    fun `a hint over a wrong pencil reveals the cat anyway`() {
+        val state = dealt(6)
+        val truth = Square(0, state.catCols[0])
+        val pencilled = MeowdokuRules.applyMove(state, 0, TogglePencil(truth))
+        val revealed = MeowdokuRules.applyMove(pencilled, 0, TakeHint)
+        assertTrue(truth in revealed.cats)
+        assertFalse(truth in revealed.marks)
+    }
+
+    @Test
+    fun `the computer can finish any board it is handed`() {
+        var state = dealt(7)
+        var guard = 0
+        while (!MeowdokuRules.isFinished(state) && guard++ < 100) {
+            val legal = MeowdokuRules.legalMoves(state, 0)
+            assertFalse("stuck with cats still missing", legal.isEmpty())
+            state = MeowdokuRules.applyMove(state, 0, MeowdokuAi.chooseMove(state, 0, legal))
+        }
+        assertTrue("the AI did not solve the board", state.solved)
+    }
+
+    // ---- state across the wire and the save slot ---------------------------
+
+    @Test
+    fun `state and moves survive their json`() {
+        val state = dealt(6)
+        val decoded = MeowdokuRules.decodeState(MeowdokuRules.encodeState(state))
+        assertEquals(state, decoded)
+
+        val move: MeowdokuMove = PlaceCat(Square(1, 1))
+        assertEquals(move, MeowdokuRules.decodeMove(MeowdokuRules.encodeMove(move)))
+        assertEquals(TakeHint, MeowdokuRules.decodeMove(MeowdokuRules.encodeMove(TakeHint)))
+    }
+
+    @Test
+    fun `nothing is hidden from the only seat`() {
+        val state = dealt(6)
+        assertEquals(state, MeowdokuRules.viewFor(state, 0))
+    }
+
+    @Test
+    fun `a table with two seats is refused`() {
+        val config = TableConfig(
+            gameId = "meowdoku",
+            seats = listOf(
+                PlayerSlot(0, "P0", PlayerKind.HUMAN_LOCAL, 0),
+                PlayerSlot(1, "P1", PlayerKind.AI, 1),
+            ),
+            optionsJson = json.encodeToString(MeowdokuOptions()),
+            seed = 1L,
+        )
+        assertThrows(IllegalArgumentException::class.java) {
+            MeowdokuRules.initialState(config)
+        }
+    }
+
+    @Test
+    fun `the options guard their own board`() {
+        assertThrows(IllegalArgumentException::class.java) { MeowdokuOptions(side = 3) }
+        assertThrows(IllegalArgumentException::class.java) { MeowdokuOptions(side = 11) }
+        assertThrows(IllegalArgumentException::class.java) { MeowdokuOptions(hearts = 0) }
+    }
+}

app/src/test/java/org/prolibertate/games/game/yahtzee/YahtzeeStatsTest.kt

@@ -0,0 +1,30 @@
+package org.prolibertate.games.game.yahtzee
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Test
+
+class YahtzeeStatsTest {
+    private fun game(total: Int, bonus: Boolean = false, yahtzees: Int = 0, won: Boolean = true) =
+        YahtzeeRecord(total, bonus, yahtzees, zeros = 0, players = 2, won = won)
+
+    @Test
+    fun firstGameHasNothingToCompareTo() {
+        val c = compareToHistory(emptyList(), game(200))
+        assertEquals(1, c.rank)
+        assertEquals(0, c.previousGames)
+        assertNull(c.bestBefore)
+        assertNull(c.averageBefore)
+    }
+
+    @Test
+    fun ranksAgainstPreviousGames() {
+        val history = listOf(game(150, bonus = true, yahtzees = 1), game(250), game(200, won = false))
+        val c = compareToHistory(history, game(220))
+        assertEquals(2, c.rank)
+        assertEquals(4, c.gamesRanked)
+        assertEquals(250, c.bestBefore)
+        assertEquals(200.0, c.averageBefore!!, 0.001)
+        assertEquals(1, c.yahtzeesBefore)
+    }
+}

app/src/test/java/org/prolibertate/games/net/MatchSaverTest.kt

@@ -0,0 +1,191 @@
+package org.prolibertate.games.net
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.runBlocking
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Rule
+import org.junit.Test
+import org.junit.rules.TemporaryFolder
+import org.prolibertate.games.game.engine.GameAi
+import org.prolibertate.games.game.engine.GameRules
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.SavedGameStore
+import org.prolibertate.games.game.engine.TableConfig
+import java.io.File
+
+/**
+ * Saving a table as it is played, and starting a table from a save.
+ *
+ * The game here is a counter: one seat, a move adds one, and it is finished at
+ * [GOAL]. It has hidden state — [Counter.secret] — so the tests can check that
+ * what is saved is the true state, not the view a player is shown.
+ */
+class MatchSaverTest {
+
+    @get:Rule
+    val folder = TemporaryFolder()
+
+    private val scopes = mutableListOf<CoroutineScope>()
+
+    @After
+    fun tearDown() {
+        scopes.forEach { it.cancel() }
+    }
+
+    private data class Counter(val n: Int, val secret: String)
+
+    private object Rules : GameRules<Counter, String> {
+        override val gameId = "counter"
+        override fun initialState(config: TableConfig) = Counter(0, "hidden-${config.seed}")
+        override fun currentSeat(state: Counter): Int? = if (state.n >= GOAL) null else 0
+        override fun legalMoves(state: Counter, seat: Int) = if (state.n >= GOAL) emptyList() else listOf("add")
+        override fun applyMove(state: Counter, seat: Int, move: String) = state.copy(n = state.n + 1)
+        override fun isFinished(state: Counter) = state.n >= GOAL
+        override fun summary(state: Counter) = "at ${state.n}"
+        override fun viewFor(state: Counter, seat: Int) = state.copy(secret = "")
+        override fun encodeState(state: Counter) = "${state.n}|${state.secret}"
+        override fun decodeState(json: String): Counter {
+            val (n, secret) = json.split("|", limit = 2)
+            return Counter(n.toInt(), secret)
+        }
+
+        override fun encodeMove(move: String) = move
+        override fun decodeMove(json: String) = json
+    }
+
+    private val config = TableConfig(
+        gameId = "counter",
+        seats = listOf(PlayerSlot(0, "You", PlayerKind.HUMAN_LOCAL, 0)),
+        optionsJson = "{}",
+        seed = 7L,
+    )
+
+    private fun scope() = CoroutineScope(Job() + Dispatchers.Default).also { scopes += it }
+
+    private fun controller(): MatchController<Counter, String> = MatchController(
+        rules = Rules,
+        ai = object : GameAi<Counter, String> {
+            override fun chooseMove(state: Counter, seat: Int, legal: List<String>) = legal.first()
+        },
+        config = config,
+        scope = scope(),
+        role = MatchController.Role.HOST,
+        localSeats = setOf(0),
+        primarySeat = 0,
+    )
+
+    private fun store() = SavedGameStore(File(folder.root, "saves"))
+
+    private fun waitFor(what: String, check: () -> Boolean) = runBlocking {
+        repeat(200) {
+            if (check()) return@runBlocking
+            delay(10)
+        }
+        error("Timed out waiting for $what")
+    }
+
+    private fun saver(s: SavedGameStore, c: MatchController<Counter, String>) =
+        MatchSaver(s, "counter", config, localSeat = 0, scope = scope(), clock = { 123L }).also {
+            it.start()
+            c.onHostState = it::offer
+        }
+
+    @Test
+    fun `every position the table reaches is kept, with the true state`() {
+        val s = store()
+        val c = controller()
+        saver(s, c)
+        c.startAsHost(emptyList())
+        waitFor("the deal") { c.state.value != null }
+        c.submit("add")
+        c.submit("add")
+        waitFor("two moves") { s.load("counter")?.stateJson?.startsWith("2|") == true }
+
+        val saved = s.load("counter")!!
+        assertEquals("2|hidden-7", saved.stateJson) // the hidden part is saved; the view blanks it
+        assertEquals("at 2", saved.summary)
+        assertEquals(123L, saved.savedAtMillis)
+        assertEquals(config, saved.config)
+    }
+
+    @Test
+    fun `a table started from a save carries on from where it stood`() {
+        val s = store()
+        val first = controller()
+        saver(s, first)
+        first.startAsHost(emptyList())
+        waitFor("the deal") { first.state.value != null }
+        repeat(3) { first.submit("add") }
+        waitFor("three moves") { s.load("counter")?.stateJson?.startsWith("3|") == true }
+        first.close()
+
+        val second = controller()
+        assertTrue(second.restore(s.load("counter")!!.stateJson))
+        second.startAsHost(emptyList())
+        waitFor("the restored table") { second.state.value != null }
+        assertEquals(3, second.state.value!!.n)
+        second.submit("add")
+        waitFor("a move after resuming") { second.state.value!!.n == 4 }
+    }
+
+    @Test
+    fun `a save the game cannot read is refused and the table is dealt afresh`() {
+        val c = controller()
+        assertFalse(c.restore("not a counter"))
+        c.startAsHost(emptyList())
+        waitFor("a fresh deal") { c.state.value != null }
+        assertEquals(0, c.state.value!!.n)
+    }
+
+    @Test
+    fun `a finished game is not kept`() {
+        val s = store()
+        val c = controller()
+        saver(s, c)
+        c.startAsHost(emptyList())
+        waitFor("the deal") { s.load("counter") != null }
+        repeat(GOAL) { c.submit("add") }
+        waitFor("the finish") { c.finished.value }
+        waitFor("the slot to clear") { s.load("counter") == null }
+    }
+
+    @Test
+    fun `flush writes the position the background writer has not reached`() {
+        val s = store()
+        val saver = MatchSaver(s, "counter", config, 0, scope(), clock = { 1L })
+        // Not started: nothing is written in the background at all.
+        saver.offer(MatchController.HostSnapshot(false, "at 5") { "5|x" })
+        assertNull(s.load("counter"))
+        saver.flush()
+        assertEquals("5|x", s.load("counter")!!.stateJson)
+    }
+
+    @Test
+    fun `ending a game on purpose forgets it and writes no more`() {
+        val s = store()
+        val saver = MatchSaver(s, "counter", config, 0, scope(), clock = { 1L })
+        saver.offer(MatchController.HostSnapshot(false, "at 1") { "1|x" })
+        saver.flush()
+        assertNotNull(s.load("counter"))
+        saver.discard()
+        assertNull(s.load("counter"))
+        // Leaving after ending must not put it back.
+        saver.offer(MatchController.HostSnapshot(false, "at 2") { "2|x" })
+        saver.flush()
+        assertNull(s.load("counter"))
+    }
+
+    private companion object {
+        const val GOAL = 5
+    }
+}

app/src/test/java/org/prolibertate/games/net/SaveRoundTripAllGamesTest.kt

@@ -0,0 +1,177 @@
+package org.prolibertate.games.net
+
+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.GameAi
+import org.prolibertate.games.game.engine.GameRules
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+import org.prolibertate.games.ui.seatCountFor
+import org.prolibertate.games.game.backgammon.BackgammonAi
+import org.prolibertate.games.game.backgammon.BackgammonOptions
+import org.prolibertate.games.game.backgammon.BackgammonRules
+import org.prolibertate.games.game.catan.CatanAi
+import org.prolibertate.games.game.catan.CatanOptions
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.checkers.CheckersAi
+import org.prolibertate.games.game.checkers.CheckersOptions
+import org.prolibertate.games.game.checkers.CheckersRules
+import org.prolibertate.games.game.chess.ChessAi
+import org.prolibertate.games.game.chess.ChessOptions
+import org.prolibertate.games.game.chess.ChessRules
+import org.prolibertate.games.game.crazyeights.CrazyEightsAi
+import org.prolibertate.games.game.crazyeights.CrazyEightsOptions
+import org.prolibertate.games.game.crazyeights.CrazyEightsRules
+import org.prolibertate.games.game.cribbage.CribbageAi
+import org.prolibertate.games.game.cribbage.CribbageOptions
+import org.prolibertate.games.game.cribbage.CribbageRules
+import org.prolibertate.games.game.euchre.EuchreAi
+import org.prolibertate.games.game.euchre.EuchreOptions
+import org.prolibertate.games.game.euchre.EuchreRules
+import org.prolibertate.games.game.freecell.FreeCellOptions
+import org.prolibertate.games.game.freecell.FreeCellRules
+import org.prolibertate.games.game.golf.GolfAi
+import org.prolibertate.games.game.golf.GolfOptions
+import org.prolibertate.games.game.golf.GolfRules
+import org.prolibertate.games.game.hearts.HeartsAi
+import org.prolibertate.games.game.hearts.HeartsOptions
+import org.prolibertate.games.game.hearts.HeartsRules
+import org.prolibertate.games.game.kaiser.KaiserAi
+import org.prolibertate.games.game.kaiser.KaiserOptions
+import org.prolibertate.games.game.kaiser.KaiserRules
+import org.prolibertate.games.game.klondike.KlondikeAi
+import org.prolibertate.games.game.klondike.KlondikeOptions
+import org.prolibertate.games.game.klondike.KlondikeRules
+import org.prolibertate.games.game.mastermind.MastermindAi
+import org.prolibertate.games.game.mastermind.MastermindOptions
+import org.prolibertate.games.game.mastermind.MastermindRules
+import org.prolibertate.games.game.morris.MorrisAi
+import org.prolibertate.games.game.morris.MorrisOptions
+import org.prolibertate.games.game.morris.MorrisRules
+import org.prolibertate.games.game.pegsolitaire.PegSolitaireAi
+import org.prolibertate.games.game.pegsolitaire.PegSolitaireOptions
+import org.prolibertate.games.game.pegsolitaire.PegSolitaireRules
+import org.prolibertate.games.game.pirates.PiratesAi
+import org.prolibertate.games.game.pirates.PiratesOptions
+import org.prolibertate.games.game.pirates.PiratesRules
+import org.prolibertate.games.game.president.PresidentAi
+import org.prolibertate.games.game.president.PresidentOptions
+import org.prolibertate.games.game.president.PresidentRules
+import org.prolibertate.games.game.pyramid.PyramidOptions
+import org.prolibertate.games.game.pyramid.PyramidRules
+import org.prolibertate.games.game.sequence.SequenceAi
+import org.prolibertate.games.game.sequence.SequenceOptions
+import org.prolibertate.games.game.sequence.SequenceRules
+import org.prolibertate.games.game.solitaire.FirstLegalAi
+import org.prolibertate.games.game.spider.SpiderOptions
+import org.prolibertate.games.game.spider.SpiderRules
+import org.prolibertate.games.game.tayu.TayuAi
+import org.prolibertate.games.game.tayu.TayuOptions
+import org.prolibertate.games.game.tayu.TayuRules
+import org.prolibertate.games.game.wizard.WizardAi
+import org.prolibertate.games.game.wizard.WizardOptions
+import org.prolibertate.games.game.wizard.WizardRules
+import org.prolibertate.games.game.yahtzee.YahtzeeAi
+import org.prolibertate.games.game.yahtzee.YahtzeeOptions
+import org.prolibertate.games.game.yahtzee.YahtzeeRules
+
+/**
+ * Every game can be saved and picked up again.
+ *
+ * For each game in the catalogue a table is dealt and played by the computer, and
+ * at every single move the whole true state is encoded and decoded again — which
+ * is exactly what saving it to disk and resuming does — and play carries on from
+ * the decoded copy. A game whose state does not survive that, or that cannot make
+ * a legal move from a state it has been through it, fails here.
+ */
+class SaveRoundTripAllGamesTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun <S : Any, M : Any> exercise(
+        gameId: String,
+        rules: GameRules<S, M>,
+        ai: GameAi<S, M>,
+        optionsJson: String,
+        steps: Int = 120,
+    ) {
+        val seats = seatCountFor(gameId, optionsJson)
+        val config = TableConfig(
+            gameId = gameId,
+            seats = (0 until seats).map {
+                PlayerSlot(it, "P$it", if (it == 0) PlayerKind.HUMAN_LOCAL else PlayerKind.AI, it)
+            },
+            optionsJson = optionsJson,
+            seed = 20240607L,
+        )
+        var state = rules.initialState(config)
+        var moves = 0
+        repeat(steps) {
+            if (rules.isFinished(state)) return
+            // The save and the resume: what goes to disk, and what comes back.
+            val saved = rules.encodeState(state)
+            val back = rules.decodeState(saved)
+            assertEquals("$gameId: a saved state encodes differently after a resume", saved, rules.encodeState(back))
+            assertEquals(
+                "$gameId: a resumed state is not on the same seat's turn",
+                rules.currentSeat(state),
+                rules.currentSeat(back),
+            )
+            assertEquals(
+                "$gameId: a resumed state has different legal moves",
+                rules.currentSeat(state)?.let { rules.legalMoves(state, it) },
+                rules.currentSeat(back)?.let { rules.legalMoves(back, it) },
+            )
+            state = back
+
+            val seat = rules.currentSeat(state) ?: return // waiting on a scoreboard, which is not a move
+            val legal = rules.legalMoves(state, seat)
+            if (legal.isEmpty()) return
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("$gameId: move $move is not legal after a resume", rules.isLegalMove(state, seat, move))
+            state = rules.applyMove(state, seat, move)
+            moves++
+        }
+        assertTrue("$gameId: made no moves", moves > 0)
+    }
+
+    private inline fun <reified O> opts(o: O) = json.encodeToString(o)
+
+    @Test fun euchre() = exercise(GameCatalog.EUCHRE, EuchreRules, EuchreAi(), opts(EuchreOptions()))
+    @Test fun sequence() = exercise(GameCatalog.SEQUENCE, SequenceRules, SequenceAi(), opts(SequenceOptions()))
+    @Test fun president() = exercise(GameCatalog.PRESIDENT, PresidentRules, PresidentAi(), opts(PresidentOptions()))
+    @Test fun golf() = exercise(GameCatalog.GOLF, GolfRules, GolfAi(), opts(GolfOptions()))
+    @Test fun kaiser() = exercise(GameCatalog.KAISER, KaiserRules, KaiserAi(), opts(KaiserOptions()))
+    @Test fun wizard() = exercise(GameCatalog.WIZARD, WizardRules, WizardAi(), opts(WizardOptions()))
+    @Test fun crazyEights() = exercise(GameCatalog.CRAZY_EIGHTS, CrazyEightsRules, CrazyEightsAi(), opts(CrazyEightsOptions()))
+    @Test fun cribbage() = exercise(GameCatalog.CRIBBAGE, CribbageRules, CribbageAi(), opts(CribbageOptions()))
+    @Test fun tayu() = exercise(GameCatalog.TAYU, TayuRules, TayuAi(), opts(TayuOptions()))
+    @Test fun checkers() = exercise(GameCatalog.CHECKERS, CheckersRules, CheckersAi(), opts(CheckersOptions()))
+    @Test fun backgammon() = exercise(GameCatalog.BACKGAMMON, BackgammonRules, BackgammonAi(), opts(BackgammonOptions()))
+    @Test fun mastermind() = exercise(GameCatalog.MASTERMIND, MastermindRules, MastermindAi(), opts(MastermindOptions()))
+    @Test fun pirates() = exercise(GameCatalog.PIRATES, PiratesRules, PiratesAi(), opts(PiratesOptions()))
+    @Test fun hearts() = exercise(GameCatalog.HEARTS, HeartsRules, HeartsAi, opts(HeartsOptions()))
+    @Test fun pegSolitaire() = exercise(GameCatalog.PEG_SOLITAIRE, PegSolitaireRules, PegSolitaireAi, opts(PegSolitaireOptions()))
+    @Test fun yahtzee() = exercise(GameCatalog.YAHTZEE, YahtzeeRules, YahtzeeAi, opts(YahtzeeOptions()))
+    @Test fun klondike() = exercise(GameCatalog.KLONDIKE, KlondikeRules, KlondikeAi, opts(KlondikeOptions()))
+    @Test fun freecell() = exercise(GameCatalog.FREECELL, FreeCellRules, FirstLegalAi(), opts(FreeCellOptions()))
+    @Test fun spider() = exercise(GameCatalog.SPIDER, SpiderRules, FirstLegalAi(), opts(SpiderOptions()))
+    @Test fun pyramid() = exercise(GameCatalog.PYRAMID, PyramidRules, FirstLegalAi(), opts(PyramidOptions()))
+    @Test fun morris() = exercise(GameCatalog.MORRIS, MorrisRules, MorrisAi(), opts(MorrisOptions()))
+    @Test fun chess() = exercise(GameCatalog.CHESS, ChessRules, ChessAi(), opts(ChessOptions()), steps = 24)
+    @Test fun catan() = exercise(GameCatalog.CATAN, CatanRules, CatanAi(), opts(CatanOptions()), steps = 400)
+
+    @Test
+    fun catanCitiesAndKnights() = exercise(
+        GameCatalog.CATAN,
+        CatanRules,
+        CatanAi(),
+        opts(CatanOptions(3, 13, org.prolibertate.games.game.catan.CatanRuleSet.CITIES_AND_KNIGHTS)),
+        steps = 600,
+    )
+}

app/src/test/java/org/prolibertate/games/net/ScorekeeperSessionTest.kt

@@ -145,6 +145,11 @@ class ScorekeeperSessionTest {
         await("$name to be asking") { host.state.requests.any { it.id == deviceId } }
         host.session.allow(deviceId)
         await("$name to be let in") { guest.state.value.connected }
+        // The sheet follows the connection over the socket, so `connected` can
+        // flip while it is still in flight. Callers read the guest's sheet at
+        // once (its players, its rounds), and on a slow runner that was an empty
+        // one: wait until the guest is looking at the host's.
+        await("$name to receive the sheet") { guest.state.value.sheet == host.state.sheet }
         return guest
     }
 
@@ -164,6 +169,9 @@ class ScorekeeperSessionTest {
 
         await("the guest to be let in") { guest.state.value.connected }
         assertFalse(guest.state.value.awaiting)
+        // The sheet follows the connection over the socket, so on a slow runner
+        // it can still be in flight when `connected` flips: wait for it.
+        await("the guest to receive the sheet") { guest.state.value.sheet == host.state.sheet }
         assertEquals(host.state.sheet, guest.state.value.sheet)
         assertTrue(guest.state.value.sheet.started)
         assertTrue(host.state.requests.isEmpty())

app/src/test/java/org/prolibertate/games/score/RecentNamesTest.kt

@@ -0,0 +1,30 @@
+package org.prolibertate.games.score
+
+import org.junit.Test
+import org.junit.Assert.assertEquals
+
+class RecentNamesTest {
+    @Test
+    fun newestComesFirst() {
+        assertEquals(listOf("Bo", "Al"), RecentNames.with(listOf("Al"), "Bo"))
+    }
+
+    @Test
+    fun repeatMovesToFrontIgnoringCase() {
+        assertEquals(listOf("al", "Bo"), RecentNames.with(listOf("Bo", "Al"), " al "))
+    }
+
+    @Test
+    fun blankChangesNothing() {
+        assertEquals(listOf("Al"), RecentNames.with(listOf("Al"), "   "))
+    }
+
+    @Test
+    fun keepsOnlyTen() {
+        val names = (1..10).map { "n$it" }
+        val result = RecentNames.with(names, "new")
+        assertEquals(10, result.size)
+        assertEquals("new", result.first())
+        assertEquals("n9", result.last())
+    }
+}

app/src/test/java/org/prolibertate/games/score/ScoreSheetTest.kt

@@ -199,6 +199,14 @@ class ScoreSheetTest {
         assertEquals(ScoringMode.ROUNDS, StartSheet(3).applyTo(ScoreSheet()).mode)
     }
 
+    @Test
+    fun startingWithNamesSeatsThemInOrderAndLeavesTheRestUnnamed() {
+        val sheet = StartSheet(3, names = listOf("Ann", "")).applyTo(ScoreSheet())
+        assertEquals(listOf("Ann", "", ""), sheet.players.map { it.name })
+        assertEquals("Ann", sheet.displayName(sheet.players[0]))
+        assertEquals("Player 2", sheet.displayName(sheet.players[1]))
+    }
+
     @Test
     fun `tally entries add up per player and can be taken back`() {
         val sheet = ScoreSheet.of(2, ScoringMode.TALLY)

app/src/test/java/org/prolibertate/games/ui/SavedGameTextTest.kt

@@ -0,0 +1,27 @@
+package org.prolibertate.games.ui
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class SavedGameTextTest {
+    private val minute = 60_000L
+    private val hour = 60 * minute
+    private val day = 24 * hour
+
+    @Test
+    fun `how long ago reads like a person would say it`() {
+        assertEquals("just now", agoText(1_000, 1_000))
+        assertEquals("just now", agoText(30_000, 0))
+        assertEquals("a minute ago", agoText(minute + 20_000, 0))
+        assertEquals("5 minutes ago", agoText(5 * minute, 0))
+        assertEquals("an hour ago", agoText(90 * minute, 0))
+        assertEquals("3 hours ago", agoText(3 * hour, 0))
+        assertEquals("yesterday", agoText(30 * hour, 0))
+        assertEquals("4 days ago", agoText(4 * day, 0))
+    }
+
+    @Test
+    fun `a clock that ran backwards does not say nonsense`() {
+        assertEquals("just now", agoText(0, 10 * minute))
+    }
+}

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

@@ -0,0 +1,291 @@
+package org.prolibertate.games.ui.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.catan.AcceptCounter
+import org.prolibertate.games.game.catan.AcceptTrade
+import org.prolibertate.games.game.catan.CounterGoods
+import org.prolibertate.games.game.catan.DismissCounters
+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.BuildSettlement
+import org.prolibertate.games.game.catan.BuildWall
+import org.prolibertate.games.game.catan.BuyImprovement
+import org.prolibertate.games.game.catan.CatanAi
+import org.prolibertate.games.game.catan.CatanBoard
+import org.prolibertate.games.game.catan.CatanMove
+import org.prolibertate.games.game.catan.CatanOptions
+import org.prolibertate.games.game.catan.CatanPhase
+import org.prolibertate.games.game.catan.CatanRuleSet
+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.DeclineTrade
+import org.prolibertate.games.game.catan.DiscardGoods
+import org.prolibertate.games.game.catan.DropProgress
+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.GiveGoods
+import org.prolibertate.games.game.catan.GoodsBankTrade
+import org.prolibertate.games.game.catan.HireKnight
+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.PickDeck
+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.PlayProgress
+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.RollDice
+import org.prolibertate.games.game.catan.SetupPlace
+import org.prolibertate.games.game.catan.SpyTake
+import org.prolibertate.games.game.catan.TakeAqueduct
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+/**
+ * Cities & Knights has no device in this test suite, so the screen's logic is
+ * checked another way: engines play whole games, and at every position the
+ * player on the clock is treated as the local one. For every move the engine says
+ * is legal, [CatanInteraction] (and the dialogs' own filters) must offer a way to
+ * make it — a tap, a button or a dialog choice. A legal move that no control can
+ * produce would be a stuck game on a real phone.
+ */
+class CatanCkInteractionTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(players: Int, seed: Long) = TableConfig(
+        gameId = GameCatalog.CATAN,
+        seats = (0 until players).map { PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it) },
+        optionsJson = json.encodeToString(
+            CatanOptions(players, pointsToWin = 13, ruleSet = CatanRuleSet.CITIES_AND_KNIGHTS),
+        ),
+        seed = seed,
+    )
+
+    /** How a move reaches the engine from the screen, or null if nothing can produce it. */
+    private fun reachable(state: CatanState, legal: List<CatanMove>, move: CatanMove): String? {
+        fun tapVertex(vertex: Int, building: BuildKind? = null, moving: Int? = null, armed: ArmedCard? = null): TapOutcome =
+            CatanInteraction.onVertexTap(vertex, legal, building, null, moving, armed)
+
+        return when (move) {
+            is SetupPlace -> {
+                val vertex = CatanInteraction.targets(state, legal, null, null).vertices
+                val edges = CatanInteraction.targets(state, legal, null, move.vertex).edges
+                "setup".takeIf {
+                    move.vertex in vertex && move.edge in edges &&
+                        CatanInteraction.onVertexTap(move.vertex, legal, null, null) is TapOutcome.PickSetupVertex &&
+                        CatanInteraction.onEdgeTap(move.edge, legal, null, move.vertex) == TapOutcome.Submit(move)
+                }
+            }
+
+            is BuildRoad -> {
+                val targets = CatanInteraction.targets(state, legal, BuildKind.ROAD, null)
+                "road".takeIf {
+                    move.edge in targets.edges &&
+                        CatanInteraction.onEdgeTap(move.edge, legal, BuildKind.ROAD, null) == TapOutcome.Submit(move)
+                }
+            }
+
+            is BuildSettlement -> viaBuild(state, legal, BuildKind.SETTLEMENT, move.vertex, move)
+            is BuildCity -> viaBuild(state, legal, BuildKind.CITY, move.vertex, move)
+            is BuildWall -> viaBuild(state, legal, BuildKind.WALL, move.vertex, move)
+            is HireKnight -> viaBuild(state, legal, BuildKind.KNIGHT, move.vertex, move)
+
+            is MoveRobber -> {
+                val hex = CatanBoard.hexIndex.getValue(move.hex)
+                val targets = CatanInteraction.targets(state, legal, null, null)
+                val tap = CatanInteraction.onHexTap(hex, legal)
+                "robber".takeIf {
+                    hex in targets.hexes &&
+                        (tap == TapOutcome.Submit(move) || (tap is TapOutcome.PickRobberVictim && move.victim in tap.victims))
+                }
+            }
+
+            is MoveKnight -> {
+                val targets = CatanInteraction.targets(state, legal, null, null, movingKnight = move.from)
+                "moveKnight".takeIf {
+                    move.to in targets.vertices && tapVertex(move.to, moving = move.from) == TapOutcome.Submit(move) &&
+                        move.from in CatanInteraction.targets(state, legal, null, null).knights &&
+                        CatanInteraction.knightActions(legal, move.from).any { it is MoveKnight }
+                }
+            }
+
+            is ActivateKnight, is ChaseRobber, is PromoteKnight -> {
+                val vertex = when (move) {
+                    is ActivateKnight -> move.vertex
+                    is ChaseRobber -> move.vertex
+                    else -> (move as PromoteKnight).vertex
+                }
+                val smith = legal.any { it is EndSmith }
+                if (move is PromoteKnight && smith) {
+                    val targets = CatanInteraction.targets(state, legal, null, null)
+                    "smith".takeIf {
+                        vertex in targets.vertices && tapVertex(vertex) == TapOutcome.Submit(move)
+                    }
+                } else {
+                    val targets = CatanInteraction.targets(state, legal, null, null)
+                    "knightMenu".takeIf {
+                        vertex in targets.knights && tapVertex(vertex) == TapOutcome.PickKnight(vertex) &&
+                            move in CatanInteraction.knightActions(legal, vertex)
+                    }
+                }
+            }
+
+            is PillageCity -> viaChore(state, legal, move.vertex, move)
+            is PlaceMetropolis -> viaChore(state, legal, move.vertex, move)
+            is RelocateKnight -> viaChore(state, legal, move.to, move)
+            is RemoveKnight -> viaChore(state, legal, move.vertex, move)
+            is PlaceKnight -> viaChore(state, legal, move.vertex, move)
+
+            is PlayProgress -> viaCard(state, legal, move)
+
+            is BuyImprovement -> "improve".takeIf { move.track in CatanInteraction.improvable(legal) }
+
+            is GoodsBankTrade ->
+                "bankTrade".takeIf { move.get in CatanInteraction.goodsBankTrades(legal)[move.give].orEmpty() }
+
+            RollDice(), is RollDice -> "roll".takeIf { CatanInteraction.canRoll(legal) }
+            EndTurn -> "endTurn".takeIf { CatanInteraction.canEndTurn(legal) }
+            EndFreeRoads -> "endRoads".takeIf { CatanInteraction.canEndFreeRoads(legal) }
+            EndSmith -> "endSmith".takeIf { CatanInteraction.canEndSmith(legal) }
+            AcceptTrade, DeclineTrade -> "tradeReply".takeIf { CatanInteraction.tradeResponses(legal) != (false to false) }
+
+            // Answered in a dialog that offers exactly the moves in the legal list.
+            is PickDeck, is DropProgress, is TakeAqueduct, is SpyTake -> "choreDialog"
+
+            // Structural: the discard and give dialogs build these and ask the engine.
+            is DiscardGoods, is GiveGoods -> "goodsDialog"
+            is OfferGoods, is CounterGoods -> "tradeDialog"
+            is AcceptCounter, DismissCounters -> "counterDialog"
+
+            else -> null
+        }
+    }
+
+    private fun viaBuild(state: CatanState, legal: List<CatanMove>, kind: BuildKind, vertex: Int, move: CatanMove): String? {
+        val targets = CatanInteraction.targets(state, legal, kind, null)
+        return "build $kind".takeIf {
+            vertex in targets.vertices &&
+                CatanInteraction.onVertexTap(vertex, legal, kind, null) == TapOutcome.Submit(move) &&
+                kind in CatanInteraction.canBuild(legal)
+        }
+    }
+
+    private fun viaChore(state: CatanState, legal: List<CatanMove>, vertex: Int, move: CatanMove): String? {
+        val targets = CatanInteraction.targets(state, legal, null, null)
+        return "chore".takeIf {
+            vertex in targets.vertices &&
+                CatanInteraction.onVertexTap(vertex, legal, null, null) == TapOutcome.Submit(move)
+        }
+    }
+
+    private fun viaCard(state: CatanState, legal: List<CatanMove>, move: PlayProgress): String? {
+        val seat = CatanRules.currentSeat(state) ?: return null
+        val entry = CatanInteraction.progressHand(state, seat, legal).firstOrNull { it.card.id == move.card }
+            ?: return null
+        val kind = entry.card.kind
+        if (move !in entry.plays) return null
+        if (kind !in CatanInteraction.BOARD_CARDS) return "cardDialog"
+
+        val armed = ArmedCard(kind, entry.plays)
+        val targets = CatanInteraction.targets(state, legal, null, null, armed = armed)
+        return when (kind) {
+            org.prolibertate.games.game.catan.ProgressType.DIPLOMAT ->
+                "armed".takeIf {
+                    move.edge in targets.edges &&
+                        CatanInteraction.onEdgeTap(move.edge!!, legal, null, null, armed) == TapOutcome.Submit(move)
+                }
+
+            org.prolibertate.games.game.catan.ProgressType.MERCHANT ->
+                "armed".takeIf {
+                    move.hexA in targets.hexes &&
+                        CatanInteraction.onHexTap(move.hexA!!, legal, armed) == TapOutcome.Submit(move)
+                }
+
+            org.prolibertate.games.game.catan.ProgressType.INVENTOR -> {
+                val first = CatanInteraction.onHexTap(move.hexA!!, legal, armed)
+                if (first != TapOutcome.PickFirstHex(move.hexA!!)) return null
+                val second = armed.copy(firstHex = move.hexA)
+                val partners = CatanInteraction.targets(state, legal, null, null, armed = second).hexes
+                "armed".takeIf {
+                    move.hexB in partners &&
+                        CatanInteraction.onHexTap(move.hexB!!, legal, second) == TapOutcome.Submit(move)
+                }
+            }
+
+            else ->
+                "armed".takeIf {
+                    move.vertex in targets.vertices &&
+                        CatanInteraction.onVertexTap(move.vertex!!, legal, null, null, null, armed) == TapOutcome.Submit(move)
+                }
+        }
+    }
+
+    private fun playAndCheck(players: Int, seed: Long): Map<String, Int> {
+        val ai = CatanAi()
+        var state = CatanRules.initialState(config(players, seed))
+        val seen = mutableMapOf<String, Int>()
+        var moves = 0
+        while (!CatanRules.isFinished(state) && moves++ < 20_000) {
+            val seat = CatanRules.currentSeat(state) ?: break
+            val legal = CatanRules.legalMoves(state, seat)
+            for (move in legal) {
+                val how = reachable(state, legal, move)
+                assertTrue(
+                    "seed $seed: no control produces $move in ${state.phase} " +
+                        "(chore ${state.ck?.chores?.firstOrNull()}); log tail: ${state.log.takeLast(3)}",
+                    how != null,
+                )
+                seen.merge(how!!, 1, Int::plus)
+            }
+            state = CatanRules.applyMove(state, seat, ai.chooseMove(state, seat, legal))
+        }
+        return seen
+    }
+
+    @Test
+    fun `every legal move in a full game has a control that produces it`() {
+        val total = mutableMapOf<String, Int>()
+        listOf(3 to 21L, 4 to 22L, 3 to 23L, 4 to 24L).forEach { (players, seed) ->
+            playAndCheck(players, seed).forEach { (k, v) -> total.merge(k, v, Int::plus) }
+        }
+        println("CK UI coverage: ${total.toSortedMap()}")
+        // The ways the screen builds, moves and answers all got exercised.
+        listOf("setup", "road", "build SETTLEMENT", "build CITY", "knightMenu", "improve", "bankTrade", "roll", "endTurn")
+            .forEach { assertTrue("never exercised: $it in $total", (total[it] ?: 0) > 0) }
+    }
+
+    @Test
+    fun `a sleeping knight with nothing to do can still be tapped for its menu`() {
+        val base = CatanRules.initialState(config(3, 5L))
+            .copy(phase = CatanPhase.PLAYING, turn = 0, turnNumber = 1)
+        val state = base.copy(
+            ck = base.ck!!.copy(knights = listOf(org.prolibertate.games.game.catan.Knight(10, 0, 1))),
+        )
+        val legal = CatanRules.legalMoves(state, 0)
+        assertTrue("no grain, so nothing to do", CatanInteraction.knightActions(legal, 10).isEmpty())
+
+        val targets = CatanInteraction.targets(state, legal, null, null, localSeat = 0)
+        assertTrue(10 in targets.idleKnights)
+        assertTrue("no tap ring for a knight with nothing to do", 10 !in targets.knights)
+        assertTrue(10 in targets.tappableVertices)
+        assertEquals(
+            TapOutcome.PickKnight(10),
+            CatanInteraction.onVertexTap(10, legal, null, null, ownKnights = setOf(10)),
+        )
+        // On somebody else's turn the legal list is empty and nothing is offered.
+        assertTrue(CatanInteraction.targets(state, emptyList(), null, null, localSeat = 0).idleKnights.isEmpty())
+    }
+}

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

@@ -0,0 +1,75 @@
+package org.prolibertate.games.ui.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.catan.CatanAi
+import org.prolibertate.games.game.catan.CatanOptions
+import org.prolibertate.games.game.catan.CatanRuleSet
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.catan.ProgressType
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+import org.prolibertate.games.ui.catanDefaultPoints
+import org.prolibertate.games.ui.catanPointsChoices
+import org.prolibertate.games.ui.catanSwitchRules
+
+class CatanCkTextTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    @Test
+    fun `every position of a Cities and Knights game has a prompt for every seat`() {
+        val config = TableConfig(
+            gameId = GameCatalog.CATAN,
+            seats = (0 until 3).map { PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it) },
+            optionsJson = json.encodeToString(
+                CatanOptions(3, 13, CatanRuleSet.CITIES_AND_KNIGHTS),
+            ),
+            seed = 31L,
+        )
+        var state = CatanRules.initialState(config)
+        val ai = CatanAi()
+        var moves = 0
+        while (!CatanRules.isFinished(state) && moves++ < 20_000) {
+            for (me in 0 until 3) {
+                val seats = CatanSeats(me, listOf("A", "B", "C"))
+                val text = CatanText.prompt(state, seats, setupVertexChosen = false, building = null)
+                assertTrue("blank prompt in ${state.phase} for seat $me", text.isNotBlank())
+            }
+            val seat = CatanRules.currentSeat(state) ?: break
+            state = CatanRules.applyMove(state, seat, ai.chooseMove(state, seat, CatanRules.legalMoves(state, seat)))
+        }
+    }
+
+    @Test
+    fun `every progress card has a name and a description`() {
+        ProgressType.entries.forEach {
+            assertTrue(CatanText.progress(it).isNotBlank())
+            assertTrue("no help for $it", CatanText.progressHelp(it).length > 10)
+        }
+    }
+
+    @Test
+    fun `the setup screen offers each rule set its own targets and switches sensibly`() {
+        assertEquals(listOf(5, 8, 10, 12), catanPointsChoices(CatanRuleSet.BASE))
+        assertEquals(listOf(8, 10, 13, 15), catanPointsChoices(CatanRuleSet.CITIES_AND_KNIGHTS))
+        assertEquals(10, catanDefaultPoints(CatanRuleSet.BASE))
+        assertEquals(13, catanDefaultPoints(CatanRuleSet.CITIES_AND_KNIGHTS))
+
+        val base = CatanOptions()
+        val ck = catanSwitchRules(base, CatanRuleSet.CITIES_AND_KNIGHTS)
+        assertEquals(CatanRuleSet.CITIES_AND_KNIGHTS, ck.ruleSet)
+        assertEquals("the published target for the new rules", 13, ck.pointsToWin)
+        assertEquals(10, catanSwitchRules(ck, CatanRuleSet.BASE).pointsToWin)
+
+        // A short game picked on purpose is kept when both menus have it.
+        val short = catanSwitchRules(base.copy(pointsToWin = 8), CatanRuleSet.CITIES_AND_KNIGHTS)
+        assertEquals(8, short.pointsToWin)
+        assertEquals(3, ck.playerCount)
+    }
+}

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

@@ -0,0 +1,53 @@
+package org.prolibertate.games.ui.game.catan
+
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import org.prolibertate.games.game.GameCatalog
+import org.prolibertate.games.game.catan.BuildingType
+import org.prolibertate.games.game.catan.CatanBuilding
+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.catan.Resource
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+/** Shared fixtures for the Katan UI-logic tests: real islands, bent to taste. */
+internal object CatanFixtures {
+
+    private val json = Json { encodeDefaults = true }
+
+    fun config(players: Int = 3, seed: Long = 7L) = TableConfig(
+        gameId = GameCatalog.CATAN,
+        seats = (0 until players).map { PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it) },
+        optionsJson = json.encodeToString(CatanOptions(playerCount = players)),
+        seed = seed,
+    )
+
+    /** A fresh table, on the first setup placement. */
+    fun start(players: Int = 3, seed: Long = 7L): CatanState =
+        CatanRules.initialState(config(players, seed))
+
+    /** A mid-game state on [turn]'s turn, then adjusted by [adjust]. */
+    fun playing(
+        turn: Int = 0,
+        players: Int = 3,
+        adjust: CatanState.() -> CatanState = { this },
+    ): CatanState = start(players)
+        .copy(phase = CatanPhase.PLAYING, turn = turn, turnNumber = 1)
+        .adjust()
+
+    fun hand(vararg cards: Pair<Resource, Int>): Map<Resource, Int> =
+        Resource.entries.associateWith { cards.toMap()[it] ?: 0 }
+
+    fun CatanState.withHand(seat: Int, hand: Map<Resource, Int>): CatanState =
+        copy(resources = resources.toMutableList().also { it[seat] = hand })
+
+    fun CatanState.withBuilding(vertex: Int, type: BuildingType, owner: Int): CatanState =
+        copy(buildings = buildings.toMutableList().also { it[vertex] = CatanBuilding(type, owner) })
+
+    fun CatanState.withRoad(edge: Int, owner: Int): CatanState =
+        copy(roads = roads.toMutableList().also { it[edge] = owner })
+}

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

@@ -0,0 +1,117 @@
+package org.prolibertate.games.ui.game.catan
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.catan.CatanBoard
+import kotlin.math.abs
+import kotlin.math.sqrt
+
+class CatanGeometryTest {
+
+    private val sizes = listOf(360f to 800f, 800f to 360f, 500f to 500f, 1000f to 1000f / CatanGeometry.ASPECT)
+
+    private fun dist(a: Pt, b: Pt): Float = sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y))
+
+    @Test
+    fun `the whole island fits inside the box at every shape`() {
+        for ((w, h) in sizes) {
+            val layout = CatanGeometry.fit(w, h)
+            for (v in 0 until CatanBoard.VERTEX_COUNT) {
+                val p = layout.vertex(v)
+                assertTrue("vertex $v x=${p.x} outside 0..$w", p.x in 0f..w)
+                assertTrue("vertex $v y=${p.y} outside 0..$h", p.y in 0f..h)
+            }
+            for (e in CatanBoard.PORT_POSITIONS) {
+                val p = layout.portAnchor(e)
+                assertTrue("harbour marker x=${p.x} outside 0..$w at ${w}x$h", p.x in 0f..w)
+                assertTrue("harbour marker y=${p.y} outside 0..$h at ${w}x$h", p.y in 0f..h)
+            }
+        }
+    }
+
+    @Test
+    fun `the layout is as large as the box allows`() {
+        // Tall and narrow is limited by width, short and wide by height; either
+        // way the island should use most of the limiting side.
+        val tall = CatanGeometry.fit(360f, 800f)
+        val wide = CatanGeometry.fit(800f, 360f)
+        assertTrue(tall.radius > 20f)
+        assertTrue(wide.radius > 20f)
+        val xs = (0 until CatanBoard.VERTEX_COUNT).map { tall.vertex(it).x }
+        assertTrue("island should span most of the width", xs.max() - xs.min() > 360f * 0.7f)
+    }
+
+    @Test
+    fun `every edge is one hex radius long and every hex corner is one radius from its centre`() {
+        val layout = CatanGeometry.fit(500f, 500f)
+        for (e in 0 until CatanBoard.EDGE_COUNT) {
+            val (a, b) = layout.edgeEnds(e)
+            assertEquals("edge $e length", layout.radius, dist(a, b), layout.radius * 0.01f)
+        }
+        for (h in 0 until CatanBoard.HEX_COUNT) {
+            val centre = layout.hexCenter(h)
+            for (corner in layout.hexCorners(h)) {
+                assertEquals("hex $h corner", layout.radius, dist(centre, corner), layout.radius * 0.01f)
+            }
+        }
+    }
+
+    @Test
+    fun `all fifty-four vertices sit at distinct places`() {
+        val layout = CatanGeometry.fit(500f, 500f)
+        val places = (0 until CatanBoard.VERTEX_COUNT).map {
+            val p = layout.vertex(it)
+            Math.round(p.x) to Math.round(p.y)
+        }.toSet()
+        assertEquals(CatanBoard.VERTEX_COUNT, places.size)
+    }
+
+    @Test
+    fun `a tap on a vertex finds that vertex, and a tap far away finds nothing`() {
+        val layout = CatanGeometry.fit(500f, 500f)
+        val all = (0 until CatanBoard.VERTEX_COUNT).toList()
+        for (v in all) {
+            val p = layout.vertex(v)
+            assertEquals(v, layout.nearestVertex(p, layout.radius * 0.5f, all))
+            // A slightly clumsy tap still lands on it.
+            assertEquals(v, layout.nearestVertex(Pt(p.x + layout.radius * 0.2f, p.y - layout.radius * 0.15f), layout.radius * 0.55f, all))
+        }
+        assertNull(layout.nearestVertex(Pt(-100f, -100f), layout.radius * 0.5f, all))
+    }
+
+    @Test
+    fun `hit testing only considers the candidates it is given`() {
+        val layout = CatanGeometry.fit(500f, 500f)
+        val at = layout.vertex(5)
+        assertNull(layout.nearestVertex(at, layout.radius * 0.3f, listOf(6)))
+        assertEquals(6, layout.nearestVertex(layout.vertex(6), layout.radius * 0.3f, listOf(6)))
+        assertEquals(3, layout.nearestEdge(layout.edgeMidpoint(3), 5f, listOf(3, 4)))
+        assertEquals(7, layout.nearestHex(layout.hexCenter(7), 5f, listOf(7, 8)))
+    }
+
+    @Test
+    fun `the nearest candidate wins when several are in reach`() {
+        val layout = CatanGeometry.fit(500f, 500f)
+        val a = 10
+        val b = CatanBoard.VERTEX_NEIGHBORS[a].first()
+        val pa = layout.vertex(a)
+        val pb = layout.vertex(b)
+        // A point two-thirds of the way toward b is nearer b, though both are in reach.
+        val at = Pt(pa.x + (pb.x - pa.x) * 0.66f, pa.y + (pb.y - pa.y) * 0.66f)
+        assertEquals(b, layout.nearestVertex(at, layout.radius * 2f, listOf(a, b)))
+    }
+
+    @Test
+    fun `harbour markers sit outside the coast`() {
+        val layout = CatanGeometry.fit(500f, 500f)
+        val centre = Pt(500f / 2f, 500f / 2f)
+        for (e in CatanBoard.PORT_POSITIONS) {
+            val anchor = layout.portAnchor(e)
+            val mid = layout.edgeMidpoint(e)
+            assertTrue("harbour on edge $e should be past the coast", dist(anchor, centre) > dist(mid, centre))
+            assertTrue("and not floating far from it", abs(dist(anchor, mid) - layout.radius * PORT_OFFSET) < 1f)
+        }
+    }
+}

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

@@ -0,0 +1,56 @@
+package org.prolibertate.games.ui.game.catan
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Test
+import org.prolibertate.games.game.catan.BuildRoad
+import org.prolibertate.games.game.catan.BuildSettlement
+import org.prolibertate.games.game.catan.EndTurn
+
+/** The pure half of the landscape HUD: drag-to-build snapping and the staged ✓ / ✗ placement. */
+class CatanHudTest {
+
+    @Test
+    fun `a build tap is staged, not sent, but only while a build mode is armed`() {
+        val road = BuildRoad(0)
+
+        val outcome = TapOutcome.Submit(road)
+        assertEquals(road, CatanInteraction.stageable(outcome, BuildKind.ROAD))
+        assertNull(CatanInteraction.stageable(outcome, null))
+        // Ending the turn is never a placement.
+        assertNull(CatanInteraction.stageable(TapOutcome.Submit(EndTurn), BuildKind.ROAD))
+        assertNull(CatanInteraction.stageable(TapOutcome.Ignored, BuildKind.ROAD))
+    }
+
+    @Test
+    fun `the ghost of a staged move sits on its crossing or its edge`() {
+        assertEquals(CatanInteraction.Spot(vertex = 4), CatanInteraction.spotOf(BuildSettlement(4)))
+        assertEquals(CatanInteraction.Spot(edge = 9), CatanInteraction.spotOf(BuildRoad(9)))
+        assertEquals(CatanInteraction.Spot(), CatanInteraction.spotOf(null))
+    }
+
+    @Test
+    fun `a dragged finger snaps to the nearest lit crossing within reach, and off the board to nothing`() {
+        val layout = CatanGeometry.fit(800f, 600f)
+        val lit = setOf(3, 10, 21)
+        val targets = BoardTargets(vertices = lit)
+        val target = layout.vertex(10)
+
+        // A little off the crossing, well inside reach.
+        val near = Pt(target.x + layout.radius * 0.3f, target.y - layout.radius * 0.2f)
+        assertEquals(CatanInteraction.Spot(vertex = 10), CatanInteraction.snap(layout, targets, near, layout.radius * 1.2f))
+
+        // Far from every lit crossing.
+        assertNull(CatanInteraction.snap(layout, targets, Pt(-500f, -500f), layout.radius * 1.2f))
+    }
+
+    @Test
+    fun `with edges lit and no crossings, the drop snaps to an edge`() {
+        val layout = CatanGeometry.fit(800f, 600f)
+        val targets = BoardTargets(edges = setOf(5, 6))
+        val mid = layout.edgeMidpoint(6)
+        assertNotNull(CatanInteraction.snap(layout, targets, mid, layout.radius))
+        assertEquals(CatanInteraction.Spot(edge = 6), CatanInteraction.snap(layout, targets, mid, layout.radius))
+    }
+}

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

@@ -0,0 +1,348 @@
+package org.prolibertate.games.ui.game.catan
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.catan.BuildCity
+import org.prolibertate.games.game.catan.BuildRoad
+import org.prolibertate.games.game.catan.BuildSettlement
+import org.prolibertate.games.game.catan.BuildingType
+import org.prolibertate.games.game.catan.CatanBoard
+import org.prolibertate.games.game.catan.CatanPhase
+import org.prolibertate.games.game.catan.CatanRules
+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.MaritimeTrade
+import org.prolibertate.games.game.catan.MoveRobber
+import org.prolibertate.games.game.catan.PlayKnight
+import org.prolibertate.games.game.catan.PlayMonopoly
+import org.prolibertate.games.game.catan.PlayYearOfPlenty
+import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.SetupPlace
+import org.prolibertate.games.ui.game.catan.CatanFixtures.hand
+import org.prolibertate.games.ui.game.catan.CatanFixtures.playing
+import org.prolibertate.games.ui.game.catan.CatanFixtures.start
+import org.prolibertate.games.ui.game.catan.CatanFixtures.withBuilding
+import org.prolibertate.games.ui.game.catan.CatanFixtures.withHand
+import org.prolibertate.games.ui.game.catan.CatanFixtures.withRoad
+
+class CatanInteractionTest {
+
+    private val rich = hand(
+        Resource.LUMBER to 5, Resource.BRICK to 5, Resource.WOOL to 5,
+        Resource.GRAIN to 5, Resource.ORE to 5,
+    )
+
+    // --- Setup ---------------------------------------------------------------
+
+    @Test
+    fun `setup first offers every settlement spot, then only the roads beside the chosen one`() {
+        val state = start()
+        val legal = CatanRules.legalMoves(state, 0)
+        val setup = legal.filterIsInstance<SetupPlace>()
+
+        val first = CatanInteraction.targets(state, legal, null, null)
+        assertEquals(setup.map { it.vertex }.toSet(), first.vertices)
+        assertTrue(first.edges.isEmpty() && first.hexes.isEmpty())
+
+        val vertex = first.vertices.first()
+        val second = CatanInteraction.targets(state, legal, null, vertex)
+        assertTrue(second.vertices.isEmpty())
+        assertEquals(setup.filter { it.vertex == vertex }.map { it.edge }.toSet(), second.edges)
+    }
+
+    @Test
+    fun `a setup placement is two taps - the settlement, then its road`() {
+        val state = start()
+        val legal = CatanRules.legalMoves(state, 0)
+        val vertex = CatanInteraction.targets(state, legal, null, null).vertices.first()
+        val edge = CatanInteraction.targets(state, legal, null, vertex).edges.first()
+
+        assertEquals(TapOutcome.PickSetupVertex(vertex), CatanInteraction.onVertexTap(vertex, legal, null, null))
+        assertEquals(TapOutcome.Submit(SetupPlace(vertex, edge)), CatanInteraction.onEdgeTap(edge, legal, null, vertex))
+        // A road tapped before any settlement is chosen means nothing.
+        assertEquals(TapOutcome.Ignored, CatanInteraction.onEdgeTap(edge, legal, null, null))
+    }
+
+    @Test
+    fun `a road that does not touch the chosen settlement is refused`() {
+        val state = start()
+        val legal = CatanRules.legalMoves(state, 0)
+        val vertex = CatanInteraction.targets(state, legal, null, null).vertices.first()
+        val beside = CatanBoard.VERTEX_EDGES[vertex].toSet()
+        val far = (0 until CatanBoard.EDGE_COUNT).first { it !in beside }
+        assertEquals(TapOutcome.Ignored, CatanInteraction.onEdgeTap(far, legal, null, vertex))
+    }
+
+    // --- Building -------------------------------------------------------------
+
+    /** Seat 0 owns a settlement at vertex 0 and a road two edges long leading away from it. */
+    private fun established(): Triple<org.prolibertate.games.game.catan.CatanState, Int, Int> {
+        val e1 = CatanBoard.VERTEX_EDGES[0][0]
+        val w = CatanBoard.otherEnd(e1, 0)
+        val e2 = CatanBoard.VERTEX_EDGES[w].first { it != e1 }
+        val x = CatanBoard.otherEnd(e2, w)
+        val state = playing {
+            withHand(0, rich).withBuilding(0, BuildingType.SETTLEMENT, 0).withRoad(e1, 0).withRoad(e2, 0)
+        }
+        return Triple(state, x, e2)
+    }
+
+    @Test
+    fun `nothing on the board is tappable until a build mode is chosen`() {
+        val (state, _, _) = established()
+        val legal = CatanRules.legalMoves(state, 0)
+        assertTrue(CatanInteraction.targets(state, legal, null, null).isEmpty)
+    }
+
+    @Test
+    fun `build modes target exactly what the engine allows`() {
+        val (state, x, _) = established()
+        val legal = CatanRules.legalMoves(state, 0)
+
+        assertEquals(
+            legal.filterIsInstance<BuildRoad>().map { it.edge }.toSet(),
+            CatanInteraction.targets(state, legal, BuildKind.ROAD, null).edges,
+        )
+        assertTrue(x in CatanInteraction.targets(state, legal, BuildKind.SETTLEMENT, null).vertices)
+        assertEquals(setOf(0), CatanInteraction.targets(state, legal, BuildKind.CITY, null).vertices)
+        assertEquals(setOf(BuildKind.ROAD, BuildKind.SETTLEMENT, BuildKind.CITY), CatanInteraction.canBuild(legal))
+    }
+
+    @Test
+    fun `a tap builds only when the matching mode is armed and the spot is legal`() {
+        val (state, x, _) = established()
+        val legal = CatanRules.legalMoves(state, 0)
+        val road = legal.filterIsInstance<BuildRoad>().first().edge
+
+        assertEquals(TapOutcome.Submit(BuildSettlement(x)), CatanInteraction.onVertexTap(x, legal, BuildKind.SETTLEMENT, null))
+        assertEquals(TapOutcome.Submit(BuildCity(0)), CatanInteraction.onVertexTap(0, legal, BuildKind.CITY, null))
+        assertEquals(TapOutcome.Submit(BuildRoad(road)), CatanInteraction.onEdgeTap(road, legal, BuildKind.ROAD, null))
+
+        // No mode armed: nothing happens.
+        assertEquals(TapOutcome.Ignored, CatanInteraction.onVertexTap(x, legal, null, null))
+        assertEquals(TapOutcome.Ignored, CatanInteraction.onEdgeTap(road, legal, null, null))
+        // A settlement on an occupied crossing is not offered.
+        assertEquals(TapOutcome.Ignored, CatanInteraction.onVertexTap(0, legal, BuildKind.SETTLEMENT, null))
+        // The wrong mode for the spot.
+        assertEquals(TapOutcome.Ignored, CatanInteraction.onVertexTap(x, legal, BuildKind.CITY, null))
+    }
+
+    @Test
+    fun `without the cards, nothing can be built`() {
+        val (state, _, _) = established()
+        val broke = state.withHand(0, hand())
+        val legal = CatanRules.legalMoves(broke, 0)
+        assertTrue(CatanInteraction.canBuild(legal).isEmpty())
+        assertFalse(CatanInteraction.canBuyDevCard(legal))
+        assertTrue(CatanInteraction.canEndTurn(legal))
+    }
+
+    @Test
+    fun `free roads from a road building card need no build mode`() {
+        val (state, _, _) = established()
+        val free = state.copy(phase = CatanPhase.FREE_ROADS, pendingFreeRoads = 2)
+        val legal = CatanRules.legalMoves(free, 0)
+        val targets = CatanInteraction.targets(free, legal, null, null)
+        assertTrue(targets.edges.isNotEmpty())
+        val edge = targets.edges.first()
+        assertEquals(TapOutcome.Submit(BuildRoad(edge)), CatanInteraction.onEdgeTap(edge, legal, null, null))
+        assertTrue(CatanInteraction.canEndFreeRoads(legal))
+    }
+
+    // --- The robber ---------------------------------------------------------------
+
+    @Test
+    fun `the robber may go to any hex but the one it is on`() {
+        val state = playing { copy(phase = CatanPhase.ROBBER) }
+        val legal = CatanRules.legalMoves(state, 0)
+        val targets = CatanInteraction.targets(state, legal, null, null)
+        assertEquals((0 until CatanBoard.HEX_COUNT).filter { it != state.robber }.toSet(), targets.hexes)
+
+        val hex = targets.hexes.first()
+        // Nobody has built anything, so there is nobody to rob: the move goes straight through.
+        assertEquals(
+            TapOutcome.Submit(MoveRobber(CatanBoard.HEXES[hex], null)),
+            CatanInteraction.onHexTap(hex, legal),
+        )
+        assertEquals(TapOutcome.Ignored, CatanInteraction.onHexTap(state.robber, legal))
+    }
+
+    @Test
+    fun `a hex with two possible victims asks which`() {
+        val base = playing { copy(phase = CatanPhase.ROBBER) }
+        val hex = (0 until CatanBoard.HEX_COUNT).first { it != base.robber }
+        val corners = CatanBoard.HEX_CORNERS[hex]
+        val state = base
+            .withBuilding(corners[0], BuildingType.SETTLEMENT, 1)
+            .withBuilding(corners[3], BuildingType.SETTLEMENT, 2)
+            .withHand(1, hand(Resource.ORE to 1))
+            .withHand(2, hand(Resource.GRAIN to 1))
+        val legal = CatanRules.legalMoves(state, 0)
+
+        val outcome = CatanInteraction.onHexTap(hex, legal)
+        assertTrue(outcome is TapOutcome.PickRobberVictim)
+        outcome as TapOutcome.PickRobberVictim
+        assertEquals(CatanBoard.HEXES[hex], outcome.hex)
+        assertEquals(setOf(1, 2), outcome.victims.toSet())
+    }
+
+    // --- Discarding -----------------------------------------------------------------
+
+    @Test
+    fun `a seven costs half the hand, rounded down`() {
+        assertEquals(4, CatanInteraction.discardQuota(9))
+        assertEquals(4, CatanInteraction.discardQuota(8))
+        assertEquals(3, CatanInteraction.discardQuota(7))
+    }
+
+    @Test
+    fun `a discard is found only when it names exactly an allowed set of cards`() {
+        val state = playing {
+            copy(phase = CatanPhase.DISCARDING, discardSeat = 0)
+                .withHand(0, hand(Resource.LUMBER to 3, Resource.BRICK to 3, Resource.WOOL to 3))
+        }
+        val legal = CatanRules.legalMoves(state, 0)
+        assertTrue(legal.all { it is Discard })
+
+        val good = listOf(Resource.LUMBER, Resource.LUMBER, Resource.BRICK, Resource.WOOL)
+        assertNotNull(CatanInteraction.discardMove(legal, good))
+        // Order does not matter.
+        assertNotNull(CatanInteraction.discardMove(legal, good.reversed()))
+        // Too few, and more than are held.
+        assertNull(CatanInteraction.discardMove(legal, good.take(3)))
+        assertNull(CatanInteraction.discardMove(legal, List(4) { Resource.LUMBER }))
+    }
+
+    // --- Trading ---------------------------------------------------------------------
+
+    @Test
+    fun `bank trades list what can be given and what it can buy`() {
+        val state = playing { withHand(0, hand(Resource.GRAIN to 4)) }
+        val legal = CatanRules.legalMoves(state, 0)
+        assertTrue(legal.any { it is MaritimeTrade })
+
+        val trades = CatanInteraction.bankTrades(legal)
+        assertEquals(setOf(Resource.GRAIN), trades.keys)
+        assertEquals(Resource.entries.filter { it != Resource.GRAIN }, trades.getValue(Resource.GRAIN))
+        assertEquals(4, CatanInteraction.bankRatio(state, 0, Resource.GRAIN))
+    }
+
+    @Test
+    fun `an offer is allowed only to another player, for something different, from cards held`() {
+        val state = playing { withHand(0, hand(Resource.LUMBER to 2)) }
+        val lumber = listOf(Resource.LUMBER)
+        val grain = listOf(Resource.GRAIN)
+
+        assertTrue(CatanInteraction.offerAllowed(state, 0, 1, lumber, grain))
+        assertFalse("to oneself", CatanInteraction.offerAllowed(state, 0, 0, lumber, grain))
+        assertFalse("nothing offered", CatanInteraction.offerAllowed(state, 0, 1, emptyList(), grain))
+        assertFalse("nothing asked", CatanInteraction.offerAllowed(state, 0, 1, lumber, emptyList()))
+        assertFalse("like for like", CatanInteraction.offerAllowed(state, 0, 1, lumber, lumber))
+        assertFalse("more than held", CatanInteraction.offerAllowed(state, 0, 1, List(3) { Resource.LUMBER }, grain))
+        assertFalse("not their turn", CatanInteraction.offerAllowed(state, 1, 0, lumber, grain))
+    }
+
+    // --- Development cards -------------------------------------------------------------
+
+    @Test
+    fun `a development card is playable unless it was bought this turn or is a victory point`() {
+        val state = playing {
+            copy(
+                devHands = listOf(
+                    listOf(
+                        DevCard(1, DevCardType.KNIGHT, boughtTurn = 0),
+                        DevCard(2, DevCardType.VICTORY_POINT, boughtTurn = 0),
+                        DevCard(3, DevCardType.KNIGHT, boughtTurn = 1),
+                    ),
+                    emptyList(),
+                    emptyList(),
+                ),
+            )
+        }
+        val legal = CatanRules.legalMoves(state, 0)
+        val hand = CatanInteraction.devHand(state, 0, legal)
+
+        // Sorted by type then id: the two knights, then the victory point.
+        assertEquals(listOf(1, 3, 2), hand.map { it.card.id })
+        assertEquals(listOf(true, false, false), hand.map { it.playable })
+        assertEquals(listOf<Any>(PlayKnight(1)), hand.first().plays)
+    }
+
+    @Test
+    fun `monopoly offers one play per resource`() {
+        val plays = Resource.entries.map { PlayMonopoly(9, it) }
+        val choices = CatanInteraction.monopolyChoices(plays)
+        assertEquals(Resource.entries.toSet(), choices.keys)
+        assertEquals(PlayMonopoly(9, Resource.ORE), choices.getValue(Resource.ORE))
+    }
+
+    @Test
+    fun `year of plenty narrows to the cards that still complete a take`() {
+        val plays = listOf(
+            PlayYearOfPlenty(4, listOf(Resource.LUMBER, Resource.BRICK)),
+            PlayYearOfPlenty(4, listOf(Resource.LUMBER, Resource.LUMBER)),
+            PlayYearOfPlenty(4, listOf(Resource.ORE)),
+        )
+        assertEquals(
+            setOf(Resource.LUMBER, Resource.BRICK, Resource.ORE),
+            CatanInteraction.plentyAvailable(plays, emptyList()),
+        )
+        assertEquals(
+            setOf(Resource.LUMBER, Resource.BRICK),
+            CatanInteraction.plentyAvailable(plays, listOf(Resource.LUMBER)),
+        )
+        assertEquals(setOf(Resource.LUMBER), CatanInteraction.plentyAvailable(plays, listOf(Resource.BRICK)))
+        assertTrue(CatanInteraction.plentyAvailable(plays, listOf(Resource.LUMBER, Resource.LUMBER)).isEmpty())
+
+        assertEquals(plays[0], CatanInteraction.plentyMove(plays, listOf(Resource.BRICK, Resource.LUMBER)))
+        assertEquals(plays[2], CatanInteraction.plentyMove(plays, listOf(Resource.ORE)))
+        assertNull(CatanInteraction.plentyMove(plays, listOf(Resource.GRAIN)))
+    }
+
+    // --- Trade replies ------------------------------------------------------------------
+
+    @Test
+    fun `the addressee of an offer is given accept and decline`() {
+        val base = playing {
+            withHand(0, hand(Resource.LUMBER to 1)).withHand(1, hand(Resource.GRAIN to 1))
+        }
+        val offer = org.prolibertate.games.game.catan.TradeOffer(
+            by = 0, to = 1, give = listOf(Resource.LUMBER), get = listOf(Resource.GRAIN),
+        )
+        val pending = base.copy(phase = CatanPhase.TRADE_PENDING, pendingTrade = offer)
+        val legal = CatanRules.legalMoves(pending, 1)
+        assertEquals(true to true, CatanInteraction.tradeResponses(legal))
+
+        // If the addressee no longer holds what was asked, only decline remains.
+        val short = pending.withHand(1, hand())
+        assertEquals(false to true, CatanInteraction.tradeResponses(CatanRules.legalMoves(short, 1)))
+    }
+
+    // --- Rolled-hex highlight --------------------------------------------------
+
+    @Test
+    fun `rolled hexes are those carrying the number, minus the robber's`() {
+        val base = playing(turn = 0)
+        val number = base.numbers.first { it != 0 && it != 7 }
+        val state = base.copy(lastDice = if (number <= 7) listOf(number - 1, 1) else listOf(6, number - 6))
+        val all = (0 until CatanBoard.HEX_COUNT).filter { state.numbers[it] == number }
+        assertTrue(all.isNotEmpty())
+        assertEquals(all.filter { it != state.robber }.toSet(), CatanInteraction.rolledHexes(state))
+        val blocked = state.copy(robber = all.first())
+        assertFalse(all.first() in CatanInteraction.rolledHexes(blocked))
+    }
+
+    @Test
+    fun `nothing is highlighted before this turn's roll, on a seven, or in setup`() {
+        val rolled = playing(turn = 0).copy(lastDice = listOf(3, 3))
+        assertTrue(CatanInteraction.rolledHexes(rolled.copy(phase = CatanPhase.AWAIT_ROLL)).isEmpty())
+        assertTrue(CatanInteraction.rolledHexes(rolled.copy(lastDice = listOf(3, 4))).isEmpty())
+        assertTrue(CatanInteraction.rolledHexes(rolled.copy(phase = CatanPhase.SETUP_FIRST)).isEmpty())
+        assertTrue(CatanInteraction.rolledHexes(rolled.copy(lastDice = emptyList())).isEmpty())
+    }
+}

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

@@ -0,0 +1,149 @@
+package org.prolibertate.games.ui.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.catan.BuildShip
+import org.prolibertate.games.game.catan.BuildingType
+import org.prolibertate.games.game.catan.CatanAi
+import org.prolibertate.games.game.catan.CatanBuilding
+import org.prolibertate.games.game.catan.CatanOptions
+import org.prolibertate.games.game.catan.CatanPhase
+import org.prolibertate.games.game.catan.CatanRuleSet
+import org.prolibertate.games.game.catan.CatanRules
+import org.prolibertate.games.game.catan.CatanState
+import org.prolibertate.games.game.catan.MovePirate
+import org.prolibertate.games.game.catan.MoveRobber
+import org.prolibertate.games.game.catan.MoveShip
+import org.prolibertate.games.game.catan.PickGold
+import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.game.catan.Terrain
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+/** What the screen offers on a Seafarers board: ships, the pirate, and gold. */
+class CatanSeafarersInteractionTest {
+
+    private fun fresh(): CatanState {
+        val options = CatanOptions(playerCount = 3, pointsToWin = 12, ruleSet = CatanRuleSet.SEAFARERS)
+        return CatanRules.initialState(
+            TableConfig(
+                gameId = GameCatalog.CATAN,
+                seats = (0 until 3).map { PlayerSlot(it, "P$it", PlayerKind.AI, it) },
+                optionsJson = Json { encodeDefaults = true }.encodeToString(options),
+                seed = 7L,
+            ),
+        )
+    }
+
+    /** Seat 0, mid-game, a harbour town on the coast of the home island and plenty of cards. */
+    private fun harbour(): CatanState {
+        val s = fresh().copy(
+            phase = CatanPhase.PLAYING,
+            turn = 0,
+            turnNumber = 1,
+            resources = List(3) { Resource.entries.associateWith { 5 } },
+        )
+        val topo = s.topo
+        val v = (0 until topo.VERTEX_COUNT).first { vertex ->
+            topo.vertexIsland[vertex] == s.sea!!.home &&
+                topo.VERTEX_EDGES[vertex].any { topo.edgeSea[it] && !topo.edgeLand[it] }
+        }
+        return s.copy(buildings = s.buildings.toMutableList().also { it[v] = CatanBuilding(BuildingType.SETTLEMENT, 0) })
+    }
+
+    @Test
+    fun `the ship is on the build menu, and arming it lights the sea edges a ship can take`() {
+        val s = harbour()
+        val legal = CatanRules.legalMoves(s, 0)
+        assertTrue(BuildKind.SHIP in CatanInteraction.canBuild(legal))
+
+        val targets = CatanInteraction.targets(s, legal, BuildKind.SHIP, null)
+        assertEquals(legal.filterIsInstance<BuildShip>().map { it.edge }.toSet(), targets.edges)
+
+        val edge = targets.edges.first { !s.topo.edgeLand[it] }
+        assertEquals(
+            TapOutcome.Submit(BuildShip(edge)),
+            CatanInteraction.onEdgeTap(edge, legal, BuildKind.SHIP, null),
+        )
+        // The same tap with the road armed means nothing: a road cannot lie between two sea hexes.
+        assertEquals(TapOutcome.Ignored, CatanInteraction.onEdgeTap(edge, legal, BuildKind.ROAD, null))
+        // A build tap waits for ✓ like any other piece.
+        assertEquals(BuildShip(edge), CatanInteraction.stageable(TapOutcome.Submit(BuildShip(edge)), BuildKind.SHIP))
+    }
+
+    @Test
+    fun `tapping a ship that can sail picks it up, and the next tap on a lit sea edge sails it`() {
+        val s0 = harbour()
+        val built = CatanRules.legalMoves(s0, 0).filterIsInstance<BuildShip>().first()
+        val s = CatanRules.applyMove(s0, 0, built)
+            .let { it.copy(sea = it.sea!!.copy(builtThisTurn = emptyList())) }
+        val legal = CatanRules.legalMoves(s, 0)
+
+        val idle = CatanInteraction.targets(s, legal, null, null)
+        assertEquals(setOf(built.edge), idle.ships)
+        assertEquals(TapOutcome.PickShip(built.edge), CatanInteraction.onEdgeTap(built.edge, legal, null, null))
+
+        val sailing = CatanInteraction.targets(s, legal, null, null, movingShip = built.edge)
+        val to = sailing.edges.first()
+        assertEquals(
+            TapOutcome.Submit(MoveShip(built.edge, to)),
+            CatanInteraction.onEdgeTap(to, legal, null, null, movingShip = built.edge),
+        )
+    }
+
+    @Test
+    fun `after a seven a land hex moves the robber and a sea hex moves the pirate`() {
+        val s = harbour().copy(phase = CatanPhase.ROBBER)
+        val legal = CatanRules.legalMoves(s, 0)
+        val targets = CatanInteraction.targets(s, legal, null, null)
+        val land = targets.hexes.first { s.terrains[it] != Terrain.SEA }
+        val sea = targets.hexes.first { s.terrains[it] == Terrain.SEA }
+
+        val robber = CatanInteraction.onHexTap(land, legal, topo = s.topo)
+        assertTrue(robber is TapOutcome.Submit && robber.move is MoveRobber)
+        val pirate = CatanInteraction.onHexTap(sea, legal, topo = s.topo)
+        assertTrue(pirate is TapOutcome.Submit && pirate.move is MovePirate)
+    }
+
+    @Test
+    fun `a gold pick is found by the cards it names`() {
+        val picks = listOf(PickGold(listOf(Resource.ORE)), PickGold(listOf(Resource.WOOL)))
+        assertEquals(PickGold(listOf(Resource.WOOL)), CatanInteraction.goldMove(picks, listOf(Resource.WOOL)))
+        assertEquals(null, CatanInteraction.goldMove(picks, listOf(Resource.WOOL, Resource.WOOL)))
+        assertEquals(1, CatanInteraction.goldCount(picks))
+    }
+
+    @Test
+    fun `the engines' own choices are always something the screen can make`() {
+        // Every legal move in a played-out game is reachable: a tap, a button or a dialog choice.
+        val ai = CatanAi()
+        var s = fresh()
+        var n = 0
+        while (!CatanRules.isFinished(s) && n++ < 600) {
+            val seat = CatanRules.currentSeat(s) ?: break
+            val legal = CatanRules.legalMoves(s, seat)
+            val ships = legal.filterIsInstance<BuildShip>()
+            if (s.phase == CatanPhase.PLAYING && ships.isNotEmpty()) {
+                val armed = CatanInteraction.targets(s, legal, BuildKind.SHIP, null)
+                ships.forEach { ship ->
+                    assertTrue("ship ${ship.edge} not lit", ship.edge in armed.edges)
+                    assertEquals(TapOutcome.Submit(ship), CatanInteraction.onEdgeTap(ship.edge, legal, BuildKind.SHIP, null))
+                }
+            }
+            legal.filterIsInstance<MoveShip>().forEach { sail ->
+                val lit = CatanInteraction.targets(s, legal, null, null, movingShip = sail.from)
+                assertTrue(sail.to in lit.edges)
+                assertEquals(
+                    TapOutcome.Submit(sail),
+                    CatanInteraction.onEdgeTap(sail.to, legal, null, null, movingShip = sail.from),
+                )
+            }
+            s = CatanRules.applyMove(s, seat, ai.chooseMove(s, seat, legal))
+        }
+    }
+}

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

@@ -0,0 +1,101 @@
+package org.prolibertate.games.ui.game.catan
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.catan.CatanPhase
+import org.prolibertate.games.game.catan.Port
+import org.prolibertate.games.game.catan.Resource
+import org.prolibertate.games.ui.game.catan.CatanFixtures.hand
+import org.prolibertate.games.ui.game.catan.CatanFixtures.playing
+import org.prolibertate.games.ui.game.catan.CatanFixtures.start
+import org.prolibertate.games.ui.game.catan.CatanFixtures.withHand
+
+class CatanTextTest {
+
+    private val names = listOf("Ann", "Bo", "Cy")
+
+    @Test
+    fun `seats are named, with You for the local player and a number when a name is unknown`() {
+        val seats = CatanSeats(me = 1, names = names)
+        assertEquals("You", seats.label(1))
+        assertEquals("Ann", seats.label(0))
+        assertEquals("you", seats.lower(1))
+        assertEquals("Seat 4", seats.label(3))
+        assertEquals("Seat 1", CatanSeats(me = 1).label(0))
+        assertEquals("Seat 1", CatanSeats(me = 1, names = listOf("  ")).label(0))
+    }
+
+    @Test
+    fun `setup prompts say what to place next`() {
+        val state = start()
+        val mine = CatanSeats(0, names)
+        assertTrue(CatanText.prompt(state, mine, setupVertexChosen = false, building = null).contains("Place a settlement"))
+        assertTrue(CatanText.prompt(state, mine, setupVertexChosen = true, building = null).contains("road"))
+        assertTrue(CatanText.prompt(state, CatanSeats(1, names), false, null).startsWith("Ann is placing"))
+        val second = state.copy(phase = CatanPhase.SETUP_SECOND, setupIndex = 3)
+        assertTrue(CatanText.prompt(second, CatanSeats(2, names), false, null).contains("second settlement"))
+    }
+
+    @Test
+    fun `the turn prompts follow the phase`() {
+        val roll = playing().copy(phase = CatanPhase.AWAIT_ROLL)
+        assertTrue(CatanText.prompt(roll, CatanSeats(0, names), false, null).contains("Roll the dice"))
+        assertEquals("Ann is rolling…", CatanText.prompt(roll, CatanSeats(1, names), false, null))
+
+        val turn = playing()
+        assertTrue(CatanText.prompt(turn, CatanSeats(0, names), false, null).contains("Your turn"))
+        assertEquals("Tap an edge to build a road.", CatanText.prompt(turn, CatanSeats(0, names), false, BuildKind.ROAD))
+        assertEquals("Bo is playing…", CatanText.prompt(playing(turn = 1), CatanSeats(0, names), false, null))
+
+        val robber = playing().copy(phase = CatanPhase.ROBBER)
+        assertTrue(CatanText.prompt(robber, CatanSeats(0, names), false, null).contains("robber"))
+    }
+
+    @Test
+    fun `the discard prompt names the quota`() {
+        val state = playing {
+            copy(phase = CatanPhase.DISCARDING, discardSeat = 0)
+                .withHand(0, hand(Resource.LUMBER to 9))
+        }
+        assertTrue(CatanText.prompt(state, CatanSeats(0, names), false, null).contains("discard 4"))
+        assertTrue(CatanText.prompt(state, CatanSeats(1, names), false, null).contains("Ann must discard half"))
+    }
+
+    @Test
+    fun `road building counts down in the singular and the plural`() {
+        val two = playing().copy(phase = CatanPhase.FREE_ROADS, pendingFreeRoads = 2)
+        val one = two.copy(pendingFreeRoads = 1)
+        assertTrue(CatanText.prompt(two, CatanSeats(0, names), false, null).endsWith("2 more roads."))
+        assertTrue(CatanText.prompt(one, CatanSeats(0, names), false, null).endsWith("1 more road."))
+    }
+
+    @Test
+    fun `the end of the game names the winner`() {
+        val over = playing().copy(phase = CatanPhase.GAME_OVER, winner = 1)
+        assertEquals("Bo won the game.", CatanText.prompt(over, CatanSeats(0, names), false, null))
+        assertEquals("You won!", CatanText.winnerHeadline(over, CatanSeats(1, names)))
+        assertEquals("Bo won", CatanText.winnerHeadline(over, CatanSeats(0, names)))
+    }
+
+    @Test
+    fun `cards read as a sorted tally`() {
+        assertEquals(
+            "2 Lumber + 1 Grain",
+            CatanText.cards(listOf(Resource.GRAIN, Resource.LUMBER, Resource.LUMBER)),
+        )
+        assertEquals("nothing", CatanText.cards(emptyList()))
+        assertEquals(
+            "Ann offers 1 Lumber to you for 2 Ore",
+            CatanText.tradeSummary("Ann", "you", listOf(Resource.LUMBER), listOf(Resource.ORE, Resource.ORE)),
+        )
+    }
+
+    @Test
+    fun `costs and harbours read as the rules state them`() {
+        assertEquals("1 lumber + 1 brick", CatanText.ROAD_COST)
+        assertEquals("2 grain + 3 ore", CatanText.CITY_COST)
+        assertEquals("2:1 ore", CatanText.portName(Port(edge = 0, resource = Resource.ORE, ratio = 2)))
+        assertEquals("3:1 any", CatanText.portName(Port(edge = 0, resource = null, ratio = 3)))
+    }
+}

app/src/test/java/org/prolibertate/games/update/UpdatePolicyTest.kt

@@ -53,28 +53,6 @@ class UpdatePolicyTest {
         assertNull(versionCodeOfTag("nightly"))
     }
 
-    // -- Where the download happens ----------------------------------------
-
-    @Test
-    fun `a release asset is fetched from this app's host, keeping its path`() {
-        // The instance reports its canonical host; the app was told to trust
-        // another. Same bytes, one host, whatever the server names itself.
-        assertEquals(
-            "https://git.wallacenet.ca/devadmin/ProLibertateGames/releases/download/" +
-                "v1.4.1001-dev/ProLibertateGames-v1.4.1001-dev.apk",
-            onReportedHost(
-                "https://git.saskvalleytech.com/devadmin/ProLibertateGames/releases/download/" +
-                    "v1.4.1001-dev/ProLibertateGames-v1.4.1001-dev.apk",
-                "git.wallacenet.ca",
-            ),
-        )
-        // A URL that already says the right host is left exactly as it is.
-        val already = "https://git.wallacenet.ca/devadmin/ProLibertateGames/releases/download/v1.4.1/a.apk"
-        assertEquals(already, onReportedHost(already, "git.wallacenet.ca"))
-        // Anything unparseable survives untouched rather than being dropped.
-        assertEquals("not a url", onReportedHost("not a url", "git.wallacenet.ca"))
-    }
-
     // -- The wall -----------------------------------------------------------
 
     @Test
@@ -151,7 +129,7 @@ class UpdatePolicyTest {
         assertNull("an up-to-date app has no business interrupting", launchOffer(UpdateVerdict.UpToDate))
         assertNull(
             "a phone with no network has nothing to apologise for",
-            launchOffer(UpdateVerdict.Refused("Unable to resolve host git.wallacenet.ca")),
+            launchOffer(UpdateVerdict.Refused("Unable to resolve host api.github.com")),
         )
         // Including the refusal that this whole change exists to produce: being
         // shown the other channel's build is not a thing to be told about.

docs/CI.md

@@ -1,141 +0,0 @@
-# CI, releases, and OTA — decisions and how to build
-
-Status as of the ProLibertateGames bootstrap (WALA-118).
-
-## Decisions
-
-1. **The release channel is this instance's own releases.** The app ships from
-   <https://git.wallacenet.ca/devadmin/ProLibertateGames>, and the in-app updater
-   reads that repo's releases over Gitea's REST API. GitHub is not a channel for
-   this project; the only GitHub URLs left are the `upstream` remote and the
-   attribution link in the README.
-
-   The repo is **public on purpose**: the updater downloads anonymously, with no
-   token embedded in the APK. A private repo would make every check fail
-   (the API answers 404 to anonymous callers), not leak anything — but it would
-   also stop updates dead.
-
-2. **CI lives in Actions-compatible workflows in `.github/workflows/`.**
-   Gitea Actions runs workflows from `.github/workflows/` (or `.gitea/workflows/`),
-   so these files serve both a GitHub-style runner and the Gitea instance.
-   Publishing goes through `scripts/publish-release.sh` — Gitea's REST API, the
-   same routes the app's updater reads — rather than the `gh` CLI, which a runner
-   image need not carry.
-
-   | Workflow | Trigger | Publishes |
-   | --- | --- | --- |
-   | `ci.yml` | push to `dev`, PRs into `dev`/`main`, manual | dev prerelease, from `dev` only |
-   | `release.yml` | push to `main`, manual | production release, from `main` only |
-
-   Pull requests build and check but never publish. Prereleases are marked so
-   the "latest release" endpoint — which skips them — can never hand a dev build
-   to a production install.
-
-3. **A runner has to be registered before any of that executes.** As of the
-   bootstrap the instance has **no Actions runner**, so the workflows are
-   correct but idle: a Gitea runner (Docker or host) must be registered against
-   the instance and able to resolve `actions/checkout`,
-   `actions/setup-java`, `android-actions/setup-android` and
-   `actions/upload-artifact`. Until then the manual build below and the manual
-   publish script are the working paths.
-
-4. **The local build is the guaranteed path.** Workflows need a runner that may
-   not exist yet; `./gradlew assembleDebug` + `./gradlew testDebugUnitTest`
-   work on any machine with JDK 17 and the Android SDK (compileSdk 34), and CI's
-   green means exactly these two commands plus lint.
-
-## Build numbers, tags, and why updates never downgrade
-
-An APK is **`<series>.<build number>`**, the release tag is **`v<series>.<build
-number>`**, and the build number is what Android sees as `versionCode`:
-
-```
-build number = CI run number + plgVersionRunOffset      (gradle.properties)
-```
-
-- `plgVersionSeries` (currently `1.4`) is the human-facing series, set by hand
-  in `gradle.properties`.
-- `plgVersionRunOffset` (currently `1000`) is a **permanent floor**, also set by
-  hand in `gradle.properties`, set once at bootstrap and never changed.
-
-Why the offset exists: Gitea Actions restarts run numbers at 1 for each
-workflow, so without it the first release of a fresh instance would be build
-`1` — the number an unstamped local build already carries — and any reset of
-the counter would hand Android a *lower* `versionCode`, which it refuses as a
-downgrade. With the offset, every stamped build starts at 1001 and only ever
-climbs, because the run number is monotonic and the offset never moves. The
-gradle build and both workflows read the same two properties, so the tag and
-the APK inside it cannot name different versions.
-
-The series is a name for people: bumping it changes nothing about ordering,
-because `versionCode` never includes the series.
-
-Unstamped builds (local, or a PR build) are `versionCode 1`, below every
-release — the honest answer for a build nobody stamped.
-
-## Manual build (works today, no runner needed)
-
-```sh
-# JDK 17, Android SDK with platform 34 + build-tools 34
-export JAVA_HOME=...        # a JDK 17 install
-export ANDROID_HOME=...     # SDK root (or set sdk.dir in local.properties)
-
-./gradlew assembleDebug          # dev-channel app (default: ca.wallacenet.prolibertategames.dev)
-PLG_CHANNEL=production ./gradlew assembleDebug   # production app (ca.wallacenet.prolibertategames)
-./gradlew testDebugUnitTest      # JVM unit tests
-./gradlew lintDebug              # Android lint (CI runs this too)
-```
-
-The two variants install side by side: different applicationId, different
-launcher name (`Pro Libertate Games DEV` vs `Pro Libertate Games`), different
-tartan sett.
-
-## Manual release (works today, no runner needed)
-
-```sh
-GITEA_TOKEN=… ./scripts/publish-release.sh v1.4.1001 app/build/outputs/apk/debug/app-debug.apk release "$(git rev-parse HEAD)"
-```
-
-The script takes `<tag> <apk> <prerelease|release> [target-sha]`, creates the
-release through `POST /api/v1/repos/{owner}/{repo}/releases`, attaches the APK
-through `POST …/releases/{id}/assets` — which is the upload route Gitea's
-Swagger declares for this instance (1.27.3) — and then reads the release back
-and corrects its state if it did not stick. That last step is not decoration:
-this instance has been observed to accept `draft: false` at create time and
-store the release as a draft after the attachment lands, and a draft is
-invisible to the updater, so the script verifies rather than assumes. If the
-tag already exists it publishes into the existing release instead of failing,
-so a retry is safe.
-
-## What the in-app updater reads
-
-`app/src/main/java/org/prolibertate/games/update/Updater.kt`:
-
-| Channel | Endpoint |
-| --- | --- |
-| production | `GET /api/v1/repos/devadmin/ProLibertateGames/releases/latest` |
-| dev | `GET /api/v1/repos/devadmin/ProLibertateGames/releases?limit=30` |
-
-- `/releases/latest` is documented by Gitea as *the most recent non-prerelease,
-  non-draft release* — the same rule GitHub implements, so the production
-  channel keeps skipping dev builds.
-- The dev path takes the highest `versionCode` among the prereleases rather
-  than whatever came first on the page, so it does not depend on server
-  ordering.
-- The JSON shape is the one the code already parsed from GitHub: `tag_name`,
-  `prerelease`, `draft`, and assets carrying `browser_download_url`. Gitea says
-  `limit` where GitHub says `per_page`.
-- Each asset must be named so it contains its tag —
-  `ProLibertateGames-v1.4.1001.apk` for tag `v1.4.1001` — because the updater
-  picks the versioned APK out of the release's assets by that rule.
-
-`BuildConfig.OTA_ENABLED` is a kill switch, not a channel decision: it is
-`true`, and setting it `false` makes every check report that and fetch nothing.
-`UpdatePolicy.kt` — channel rules, tag parsing, verdicts — is pure and stays
-under test either way.
-
-## Keystore
-
-`app/debug.keystore` is committed deliberately and must never be rotated:
-every build — local, CI, release — signs with it, so an OTA update installs
-over the previous build instead of being rejected for a signature mismatch.

docs/RE-catan-universe.md

@@ -0,0 +1,73 @@
+# Catan Universe 2.7.5 — what the reverse engineering showed
+
+Source: `Catan+Universe_2.7.5_APKPure.xapk` (Unity, IL2CPP). Method: the Unity scenes
+(`level3` is the match scene) were parsed with UnityPy for the uGUI hierarchy (names,
+anchors, sizes, which objects start hidden), and `global-metadata.dat` was searched for
+class, method and game-action names. Code bodies were not decompiled; behaviour below
+that is not visible in a hierarchy is marked *inferred*.
+
+The game is **landscape-only**; the canvas is laid out against a 1920×1080 reference.
+
+## Match HUD (`InGameUI_mobile`)
+
+| Region | Contents |
+| --- | --- |
+| Top | `PlayerFrames`: one frame per player (avatar, colour, VP, card count, timer), a "shuffle stats" button at the right |
+| Bottom bar | `ResourceContainer`, centred (anchors 25–75 % of the width, 90 px tall): one entry per resource (Lumber, Brick, Wool, Grain, Ore; Cloth, Coins, Paper for C&K; Fish, Feather, Coca for other expansions, hidden otherwise) |
+| Bottom right | `BtnTurn` (140 px, roll / end turn), `BtnTrade` immediately to its left (counter-offer and "blocked" badge variants), `BtnAddDevCard`, a chat/log `BubblePanel` |
+| Left edge | `Drag&DropBuild`: a column of piece icons. **The player drags a piece from it onto the board** (`Drag&DropBuildRemove` is the drop target that cancels) |
+| Mid right | `ConfirmButtonGroup`: a ✓ (`CatanConfirmBuildButton`) over a ✗ (`CatanCancelBuildButton`). A drop only *previews*; the ✓ commits |
+| Board | `CandidateFactory` makes highlight markers for every legal spot (corner, edge, face); `QuickBuildTrigger{Corner,Edge,Face}` are hit zones for a one-tap/hold build; a candidate ticker shows the one-line instruction |
+| Centre | Played-card panel, progress-card chooser, discard panel (`CardPanel` slides up over the bottom bar with a header) |
+
+Gestures (`CatanGestureHandler`, `BaseGesture`, `TapHoldHandler`): one finger pans the
+board, two-finger pinch zooms (`GetPinchZoomMagnitude`, `AutomaticZoom`), tap selects a
+candidate, hold opens quick-build. Camera is a fixed-pitch table view.
+
+## Trade board (`TradeBoard_mobile`)
+
+A full-width panel that slides up over the bottom of the screen (`Animator`, collapsible):
+
+```
+┌────────────────────────────────────────────────────────────┬──────┐
+│ [Player] [Bank]   headline / description     ☐ Block trade │ P1 P2│ header
+├────────────────────────────────────────────────────────────┤ P3 P4│ (135 px)
+│ OPPONENT row  — cards you get (tinted by the opponent's    │      │
+│                 colour)                                    │ Hide │
+│        ⇣⇣⇣  arrows  (or the bank ratio chips 4:1 3:1 2:1)  │ Deny │
+│ PLAYER row    — cards you give (tinted by your colour)     │Accept│
+└────────────────────────────────────────────────────────────┴──────┘
+```
+
+* **Header.** A *Player / Bank* toggle (extra toggles for the Inka 3:2 / 2:1 rules). A
+  **Block trade** checkbox refuses all incoming offers. One round button per rival
+  (`Player1…5`, with a selected border) picks whom the offer is addressed to; none
+  selected means everyone.
+* **Content.** Two rows of resource cards separated by arrows. The top row is what you
+  *want*, the bottom row what you *give*. Tapping a card in a row adds one; tapping a
+  selected card removes one (*inferred from `AddFieldToTradePayment`/`ApplyCancelTradeResource`*).
+  In Bank mode a ratio row (`CardRatios`) shows the best rate per resource (harbours).
+* **Right column (180 px).** Hide/collapse, **Deny** (✗), **Accept** (✓). When you
+  are the one receiving an offer, ✓ accepts and the chip-icon variant `Icon_CounterOffer`
+  turns the ✓ into a *counter-offer* send. A circular turn timer wraps the ✓.
+* **Incoming offers** (`IncomingTradeContainer`) show in the same panel; the offerer's
+  colour tints the opponent row. Counter-offers land back in the proposer's panel with
+  an `AcceptCounterOfferButtonImage`.
+
+## Seafarers game actions (from the metadata)
+
+`CatanSeafarer_*_GameAction` names show what the mode adds to the base game:
+
+* **Ships:** `BuildShip`, `MoveShip` (only the ship at the open end of a route, not on
+  the turn it was built), `BuildFreeRoad`; roads and ships share `AvailableCandidatesRoadAndShip`.
+* **Pirate** alongside the robber: `RobberPirat_Move`, `RobberPirat_SelectPlayer`;
+  ships cannot be built or moved past a pirate-blocked edge.
+* **Gold fields:** `ChooseGoldfieldResource` (a hex that pays any resource of choice).
+* **Fog islands:** `Check_FogField`, `DistributeFogField` (hidden hex revealed when a
+  road/ship reaches it, the player takes the resource), `Shuffle_Islands`, `Shuffle_TileValueList`.
+* **Treasure islands / Oasis / Great Canal** are Catan Universe scenario extras and are
+  **not** part of the physical Seafarers rules; they are out of scope here.
+* **Setup:** `StartPhase_BuildSettlement`, `StartPhase_BuildRoadShip`, `PlaceValueChip`
+  (number tokens placed per scenario), `Shuffle_Harbors`.
+* **Island bonus:** special victory points for the first settlement on a new island
+  (`AllIslandIds`, `CatanIslandState`).

docs/README.md

@@ -24,8 +24,10 @@ Naming: the catalogue id, lowercase, e.g. `crazy8s` → `RULES-crazy8s.md`.
 | Golf | [RULES-golf.md](RULES-golf.md) |
 | Hearts | — (TODO) |
 | Kaiser | [RULES-kaiser.md](RULES-kaiser.md) |
+| Katan (catalogue id `catan`) | [RULES-catan.md](RULES-catan.md) — and its expansion rule sets, [RULES-catan-ck.md](RULES-catan-ck.md) and [RULES-catan-seafarers.md](RULES-catan-seafarers.md) |
 | Klondike | — (TODO) |
 | Mastermind | [RULES-mastermind.md](RULES-mastermind.md) |
+| Meowdoku | [RULES-meowdoku.md](RULES-meowdoku.md) |
 | Morris | [RULES-morris.md](RULES-morris.md) |
 | Peg solitaire | — (TODO) |
 | Pirates | [RULES-pirates.md](RULES-pirates.md) |
@@ -39,7 +41,12 @@ Naming: the catalogue id, lowercase, e.g. `crazy8s` → `RULES-crazy8s.md`.
 
 ## Other docs
 
-- [CI.md](CI.md) — build, CI, releases, OTA decisions.
+- Build, CI, releases and OTA are described in the CI section of the root
+  [README](../README.md).
+- [SAVED-GAMES.md](SAVED-GAMES.md) — how a game in progress is kept between sessions, and what is
+  not kept.
+- [UI-catan.md](UI-catan.md) — how the Katan screen is layered, and how to restyle,
+  re-copy or re-lay-out it without touching the rules.
 - `licenses/` — third-party licences that must travel with the app
   (Uncial Antiqua under the SIL OFL; the app itself is GPL-3.0, see `/LICENSE`).
 - Repo-level agent notes live in [`CLAUDE.md`](../CLAUDE.md) at the root.

docs/RULES-catan-ck.md

@@ -0,0 +1,222 @@
+# Katan: Cities & Knights — implemented rules
+
+This is the second rule set of Katan (see [RULES-catan.md](RULES-catan.md) for the
+base game). It is chosen on the setup screen — **Rules: Base game / Cities &
+Knights** — and stored as `CatanOptions.ruleSet` (`CatanRuleSet.CITIES_AND_KNIGHTS`).
+A table plays one or the other; the choice reaches guests with the rest of the
+options.
+
+The expansion is a whole rule set rather than a toggle, because it replaces rules
+(no development cards, no Largest Army, a different seven) as well as adding them.
+Everything it needs lives behind `CatanState.ck`, which is `null` in the base game,
+so a base game's state and rules are untouched. The code is:
+
+| File | Holds |
+| --- | --- |
+| `CatanCkModel.kt` | the data: commodities, improvement tracks, progress cards, knights, the chore queue, every new move |
+| `CatanCk.kt` | the rules: legal moves, applying them, the roll, the barbarians, scoring |
+| `CatanCkAi.kt` | the computer opponent for this rule set |
+| `CatanRules.kt` | the single entry point; calls into `CatanCk` whenever `state.ck != null` |
+
+Behaviour is pinned by `CatanCkRulesTest` (each rule on a crafted position) and
+`CatanCkSelfPlayTest` (whole games, engine against engine). Three or four players,
+as in the base game.
+
+## Verification
+
+The rules were checked against the in-game almanac of Catan Universe (rules text
+only: costs, card wordings, the barbarian and improvement rules). Where the almanac
+is silent or ambiguous the reading chosen is listed under *Choices made here* below.
+
+## What changes from the base game
+
+| | Base game | Cities & Knights |
+| --- | --- | --- |
+| Points to win | 10 | **13** (setup offers 8 / 10 / 13 / 15) |
+| Development cards | 25-card deck | **none** — knights and progress cards replace them |
+| Largest Army | 5 *(see RULES-catan.md)* | **none** |
+| Longest Road | 5 *(see RULES-catan.md)* | **2** |
+| Second setup piece | settlement | **city** (resources only, no commodities) |
+| Dice | two | **two number dice + the event die** |
+| A seven | discard half over 7; robber moves | discard half over **7 + 2 per wall**; the robber **only moves after the first barbarian attack** |
+| Cities | 2 of a resource | forest: 1 lumber + **1 paper**; pasture: 1 wool + **1 cloth**; mountains: 1 ore + **1 coin**; hills / fields: 2 of the resource |
+
+## The dice
+
+The yellow die and the red die are added for production, as in the base game. The
+**event die** has three ships and one gate each of yellow (trade), blue (politics)
+and green (science). It is resolved **before** production:
+
+- **Ship** — the barbarians come one step nearer (they start 7 steps out).
+- **Gate** — every player with at least one level of improvement in that colour,
+  **in turn order from the roller**, whose **red die is no higher than their level**
+  in that track, draws a progress card of that colour.
+
+`RollDice(forced, event)` stages both for tests, like the base game's forced roll.
+An **Alchemist** played before the roll sets the two number dice (the event die is
+still rolled).
+
+## Commodities
+
+Three commodities — **cloth, coin, paper** — join the five resources. The bank holds
+12 of each (19 of each resource). Hands, discards, thefts and trades all treat them as
+cards; progress cards are not cards for any of these purposes.
+
+When the bank cannot meet the demand for a card type: with **one** seat owed it,
+that seat takes what is left; with **two or more** owed, nobody receives it.
+
+## The barbarians
+
+The strip shows how many steps away the ship is. On the seventh ship it **lands**:
+
+- Barbarian strength is the **number of cities on the board** (a metropolis is a city).
+- Catan's strength is the sum of the strengths of every **active** knight (basic 1,
+  strong 2, mighty 3).
+- If Catan's strength is **at least** the barbarians', Catan holds: the player with
+  the strictly highest contribution takes a **Defender of Catan** card (one point);
+  if several tie for highest, **each draws a progress card from a deck of their
+  choice** instead.
+- Otherwise Catan falls: among the players who own a city that is not a metropolis,
+  those who contributed **least** each lose one city, **to their own choice**. A lost
+  city becomes a settlement (or, if the seat has no settlement piece left, is removed),
+  and its wall goes. **A metropolis can never be pillaged.**
+- Either way every knight stands down, the ship returns to seven steps, and the
+  **robber wakes** — until now it has not been on the board.
+
+## Knights
+
+Each seat has **two knights of each strength** (six in all).
+
+| Action | Cost | Rule |
+| --- | --- | --- |
+| Hire | 1 ore + 1 wool | a **basic** knight on an empty crossing at the end of one of your roads; only if one of your two basic knights is free |
+| Activate | 1 grain | a sleeping knight wakes; only active knights count against the barbarians |
+| Promote | 1 ore + 1 wool | one level, once per knight per turn; a **mighty** knight needs **level three of politics** (the fortress); the next level's pieces must be free |
+| Move | — | an active knight moves along **its own roads** to an empty crossing, or onto a **strictly weaker** foreign knight, driving it off; it then rests |
+| Chase the robber | — | an active knight on a crossing of the robber's hex sends the robber off (only once the robber is awake); it then rests, and the robber move follows |
+
+- **A knight cannot act on the turn it woke.** It can be woken again after it acts.
+- A driven-off knight is moved by **its owner** along its own roads to any empty
+  crossing it can reach; if there is none, it is lost.
+- A knight is a wall, like an opposing building: roads cannot be laid past an enemy
+  knight, a settlement cannot be built on a knight, and the knight cuts **Longest Road**.
+- Knights can act (wake, move, chase) **before the roll** as well as after.
+
+## City walls
+
+2 brick, on a city without a wall, **three per player**. Each wall raises the hand
+limit on a seven by two (so a seven discards when you hold more than `7 + 2 × walls`).
+
+## City improvements
+
+Three tracks, five levels each, bought with the track's commodity: **trade (cloth,
+yellow), politics (coin, blue), science (paper, green)**. Level *n* costs *n* of the
+commodity. You must own a city to improve.
+
+| Track | Level 3 gives |
+| --- | --- |
+| Trade | commodities trade with the bank **2:1** |
+| Politics | knights may be promoted to **mighty** |
+| Science | the **aqueduct**: when the dice pay you nothing, take any resource |
+
+The level names (Trading Post … Grand Bazaar, Town Hall … Palace, Abbey … University)
+are this app's own.
+
+### Metropolises
+
+The first player to reach **level four** in a track takes that track's **metropolis**
+(a marker on one of their cities: +2 points; a city carries at most one). Reaching
+**level five** takes it from a holder who is still on four. A player with several
+cities chooses which; with one it is placed at once; a player with no free city
+**waits**, and claims it when a city is built.
+
+## Progress cards
+
+54 cards: 18 in each of three decks. A card played returns to the **bottom** of its
+deck. A hand holds **four**; a fifth must be given back at once. They can be played at
+any point of your own turn (before or after the roll), except where noted.
+
+**Science (green)** — Alchemist ×2 *(before the roll only)*, Crane ×2, Engineer, Inventor ×2,
+Irrigation ×2, Medicine ×2, Mining ×2, Printer, Road Building ×2, Smith ×2.
+
+**Politics (blue)** — Bishop ×2 *(after the first attack)*, Constitution, Deserter ×2,
+Diplomat ×2, Intrigue ×2, Saboteur ×2, Spy ×3, Warlord ×2, Wedding ×2.
+
+**Trade (yellow)** — Commercial Harbor ×2, Master Merchant ×2, Merchant ×6,
+Merchant Fleet ×2, Resource Monopoly ×4, Trade Monopoly ×2.
+
+**Printer** and **Constitution** are one point each and are **laid face up the moment
+they are drawn**; they never sit in a hand.
+
+How each plays is shown on the card in the app (`CatanText.progressHelp`); the engine's
+behaviour is in `CatanCk.applyProgress`. Points worth knowing:
+
+- **Saboteur** hits every other player with **as many points as you or more**, who each
+  discard half their cards (rounded down). **Wedding** takes two cards (or what they
+  have) from each player with **more** points. **Master Merchant** needs a victim with
+  more points, and takes two cards you choose.
+- **Spy**: you see the target's progress cards and take one; nobody else sees them.
+- **Merchant**: placed beside one of your buildings; you trade that hex's resource 2:1
+  and hold a victory point until someone else plays a Merchant.
+- **Deserter**: the victim removes a knight of *their* choice; you place a free one of the
+  same strength (or a basic if yours is not free), awake or asleep as theirs was.
+- **Diplomat**: removes a road with a loose end (an end touching no other road, building
+  or knight); if it was yours you may rebuild it anywhere for free.
+- **Inventor** swaps two tokens, never a 2, 6, 8 or 12.
+
+## The chore queue
+
+Anything that needs an answer from somebody — a discard, a city to lose, a progress card
+to hand over, a metropolis site, a knight to place — is queued as a **chore**
+(`CatanPhase.CHORE`, `CkState.chores`). The game waits on the seat the first chore names
+(not always the player whose turn it is), then resumes where `CkState.back` says. This is
+how a seven, a barbarian landing, a wedding or a spy are all one mechanism, and why
+the AI and the network driver needed no new concepts.
+
+The two free-form chores — **discarding** and **handing over** cards — are structural
+like the base game's trade offers: the engine checks them in `isLegalMove` and the legal
+list carries one example, so a seat is never without a move.
+
+## Scoring and winning
+
+Settlement 1, city 2, **metropolis +2**, **Longest Road 2**, **Defender of Catan 1** each,
+**Printer / Constitution 1** each, **the Merchant 1**. Nothing is hidden. Win at 13 (default),
+checked after every move and when a turn arrives.
+
+## Choices made here, and why
+
+- **The red die must be no higher than the improvement level** to draw a progress card
+  (level 1 draws on a 1, level 5 on 1–5). The almanac says the red die must match a
+  number on one of your improvements and that the number rises with the level; this is
+  the reading that makes both true.
+- **One resource is offered to every player for a Commercial Harbor.** The printed card
+  lets you offer a different one to each.
+- **The merchant cannot go on the desert**, which produces nothing to trade.
+- **Improvements need a city** to be built.
+- **A 3:1 harbour trades commodities too**; a 2:1 harbour trades only its own resource.
+- **A knight that cannot find a refuge is lost**, as the almanac says of an intrigue.
+- **A claim on a metropolis with no city to carry it waits** and is made when a city is
+  built.
+- **Domestic trade** works as in the base game — an offer to one seat or to the whole
+  table, asked in seat order, each seat accepting, declining or countering — and may
+  include commodities (`OfferGoods`, `CounterGoods`; accepting and dismissing counters
+  reuse the base game's `AcceptCounter` and `DismissCounters`).
+- **No Seafarers, no 5–6 player extension**, no scenario or variant of any kind.
+
+## The computer opponent
+
+`CatanCkAi` plays a safe, unambitious game: it settles and raises cities as the base AI
+does, spends commodities on improvements as soon as it can (leaning to politics), hires
+and wakes knights as the barbarians draw near, chases the robber off hexes it needs, plays
+the progress cards whose value is obvious, and answers every chore with the card it values
+least. It never plans a knight's route, never plays an Alchemist, Inventor, Diplomat,
+Deserter or Intrigue, and makes no domestic offers (though it answers them). Every engine
+game in `CatanCkSelfPlayTest` ends in a win at thirteen points.
+
+## Known gaps
+
+- The screen is built and its logic is tested, but **not yet verified on two real
+  devices**; the catalogue entry stays a dev-channel preview.
+- No animation for the event die, the barbarian landing or a knight's move.
+- The Commercial Harbor offers a single resource type (see above).
+- The AI is not a strong opponent and makes no claim to be.

docs/RULES-catan-seafarers.md

@@ -0,0 +1,71 @@
+# Katan: Seafarers
+
+The Seafarers rule set is chosen at setup next to *Base game* and *Cities & Knights*. It is the base
+game ([RULES-catan.md](RULES-catan.md)) with a sea, ships, a pirate, gold fields and islands to
+settle. Code: `game/catan/CatanSeaRules.kt` (the additions), `CatanSeaBoard.kt` (the map),
+`CatanBoard.kt` (`Topology`, the geometry shared by every map), state behind `CatanState.sea`
+(null in the other rule sets). It cannot be combined with Cities & Knights.
+
+Where the published rules leave room, or where this game differs, it says so below.
+
+## The map
+
+One map, *Heading for New Shores*: a large **home island** (21 hexes, one desert) and three small
+islands (3, 3 and 2 hexes) across the water, inside a ring of sea. Which land hexes are gold, which
+are the desert and where the sea lies is fixed; the **resources on the other hexes, the number tokens
+and the nine harbours are shuffled** for each game. The red numbers (6, 8) are never on neighbouring
+hexes. Players take three or four seats; the default target is **12 points** (menu: 8, 10, 12, 14).
+
+The geometry is the same lattice as the base island, generalised (`Topology`): a hex is land or sea,
+a crossing can hold a town if any hex touching it is land, an edge can hold a road if any hex touching
+it is land and a ship if any hex touching it is sea (so a coastal edge takes either, never both).
+
+## What changes
+
+**Setup.** Both starting settlements (and their roads) go on the home island. A starting piece is a
+road, never a ship. The second settlement collects from the hexes round it as usual (gold pays nothing
+at setup).
+
+**Ships.** A ship costs 1 lumber and 1 wool and lies on a sea edge.
+
+* It must join your fleet or a town of yours: one end of the edge touches your town, or another of your ships.
+  An opponent's town is a wall.
+* Roads and ships connect **only at a town of your own**: a road cannot start from a ship's end, nor a
+  ship from a road's, unless a settlement or city of yours stands on that crossing. A settlement may be
+  built at the end of a ship route exactly as at the end of a road route.
+* No more than 15 ships. Road Building may lay two roads, two ships or one of each.
+* **Sailing.** Once per turn you may move one ship, never one built or moved this turn, and only a ship at the
+  **open end** of a route (one end touches nothing else of yours). It goes to any edge it could be built on
+  with it lifted off.
+
+**The pirate.** Starts in the open sea. On a seven (and with a Knight card) the player moves either the
+robber, to any land hex, or the pirate, to any sea hex. The robber works as before. The pirate **blocks the six
+edges round its hex**: no ship may be built or sail onto them (ships already there stay). It robs one card
+at random from a player with a ship on an edge of its hex.
+
+**Gold.** A gold field has a number like any hex. When it comes up, each town beside it (one card; a city two)
+pays its owner **any resource of their choice**, chosen after the ordinary production is dealt, in seat order from
+the roller. The robber blocks a gold field like any hex. If the bank cannot supply the choice it is limited to
+what it holds.
+
+**New islands.** The first player to settle on each island other than the home island scores **2 bonus points**,
+permanently (`SeaState.islandBonus`). A second settlement there earns nothing extra.
+
+**Longest route.** Longest Road counts roads and ships together, as a path of your pieces that never runs
+through an opponent's town and changes between road and ship only at a town of yours. Five or more, as before.
+
+Everything else (development cards, trading, harbours, Largest Army, the discard on a seven) is the base game.
+
+## Not included
+
+The physical expansion has more scenarios and the Catan Universe app adds more still. These are **out of scope here**:
+fog islands, treasure islands, the oasis, the great canal, the Explorers & Pirates and Cities & Knights combinations,
+the scenarios after the first, and trade ships. The `SeaScenario` enum and `SeaBoards` are built so a second map
+is a new text map and a new enum entry.
+
+## How the AI plays it
+
+It settles first and sails second. A ship is built when a settlement spot reachable by sea (up to five steps from its
+open end) is worth having, with a bonus for an island nobody has landed on, and ahead of a development card when that
+bonus is in play. It chooses the resource it values most from gold, always moves the robber (never the pirate) and does
+not sail ships it has already launched. See `CatanAi.shipValue`.

docs/RULES-catan.md

@@ -0,0 +1,345 @@
+# Katan — implemented rules
+
+This is the ruleset the engine enforces. Anything marked **toggle** is exposed
+in the game setup screen.
+
+Katan is this app's name for the island game the collection is built around.
+The catalogue id is `catan` (so this file is `RULES-catan.md` and the code lives
+in `game/catan/`), but the printed name is trademarked, so the game is listed
+and titled **Katan**. The rules themselves are the base game for three to four
+players, as published.
+
+The engine is a pure state machine (`CatanRules`) with no Android types, and its
+behaviour is pinned by `CatanBoardTest`, `CatanRulesTest` and `CatanAiTest`.
+
+## Rule sets
+
+A table plays one of two rule sets, chosen on the setup screen
+(`CatanOptions.ruleSet`):
+
+- **Base game** — everything in this document.
+- **Cities & Knights** — the expansion, documented in
+  [RULES-catan-ck.md](RULES-catan-ck.md). It reuses this document's board, setup,
+  building, robber and trade rules and changes or replaces the rest; its state lives
+  behind `CatanState.ck`, which is `null` in the base game.
+
+## Table
+
+- **Rules — *toggle*.** Base game or Cities & Knights (`CatanOptions.ruleSet`).
+- **Players — *toggle*.** Three or four. `CatanOptions.playerCount`; the engine
+  refuses anything else.
+- **Points to win — *toggle*.** Defaults to 10. `CatanOptions.pointsToWin`, at
+  least 2. A lower target makes a test game short.
+
+The setup screen exposes all three (players: 3 or 4; game to 5, 8, 10 or 12 points in the
+base game, 8, 10, 13 or 15 in Cities & Knights, whose published target is 13).
+
+## Board
+
+The island is the standard layout, derived once from axial hex coordinates in
+`CatanBoard` and checked at class-init:
+
+- **19 hexes**, the hexes within distance 2 of the centre.
+- **54 vertices** and **72 edges**, shared between neighbouring hexes by exact
+  integer position, not floating point. `HEX_CORNERS`, `EDGE_VERTICES`,
+  `VERTEX_EDGES`, `VERTEX_HEXES` and `EDGE_HEXES` are the shared graph.
+- **30 coastal edges**, one closed ring.
+- **9 harbours**, on fixed positions around the coast.
+
+Terrain is dealt from the physical mix and shuffled: **4 forest, 4 pasture,
+4 fields, 3 hills, 3 mountains, 1 desert**.
+
+Number tokens are the 18 the game ships, shuffled over the land hexes: four red
+tokens (**6, 6, 8, 8**) and fourteen others
+(**2, 3, 3, 4, 4, 5, 5, 9, 9, 10, 10, 11, 11, 12**). Seven never appears. The
+desert bears no token and the robber starts on it.
+
+### Keeping 6s and 8s apart
+
+The published game asks that the two red numbers not sit on adjacent hexes, and
+`generate` guarantees it rather than hoping for it:
+
+1. Shuffle the land and take four hexes; accept the draw if none of the four
+   touch each other. Retry up to 60 times.
+2. If no draw separates them, fall back to four of the six board-corner hexes,
+   which are pairwise non-adjacent by construction and at most one of which can
+   be the desert.
+
+`no seed puts two red tokens on adjacent hexes` runs the whole thing over seeds
+1..500.
+
+Harbours: the nine **positions** are fixed (the physical frame is not shuffled),
+but the nine **types** are shuffled onto them — **five 2:1 resource harbours**
+(one per resource) and **four generic 3:1 harbours**. The frame positions are
+chosen so no two harbours sit closer than three coastal edges apart.
+
+## Setup
+
+Placement runs in snake order: seats `0, 1, …, n-1` then `n-1, …, 1, 0`, each
+placing one settlement and one road. During setup the distance rule still holds
+(a settlement may not sit one edge from any other building) but the road need
+not connect to anything already placed.
+
+A player's **second** settlement earns one resource card for each adjacent
+producing hex, supply permitting — duplicates counted, so a second settlement on
+two forests earns two lumber. The first pass earns nothing.
+
+After the last placement, seat 0 leads and the first real turn begins.
+
+## Turn
+
+A turn runs through the phases in `CatanPhase`:
+
+1. **AWAIT_ROLL** — the player on the clock rolls.
+2. A seven goes to **DISCARDING** and then **ROBBER**; anything else produces and
+   goes straight to **PLAYING**.
+3. **PLAYING** — build, trade, buy and play development cards, then end the turn.
+4. **FREE_ROADS** is a detour inside PLAYING while a Road Building card is being
+   spent.
+
+### Rolling
+
+The dice are derived from the game seed and a monotonic counter (`rngStep`), not
+from a random generator stored in the state: the same seed and the same moves
+replay identically. `RollDice(forced = …)` exists so tests can stage a number;
+it is deliberately **not** a member of the enumerated move list, so a client
+cannot send one over the network — only code holding the state directly can use
+it.
+
+### Production
+
+For a non-seven total, each hex whose number matches pays its producing terrain:
+a settlement takes **1**, a city takes **2**. The robber's hex pays nothing.
+
+**When the bank cannot meet the demand for a resource, nobody receives that
+resource this roll.** This is the official ruling, implemented per-resource:
+demand is totalled first and, if it exceeds the bank's supply, every gain of
+that resource is dropped.
+
+## The robber
+
+A **seven** sends the robber: first every player holding **more than seven**
+resource cards discards half their hand (rounded down, so nine cards means four
+gone), in seat order starting from the lowest overfull seat; then the roller
+moves the robber and may steal.
+
+The robber **must move to a different hex**. Moving onto a hex lets the roller
+steal one card from one opponent who has a building on that hex and at least one
+card in hand. The card stolen is chosen at random, derived like the dice. A
+hex with no opponent holding cards offers only the move, no steal.
+
+A played Knight enters the same ROBBER phase, so the robber move after a Knight
+is the same code path.
+
+## Trading
+
+### Domestic
+
+An offer is addressed to **one** seat or, with `to = null`, to **everyone**, and
+names two card multisets: what the offerer gives, what they want.
+
+Seats are asked **one at a time**, in seat order after the offerer (seats holding
+no cards are skipped; an addressed offer asks only its addressee). The seat being
+asked may:
+
+- **accept** — the trade happens at once and the offer closes (first accept wins);
+- **decline** — the offer moves on to the next seat;
+- **counter** (`CounterTrade`) — propose different terms: what they would give and
+  what they want from the offerer. A counter must differ from the offer as made
+  (that is an accept), and both sides must hold the cards. The offer moves on.
+
+When every seat has answered and nobody accepted: with no counters the offer
+simply lapses; with counters the phase becomes `TRADE_COUNTERS` and the offerer
+either **takes one** (`AcceptCounter(seat)`, still checked for affordability) or
+**turns them all down** (`DismissCounters`).
+
+An offer is legal only when the offerer's turn is in PLAYING, the addressee is
+another seat, both legs are non-empty, the two legs are not the same multiset
+(`countOf(give) != countOf(get)` — like-for-like is not a trade), and the
+offerer actually holds the cards being offered.
+
+A seat may **accept** only if it holds what was asked and the offerer still holds
+what was promised; otherwise only decline (or counter) is offered. A refusal
+leaves every card where it was.
+
+Offers are free-form intents rather than enumerated moves (the space of card
+multisets is combinatorial), so they are validated structurally by
+`CatanRules.isLegalMove` and checked by the network driver's gate like any other
+move.
+
+### Maritime
+
+Bank trade gives `ratio` of one resource for one of another, where the ratio is
+the best the seat can get: **4:1** through the bank, **3:1** through a generic
+harbour, **2:1** through a harbour matching the resource being given. A harbour
+counts when the seat owns a settlement or city on **either** endpoint vertex of
+its edge.
+
+## Building and development cards
+
+| Build | Cost |
+| --- | --- |
+| Road | 1 lumber + 1 brick |
+| Settlement | 1 lumber + 1 brick + 1 wool + 1 grain |
+| City | 2 grain + 3 ore |
+| Development card | 1 wool + 1 grain + 1 ore |
+
+A settlement goes on an **empty vertex** at least two edges from every standing
+building and connected to the seat's own road network. A city upgrades one of
+the seat's own settlements. A road goes on an empty edge that connects to the
+seat's network: it must start from a crossing where the seat has a building, or
+where one of its roads ends.
+
+**An opponent's settlement or city on a crossing breaks the network there.** A
+road cannot be laid past it, even from a crossing where one of your own roads
+ends — only a crossing you own a building on is a way through. The same rule
+applies to the free roads of a Road Building card, and it is the same wall that
+cuts Longest Road (below).
+
+**Pieces are limited**: each player has **15 roads, 5 settlements and 4 cities**.
+A player who has laid them all cannot build another of that kind. Raising a
+settlement into a city returns the settlement to the supply, so the five
+settlements remain available to be laid again.
+
+The development deck is the published 25 cards: **14 Knights, 2 Road Building,
+2 Monopoly, 2 Year of Plenty, 5 Victory Point**. Cards are bought blind from the
+top of the deck.
+
+Timing rules the engine enforces:
+
+- **One development card per turn.** `devCardPlayedThisTurn` gates every play.
+- **A card cannot be played the turn it was bought.** Each card records
+  `boughtTurn` and is skipped while that equals the current turn.
+- **Victory Point cards are never played.** They are counted straight from the
+  hand by `victoryPoints`, and are only revealed by winning.
+- **Knight** → the robber phase, and counts toward Largest Army.
+- **Road Building** → two free road placements (FREE_ROADS); the player may
+  forfeit any that remain.
+- **Monopoly** → seizes every card of the named resource from the other seats.
+- **Year of Plenty** → takes up to two cards from the bank; taking two of a kind
+  requires the bank to hold both.
+
+## Scoring and winning
+
+Victory points are:
+
+- **Settlement 1, city 2.**
+- **Longest Road 5** — the longest single road of **five or more** segments.
+- **Largest Army 5** — first to **three** played knights.
+- **Victory Point cards**, one each.
+
+A seat wins on reaching **points to win** (default 10). The win is checked after
+every build, when a turn ends, and when a seat's turn arrives — the last covers
+points that changed on someone else's turn, such as a broken Longest Road being
+re-awarded. A seat already at the target therefore wins at the start of its own
+turn rather than having to act.
+
+### Longest Road
+
+The award goes to the longest **simple path** over a seat's own roads. The path
+never passes *through* an opponent's building (it may run up to one) and never
+revisits a vertex — so a figure of two loops sharing an intersection counts as
+one road of five, not two roads, because the intersection is a branch.
+
+Once held, the award is kept until another seat builds a **strictly longer**
+road; an equal length leaves it where it is. If the holder's road falls below
+five segments the award reopens to the longest road of five or more, lowest seat
+first on a tie. A settlement placed across an opponent's road breaks it, and the
+award is recomputed for everyone after any settlement.
+
+### Largest Army
+
+First to three knights takes it. It is stolen only by a **strictly larger** army:
+a tie leaves the incumbent ahead, exactly as Longest Road does.
+
+## The computer opponent
+
+`CatanAi` plays a legal, mildly strategic game so a solo player can host against
+computers, with the lobby filling empty seats.
+
+It reads **only public information** — terrain, numbers, buildings, roads,
+resource counts, development-card counts and knights played — plus its own hand.
+It never looks into the deck, another seat's development cards, or the seed
+beyond the roll the rules derive from it. That is a design constraint, not an
+accident: it runs on the host, where the authoritative state is fully visible.
+
+What it does:
+
+- **Setup.** Rates a settlement by the production its three hexes give (weighted
+  by the token odds and by how much it wants each resource), plus a bonus for
+  resource variety and for sitting on a harbour, plus a small term for where the
+  accompanying road points.
+- **Main phase**, in priority order: raise a city, build a settlement, play a
+  knight, play Year of Plenty or Monopoly when it closes a gap, play Road
+  Building when two segments are useful, buy a development card, build a road
+  that reaches a spot worth settling, trade at the bank only when the trade
+  completes a build this turn, make one domestic offer that closes a build, else
+  end the turn.
+- **The robber.** Moves onto the hex where it blocks the most opposing
+  production (weighted by token odds), preferring to rob whoever is holding the
+  most cards and the most points.
+- **Trades.** Accepts an offer when what arrives is worth more than what leaves
+  by its own resource valuations; a mild table, not a shark.
+- **Discards.** Throws away what it values least (wool, then brick, then lumber,
+  before grain and ore).
+
+It makes **at most one domestic offer a turn**. A declined offer changes nothing,
+so re-offering the same thing would only bounce between two seats forever; the
+engine allows more offers, the AI chooses not to.
+
+`CatanAiTest` plays three- and four-seat tables of engines out to a result from
+several seeds, refusing any illegal move the AI chooses, and checks the winner
+reached the target.
+
+## Provenance and rule choices
+
+The rules are the published base game. Where the published rules leave room, the
+engine picks one reading and records it here.
+
+**Followed from the published rules:** the board and its component mix; the
+number tokens; 6s and 8s not adjacent; snake-order setup and second-settlement
+income; production weighting; the robber on a seven; discard half over seven;
+domestic and maritime trade; build costs; the 25-card development deck and its
+timing rules; Longest Road and Largest Army worth five; victory at ten.
+
+**Choices made here, and why:**
+
+- **A bank short of a resource pays nobody that roll.** This is the official
+  ruling, and it is implemented per-resource rather than per-player.
+- **Longest Road and Largest Army are kept on a tie**, and stolen only by a
+  strictly longer road or a strictly larger army. The alternative reading lets a
+  tie steal the award; "strictly better" is the common tournament reading and
+  keeps the award from flickering.
+- **A ring road counts as a simple path.** No vertex is revisited, so six
+  segments around one hex are worth five, not six.
+- **The win is checked when a seat's turn arrives**, not only on that seat's own
+  action, so points that move on another player's turn still win.
+- **A bought Victory Point card does not win immediately.** It is counted when
+  the win is next checked (a build or the end of the turn), which is when the
+  holder would reveal it.
+- **Year of Plenty two-of-a-kind needs the bank to hold both cards**, not one.
+- **The robber must move.** Some printings allow staying put; this engine always
+  requires a different hex.
+- **Offers may be open to the whole table** and can be countered; the first accept wins (see Trading).
+
+## Known gaps
+
+- **Longest Road and Largest Army are worth 5 each here.** The published base game awards
+  **2** each (Catan Universe's almanac says so for Largest Army, and the printed rules
+  for both). Cities & Knights scores Longest Road at 2, as printed. Left unchanged in
+  the base game so far; it is a one-constant change in `publicVictoryPoints`.
+- **A bank short of a resource pays nobody that roll**, even when only one player is owed
+  it. The published ruling lets a lone claimant take what is left; Cities & Knights does.
+- **No timer or cancel on offers.** An offer waits for each asked seat in turn; the offerer cannot withdraw it mid-round, and a player who never answers stalls the table.
+- **The AI never counters.** It accepts, declines, and picks among counters it is sent, but does not propose them.
+- **No trading away a development card.** Not part of the base game.
+- **The screen is built, not yet verified on two devices.** The Katan screen and
+  setup options exist (see [UI-catan.md](UI-catan.md)); the catalogue entry is a
+  dev-channel preview until two-device play has been verified.
+- **The AI does not look ahead.** It scores one move deep with a fixed resource
+  valuation. It plays legally and plausibly; it is not a strong opponent, and no
+  strength claim is made.
+- **The board is the standard published layout, generated.** Unlike the Sequence
+  board there is no unverified substitute here — the geometry is the real one —
+  but the *island* (terrain and token placement) is freshly generated each game,
+  so it will not match any particular physical set-up. That is the intent.

docs/RULES-meowdoku.md

@@ -0,0 +1,98 @@
+# Meowdoku
+
+A board of colours, and a cat in every row, column and colour — no two sharing
+even a corner.
+
+## The puzzle
+
+The board is **N by N** and coloured into **N regions**. Exactly one cat hides
+in every row, every column and every region, and no two cats may touch — not
+along a side and not at a corner, so a cat rules out all eight squares around
+itself. Those four constraints together always leave exactly one arrangement.
+
+Uniqueness is not decoration. The game is deduction, and a second answer means
+a square the player cannot prove either way. Every board is therefore generated
+and then searched: build the colours, count the ways a board can be answered,
+and if it is more than one, throw the board away and deal another. The count is
+a plain depth-first search over the rows with the obvious exclusions propagated,
+and it sees only the colours and the rules — never the cats it was grown from.
+
+## Playing it
+
+Controls are the original's, and they carry the game's whole psychology:
+
+- **One tap crosses a square over.** Free, instant, erasable — the note you
+  make while thinking.
+- **A second tap on the same square within 350 ms is the cat attempt.** The
+  board judges it against the answer it was dealt: correct, the cross is
+  replaced by a cat; wrong, the cross stays and a heart goes. This is why a
+  guess feels like a decision: your own note has to survive one more tap
+  before it becomes a bet.
+- **Drag to cross a line.** The stroke paints the same note every square it
+  enters: start on a blank square and it crosses the row or column you drag
+  along; start on a crossed square and the stroke erases them instead. Cats
+  are skipped — placed cats are permanent.
+
+A square you pencilled over can still be tapped for a cat, and the cross is
+forgiven: the attempt replaces it if it is right. The one thing no gesture
+undoes is a cat once placed.
+
+The original ships a fifth gesture — a **draft** scratchpad mode, a tool you
+buy, where crosses and cats are laid down without judgement and applied all at
+once — and it is left out here with the rest of the shop: a scratchpad whose
+notes cost nothing is what tapping already is.
+
+A **Hint** spends a token and shows the cat in the first row that still lacks
+one, replacing any cross drawn over it. The original sells these as tools; here
+they are simply counted, three per board by default, which keeps the hint a
+decision rather than a reflex.
+
+## The heart
+
+Why a wrong tap costs anything at all: the puzzle is only hard if guessing is.
+A board with no penalty is a board you can solve by tapping every square, and
+the hearts are what make the deduction on a colour you have not reasoned about
+yet feel like a choice. Three is the number the original deals, and it stays
+three by default.
+
+## Options
+
+| | |
+| --- | --- |
+| **Board** | 4×4 up to 10×10; the number of cats equals the side |
+| **Hearts** | 1 to 5, default 3 |
+| **Hints** | 0 to 3, default 3 |
+
+Boards are dealt from the table's seed, so a saved game resumes to the same
+cats in the same colours, and **New puzzle** moves the seed to deal a different
+board. Smaller sides are gentler: a 4×4 is the shortest way to learn what
+no-touch does to a corner, and the ten-wide boards are for people who have
+already made that mistake.
+
+## How a board is dealt
+
+The order matters, and it is the order the original game uses:
+
+1. **Settle the cats first.** One per row, one per column, no two touching,
+   chosen by backtracking over shuffled column orders.
+2. **Grow the colours around them.** Each region starts as its cat's square and
+   expands outwards one square at a time; some regions are grown as straight
+   bars along the cat's row or column, which is what stops the board reading as
+   texture, and the rest take whichever neighbour is smallest so nothing
+   sprawls while another dies young.
+3. **Check the answer.** Count solutions up to two; keep the board only when
+   the count comes back exactly one.
+
+The generator's rejection loop is why the same seed can take a few attempts:
+most boards are unique on the first try, and the odd seed has to walk until it
+finds one.
+
+## Where this engine differs from the original
+
+The app is a game collection, not a live-service puzzle, so what sits around
+the original's gameplay is left behind: lives-as-monetisation (watching an ad
+for a heart), daily streaks and leaderboards, an Elo-matched bank of
+hand-authored levels, and the cosmetic layer (cat animations, combo feedback,
+confetti). This engine **deals its boards from a seed** instead of shipping a
+level bank, and the rules are the part worth keeping: the cats, the colours,
+the no-touch, the hearts, the one answer.

docs/SAVED-GAMES.md

@@ -0,0 +1,43 @@
+# Saved games
+
+A game played against the computer (or on one device) is kept as it is played, and can be
+picked up again after the app has been closed.
+
+## What the player sees
+
+- **Main menu → Continue.** Each game left half-played is listed, most recent first
+  ("Chess · saved 5 minutes ago"); tapping it resumes.
+- **A game's setup screen** shows a *Game in progress* card with **Resume** and **Discard**.
+  Starting a new game from that screen replaces the saved one.
+- **Leaving the table** (the back arrow, or the app being closed or sent to the background)
+  keeps the position. **End game → End the game** is the deliberate way to throw it away.
+- A game that is **finished** is not kept.
+- A **networked** table is not kept: the other player's seat cannot be held for them. Only a
+  table with no remote human at it (`PlayerKind.HUMAN_REMOTE`) is saved.
+
+One slot per game: there is one saved Chess game, one saved Katan game, and so on.
+
+## How it works
+
+| Piece | Where | Does |
+| --- | --- | --- |
+| `SavedMatch`, `SavedGameStore` | `game/engine/SavedGame.kt` | one JSON file per game under `filesDir/saved-games/`, written atomically (temp file, then renamed); an unreadable file is deleted and read as absent |
+| `MatchController.onHostState`, `restore` | `net/MatchController.kt` | the host reports every position it reaches; `restore(json)` starts the table from a saved position instead of dealing |
+| `MatchSaver` | `net/MatchSaver.kt` | takes the newest position and writes it off the main thread; `flush()` writes synchronously on leaving or on `ON_STOP`; `discard()` forgets the game |
+| `StartMatch` | `ui/PlayScreen.kt` | wires the two together for every game; consumes the resume state once, so a solitaire "new deal" is not put back |
+| `LocalEndGameHandle` | `ui/EndGameHandle.kt` | how each *End game* dialog tells the table to forget its save |
+
+What is saved is `rules.encodeState` of the **host's true state** (hidden cards included),
+plus the `TableConfig` (seed, seats, options) and the local seat. Nothing in the store knows
+which game it is holding, so a new game is saved with no work, provided its state encodes.
+
+A save this build cannot decode (one written by an older version whose state has since
+changed shape) is thrown away and a fresh game is dealt.
+
+## Tests
+
+- `SavedGameStoreTest` — the files: round trip, one slot, ordering, corruption, a cut-off write.
+- `MatchSaverTest` — saving as a table is played, resuming from a save, finished games, flush, discard.
+- `SaveRoundTripAllGamesTest` — **every game in the catalogue**: the whole state is encoded and
+  decoded at every move of a computer-played game, and play carries on from the decoded copy.
+  A new game should be added to it.