Katan: expansions as toggles, scenario chosen in options

Replace the single CatanRuleSet with a set of expansions and add a
scenario field; saves with the old ruleSet still decode. Setup shows
a toggle per expansion and a map picker for Seafarers. Combining
expansions is rejected for now (lifted in a later phase).

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

.github/workflows/release.yml

@@ -49,8 +49,8 @@ jobs:
       - name: Set up Android SDK
         uses: android-actions/setup-android@v4
 
-      - name: Build debug APK
-        run: ./gradlew assembleDebug --no-daemon --stacktrace
+      - name: Build release APK
+        run: ./gradlew assembleRelease --no-daemon --stacktrace
 
       - name: Stage APK for release
         id: stage
@@ -65,7 +65,7 @@ jobs:
           test -n "$offset"
           # Same arithmetic as build.gradle.kts, so the tag names the APK's own number.
           version="v${series}.$(( ${{ github.run_number }} + offset ))"
-          src="app/build/outputs/apk/debug/app-debug.apk"
+          src="app/build/outputs/apk/release/app-release.apk"
           dest="ProLibertateGames-${version}.apk"
           cp "$src" "$dest"
           # The same build again under a name that never changes. GitHub's

CLAUDE.md

@@ -51,8 +51,8 @@ integration:
 
 ## Katan
 
-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
+The island game is catalogue id `catan`, shown as **Katan**. It has two expansions
+(toggles, `CatanOptions.expansions`; none on is the base game): the base game (`docs/RULES-catan.md`), Cities & Knights
 (`docs/RULES-catan-ck.md`, code in `game/catan/CatanCk*.kt`, state behind
 `CatanState.ck`, which is null in the base game) and Seafarers
 (`docs/RULES-catan-seafarers.md`, code in `game/catan/CatanSea*.kt`, state behind

app/build.gradle.kts

@@ -104,6 +104,11 @@ android {
 
     buildTypes {
         release {
+            // Signed with the same key as the debug builds, so a release installs
+            // over what is already on a device; a different key would make the
+            // updater's installs fail with a signature mismatch.
+            signingConfig = signingConfigs.getByName("debug")
+            isDebuggable = false
             isMinifyEnabled = false
             proguardFiles(
                 getDefaultProguardFile("proguard-android-optimize.txt"),

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

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

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

@@ -1,5 +1,8 @@
 package org.prolibertate.games.game.catan
 
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.GameAi
 
 /**
@@ -17,39 +20,48 @@ import org.prolibertate.games.game.engine.GameAi
  * dev-card counts, knights played — plus its own hand, and never looks
  * into the deck, another seat's development cards, or the seed beyond the
  * roll the rules derive from it.
+ *
+ * Each seat's [AiProfiles] entry shapes how it plays. The default profile
+ * (medium, balanced) is the AI described above. Easy settles for worse
+ * spots, trades and builds, now and then ends its turn early, and takes
+ * slightly bad trades. Hard weighs setup spots by balance and port synergy,
+ * values cards by what its next build is missing, races for Longest Road,
+ * keeps the robber off its own hexes and off the table's non-leaders, and
+ * is choosier about whom it trades with. Style nudges the tradeoffs: bold
+ * seats expand, cautious seats spend down before a seven can bite, spiteful
+ * seats go after the leader.
  */
-class CatanAi : GameAi<CatanState, CatanMove> {
+class CatanAi(private val profiles: AiProfiles = AiProfiles.DEFAULT) : GameAi<CatanState, CatanMove> {
 
     /** Plays the Cities & Knights tables; this class keeps the base game. */
-    private val ck = CatanCkAi(this)
+    private val ck = CatanCkAi(this, profiles)
 
     override fun chooseMove(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+        val profile = profiles.of(seat)
         require(legal.isNotEmpty() || state.phase == CatanPhase.PLAYING) {
             "No legal move for seat $seat"
         }
         if (state.isCk) return ck.choose(state, seat, legal)
         return when (state.phase) {
             CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND ->
-                chooseSetup(state, seat, legal.filterIsInstance<SetupPlace>())
+                chooseSetup(state, seat, legal.filterIsInstance<SetupPlace>(), profile)
 
             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.GOLD -> chooseGold(state, seat, legal, profile)
 
-            CatanPhase.DISCARDING -> chooseDiscard(state, seat, legal.filterIsInstance<Discard>())
+            CatanPhase.DISCARDING -> chooseDiscard(state, seat, legal.filterIsInstance<Discard>(), profile)
 
-            CatanPhase.ROBBER -> chooseRobber(state, seat, legal.filterIsInstance<MoveRobber>())
+            CatanPhase.ROBBER -> chooseRobber(state, seat, legal.filterIsInstance<MoveRobber>(), profile)
 
-            CatanPhase.FREE_ROADS -> chooseFreeRoad(state, seat, legal)
+            CatanPhase.FREE_ROADS -> chooseFreeRoad(state, seat, legal, profile)
 
-            CatanPhase.TRADE_PENDING -> chooseResponse(state, seat, legal)
+            CatanPhase.TRADE_PENDING -> chooseResponse(state, seat, legal, profile)
 
-            CatanPhase.TRADE_COUNTERS -> chooseCounter(state, legal)
+            CatanPhase.TRADE_COUNTERS -> chooseCounter(state, seat, legal, profile)
 
-            CatanPhase.PLAYING -> choosePlaying(state, seat, legal)
+            CatanPhase.PLAYING -> choosePlaying(state, seat, legal, profile)
 
             CatanPhase.CHORE, CatanPhase.GAME_OVER -> legal.firstOrNull()
                 ?: error("Nothing to choose in phase ${state.phase}")
@@ -60,12 +72,68 @@ class CatanAi : GameAi<CatanState, CatanMove> {
     // Setup
     // -----------------------------------------------------------------------
 
-    internal fun chooseSetup(state: CatanState, seat: Int, places: List<SetupPlace>): SetupPlace {
+    internal fun chooseSetup(
+        state: CatanState,
+        seat: Int,
+        places: List<SetupPlace>,
+        profile: AiProfile = AiProfile.DEFAULT,
+    ): SetupPlace {
         require(places.isNotEmpty()) { "No legal settlement placement" }
-        return places.maxByOrNull { place ->
-            spotValue(state, place.vertex) +
-                0.25 * placeDirection(state, place)
-        } ?: places.first()
+        // A bold seat cares more where its road leads; a cautious one less.
+        val direction = 0.25 + 0.1 * profile.style.boldness
+        return when (profile.level) {
+            // Easy looks only at the spot itself, and sometimes settles for the runner-up.
+            AiLevel.EASY -> profile.pick(places.sortedByDescending { spotValue(state, it.vertex) })
+
+            AiLevel.HARD -> places.maxByOrNull { place ->
+                hardSpot(state, seat, place.vertex) + direction * placeDirection(state, place)
+            } ?: places.first()
+
+            AiLevel.MEDIUM -> places.maxByOrNull { place ->
+                spotValue(state, place.vertex) + direction * placeDirection(state, place)
+            } ?: places.first()
+        }
+    }
+
+    /**
+     * A spot as a seat that plans would see it: the plain production value,
+     * plus resources the seat does not yet draw, less piling onto one it
+     * already has plenty of, and ports worth what the seat will produce to
+     * trade through them.
+     */
+    internal fun hardSpot(state: CatanState, seat: Int, vertex: Int): Double {
+        if (state.buildings[vertex] != null) return -1.0
+        val topo = state.topo
+        val owned = HashMap<Resource, Double>()
+        for (v in state.buildings.indices) {
+            val b = state.buildings[v] ?: continue
+            if (b.owner != seat) continue
+            val mult = if (b.type == BuildingType.CITY) 2.0 else 1.0
+            for (h in topo.VERTEX_HEXES[v]) {
+                val res = state.terrains[h].produces ?: continue
+                owned[res] = (owned[res] ?: 0.0) + mult * CatanBoard.numberOdds(state.numbers[h]) / 36.0
+            }
+        }
+        val here = HashMap<Resource, Double>()
+        for (h in topo.VERTEX_HEXES[vertex]) {
+            val res = state.terrains[h].produces ?: continue
+            here[res] = (here[res] ?: 0.0) + CatanBoard.numberOdds(state.numbers[h]) / 36.0
+        }
+        var value = spotValue(state, vertex)
+        value += 0.15 * here.keys.count { (owned[it] ?: 0.0) <= 0.0 }
+        for ((res, p) in here) {
+            if ((owned[res] ?: 0.0) > 0.15) value -= 0.3 * p
+        }
+        val total = owned.values.sum() + here.values.sum()
+        for (e in topo.VERTEX_EDGES[vertex]) {
+            val port = state.ports.firstOrNull { it.edge == e } ?: continue
+            value += if (port.resource == null) {
+                0.05 + 0.15 * total
+            } else {
+                0.9 * ((owned[port.resource] ?: 0.0) + (here[port.resource] ?: 0.0))
+            }
+        }
+        return value
     }
 
     /**
@@ -87,48 +155,127 @@ class CatanAi : GameAi<CatanState, CatanMove> {
     // Dice, discards and the robber
     // -----------------------------------------------------------------------
 
-    private fun chooseDiscard(state: CatanState, seat: Int, discards: List<Discard>): Discard {
+    private fun chooseDiscard(
+        state: CatanState,
+        seat: Int,
+        discards: List<Discard>,
+        profile: AiProfile,
+    ): Discard {
         require(discards.isNotEmpty()) { "No legal discard" }
         // Throw away what it wants least; grain and ore are the city, wool
         // is mostly a dev-card tax.
-        return discards.minByOrNull { discard ->
-            discard.cards.sumOf { want(it) }
-        } ?: discards.first()
+        return when (profile.level) {
+            AiLevel.EASY -> profile.pick(discards.sortedBy { d -> d.cards.sumOf { want(it) } })
+
+            // Keep the hand that is closest to paying for something.
+            AiLevel.HARD -> {
+                val hand = state.resources[seat]
+                discards.maxByOrNull { d ->
+                    val left = hand.toMutableMap()
+                    for (c in d.cards) left[c] = (left[c] ?: 0) - 1
+                    progress(left) - 0.01 * d.cards.sumOf { want(it) }
+                } ?: discards.first()
+            }
+
+            AiLevel.MEDIUM -> discards.minByOrNull { discard ->
+                discard.cards.sumOf { want(it) }
+            } ?: discards.first()
+        }
     }
 
-    private fun chooseRobber(state: CatanState, seat: Int, moves: List<MoveRobber>): MoveRobber {
+    /** How close a hand is to the nearest of the things worth buying, a card count over a price, plus one if it pays. */
+    private fun progress(hand: Map<Resource, Int>): Double = SHOPPING.maxOf { cost ->
+        val have = cost.entries.sumOf { (r, n) -> minOf(maxOf(hand[r] ?: 0, 0), n) }
+        have.toDouble() / cost.values.sum() + if (covers(hand, cost)) 1.0 else 0.0
+    }
+
+    private fun chooseGold(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val picks = legal.filterIsInstance<PickGold>()
+        if (picks.isEmpty()) return legal.first()
+        return when (profile.level) {
+            AiLevel.EASY -> profile.pick(picks.sortedByDescending { p -> p.cards.sumOf { want(it) } })
+            AiLevel.HARD -> picks.maxByOrNull { p -> p.cards.sumOf { need(state, seat, it) } } ?: picks.first()
+            AiLevel.MEDIUM -> picks.maxByOrNull { pick -> pick.cards.sumOf { want(it) } } ?: legal.first()
+        }
+    }
+
+    private fun chooseRobber(
+        state: CatanState,
+        seat: Int,
+        moves: List<MoveRobber>,
+        profile: AiProfile,
+    ): MoveRobber {
         require(moves.isNotEmpty()) { "No legal robber move" }
         val points = CatanRules.publicVictoryPoints(state)
-        return moves.maxByOrNull { move ->
+        val hard = profile.level == AiLevel.HARD
+        val spite = profile.style.spite
+        val leader = (0 until state.playerCount).filter { it != seat }.maxByOrNull { points[it] }
+        val victimWeight = 0.3 + 0.1 * profile.style.boldness
+        fun score(move: MoveRobber): Double {
             val hex = state.topo.hexIndex.getValue(move.hex)
             var score = 0.0
             for (v in state.topo.HEX_CORNERS[hex]) {
                 val building = state.buildings[v] ?: continue
-                if (building.owner == seat) continue
                 val worth = if (building.type == BuildingType.CITY) 2 else 1
-                score += worth * CatanBoard.numberOdds(state.numbers[hex]) / 36.0
+                val raw = worth * CatanBoard.numberOdds(state.numbers[hex])
+                if (building.owner == seat) {
+                    // A hard seat will not sit the robber on its own income.
+                    if (hard) score -= 0.8 * raw / 36.0
+                    continue
+                }
+                score += raw / 36.0
+                if (building.owner == leader) score += spite * raw / 36.0
             }
             if (move.victim != null) {
-                score += 0.15 * state.resourceCount(move.victim) +
-                    0.3 * points[move.victim]
+                val cards = state.resourceCount(move.victim)
+                if (!hard || cards > 0) {
+                    score += 0.15 * cards + victimWeight * points[move.victim]
+                    if (move.victim == leader) score += 0.4 * spite
+                }
             }
-            score
-        } ?: moves.first()
+            return score
+        }
+        return if (profile.level == AiLevel.EASY) {
+            profile.pick(moves.sortedByDescending { score(it) })
+        } else {
+            moves.maxByOrNull { score(it) } ?: moves.first()
+        }
     }
 
     // -----------------------------------------------------------------------
     // The main phase
     // -----------------------------------------------------------------------
 
-    private fun choosePlaying(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
-        // A city doubles the best production the seat already owns.
-        legal.filterIsInstance<BuildCity>().maxByOrNull {
-            spotValue(state, it.vertex)
-        }?.let { return it }
+    private fun choosePlaying(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val easy = profile.level == AiLevel.EASY
+        val hard = profile.level == AiLevel.HARD
+        val boldness = profile.style.boldness
+        val endTurn = legal.lastOrNull { it is EndTurn } ?: legal.first()
 
-        legal.filterIsInstance<BuildSettlement>().maxByOrNull {
-            spotValue(state, it.vertex)
-        }?.let { return it }
+        // Easy loses the thread now and then and just passes.
+        if (easy && profile.slips() && profile.random.nextBoolean()) return endTurn
+
+        val cities = legal.filterIsInstance<BuildCity>()
+        val settlements = legal.filterIsInstance<BuildSettlement>()
+        if (hard && (cities.isNotEmpty() || settlements.isNotEmpty())) {
+            // A city doubles what the seat has; a settlement spreads it and
+            // takes a spot nobody else will. Bold seats lean to the spread.
+            val city = cities.maxByOrNull { spotValue(state, it.vertex) }
+            val settlement = settlements.maxByOrNull { hardSpot(state, seat, it.vertex) }
+            val cityScore = if (city != null) spotValue(state, city.vertex) + 0.15 else Double.NEGATIVE_INFINITY
+            val settleScore = if (settlement != null) {
+                hardSpot(state, seat, settlement.vertex) + 0.3 + 0.1 * boldness
+            } else {
+                Double.NEGATIVE_INFINITY
+            }
+            if (city != null && cityScore >= settleScore) return city
+            if (settlement != null) return settlement
+        } else {
+            // A city doubles the best production the seat already owns.
+            pickBest(cities, profile) { spotValue(state, it.vertex) }?.let { return it }
+
+            pickBest(settlements, profile) { spotValue(state, it.vertex) }?.let { return it }
+        }
 
         // Seafarers: a ship toward an island nobody has landed on is worth more than a card.
         legal.filterIsInstance<BuildShip>()
@@ -138,11 +285,15 @@ class CatanAi : GameAi<CatanState, CatanMove> {
 
         // 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 }
+        if (!(easy && profile.slips())) {
+            legal.filterIsInstance<PlayKnight>().firstOrNull()?.let { return it }
+        }
 
-        yearOfPlenty(state, legal)?.let { return it }
+        if (!(easy && profile.slips())) {
+            yearOfPlenty(state, seat, legal, profile)?.let { return it }
 
-        monopoly(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.
@@ -152,6 +303,14 @@ class CatanAi : GameAi<CatanState, CatanMove> {
             return legal.filterIsInstance<PlayRoadBuilding>().first()
         }
 
+        // Hard seat in a Longest Road race puts the road down before spending on cards.
+        val roadThreshold = 0.1 - 0.04 * boldness
+        if (hard && roadRace(state, seat)) {
+            legal.filterIsInstance<BuildRoad>()
+                .maxByOrNull { roadValue(state, it) }
+                ?.let { return it }
+        }
+
         legal.filterIsInstance<BuyDevCard>().firstOrNull()?.let { return it }
 
         // Seafarers: a ship that heads for a settlement spot worth having.
@@ -162,7 +321,7 @@ class CatanAi : GameAi<CatanState, CatanMove> {
 
         // A paid road only when it reaches toward a spot worth settling.
         legal.filterIsInstance<BuildRoad>()
-            .filter { roadValue(state, it) > 0.1 }
+            .filter { roadValue(state, it) > roadThreshold }
             .maxByOrNull { roadValue(state, it) }
             ?.let { return it }
 
@@ -173,16 +332,94 @@ class CatanAi : GameAi<CatanState, CatanMove> {
             .maxByOrNull { CatanRules.bestPortRatio(state, seat, it.give) * -1.0 }
             ?.let { return it }
 
-        offer(state, seat)?.let { return it }
+        if (hard) {
+            // Pile of one card, short of another: convert before it is stuck in hand.
+            legal.filterIsInstance<MaritimeTrade>()
+                .filter { surplusTrade(state, seat, it) }
+                .minByOrNull { CatanRules.bestPortRatio(state, seat, it.give) }
+                ?.let { return it }
+        }
 
-        return legal.lastOrNull { it is EndTurn } ?: legal.first()
+        // Stay under the seven: a cautious (or careful) seat sells down a big hand.
+        if ((hard || boldness < 0) && state.resourceCount(seat) > DISCARD_LIMIT) {
+            legal.filterIsInstance<MaritimeTrade>()
+                .maxByOrNull { t ->
+                    (state.resources[seat][t.give] ?: 0) * 10.0 -
+                        CatanRules.bestPortRatio(state, seat, t.give) * 3.0 + need(state, seat, t.get)
+                }
+                ?.let { return it }
+        }
+
+        if (!(easy && profile.slips())) {
+            offer(state, seat, profile)?.let { return it }
+        }
+
+        return endTurn
+    }
+
+    /** Picks the best of [items] by [score]; easy sometimes takes a near miss. */
+    private fun <T> pickBest(items: List<T>, profile: AiProfile, score: (T) -> Double): T? {
+        if (items.isEmpty()) return null
+        if (profile.level != AiLevel.EASY) return items.maxByOrNull(score)
+        return profile.pick(items.sortedByDescending(score))
+    }
+
+    /** The cheapest things worth saving for, as the shopping list a hard seat weighs hands against. */
+    private val SHOPPING = listOf(
+        CatanRules.CITY_COST,
+        CatanRules.SETTLEMENT_COST,
+        CatanRules.DEV_COST,
+        CatanRules.ROAD_COST,
+    )
+
+    /** The shopping list entry the hand is closest to paying for, among a city, a settlement and a card. */
+    private fun nearestTarget(hand: Map<Resource, Int>): Map<Resource, Int> =
+        listOf(CatanRules.CITY_COST, CatanRules.SETTLEMENT_COST, CatanRules.DEV_COST)
+            .minByOrNull { cost -> cost.entries.sumOf { (r, n) -> maxOf(0, n - (hand[r] ?: 0)) } }
+            ?: CatanRules.CITY_COST
+
+    /** What one card of [res] is worth to this seat right now: more if the next build lacks it, less if it is piled up. */
+    private fun need(state: CatanState, seat: Int, res: Resource): Double {
+        val hand = state.resources[seat]
+        var v = want(res)
+        if ((hand[res] ?: 0) < (nearestTarget(hand)[res] ?: 0)) v += 0.6
+        if ((hand[res] ?: 0) >= 4) v -= 0.4
+        return v
+    }
+
+    /** Whether this bank trade turns a pile (beyond any price) into a card the next build lacks. */
+    private fun surplusTrade(state: CatanState, seat: Int, move: MaritimeTrade): Boolean {
+        val hand = state.resources[seat]
+        val ratio = CatanRules.bestPortRatio(state, seat, move.give)
+        val keep = SHOPPING.maxOf { it[move.give] ?: 0 }
+        val target = nearestTarget(hand)
+        return (hand[move.give] ?: 0) - keep >= ratio &&
+            (hand[move.get] ?: 0) < (target[move.get] ?: 0)
+    }
+
+    /** Whether [seat] is in the hunt for Longest Road: close enough to the holder, or the road is unclaimed. */
+    private fun roadRace(state: CatanState, seat: Int): Boolean {
+        val holder = state.longestRoadOwner
+        if (holder == seat) return false
+        val mine = CatanRules.longestRoadFor(state, seat)
+        if (mine < 3) return false
+        return holder == null || mine + 1 >= CatanRules.longestRoadFor(state, holder)
+    }
+
+    /** The opponent with the most public points, if any. */
+    private fun leaderOf(state: CatanState, seat: Int): Int? {
+        val points = CatanRules.publicVictoryPoints(state)
+        return (0 until state.playerCount).filter { it != seat }.maxByOrNull { points[it] }
     }
 
     /** Year of Plenty: two of whatever the nearest build is shortest of. */
-    private fun yearOfPlenty(state: CatanState, legal: List<CatanMove>): PlayYearOfPlenty? {
+    private fun yearOfPlenty(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): PlayYearOfPlenty? {
         val takes = legal.filterIsInstance<PlayYearOfPlenty>()
         if (takes.isEmpty()) return null
         val shortage = shortage(state) ?: return null
+        if (profile.level == AiLevel.HARD) {
+            return takes.maxByOrNull { take -> take.take.sumOf { need(state, seat, it) } }
+        }
         return takes.maxByOrNull { take ->
             take.take.count { it == shortage } * 2 + take.take.size
         }
@@ -234,7 +471,7 @@ class CatanAi : GameAi<CatanState, CatanMove> {
      * 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? {
+    private fun offer(state: CatanState, seat: Int, profile: AiProfile): OfferTrade? {
         if (offeredThisTurn(state, seat)) return null
         val seatHand = state.resources[seat]
         val builds = listOf(CatanRules.CITY_COST, CatanRules.SETTLEMENT_COST)
@@ -247,11 +484,16 @@ class CatanAi : GameAi<CatanState, CatanMove> {
                 .filter { (seatHand[it] ?: 0) > (cost[it] ?: 0) }
                 .sortedByDescending { seatHand[it] ?: 0 }
             if (surplus.isEmpty()) continue
-            val target = (0 until state.playerCount)
+            val holders = (0 until state.playerCount)
                 .filter { it != seat }
                 .filter { (state.resources[it][need] ?: 0) > 0 }
-                .maxByOrNull { state.resources[it][need] ?: 0 }
-                ?: continue
+            val target = (if (profile.level == AiLevel.HARD) {
+                // Do not feed the leader when someone else can make the swap.
+                val points = CatanRules.publicVictoryPoints(state)
+                holders.maxByOrNull { (state.resources[it][need] ?: 0) - 0.5 * points[it] }
+            } else {
+                holders.maxByOrNull { state.resources[it][need] ?: 0 }
+            }) ?: continue
             val give = listOf(surplus.first(), surplus.first())
             val trade = OfferTrade(to = target, give = give, get = listOf(need))
             if (CatanRules.isLegalMove(state, seat, trade)) return trade
@@ -274,38 +516,73 @@ class CatanAi : GameAi<CatanState, CatanMove> {
     // 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 chooseFreeRoad(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val roads = legal.filterIsInstance<BuildRoad>().filter { roadValue(state, it) > 0.05 }
+        val road = if (profile.level == AiLevel.EASY) {
+            profile.pick(roads.sortedByDescending { roadValue(state, it) }.ifEmpty { return freeRoadFallback(legal) })
+        } else {
+            roads.maxByOrNull { roadValue(state, it) }
+        }
+        return road ?: freeRoadFallback(legal)
     }
 
-    private fun chooseResponse(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+    private fun freeRoadFallback(legal: List<CatanMove>): CatanMove =
+        legal.firstOrNull { it is EndFreeRoads }
+            ?: legal.filterIsInstance<BuildRoad>().firstOrNull()
+            ?: legal.first()
+
+    /**
+     * How much extra the incoming cards must be worth to take a swap: nothing
+     * for the standard seat, a hard or spiteful seat wants more from the
+     * table's leader, and an easy seat is not too fussy.
+     */
+    private fun tradeMargin(state: CatanState, seat: Int, other: Int, profile: AiProfile): Double {
+        var margin = 0.0
+        if (profile.level == AiLevel.EASY) margin -= 0.6
+        val leader = leaderOf(state, seat)
+        if (leader != null && other == leader) {
+            if (profile.level == AiLevel.HARD) margin += 0.4
+            margin += 0.5 * profile.style.spite
+        }
+        return margin
+    }
+
+    private fun tradeValue(state: CatanState, seat: Int, res: Resource, profile: AiProfile): Double =
+        if (profile.level == AiLevel.HARD) need(state, seat, res) else want(res)
+
+    private fun chooseResponse(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
         val accept = legal.filterIsInstance<AcceptTrade>().firstOrNull()
         val offer = state.pendingTrade
         if (accept == null || offer == null) return legal.first { it is DeclineTrade }
         // Accept when what arrives (the offerer's give) is worth more than what
         // leaves (the offerer's get): a mild table, not a shark.
-        val incoming = offer.give.sumOf { want(it) }
-        val outgoing = offer.get.sumOf { want(it) }
-        return if (incoming > outgoing) accept else legal.first { it is DeclineTrade }
+        val incoming = offer.give.sumOf { tradeValue(state, seat, it, profile) }
+        val outgoing = offer.get.sumOf { tradeValue(state, seat, it, profile) }
+        return if (incoming > outgoing + tradeMargin(state, seat, offer.by, profile)) {
+            accept
+        } else {
+            legal.first { it is DeclineTrade }
+        }
     }
 
     /**
      * Picks the counter-offer that gains the most by the same valuation, or
      * turns them all down. The AI never counters itself: it only answers.
      */
-    private fun chooseCounter(state: CatanState, legal: List<CatanMove>): CatanMove {
+    private fun chooseCounter(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
         val offer = state.pendingTrade ?: return legal.first()
+        fun gain(c: TradeCounter) = c.give.sumOf { tradeValue(state, seat, it, profile) } -
+            c.get.sumOf { tradeValue(state, seat, it, profile) }
         val best = legal.filterIsInstance<AcceptCounter>()
             .map { choice -> choice to offer.counters.first { it.by == choice.seat } }
-            .maxByOrNull { (_, c) -> c.give.sumOf { want(it) } - c.get.sumOf { want(it) } }
+            .maxByOrNull { (_, c) -> gain(c) }
         if (best != null) {
             val (choice, c) = best
-            if (c.give.sumOf { want(it) } > c.get.sumOf { want(it) }) return choice
+            if (c.give.sumOf { tradeValue(state, seat, it, profile) } >
+                c.get.sumOf { tradeValue(state, seat, it, profile) } + tradeMargin(state, seat, c.by, profile)
+            ) {
+                return choice
+            }
         }
         return legal.first { it is DismissCounters }
     }
@@ -392,4 +669,9 @@ class CatanAi : GameAi<CatanState, CatanMove> {
         Resource.BRICK -> 0.95
         Resource.WOOL -> 0.85 // abundant and only half of a dev card
     }
+
+    private companion object {
+        /** A seven makes a seat holding more than this discard half. */
+        const val DISCARD_LIMIT = 7
+    }
 }

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

@@ -1,5 +1,9 @@
 package org.prolibertate.games.game.catan
 
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
+
 /**
  * The computer opponent for Cities & Knights, reached through [CatanAi].
  *
@@ -14,26 +18,40 @@ package org.prolibertate.games.game.catan
  * hired, and are activated when the barbarians draw near), never plays the
  * progress cards whose value depends on a plan (Inventor, Alchemist, Diplomat,
  * Deserter, Intrigue), and makes no domestic offers, though it answers them.
+ *
+ * The seat's profile shapes it as in [CatanAi]: easy plays on a whim and
+ * discards badly, hard sizes its knights to the barbarian threat, values cards
+ * by what its improvements still need and keeps its robber off its own hexes,
+ * and the style leans it toward knights and expansion, toward spending down
+ * a big hand, or toward the leader.
  */
-internal class CatanCkAi(private val ai: CatanAi) {
+internal class CatanCkAi(
+    private val ai: CatanAi,
+    private val profiles: AiProfiles = AiProfiles.DEFAULT,
+) {
 
-    fun choose(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove = when (state.phase) {
+    fun choose(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+        val profile = profiles.of(seat)
+        return choose(state, seat, legal, profile)
+    }
+
+    private fun choose(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove = when (state.phase) {
         CatanPhase.SETUP_FIRST, CatanPhase.SETUP_SECOND ->
-            ai.chooseSetup(state, seat, legal.filterIsInstance<SetupPlace>())
+            ai.chooseSetup(state, seat, legal.filterIsInstance<SetupPlace>(), profile)
 
         CatanPhase.AWAIT_ROLL -> legal.first { it is RollDice }
 
-        CatanPhase.CHORE -> chooseChore(state, seat, legal)
+        CatanPhase.CHORE -> chooseChore(state, seat, legal, profile)
 
-        CatanPhase.ROBBER -> chooseRobber(state, seat, legal.filterIsInstance<MoveRobber>())
+        CatanPhase.ROBBER -> chooseRobber(state, seat, legal.filterIsInstance<MoveRobber>(), profile)
 
-        CatanPhase.FREE_ROADS -> chooseFreeRoad(state, seat, legal)
+        CatanPhase.FREE_ROADS -> chooseFreeRoad(state, seat, legal, profile)
 
-        CatanPhase.TRADE_PENDING -> chooseResponse(state, seat, legal)
+        CatanPhase.TRADE_PENDING -> chooseResponse(state, seat, legal, profile)
 
         CatanPhase.TRADE_COUNTERS -> chooseCounter(state, legal)
 
-        CatanPhase.PLAYING -> choosePlaying(state, seat, legal)
+        CatanPhase.PLAYING -> choosePlaying(state, seat, legal, profile)
 
         CatanPhase.DISCARDING, CatanPhase.GOLD, CatanPhase.GAME_OVER -> legal.firstOrNull()
             ?: error("Nothing to choose in phase ${state.phase}")
@@ -43,18 +61,25 @@ internal class CatanCkAi(private val ai: CatanAi) {
     // Chores
     // -----------------------------------------------------------------------
 
-    private fun chooseChore(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+    private fun chooseChore(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
         val ck = state.ck!!
         return when (val chore = ck.chores.first()) {
             is DiscardChore -> {
                 val n = minOf(chore.count, CatanCk.goodsCount(state, seat))
-                DiscardGoods(CatanCk.goodsList(state, seat).sortedBy { worth(state, seat, it) }.take(n))
+                val hand = CatanCk.goodsList(state, seat)
+                // Easy now and then throws away whatever comes to hand.
+                val order = if (profile.slips()) {
+                    hand.shuffled(profile.random)
+                } else {
+                    hand.sortedBy { worth(state, seat, it, profile) }
+                }
+                DiscardGoods(order.take(n))
             }
 
             is GiveChore -> {
                 val pool = CatanCk.goodsList(state, seat)
                     .filter { !chore.commoditiesOnly || it.isCommodity }
-                    .sortedBy { worth(state, seat, it) }
+                    .sortedBy { worth(state, seat, it, profile) }
                 GiveGoods(pool.take(minOf(chore.count, pool.size)))
             }
 
@@ -98,32 +123,57 @@ internal class CatanCkAi(private val ai: CatanAi) {
     // The robber
     // -----------------------------------------------------------------------
 
-    private fun chooseRobber(state: CatanState, seat: Int, moves: List<MoveRobber>): MoveRobber {
+    private fun chooseRobber(state: CatanState, seat: Int, moves: List<MoveRobber>, profile: AiProfile): MoveRobber {
         require(moves.isNotEmpty()) { "No legal robber move" }
         val points = CatanRules.publicVictoryPoints(state)
-        return moves.maxByOrNull { move ->
+        val hard = profile.level == AiLevel.HARD
+        val spite = profile.style.spite
+        val leader = (0 until state.playerCount).filter { it != seat }.maxByOrNull { points[it] }
+        val victimWeight = 0.3 + 0.1 * profile.style.boldness
+        fun score(move: MoveRobber): Double {
             val hex = CatanBoard.hexIndex.getValue(move.hex)
             var score = 0.0
             for (v in CatanBoard.HEX_CORNERS[hex]) {
                 val building = state.buildings[v] ?: continue
                 val worth = if (building.type == BuildingType.CITY) 2 else 1
                 val odds = CatanBoard.numberOdds(state.numbers[hex]) / 36.0
-                score += if (building.owner == seat) -worth * odds else worth * odds
+                score += if (building.owner == seat) {
+                    -worth * odds * (if (hard) 1.5 else 1.0)
+                } else {
+                    worth * odds + if (building.owner == leader) spite * worth * odds else 0.0
+                }
             }
             if (move.victim != null) {
-                score += 0.15 * CatanCk.goodsCount(state, move.victim) + 0.3 * points[move.victim]
+                val cards = CatanCk.goodsCount(state, move.victim)
+                if (!hard || cards > 0) {
+                    score += 0.15 * cards + victimWeight * points[move.victim]
+                    if (move.victim == leader) score += 0.4 * spite
+                }
             }
-            score
-        } ?: moves.first()
+            return score
+        }
+        return if (profile.level == AiLevel.EASY) {
+            profile.pick(moves.sortedByDescending { score(it) })
+        } else {
+            moves.maxByOrNull { score(it) } ?: moves.first()
+        }
     }
 
     // -----------------------------------------------------------------------
     // The main phase
     // -----------------------------------------------------------------------
 
-    private fun choosePlaying(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+    private fun choosePlaying(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
         val ck = state.ck!!
-        val soon = ck.barbarians <= 3
+        val easy = profile.level == AiLevel.EASY
+        val hard = profile.level == AiLevel.HARD
+        val boldness = profile.style.boldness
+        // A cautious seat starts getting ready a step earlier.
+        val soon = ck.barbarians <= (if (boldness < 0) 4 else 3)
+        val endTurn = legal.lastOrNull { it is EndTurn }
+
+        // Easy loses the thread now and then and just passes.
+        if (easy && endTurn != null && profile.slips() && profile.random.nextBoolean()) return endTurn
 
         // Chase the robber off a hex it is squatting on.
         if (ck.attacked) {
@@ -138,11 +188,29 @@ internal class CatanCkAi(private val ai: CatanAi) {
             .maxByOrNull { production(state, it.vertex!!) }
             ?.let { return it }
 
-        legal.filterIsInstance<BuildCity>().maxByOrNull { production(state, it.vertex) }
-            ?.let { return it }
+        val cities = legal.filterIsInstance<BuildCity>()
+        val settlements = legal.filterIsInstance<BuildSettlement>()
+        if (hard) {
+            val city = cities.maxByOrNull { production(state, it.vertex) }
+            val settlement = settlements.maxByOrNull { ai.hardSpot(state, seat, it.vertex) }
+            val cityScore = if (city != null) production(state, city.vertex) + 0.15 else Double.NEGATIVE_INFINITY
+            val settleScore = if (settlement != null) {
+                ai.hardSpot(state, seat, settlement.vertex) + 0.3 + 0.1 * boldness
+            } else {
+                Double.NEGATIVE_INFINITY
+            }
+            if (city != null && cityScore >= settleScore) return city
+            if (settlement != null) return settlement
+        } else if (easy) {
+            if (cities.isNotEmpty()) return profile.pick(cities.sortedByDescending { production(state, it.vertex) })
+            if (settlements.isNotEmpty()) {
+                return profile.pick(settlements.sortedByDescending { ai.spotValue(state, it.vertex) })
+            }
+        } else {
+            cities.maxByOrNull { production(state, it.vertex) }?.let { return it }
 
-        legal.filterIsInstance<BuildSettlement>().maxByOrNull { ai.spotValue(state, it.vertex) }
-            ?.let { return it }
+            settlements.maxByOrNull { ai.spotValue(state, it.vertex) }?.let { return it }
+        }
 
         // Improvements spend cards nothing else needs. Favour the track furthest along.
         legal.filterIsInstance<BuyImprovement>()
@@ -150,16 +218,16 @@ internal class CatanCkAi(private val ai: CatanAi) {
             ?.let { return it }
 
         // Knights: stand ready by the time the barbarians land.
-        defence(state, seat, legal, soon)?.let { return it }
+        if (!(easy && profile.slips())) defence(state, seat, legal, soon, profile)?.let { return it }
 
-        progress(state, seat, legal)?.let { return it }
+        if (!(easy && profile.slips())) progress(state, seat, legal)?.let { return it }
 
         legal.filterIsInstance<BuildWall>().firstOrNull()?.let {
-            if (CatanCk.goodsCount(state, seat) >= 7) return it
+            if (CatanCk.goodsCount(state, seat) >= (if (boldness < 0) 5 else 7)) return it
         }
 
         legal.filterIsInstance<BuildRoad>()
-            .filter { ai.roadValue(state, it) > 0.1 }
+            .filter { ai.roadValue(state, it) > 0.1 - 0.04 * boldness }
             .maxByOrNull { ai.roadValue(state, it) }
             ?.let { return it }
 
@@ -168,18 +236,43 @@ internal class CatanCkAi(private val ai: CatanAi) {
             .minByOrNull { CatanCk.bankRatio(state, seat, it.give) }
             ?.let { return it }
 
-        return legal.lastOrNull { it is EndTurn } ?: legal.first()
+        // Stay under the seven: a cautious (or careful) seat sells down a big hand.
+        if ((hard || boldness < 0) && CatanCk.goodsCount(state, seat) > 7) {
+            legal.filterIsInstance<GoodsBankTrade>()
+                .maxByOrNull { t ->
+                    held(state, seat, t.give) * 10.0 - CatanCk.bankRatio(state, seat, t.give) * 3.0 +
+                        worth(state, seat, t.get, profile)
+                }
+                ?.let { return it }
+        }
+
+        return endTurn ?: legal.first()
     }
 
     /** Hire, promote and activate so the knights are standing when the barbarians land. */
-    private fun defence(state: CatanState, seat: Int, legal: List<CatanMove>, soon: Boolean): CatanMove? {
+    private fun defence(
+        state: CatanState,
+        seat: Int,
+        legal: List<CatanMove>,
+        soon: Boolean,
+        profile: AiProfile,
+    ): CatanMove? {
         val mine = CatanCk.knightsOf(state, seat)
         val grainLeft = state.resources[seat][Resource.GRAIN] ?: 0
 
+        // Hard sizes the defence to the threat: the barbarians bring one strength
+        // per city on the board, and once the table's active knights outweigh them
+        // and this seat pulls its weight, the rest of its goods go elsewhere.
+        if (profile.level == AiLevel.HARD && soon && CatanCk.strength(state, seat) >= 1) {
+            val threat = state.buildings.count { it?.type == BuildingType.CITY }
+            val table = (0 until state.playerCount).sumOf { CatanCk.strength(state, it) }
+            if (table > threat) return null
+        }
+
         if (soon) {
             legal.filterIsInstance<ActivateKnight>().firstOrNull()?.let { return it }
         }
-        val want = if (soon) 4 else 2
+        val want = if (soon) 4 else if (profile.style.boldness > 0.5) 3 else 2
         if (mine.size < want) {
             legal.filterIsInstance<HireKnight>().maxByOrNull { ai.spotValue(state, it.vertex) }?.let { hire ->
                 // Keep a grain back for waking it, once the ship is close.
@@ -289,26 +382,44 @@ internal class CatanCkAi(private val ai: CatanAi) {
         }
     }
 
-    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) }
+    private fun chooseFreeRoad(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
+        val roads = legal.filterIsInstance<BuildRoad>().filter { ai.roadValue(state, it) > 0.05 }
+        val road = when {
+            roads.isEmpty() -> null
+            profile.level == AiLevel.EASY -> profile.pick(roads.sortedByDescending { ai.roadValue(state, it) })
+            else -> roads.maxByOrNull { ai.roadValue(state, it) }
+        }
+        return road
             ?: legal.firstOrNull { it is EndFreeRoads }
             ?: legal.first()
+    }
 
-    private fun chooseResponse(state: CatanState, seat: Int, legal: List<CatanMove>): CatanMove {
+    /** Extra the incoming cards must be worth: easy is not fussy, hard and spiteful seats are tougher on the leader. */
+    private fun tradeMargin(state: CatanState, seat: Int, other: Int, profile: AiProfile): Double {
+        var margin = 0.0
+        if (profile.level == AiLevel.EASY) margin -= 0.6
+        val points = CatanRules.publicVictoryPoints(state)
+        val leader = (0 until state.playerCount).filter { it != seat }.maxByOrNull { points[it] }
+        if (leader != null && other == leader) {
+            if (profile.level == AiLevel.HARD) margin += 0.4
+            margin += 0.5 * profile.style.spite
+        }
+        return margin
+    }
+
+    private fun chooseResponse(state: CatanState, seat: Int, legal: List<CatanMove>, profile: AiProfile): CatanMove {
         val decline = legal.first { it is DeclineTrade }
         val accept = legal.firstOrNull { it is AcceptTrade } ?: return decline
         val offer = state.ck?.goodsOffer
         if (offer != null) {
-            val incoming = offer.give.sumOf { worth(state, seat, it) }
-            val outgoing = offer.get.sumOf { worth(state, seat, it) }
-            return if (incoming > outgoing) accept else decline
+            val incoming = offer.give.sumOf { worth(state, seat, it, profile) }
+            val outgoing = offer.get.sumOf { worth(state, seat, it, profile) }
+            return if (incoming > outgoing + tradeMargin(state, seat, offer.by, profile)) accept else decline
         }
         val plain = state.pendingTrade ?: return decline
         val incoming = plain.give.sumOf { ai.want(it) }
         val outgoing = plain.get.sumOf { ai.want(it) }
-        return if (incoming > outgoing) accept else decline
+        return if (incoming > outgoing + tradeMargin(state, seat, plain.by, profile)) accept else decline
     }
 
     /** Counters to a human's... the AI never makes an offer, so this only guards the phase: take none. */
@@ -320,12 +431,22 @@ internal class CatanCkAi(private val ai: CatanAi) {
     // -----------------------------------------------------------------------
 
     /** 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) {
+    private fun worth(state: CatanState, seat: Int, good: Good, profile: AiProfile = AiProfile.DEFAULT): Double {
+        val base = good.resource?.let { ai.want(it) } ?: when (good) {
             Good.PAPER -> 0.95
             Good.COIN -> 0.9
             else -> 0.85
         }
+        if (profile.level != AiLevel.HARD) return base
+        // Hard keeps the commodity an improvement is about to need.
+        var bonus = if (good.resource == Resource.ORE || good.resource == Resource.GRAIN) 0.1 else 0.0
+        for (track in Track.entries) {
+            if (Good.of(track.commodity) != good) continue
+            val level = CatanCk.improvement(state, seat, track)
+            if (level < IMPROVEMENT_MAX && held(state, seat, good) <= level + 1) bonus += 0.5
+        }
+        return base + bonus
+    }
 
     /** Which track to lean toward when two are level: politics for the knights, then science. */
     private fun trackLean(track: Track): Int = when (track) {

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

@@ -1,7 +1,16 @@
 package org.prolibertate.games.game.catan
 
+import kotlinx.serialization.KSerializer
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+import kotlinx.serialization.json.JsonArray
+import kotlinx.serialization.json.JsonDecoder
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.JsonPrimitive
+import kotlinx.serialization.json.jsonObject
 
 /** Sentinel stored in [CatanState.roads] for an unclaimed road position. */
 const val NO_PLAYER = -1
@@ -151,12 +160,9 @@ enum class CatanPhase {
     CHORE,
 }
 
-/** Which rules a table plays. The expansion is a whole rule set, not a toggle. */
+/** An expansion a table can switch on. The base game is what is left with none selected. */
 @Serializable
-enum class CatanRuleSet {
-    /** The base game: development cards, Largest Army, a robber from the start. */
-    BASE,
-
+enum class CatanExpansion {
     /** Cities & Knights: commodities, knights, barbarians, city improvements. */
     CITIES_AND_KNIGHTS,
 
@@ -164,15 +170,58 @@ enum class CatanRuleSet {
     SEAFARERS,
 }
 
-@Serializable
+/**
+ * What a table plays: the expansions switched on, and the Seafarers map when that one is.
+ *
+ * Saves written before expansions became toggles carry `"ruleSet"` instead of `"expansions"`;
+ * [CatanOptionsSerializer] reads either.
+ */
+@Serializable(with = CatanOptionsSerializer::class)
 data class CatanOptions(
     val playerCount: Int = 3,
     val pointsToWin: Int = 10,
-    val ruleSet: CatanRuleSet = CatanRuleSet.BASE,
+    val expansions: Set<CatanExpansion> = emptySet(),
+    val scenario: SeaScenario = SeaScenario.NEW_SHORES,
 ) {
     init {
         require(playerCount in 3..4) { "The island seats three or four players" }
         require(pointsToWin >= 2) { "pointsToWin must be at least 2" }
+        // Lifted once Cities & Knights runs on a Seafarers map.
+        require(expansions.size <= 1) { "Combining expansions is not supported yet" }
+    }
+
+    val seafarers: Boolean get() = CatanExpansion.SEAFARERS in expansions
+    val citiesAndKnights: Boolean get() = CatanExpansion.CITIES_AND_KNIGHTS in expansions
+}
+
+/** The wire shape of [CatanOptions]. */
+@Serializable
+private class CatanOptionsWire(
+    val playerCount: Int = 3,
+    val pointsToWin: Int = 10,
+    val expansions: Set<CatanExpansion> = emptySet(),
+    val scenario: SeaScenario = SeaScenario.NEW_SHORES,
+)
+
+/** Reads the legacy single `ruleSet` field as an expansion set. */
+object CatanOptionsSerializer : KSerializer<CatanOptions> {
+    override val descriptor: SerialDescriptor = CatanOptionsWire.serializer().descriptor
+
+    override fun serialize(encoder: Encoder, value: CatanOptions) = encoder.encodeSerializableValue(
+        CatanOptionsWire.serializer(),
+        CatanOptionsWire(value.playerCount, value.pointsToWin, value.expansions, value.scenario),
+    )
+
+    override fun deserialize(decoder: Decoder): CatanOptions {
+        val input = decoder as JsonDecoder
+        var obj = input.decodeJsonElement().jsonObject
+        val legacy = (obj["ruleSet"] as? JsonPrimitive)?.content
+        if (legacy != null) {
+            val expansions = if (legacy == "BASE") emptyList() else listOf(JsonPrimitive(legacy))
+            obj = JsonObject(obj - "ruleSet" + ("expansions" to JsonArray(expansions)))
+        }
+        val wire = input.json.decodeFromJsonElement(CatanOptionsWire.serializer(), obj)
+        return CatanOptions(wire.playerCount, wire.pointsToWin, wire.expansions, wire.scenario)
     }
 }
 
@@ -198,6 +247,8 @@ data class CatanState(
     val turn: Int,
     /** How many setup placements are done, 0 until 2 * playerCount. */
     val setupIndex: Int,
+    /** The seat that places first and takes the first turn; drawn from the table seed. */
+    val firstSeat: Int = 0,
     /** Monotonic turn counter, 0 during setup, 1 from the first real turn. */
     val turnNumber: Int,
     /** Terrain per hex, indexed like [CatanBoard.HEXES]. */

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

@@ -54,15 +54,15 @@ object CatanRules : GameRules<CatanState, CatanMove> {
             "Seat count ${config.seats.size} does not match ${options.playerCount} players"
         }
 
-        val sea = options.ruleSet == CatanRuleSet.SEAFARERS
-        val scenario = SeaScenario.NEW_SHORES
+        val sea = options.seafarers
+        val scenario = options.scenario
         val seaBoard = if (sea) SeaBoards.generate(scenario, config.seed) else null
         val topo = if (seaBoard != null) SeaBoards.topology(scenario) else CatanBoard.base
         val board = seaBoard?.let { CatanBoard.Generated(it.terrains, it.numbers, it.robber, it.ports) }
             ?: CatanBoard.generate(config.seed)
         // A different random stream than the island, so the same seed still
         // produces both a fixed island and a fixed deck.
-        val ck = options.ruleSet == CatanRuleSet.CITIES_AND_KNIGHTS
+        val ck = options.citiesAndKnights
         // Cities & Knights has no development cards: knights and progress
         // cards take their place.
         val devDeck = if (ck) {
@@ -73,12 +73,17 @@ object CatanRules : GameRules<CatanState, CatanMove> {
                 .shuffled(Random(config.seed + 1))
         }
 
+        // Seat 0 used to lead every game; a separate stream from the board and
+        // the deck keeps the same seed giving the same table.
+        val firstSeat = Random(config.seed + 2).nextInt(options.playerCount)
+
         return CatanState(
             options = options,
             seed = config.seed,
             phase = CatanPhase.SETUP_FIRST,
-            turn = 0,
+            turn = firstSeat,
             setupIndex = 0,
+            firstSeat = firstSeat,
             turnNumber = 0,
             terrains = board.terrains,
             numbers = board.numbers,
@@ -121,8 +126,9 @@ object CatanRules : GameRules<CatanState, CatanMove> {
 
     override fun currentSeat(state: CatanState): Int? = when (state.phase) {
         CatanPhase.GAME_OVER -> null
-        CatanPhase.SETUP_FIRST -> state.setupIndex
-        CatanPhase.SETUP_SECOND -> 2 * state.playerCount - 1 - state.setupIndex
+        CatanPhase.SETUP_FIRST -> (state.firstSeat + state.setupIndex) % state.playerCount
+        CatanPhase.SETUP_SECOND ->
+            (state.firstSeat + 2 * state.playerCount - 1 - state.setupIndex) % state.playerCount
         CatanPhase.DISCARDING -> state.discardSeat
         CatanPhase.TRADE_PENDING -> state.pendingTrade?.asking?.takeIf { it >= 0 }
             ?: state.ck?.goodsOffer?.asking?.takeIf { it >= 0 }
@@ -512,9 +518,9 @@ object CatanRules : GameRules<CatanState, CatanMove> {
         return when {
             newIndex >= 2 * n -> s.copy(
                 phase = CatanPhase.AWAIT_ROLL,
-                turn = 0,
+                turn = state.firstSeat,
                 turnNumber = 1,
-                log = s.log + "Setup done — seat 0 leads.",
+                log = s.log + "Setup done — seat ${state.firstSeat} leads.",
             )
 
             newIndex == n -> s.copy(phase = CatanPhase.SETUP_SECOND)

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

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

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

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

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

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

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

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

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

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

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

@@ -43,6 +43,8 @@ data class TableConfig(
     val optionsJson: String,
     /** Shared shuffle seed so a hand is reproducible from its state. */
     val seed: Long,
+    /** How hard the computer seats play. Old saves and old hosts omit it and get the standard opponent. */
+    val aiDifficulty: AiDifficulty = AiDifficulty.MEDIUM,
 )
 
 /**

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

@@ -57,6 +57,7 @@ import org.prolibertate.games.update.UpdateChannel
 import org.prolibertate.games.update.Updater
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
+import org.prolibertate.games.game.engine.AiDifficulty
 import org.prolibertate.games.game.engine.SavedGameStore
 import org.prolibertate.games.game.engine.SavedMatch
 
@@ -88,8 +89,16 @@ sealed interface Route {
     data class Section(val menu: GameMenu) : Route
     data object Settings : Route
     data object Scorekeeper : Route
+
+    /** Every saved game, to carry on from or delete. */
+    data object Resume : Route
     data class Setup(val gameId: String) : Route
-    data class Lobby(val gameId: String, val optionsJson: String, val hosting: Boolean) : Route
+    data class Lobby(
+        val gameId: String,
+        val optionsJson: String,
+        val hosting: Boolean,
+        val aiDifficulty: AiDifficulty = AiDifficulty.MEDIUM,
+    ) : Route
     data class Play(
         val gameId: String,
         val config: TableConfig,
@@ -188,10 +197,8 @@ private fun AppContent(
             // Dev builds show the games that are not finished yet; production
             // releases list only what can actually be played.
             showComingSoon = showComingSoon,
-            saved = savedGames(env, stack),
-            onResume = { saved ->
-                push(Route.Play(saved.gameId, saved.config, true, saved.localSeat, saved.stateJson))
-            },
+            hasSaved = savedGames(env, stack).isNotEmpty(),
+            onResume = { push(Route.Resume) },
             onPickSection = { push(Route.Section(it)) },
             onJoinGame = { push(Route.Lobby(gameId = "", optionsJson = "{}", hosting = false)) },
             onScorekeeper = { push(Route.Scorekeeper) },
@@ -206,6 +213,25 @@ private fun AppContent(
             onBack = pop,
         )
 
+        is Route.Resume -> {
+            // Bumped when a game is deleted, so the list is read again.
+            var deletions by remember(route) { mutableIntStateOf(0) }
+            val saved by produceState(emptyList<SavedMatch>(), route, deletions) {
+                value = withContext(Dispatchers.IO) { env.saves.all() }
+            }
+            ResumeScreen(
+                saved = saved,
+                onResume = { match ->
+                    push(Route.Play(match.gameId, match.config, true, match.localSeat, match.stateJson))
+                },
+                onDelete = { match ->
+                    env.saves.clear(match.gameId)
+                    deletions++
+                },
+                onBack = pop,
+            )
+        }
+
         is Route.Settings -> SettingsScreen(
             env = env,
             settings = settings,
@@ -230,8 +256,8 @@ private fun AppContent(
                 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))
+                onHostOnline = { optionsJson, aiDifficulty ->
+                    push(Route.Lobby(route.gameId, optionsJson, hosting = true, aiDifficulty = aiDifficulty))
                 },
                 saved = saved,
                 onResume = { match ->
@@ -271,8 +297,8 @@ private fun AppContent(
 @Composable
 fun MainMenuScreen(
     showComingSoon: Boolean,
-    saved: List<SavedMatch>,
-    onResume: (SavedMatch) -> Unit,
+    hasSaved: Boolean,
+    onResume: () -> Unit,
     onPickSection: (GameMenu) -> Unit,
     onJoinGame: () -> Unit,
     onScorekeeper: () -> Unit,
@@ -322,20 +348,11 @@ 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))
-                        }
+                // Games left half-played, above everything else: coming back to
+                // the app is mostly coming back to one.
+                if (hasSaved) {
+                    Button(onClick = onResume, modifier = Modifier.fillMaxWidth()) {
+                        Text("Resume game")
                     }
                 }
 

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

@@ -30,15 +30,13 @@ import kotlinx.serialization.encodeToString
 import kotlinx.serialization.json.Json
 import org.prolibertate.games.game.GameCatalog
 import org.prolibertate.games.game.GameDescriptor
+import org.prolibertate.games.game.engine.AiDifficulty
 import org.prolibertate.games.game.engine.PlayerKind
 import org.prolibertate.games.game.engine.PlayerSlot
 import org.prolibertate.games.game.engine.SavedMatch
 import org.prolibertate.games.game.engine.TableConfig
-import org.prolibertate.games.game.backgammon.BackgammonLevel
 import org.prolibertate.games.game.backgammon.BackgammonOptions
-import org.prolibertate.games.game.checkers.CheckersLevel
 import org.prolibertate.games.game.checkers.CheckersOptions
-import org.prolibertate.games.game.chess.ChessLevel
 import org.prolibertate.games.game.chess.ChessOptions
 import org.prolibertate.games.game.crazyeights.CrazyEightsOptions
 import org.prolibertate.games.game.cribbage.CribbageOptions
@@ -56,15 +54,13 @@ import org.prolibertate.games.game.pegsolitaire.PegBoard
 import org.prolibertate.games.game.pegsolitaire.PegGoal
 import org.prolibertate.games.game.pegsolitaire.PegSolitaireOptions
 import org.prolibertate.games.game.kaiser.KaiserOptions
-import org.prolibertate.games.game.mastermind.MastermindLevel
 import org.prolibertate.games.game.mastermind.MastermindOptions
-import org.prolibertate.games.game.morris.MorrisLevel
 import org.prolibertate.games.game.morris.MorrisOptions
-import org.prolibertate.games.game.pirates.PiratesLevel
 import org.prolibertate.games.game.pirates.PiratesOptions
 import org.prolibertate.games.game.president.PresidentOptions
 import org.prolibertate.games.game.catan.CatanOptions
-import org.prolibertate.games.game.catan.CatanRuleSet
+import org.prolibertate.games.game.catan.CatanExpansion
+import org.prolibertate.games.game.catan.SeaScenario
 import org.prolibertate.games.game.sequence.SequenceOptions
 import org.prolibertate.games.game.tayu.TayuLevel
 import org.prolibertate.games.game.tayu.TayuOptions
@@ -88,7 +84,7 @@ fun GameSetupScreen(
     playerName: String,
     onBack: () -> Unit,
     onPlayOffline: (TableConfig, Int) -> Unit,
-    onHostOnline: (String) -> Unit,
+    onHostOnline: (String, AiDifficulty) -> Unit,
     /** A game of this kind left half-played, if there is one. */
     saved: SavedMatch? = null,
     onResume: (SavedMatch) -> Unit = {},
@@ -124,6 +120,7 @@ fun GameSetupScreen(
     // Pirates and Bulgars is not symmetrical, so which side you take is the
     // first thing about the game rather than a detail of it.
     var playPirates by remember { mutableStateOf(false) }
+    var aiDifficulty by remember { mutableStateOf(AiDifficulty.MEDIUM) }
 
     val optionsJson = when (descriptor.id) {
         GameCatalog.EUCHRE -> setupJson.encodeToString(euchre)
@@ -243,6 +240,22 @@ fun GameSetupScreen(
                 style = MaterialTheme.typography.bodySmall,
             )
 
+            if (!solo) {
+                ChipRow(
+                    label = "Computer difficulty",
+                    values = AiDifficulty.entries.toList(),
+                    selected = aiDifficulty,
+                    display = { it.label },
+                    onSelect = { aiDifficulty = it },
+                )
+                if (aiDifficulty == AiDifficulty.MIXED) {
+                    Text(
+                        "Each computer player gets its own level.",
+                        style = MaterialTheme.typography.bodySmall,
+                    )
+                }
+            }
+
             // Two games let the local player pick a seat rather than always
             // taking the first one: chess by colour, and Pirates and Bulgars by
             // which side of a very lopsided fight they fancy.
@@ -259,13 +272,13 @@ fun GameSetupScreen(
             }
             PrimaryAction(text = if (solo) "Play" else "Play against the computer") {
                 onPlayOffline(
-                    offlineConfig(descriptor.id, optionsJson, seatCount, playerName, localSeat),
+                    offlineConfig(descriptor.id, optionsJson, seatCount, playerName, localSeat, aiDifficulty),
                     localSeat,
                 )
             }
             if (!solo) {
                 PrimaryAction(text = "Host a game for others to join") {
-                    onHostOnline(optionsJson)
+                    onHostOnline(optionsJson, aiDifficulty)
                 }
             }
         }
@@ -279,6 +292,7 @@ private fun offlineConfig(
     seatCount: Int,
     playerName: String,
     localSeat: Int = 0,
+    aiDifficulty: AiDifficulty = AiDifficulty.MEDIUM,
 ): TableConfig = TableConfig(
     gameId = gameId,
     seats = (0 until seatCount).map { seat ->
@@ -292,6 +306,7 @@ private fun offlineConfig(
     optionsJson = optionsJson,
     // Seeded from the clock so consecutive games are not identical.
     seed = System.currentTimeMillis(),
+    aiDifficulty = aiDifficulty,
 )
 
 /**
@@ -359,47 +374,48 @@ 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)
+/** The targets the setup screen offers for a Katan game with [expansions] on. */
+internal fun catanPointsChoices(expansions: Set<CatanExpansion>): List<Int> = when {
     // Seafarers adds two points for each new island, so the target is higher.
-    CatanRuleSet.SEAFARERS -> listOf(8, 10, 12, 14)
+    CatanExpansion.SEAFARERS in expansions -> listOf(8, 10, 12, 14)
+    // Cities & Knights is played to thirteen, which is also why it runs longer.
+    CatanExpansion.CITIES_AND_KNIGHTS in expansions -> listOf(8, 10, 13, 15)
+    // Five is a short game for trying things out; ten is the published target.
+    else -> listOf(5, 8, 10, 12)
 }
 
-/** The published target for a rule set. */
-internal fun catanDefaultPoints(ruleSet: CatanRuleSet): Int = when (ruleSet) {
-    CatanRuleSet.BASE -> 10
-    CatanRuleSet.CITIES_AND_KNIGHTS -> 13
-    CatanRuleSet.SEAFARERS -> 12
+/** The published target for a game with [expansions] on. */
+internal fun catanDefaultPoints(expansions: Set<CatanExpansion>): Int = when {
+    CatanExpansion.SEAFARERS in expansions -> 12
+    CatanExpansion.CITIES_AND_KNIGHTS in expansions -> 13
+    else -> 10
 }
 
 /**
- * [options] switched to [ruleSet]. The target moves to the new rule set's own
- * default unless the one already chosen is on its menu too.
+ * [options] with [expansion] switched on or off. The target moves to the new combination's own
+ * default unless the one already chosen is on its menu too. Expansions cannot be combined yet,
+ * so switching one on switches the other off.
  */
-internal fun catanSwitchRules(options: CatanOptions, ruleSet: CatanRuleSet): CatanOptions =
-    options.copy(
-        ruleSet = ruleSet,
-        pointsToWin = options.pointsToWin.takeIf { it in catanPointsChoices(ruleSet) && it != catanDefaultPoints(options.ruleSet) }
-            ?: catanDefaultPoints(ruleSet),
+internal fun catanToggleExpansion(options: CatanOptions, expansion: CatanExpansion, on: Boolean): CatanOptions {
+    val expansions = if (on) setOf(expansion) else options.expansions - expansion
+    return options.copy(
+        expansions = expansions,
+        pointsToWin = options.pointsToWin.takeIf {
+            it in catanPointsChoices(expansions) && it != catanDefaultPoints(options.expansions)
+        } ?: catanDefaultPoints(expansions),
     )
-
-private fun 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 ->
+private fun catanExpansionName(expansion: CatanExpansion): String = when (expansion) {
+    CatanExpansion.CITIES_AND_KNIGHTS -> "Cities & Knights"
+    CatanExpansion.SEAFARERS -> "Seafarers"
+}
+
+private fun catanExpansionBlurb(expansion: CatanExpansion): String = when (expansion) {
+    CatanExpansion.CITIES_AND_KNIGHTS ->
         "Cities make commodities, knights hold off the barbarians, and improvements earn progress " +
             "cards and metropolises. No development cards; the robber sleeps until the first attack."
-    CatanRuleSet.SEAFARERS ->
+    CatanExpansion.SEAFARERS ->
         "Build ships to reach new islands. Gold fields pay any resource, a pirate guards the sea, " +
             "and the first settlement on each new island scores two extra points."
 }
@@ -407,14 +423,24 @@ private fun catanRuleSetBlurb(ruleSet: CatanRuleSet): String = when (ruleSet) {
 @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)
+        CatanExpansion.entries.forEach { expansion ->
+            ToggleRow(
+                title = catanExpansionName(expansion),
+                subtitle = catanExpansionBlurb(expansion),
+                checked = expansion in options.expansions,
+                onChange = { onChange(catanToggleExpansion(options, expansion, it)) },
+            )
+        }
+        if (options.seafarers) {
+            ChipRow(
+                label = "Map",
+                values = SeaScenario.entries,
+                selected = options.scenario,
+                display = { it.title },
+                onSelect = { onChange(options.copy(scenario = it)) },
+            )
+            Text(options.scenario.blurb, style = MaterialTheme.typography.bodySmall)
+        }
         ChipRow(
             label = "Players",
             values = listOf(3, 4),
@@ -424,7 +450,7 @@ private fun CatanOptionsEditor(options: CatanOptions, onChange: (CatanOptions) -
         )
         ChipRow(
             label = "Game to",
-            values = catanPointsChoices(options.ruleSet),
+            values = catanPointsChoices(options.expansions),
             selected = options.pointsToWin,
             display = { "$it points" },
             onSelect = { onChange(options.copy(pointsToWin = it)) },
@@ -765,13 +791,6 @@ private fun ChessOptionsEditor(
             display = { if (it) "White" else "Black" },
             onSelect = onColour,
         )
-        ChipRow(
-            label = "Opponent",
-            values = ChessLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ToggleRow(
             title = "Fifty-move rule",
             subtitle = "Fifty moves each with no capture and no pawn move is a draw",
@@ -795,13 +814,6 @@ private fun ChessOptionsEditor(
 @Composable
 private fun CheckersOptionsEditor(options: CheckersOptions, onChange: (CheckersOptions) -> Unit) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-        ChipRow(
-            label = "Opponent",
-            values = CheckersLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ToggleRow(
             title = "Flying kings",
             subtitle = "A king slides the length of a diagonal and takes from a distance, " +
@@ -836,13 +848,6 @@ private fun BackgammonOptionsEditor(
     onChange: (BackgammonOptions) -> Unit,
 ) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-        ChipRow(
-            label = "Opponent",
-            values = BackgammonLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ToggleRow(
             title = "Count gammons",
             subtitle = "A loser who bore nothing off has lost double, and one still on the " +
@@ -864,13 +869,6 @@ private fun MastermindOptionsEditor(
     onChange: (MastermindOptions) -> Unit,
 ) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-        ChipRow(
-            label = "Opponent",
-            values = MastermindLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ChipRow(
             label = "Colours",
             values = listOf(6, 8),
@@ -935,13 +933,6 @@ private fun PiratesOptionsEditor(
             display = { if (it) "the two pirates" else "the twenty-four Bulgars" },
             onSelect = onSide,
         )
-        ChipRow(
-            label = "Opponent",
-            values = PiratesLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ToggleRow(
             title = "A pirate who can take must take",
             subtitle = "The rule that huffing exists to enforce, applied directly",
@@ -967,13 +958,6 @@ private fun PiratesOptionsEditor(
 @Composable
 private fun MorrisOptionsEditor(options: MorrisOptions, onChange: (MorrisOptions) -> Unit) {
     Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-        ChipRow(
-            label = "Opponent",
-            values = MorrisLevel.entries.toList(),
-            selected = options.level,
-            display = { it.label },
-            onSelect = { onChange(options.copy(level = it)) },
-        )
         ChipRow(
             label = "Pieces each",
             values = listOf(3, 6, 9),

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

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

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

@@ -120,6 +120,7 @@ import org.prolibertate.games.game.wizard.WizardRules
 import org.prolibertate.games.game.wizard.WizardState
 import org.prolibertate.games.net.MatchController
 import org.prolibertate.games.net.MatchSaver
+import org.prolibertate.games.game.engine.AiProfiles
 import org.prolibertate.games.game.engine.PlayerKind
 import org.prolibertate.games.settings.Settings
 import org.prolibertate.games.ui.game.BackgammonScreen
@@ -174,7 +175,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<EuchreState, EuchreMove>(
                         rules = EuchreRules,
-                        ai = EuchreAi(),
+                        ai = EuchreAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -213,7 +214,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<SequenceState, SequenceMove>(
                         rules = SequenceRules,
-                        ai = SequenceAi(),
+                        ai = SequenceAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -230,7 +231,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<PresidentState, PresidentMove>(
                         rules = PresidentRules,
-                        ai = PresidentAi(),
+                        ai = PresidentAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -254,7 +255,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<GolfState, GolfMove>(
                         rules = GolfRules,
-                        ai = GolfAi(),
+                        ai = GolfAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -276,7 +277,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<KaiserState, KaiserMove>(
                         rules = KaiserRules,
-                        ai = KaiserAi(),
+                        ai = KaiserAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -312,7 +313,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<WizardState, WizardMove>(
                         rules = WizardRules,
-                        ai = WizardAi(),
+                        ai = WizardAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -350,7 +351,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<CrazyEightsState, CrazyEightsMove>(
                         rules = CrazyEightsRules,
-                        ai = CrazyEightsAi(),
+                        ai = CrazyEightsAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -377,7 +378,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<CribbageState, CribbageMove>(
                         rules = CribbageRules,
-                        ai = CribbageAi(),
+                        ai = CribbageAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -406,7 +407,7 @@ fun PlayScreen(
                         rules = TayuRules,
                         // As with chess, the strength is part of the table's own
                         // options, so this does not have to decode anything.
-                        ai = TayuAi(),
+                        ai = TayuAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -423,7 +424,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<CheckersState, CheckersMove>(
                         rules = CheckersRules,
-                        ai = CheckersAi(),
+                        ai = CheckersAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -440,7 +441,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<BackgammonState, BackgammonMove>(
                         rules = BackgammonRules,
-                        ai = BackgammonAi(),
+                        ai = BackgammonAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -459,7 +460,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<MastermindState, MastermindMove>(
                         rules = MastermindRules,
-                        ai = MastermindAi(),
+                        ai = MastermindAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -476,7 +477,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<PiratesState, PiratesMove>(
                         rules = PiratesRules,
-                        ai = PiratesAi(),
+                        ai = PiratesAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -493,7 +494,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<HeartsState, HeartsMove>(
                         rules = HeartsRules,
-                        ai = HeartsAi,
+                        ai = HeartsAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -582,7 +583,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<YahtzeeState, YahtzeeMove>(
                         rules = YahtzeeRules,
-                        ai = YahtzeeAi,
+                        ai = YahtzeeAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -684,7 +685,7 @@ fun PlayScreen(
                         rules = MorrisRules,
                         // As with chess, the strength is part of the table's own
                         // options, so this does not have to decode anything.
-                        ai = MorrisAi(),
+                        ai = MorrisAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -705,7 +706,7 @@ fun PlayScreen(
                         rules = ChessRules,
                         // Strength comes from the table's own options, so the setup
                         // screen sets it without this having to decode anything.
-                        ai = ChessAi(),
+                        ai = ChessAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,
@@ -724,7 +725,7 @@ fun PlayScreen(
                 val controller = remember(route) {
                     MatchController<CatanState, CatanMove>(
                         rules = CatanRules,
-                        ai = CatanAi(),
+                        ai = CatanAi(AiProfiles(route.config)),
                         config = route.config,
                         scope = scope,
                         role = role,

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

@@ -313,6 +313,10 @@ fun CatanHud(
 ) {
     Column(Modifier.fillMaxSize(), verticalArrangement = Arrangement.spacedBy(2.dp)) {
         HudPlayerStrip(state, seats, pointsOf, style)
+        // Cities & Knights: the ship and the improvement levels are as much part
+        // of the game as the scores, so they sit with them rather than in a panel
+        // this layout does not have room for.
+        if (state.isCk) CatanBarbarians(state, Modifier.padding(horizontal = 8.dp), style)
         Box(Modifier.weight(1f).fillMaxWidth()) {
             // The island fills the whole area; controls float over its sea margin.
             ZoomPanBox(Modifier.fillMaxSize().padding(start = 64.dp, end = 64.dp, top = 30.dp, bottom = 44.dp)) {
@@ -453,6 +457,16 @@ private fun HudPlayerStrip(
                     Modifier.size(14.dp).clip(CircleShape).background(style.seats[seat]).border(1.dp, style.pieceOutline, CircleShape),
                 )
                 Text(seats.label(seat), fontSize = 12.sp, fontWeight = FontWeight.Bold, maxLines = 1, modifier = Modifier.weight(1f))
+                // Trade, politics, science: the three improvement levels.
+                if (state.isCk) {
+                    Text(
+                        text = org.prolibertate.games.game.catan.Track.entries.joinToString(" ") {
+                            "${it.name.first()}${org.prolibertate.games.game.catan.CatanCk.improvement(state, seat, it)}"
+                        },
+                        fontSize = 12.sp,
+                        maxLines = 1,
+                    )
+                }
                 Text("${pointsOf(seat)} VP · ${state.resourceCount(seat)}🂠", fontSize = 12.sp, maxLines = 1)
             }
         }

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

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

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

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

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

@@ -25,7 +25,7 @@ class CatanCkRulesTest {
             CatanOptions(
                 playerCount = players,
                 pointsToWin = 13,
-                ruleSet = if (ck) CatanRuleSet.CITIES_AND_KNIGHTS else CatanRuleSet.BASE,
+                expansions = if (ck) setOf(CatanExpansion.CITIES_AND_KNIGHTS) else emptySet(),
             ),
         ),
         seed = seed,
@@ -138,7 +138,7 @@ class CatanCkRulesTest {
         val base = CatanRules.initialState(config(ck = false))
         assertNull(base.ck)
         assertEquals(25, base.devDeck.size)
-        assertEquals(CatanRuleSet.BASE, base.options.ruleSet)
+        assertEquals(emptySet<CatanExpansion>(), base.options.expansions)
     }
 
     @Test
@@ -157,7 +157,21 @@ class CatanCkRulesTest {
     fun `the options without a rule set still read as the base game`() {
         val old = """{"playerCount":4,"pointsToWin":10}"""
         val options = Json { ignoreUnknownKeys = true }.decodeFromString<CatanOptions>(old)
-        assertEquals(CatanRuleSet.BASE, options.ruleSet)
+        assertEquals(emptySet<CatanExpansion>(), options.expansions)
+    }
+
+    @Test
+    fun `options saved with a rule set still read as the expansion they named`() {
+        val read = { text: String -> Json { ignoreUnknownKeys = true }.decodeFromString<CatanOptions>(text) }
+        assertEquals(
+            setOf(CatanExpansion.CITIES_AND_KNIGHTS),
+            read("""{"playerCount":3,"pointsToWin":13,"ruleSet":"CITIES_AND_KNIGHTS"}""").expansions,
+        )
+        assertEquals(
+            setOf(CatanExpansion.SEAFARERS),
+            read("""{"playerCount":3,"pointsToWin":12,"ruleSet":"SEAFARERS"}""").expansions,
+        )
+        assertEquals(emptySet<CatanExpansion>(), read("""{"ruleSet":"BASE"}""").expansions)
     }
 
     @Test

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

@@ -152,7 +152,7 @@ class CatanCkSelfPlayTest {
     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),
+                CatanOptions(playerCount = 3, pointsToWin = 13, expansions = setOf(CatanExpansion.CITIES_AND_KNIGHTS)),
                 seed,
             )
             assertEquals("seed $seed", CatanPhase.GAME_OVER, state.phase)
@@ -171,7 +171,7 @@ class CatanCkSelfPlayTest {
     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),
+                CatanOptions(playerCount = 4, pointsToWin = 13, expansions = setOf(CatanExpansion.CITIES_AND_KNIGHTS)),
                 seed,
             )
             assertEquals("seed $seed", CatanPhase.GAME_OVER, state.phase)

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

@@ -115,8 +115,9 @@ class CatanRulesTest {
     // -- Setup ---------------------------------------------------------------
 
     @Test
-    fun `setup runs in snake order and then seat zero leads`() {
+    fun `setup runs in snake order from the first seat and then that seat leads`() {
         var state = CatanRules.initialState(config())
+        val first = state.firstSeat
         val order = mutableListOf<Int>()
         while (state.phase == CatanPhase.SETUP_FIRST || state.phase == CatanPhase.SETUP_SECOND) {
             val seat = CatanRules.currentSeat(state)!!
@@ -126,12 +127,21 @@ class CatanRulesTest {
                 CatanRules.legalMoves(state, seat).filterIsInstance<SetupPlace>().first(),
             )
         }
-        assertEquals(listOf(0, 1, 2, 2, 1, 0), order)
+        val forward = (0 until 3).map { (first + it) % 3 }
+        assertEquals(forward + forward.reversed(), order)
         assertEquals(CatanPhase.AWAIT_ROLL, state.phase)
-        assertEquals(0, state.turn)
+        assertEquals(first, state.turn)
         assertEquals(1, state.turnNumber)
     }
 
+    @Test
+    fun `the first seat comes from the seed and varies between tables`() {
+        val firsts = (1L..40L).map { CatanRules.initialState(config(seed = it)).firstSeat }
+        assertEquals(firsts, (1L..40L).map { CatanRules.initialState(config(seed = it)).firstSeat })
+        assertEquals(setOf(0, 1, 2), firsts.toSet())
+        assertEquals(firsts[0], CatanRules.initialState(config(seed = 1L)).turn)
+    }
+
     @Test
     fun `the second settlement earns one card from each adjacent land`() {
         var state = CatanRules.initialState(config())

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

@@ -17,7 +17,7 @@ class CatanSeafarersTest {
     private val json = Json { encodeDefaults = true }
 
     private fun options(players: Int = 3) =
-        CatanOptions(playerCount = players, pointsToWin = 12, ruleSet = CatanRuleSet.SEAFARERS)
+        CatanOptions(playerCount = players, pointsToWin = 12, expansions = setOf(CatanExpansion.SEAFARERS))
 
     private fun config(options: CatanOptions, seed: Long) = TableConfig(
         gameId = GameCatalog.CATAN,
@@ -96,7 +96,7 @@ class CatanSeafarersTest {
     @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>()
+        val moves = CatanRules.legalMoves(s, s.firstSeat).filterIsInstance<SetupPlace>()
         assertTrue(moves.isNotEmpty())
         assertTrue(moves.all { s.topo.vertexIsland[it.vertex] == s.sea!!.home })
         assertTrue(moves.all { s.topo.edgeLand[it.edge] })

app/src/test/java/org/prolibertate/games/game/checkers/CheckersAiProfileTest.kt

@@ -0,0 +1,40 @@
+package org.prolibertate.games.game.checkers
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+
+class CheckersAiProfileTest {
+
+    @Test
+    fun `every difficulty and seeded style plays only legal moves`() {
+        val seen = mutableSetOf<Pair<Any, Any>>()
+        for (difficulty in AiDifficulty.entries) for (seed in 0L until 12L) {
+            val profiles = AiProfiles(difficulty, seed)
+            for (seat in 0..1) profiles.of(seat).let { seen += it.level to it.style }
+            val ai = CheckersAi(profiles, CheckersLevel.CASUAL)
+            var state = CheckersRules.initialState(CheckersOptions(level = CheckersLevel.CASUAL))
+            var plies = 0
+            while (!CheckersRules.isFinished(state) && plies < 10) {
+                val legal = CheckersRules.legalMoves(state)
+                val move = ai.chooseMove(state, state.turn, legal)
+                assertTrue("$difficulty/$seed illegal move $move", move in legal)
+                state = CheckersRules.applyMove(state, state.turn, move)
+                plies++
+            }
+        }
+        assertTrue("expected a spread of level/style pairs, saw ${seen.size}", seen.size >= 8)
+    }
+
+    @Test
+    fun `default profile plays the same as an explicit medium table`() {
+        val state = CheckersRules.initialState(CheckersOptions(level = CheckersLevel.CASUAL))
+        val legal = CheckersRules.legalMoves(state)
+        val a = CheckersAi(level = CheckersLevel.CASUAL).chooseMove(state, state.turn, legal)
+        val b = CheckersAi(AiProfiles(AiDifficulty.MEDIUM, 5L), CheckersLevel.CASUAL)
+            .chooseMove(state, state.turn, legal)
+        assertEquals(a, b)
+    }
+}

app/src/test/java/org/prolibertate/games/game/chess/ChessAiTest.kt

@@ -3,6 +3,11 @@ package org.prolibertate.games.game.chess
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertTrue
 import org.junit.Test
+import org.prolibertate.games.game.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiLevel
+import org.prolibertate.games.game.engine.AiProfile
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.AiStyle
 
 class ChessAiTest {
 
@@ -128,4 +133,52 @@ class ChessAiTest {
             assertTrue("$level took ${millis}ms", millis < 15_000)
         }
     }
+
+    @Test
+    fun `every level and style returns a legal move over a few playouts`() {
+        val opening = "r1bqkb1r/pppp1ppp/2n2n2/4p3/2B1P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4"
+        for (diff in listOf(AiDifficulty.EASY, AiDifficulty.MEDIUM, AiDifficulty.HARD, AiDifficulty.MIXED)) {
+            for (seed in 1L..4L) {
+                val ai = ChessAi(AiProfiles(diff, seed))
+                var state = ChessRules.fromPosition(ChessOptions(level = ChessLevel.CASUAL), opening)
+                repeat(6) {
+                    if (ChessRules.isFinished(state)) return@repeat
+                    val legal = ChessRules.legalMoves(state)
+                    val move = ai.moveIn(state)
+                    assertTrue("$diff/$seed: $move illegal", legal.contains(move))
+                    state = ChessRules.applyMove(state, state.turnSeat, move)
+                }
+            }
+        }
+    }
+
+    @Test
+    fun `easy and every style still take a hanging queen`() {
+        val state = position("3r3k/8/8/3q4/8/8/8/3R2K1 w - - 0 1", ChessLevel.CLUB)
+        for (style in AiStyle.entries) {
+            val ai = ChessAi(AiProfilesFixed(AiLevel.HARD, style))
+            assertEquals("d1d5", ai.moveIn(state).toString())
+        }
+    }
+
+    @Test
+    fun `the default profile matches the no-argument ai`() {
+        val state = position("r1bqkb1r/pppp1ppp/2n2n2/4p3/2B1P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4")
+        assertEquals(ChessAi().moveIn(state), ChessAi(AiProfiles.DEFAULT).moveIn(state))
+    }
+
+    /** Profiles with one fixed level and style for every seat. */
+    private fun AiProfilesFixed(level: AiLevel, style: AiStyle): AiProfiles {
+        val diff = when (level) {
+            AiLevel.EASY -> AiDifficulty.EASY
+            AiLevel.MEDIUM -> AiDifficulty.MEDIUM
+            AiLevel.HARD -> AiDifficulty.HARD
+        }
+        // Search seeds until the derived style matches; the style space is tiny.
+        for (seed in 0L..500L) {
+            val profiles = AiProfiles(diff, seed)
+            if (profiles.of(0).style == style && profiles.of(1).style == style) return profiles
+        }
+        return AiProfiles(diff, 0L)
+    }
 }

app/src/test/java/org/prolibertate/games/game/crazyeights/CrazyEightsAiProfileTest.kt

@@ -0,0 +1,71 @@
+package org.prolibertate.games.game.crazyeights
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class CrazyEightsAiProfileTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(options: CrazyEightsOptions, seed: Long) = TableConfig(
+        gameId = "crazy8s",
+        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 play(ai: CrazyEightsAi, options: CrazyEightsOptions, seed: Long): List<CrazyEightsMove> {
+        var state = CrazyEightsRules.initialState(config(options, seed))
+        val moves = mutableListOf<CrazyEightsMove>()
+        var guard = 0
+        while (!CrazyEightsRules.isFinished(state) && guard++ < 6000) {
+            val seat = CrazyEightsRules.currentSeat(state)
+            if (seat == null) {
+                state = CrazyEightsRules.nextRound(state)
+                continue
+            }
+            val legal = CrazyEightsRules.legalMoves(state, seat)
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move", legal.contains(move))
+            moves += move
+            state = CrazyEightsRules.applyMove(state, seat, move)
+        }
+        assertTrue("game did not finish", CrazyEightsRules.isFinished(state))
+        return moves
+    }
+
+    @Test
+    fun `every difficulty and style plays complete games legally`() {
+        val variants = listOf(
+            CrazyEightsOptions(playerCount = 4, roundsToPlay = 2),
+            CrazyEightsOptions(playerCount = 2, roundsToPlay = 2, drawUntilPlayable = false),
+            CrazyEightsOptions(playerCount = 6, roundsToPlay = 2),
+        )
+        for (difficulty in listOf(AiDifficulty.EASY, AiDifficulty.HARD, AiDifficulty.MIXED)) {
+            for (seed in 0L until 9L) {
+                val options = variants[(seed % variants.size).toInt()]
+                play(CrazyEightsAi(AiProfiles(difficulty, seed)), options, 300L + seed)
+            }
+        }
+    }
+
+    @Test
+    fun `the default profile plays like a medium balanced seat`() {
+        val options = CrazyEightsOptions(playerCount = 4, roundsToPlay = 2)
+        for (seed in 1L..3L) {
+            val default = play(CrazyEightsAi(), options, seed)
+            val medium = play(CrazyEightsAi(AiProfiles(AiDifficulty.MEDIUM, 31L + seed)), options, seed)
+            assertEquals(default, medium)
+        }
+    }
+}

app/src/test/java/org/prolibertate/games/game/cribbage/CribbageAiLevelsTest.kt

@@ -0,0 +1,101 @@
+package org.prolibertate.games.game.cribbage
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.AiStyle
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class CribbageAiLevelsTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(options: CribbageOptions, seed: Long) = TableConfig(
+        gameId = "cribbage",
+        seats = (0 until options.playerCount).map {
+            PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = options.teamOf(it))
+        },
+        optionsJson = json.encodeToString(options),
+        seed = seed,
+    )
+
+    /** Seeds that between them give some seat every style at this difficulty. */
+    private fun seedsCoveringStyles(difficulty: AiDifficulty, seats: Int): List<Long> {
+        // The standard opponent is balanced by definition, so there is no style to cover.
+        if (difficulty == AiDifficulty.MEDIUM) return listOf(0L, 1L, 2L)
+        val missing = AiStyle.entries.toMutableSet()
+        val seeds = mutableListOf<Long>()
+        var seed = 0L
+        while (missing.isNotEmpty() && seed < 500) {
+            val styles = (0 until seats).map { AiProfiles(difficulty, seed).of(it).style }
+            if (styles.any { it in missing }) {
+                seeds += seed
+                missing.removeAll(styles.toSet())
+            }
+            seed++
+        }
+        assertTrue("styles never covered: $missing", missing.isEmpty())
+        return seeds
+    }
+
+    /** Plays a whole game with [ai] in every seat; returns the moves chosen. */
+    private fun play(ai: CribbageAi, options: CribbageOptions, seed: Long): List<CribbageMove> {
+        var state = CribbageRules.initialState(config(options, seed))
+        val moves = mutableListOf<CribbageMove>()
+        var guard = 0
+        while (!CribbageRules.isFinished(state) && guard++ < 20000) {
+            val seat = CribbageRules.currentSeat(state)
+            if (seat == null) {
+                state = CribbageRules.nextHand(state)
+                continue
+            }
+            val legal = CribbageRules.legalMoves(state, seat)
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move", legal.contains(move))
+            moves += move
+            state = CribbageRules.applyMove(state, seat, move)
+        }
+        assertTrue("game ran away", guard < 20000)
+        return moves
+    }
+
+    @Test
+    fun `every level and style plays a whole game legally`() {
+        val options = CribbageOptions(pointsToWin = 61)
+        listOf(AiDifficulty.EASY, AiDifficulty.MEDIUM, AiDifficulty.HARD).forEach { difficulty ->
+            seedsCoveringStyles(difficulty, options.playerCount).forEach { seed ->
+                play(CribbageAi(AiProfiles(difficulty, seed)), options, 100L + seed)
+            }
+        }
+    }
+
+    @Test
+    fun `a four handed table plays legally at every level`() {
+        val options = CribbageOptions(playerCount = 4, pointsToWin = 61)
+        listOf(AiDifficulty.EASY, AiDifficulty.HARD, AiDifficulty.MIXED).forEach { difficulty ->
+            play(CribbageAi(AiProfiles(difficulty, 3L)), options, 7L)
+        }
+    }
+
+    @Test
+    fun `the default profile plays as the standard opponent`() {
+        val options = CribbageOptions(pointsToWin = 61)
+        val standard = play(CribbageAi(), options, 55L)
+        val medium = play(CribbageAi(AiProfiles(AiDifficulty.MEDIUM, 9L)), options, 55L)
+        assertEquals(standard, medium)
+    }
+
+    @Test
+    fun `easy does not always play the best card`() {
+        val options = CribbageOptions(pointsToWin = 61)
+        val standard = play(CribbageAi(), options, 55L)
+        val easy = play(CribbageAi(AiProfiles(AiDifficulty.EASY, 9L)), options, 55L)
+        assertTrue("easy played exactly like medium", standard != easy)
+    }
+}

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

@@ -0,0 +1,77 @@
+package org.prolibertate.games.game.engine
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class AiProfilesTest {
+
+    @Test
+    fun `fixed difficulties give every seat that level`() {
+        for ((difficulty, level) in listOf(
+            AiDifficulty.EASY to AiLevel.EASY,
+            AiDifficulty.MEDIUM to AiLevel.MEDIUM,
+            AiDifficulty.HARD to AiLevel.HARD,
+        )) {
+            val profiles = AiProfiles(difficulty, seed = 42)
+            for (seat in 0..5) assertEquals(level, profiles.of(seat).level)
+        }
+    }
+
+    @Test
+    fun `medium is the balanced standard opponent and never slips`() {
+        val profiles = AiProfiles(AiDifficulty.MEDIUM, seed = 7)
+        for (seat in 0..5) {
+            val profile = profiles.of(seat)
+            assertEquals(AiStyle.BALANCED, profile.style)
+            repeat(200) { assertFalse(profile.slips()) }
+        }
+    }
+
+    @Test
+    fun `the same table always gives a seat the same personality`() {
+        val a = AiProfiles(AiDifficulty.MIXED, seed = 1234)
+        val b = AiProfiles(AiDifficulty.MIXED, seed = 1234)
+        for (seat in 0..6) {
+            assertEquals(a.of(seat).level, b.of(seat).level)
+            assertEquals(a.of(seat).style, b.of(seat).style)
+        }
+    }
+
+    @Test
+    fun `mixed tables vary by seat and across seeds`() {
+        val seen = (0L..200L).flatMap { seed ->
+            val profiles = AiProfiles(AiDifficulty.MIXED, seed)
+            (0..3).map { profiles.of(it).level to profiles.of(it).style }
+        }.toSet()
+        assertTrue(seen.map { it.first }.toSet() == AiLevel.entries.toSet())
+        assertTrue(seen.map { it.second }.toSet() == AiStyle.entries.toSet())
+    }
+
+    @Test
+    fun `only easy slips, and not every time`() {
+        val easy = AiProfiles(AiDifficulty.EASY, 1).of(0)
+        val slips = (1..1000).count { easy.slips() }
+        assertTrue("slipped $slips of 1000", slips in 200..400)
+        val hard = AiProfiles(AiDifficulty.HARD, 1).of(0)
+        repeat(200) { assertFalse(hard.slips()) }
+    }
+
+    @Test
+    fun `pick takes the best unless easy slips and then stays in the better half`() {
+        val ranked = (1..10).toList()
+        assertEquals(1, AiProfiles(AiDifficulty.HARD, 3).of(0).pick(ranked))
+        val easy = AiProfiles(AiDifficulty.EASY, 3).of(0)
+        val picks = (1..500).map { easy.pick(ranked) }
+        assertTrue(picks.all { it <= 5 })
+        assertTrue(picks.toSet().size > 1)
+    }
+
+    @Test
+    fun `a config without a difficulty reads as medium`() {
+        val config = TableConfig("chess", emptyList(), "{}", 1L)
+        assertEquals(AiDifficulty.MEDIUM, config.aiDifficulty)
+        assertEquals(AiLevel.MEDIUM, AiProfiles(config).of(0).level)
+    }
+}

app/src/test/java/org/prolibertate/games/game/euchre/EuchreAiProfilesTest.kt

@@ -0,0 +1,65 @@
+package org.prolibertate.games.game.euchre
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class EuchreAiProfilesTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(seed: Long) = TableConfig(
+        gameId = "euchre",
+        seats = (0 until 4).map {
+            PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it % 2)
+        },
+        optionsJson = json.encodeToString(EuchreOptions(pointsToWin = 4)),
+        seed = seed,
+    )
+
+    /** Plays a whole game with every seat on [ai], returning every move chosen. */
+    private fun playGame(ai: EuchreAi, seed: Long): List<EuchreMove> {
+        val moves = mutableListOf<EuchreMove>()
+        var state = EuchreRules.initialState(config(seed))
+        var guard = 0
+        while (!EuchreRules.isFinished(state) && guard++ < 3000) {
+            val seat = EuchreRules.currentSeat(state)
+            if (seat == null) {
+                state = EuchreRules.nextHand(state)
+                continue
+            }
+            val legal = EuchreRules.legalMoves(state, seat)
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move in ${state.phase}", legal.contains(move))
+            moves += move
+            state = EuchreRules.applyMove(state, seat, move)
+        }
+        assertTrue("game with seed $seed did not finish", EuchreRules.isFinished(state))
+        return moves
+    }
+
+    @Test
+    fun `every difficulty and style plays whole games legally`() {
+        for (difficulty in AiDifficulty.entries) {
+            for (seed in 1L..8L) {
+                playGame(EuchreAi(AiProfiles(difficulty, seed)), seed)
+            }
+        }
+    }
+
+    @Test
+    fun `the default profile plays as a medium balanced seat`() {
+        for (seed in 1L..3L) {
+            val standard = playGame(EuchreAi(), seed)
+            val explicit = playGame(EuchreAi(AiProfiles(AiDifficulty.MEDIUM, 99L)), seed)
+            assertEquals(standard, explicit)
+        }
+    }
+}

app/src/test/java/org/prolibertate/games/game/golf/GolfAiProfileTest.kt

@@ -0,0 +1,72 @@
+package org.prolibertate.games.game.golf
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class GolfAiProfileTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(options: GolfOptions, seed: Long) = TableConfig(
+        gameId = "golf",
+        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 play(ai: GolfAi, options: GolfOptions, seed: Long): List<GolfMove> {
+        var state = GolfRules.initialState(config(options, seed))
+        val moves = mutableListOf<GolfMove>()
+        var guard = 0
+        while (!GolfRules.isFinished(state) && guard++ < 8000) {
+            val seat = GolfRules.currentSeat(state)
+            if (seat == null) {
+                state = GolfRules.nextHole(state)
+                continue
+            }
+            val legal = GolfRules.legalMoves(state, seat)
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move", legal.contains(move))
+            moves += move
+            state = GolfRules.applyMove(state, seat, move)
+        }
+        assertTrue("game did not finish", GolfRules.isFinished(state))
+        return moves
+    }
+
+    @Test
+    fun `every difficulty and style plays complete games legally`() {
+        val variants = listOf(
+            GolfOptions(playerCount = 2, gridSize = 6, holes = 2),
+            GolfOptions(playerCount = 4, gridSize = 9, holes = 2),
+            GolfOptions(playerCount = 3, gridSize = 4, holes = 2, lineUpFinalPutt = true),
+            GolfOptions(playerCount = 6, gridSize = 8, holes = 1),
+        )
+        for (difficulty in listOf(AiDifficulty.EASY, AiDifficulty.HARD, AiDifficulty.MIXED)) {
+            for (seed in 0L until 8L) {
+                val options = variants[(seed % variants.size).toInt()]
+                play(GolfAi(AiProfiles(difficulty, seed)), options, 400L + seed)
+            }
+        }
+    }
+
+    @Test
+    fun `the default profile plays like a medium balanced seat`() {
+        val options = GolfOptions(playerCount = 3, gridSize = 6, holes = 2)
+        for (seed in 1L..3L) {
+            val default = play(GolfAi(), options, seed)
+            val medium = play(GolfAi(AiProfiles(AiDifficulty.MEDIUM, 13L + seed)), options, seed)
+            assertEquals(default, medium)
+        }
+    }
+}

app/src/test/java/org/prolibertate/games/game/hearts/HeartsAiProfileTest.kt

@@ -0,0 +1,63 @@
+package org.prolibertate.games.game.hearts
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class HeartsAiProfileTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(seed: Long) = TableConfig(
+        gameId = "hearts",
+        seats = (0 until 4).map { PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it) },
+        optionsJson = json.encodeToString(HeartsOptions(targetScore = 50)),
+        seed = seed,
+    )
+
+    /** Plays a whole game and returns every move made, asserting each was legal. */
+    private fun play(ai: HeartsAi, seed: Long): List<HeartsMove> {
+        var state = HeartsRules.initialState(config(seed))
+        val moves = mutableListOf<HeartsMove>()
+        var guard = 0
+        while (!HeartsRules.isFinished(state) && guard++ < 5000) {
+            val seat = HeartsRules.currentSeat(state)
+            if (seat == null) {
+                state = HeartsRules.startNextRound(state)
+                continue
+            }
+            val legal = HeartsRules.legalMoves(state, seat)
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move", legal.contains(move))
+            moves += move
+            state = HeartsRules.applyMove(state, seat, move)
+        }
+        assertTrue("game did not finish", HeartsRules.isFinished(state))
+        return moves
+    }
+
+    @Test
+    fun `every difficulty and style plays complete games legally`() {
+        for (difficulty in listOf(AiDifficulty.EASY, AiDifficulty.HARD, AiDifficulty.MIXED)) {
+            for (seed in 0L until 8L) {
+                play(HeartsAi(AiProfiles(difficulty, seed)), 100L + seed)
+            }
+        }
+    }
+
+    @Test
+    fun `the default profile plays like a medium balanced seat`() {
+        for (seed in 1L..3L) {
+            val default = play(HeartsAi(), seed)
+            val medium = play(HeartsAi(AiProfiles(AiDifficulty.MEDIUM, 77L + seed)), seed)
+            assertEquals(default, medium)
+        }
+    }
+}

app/src/test/java/org/prolibertate/games/game/kaiser/KaiserAiProfilesTest.kt

@@ -0,0 +1,68 @@
+package org.prolibertate.games.game.kaiser
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class KaiserAiProfilesTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(seed: Long) = TableConfig(
+        gameId = "kaiser",
+        seats = (0 until 4).map {
+            PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it % 2)
+        },
+        optionsJson = json.encodeToString(KaiserOptions()),
+        seed = seed,
+    )
+
+    /** Plays up to [hands] hands with every seat on [ai], returning every move chosen. */
+    private fun playHands(ai: KaiserAi, seed: Long, hands: Int): List<KaiserMove> {
+        val moves = mutableListOf<KaiserMove>()
+        var state = KaiserRules.initialState(config(seed))
+        var dealt = 1
+        var guard = 0
+        while (!KaiserRules.isFinished(state) && guard++ < 4000) {
+            val seat = KaiserRules.currentSeat(state)
+            if (seat == null) {
+                if (dealt >= hands) break
+                dealt++
+                state = KaiserRules.nextHand(state)
+                continue
+            }
+            val legal = KaiserRules.legalMoves(state, seat)
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move in ${state.phase}", legal.contains(move))
+            moves += move
+            state = KaiserRules.applyMove(state, seat, move)
+        }
+        return moves
+    }
+
+    @Test
+    fun `every difficulty and style plays hands legally`() {
+        for (difficulty in AiDifficulty.entries) {
+            for (seed in 1L..8L) {
+                val moves = playHands(KaiserAi(AiProfiles(difficulty, seed)), seed, hands = 4)
+                assertTrue(moves.isNotEmpty())
+            }
+        }
+    }
+
+    @Test
+    fun `the default profile plays as a medium balanced seat`() {
+        for (seed in 1L..3L) {
+            val standard = playHands(KaiserAi(), seed, hands = 3)
+            val explicit = playHands(KaiserAi(AiProfiles(AiDifficulty.MEDIUM, 99L)), seed, hands = 3)
+            assertEquals(standard, explicit)
+        }
+    }
+}

app/src/test/java/org/prolibertate/games/game/morris/MorrisAiProfileTest.kt

@@ -0,0 +1,40 @@
+package org.prolibertate.games.game.morris
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+
+class MorrisAiProfileTest {
+
+    @Test
+    fun `every difficulty and seeded style plays only legal moves`() {
+        val seen = mutableSetOf<Pair<Any, Any>>()
+        for (difficulty in AiDifficulty.entries) for (seed in 0L until 12L) {
+            val profiles = AiProfiles(difficulty, seed)
+            for (seat in 0..1) profiles.of(seat).let { seen += it.level to it.style }
+            val ai = MorrisAi(profiles, MorrisLevel.CASUAL)
+            var state = MorrisRules.initialState(MorrisOptions(level = MorrisLevel.CASUAL))
+            var plies = 0
+            while (!MorrisRules.isFinished(state) && plies < 8) {
+                val legal = MorrisRules.legalMoves(state)
+                val move = ai.chooseMove(state, state.turn, legal)
+                assertTrue("$difficulty/$seed illegal move $move", move in legal)
+                state = MorrisRules.applyMove(state, state.turn, move)
+                plies++
+            }
+        }
+        assertTrue("expected a spread of level/style pairs, saw ${seen.size}", seen.size >= 8)
+    }
+
+    @Test
+    fun `default profile plays the same as an explicit medium table`() {
+        val state = MorrisRules.initialState(MorrisOptions(level = MorrisLevel.CASUAL))
+        val legal = MorrisRules.legalMoves(state)
+        val a = MorrisAi(level = MorrisLevel.CASUAL).chooseMove(state, state.turn, legal)
+        val b = MorrisAi(AiProfiles(AiDifficulty.MEDIUM, 5L), MorrisLevel.CASUAL)
+            .chooseMove(state, state.turn, legal)
+        assertEquals(a, b)
+    }
+}

app/src/test/java/org/prolibertate/games/game/morris/MorrisAiTest.kt

@@ -29,7 +29,7 @@ class MorrisAiTest {
     )
 
     private fun choose(state: MorrisState, level: MorrisLevel = MorrisLevel.CLUB): MorrisMove =
-        MorrisAi(level).chooseMove(state, state.turn, MorrisRules.legalMoves(state))
+        MorrisAi(level = level).chooseMove(state, state.turn, MorrisRules.legalMoves(state))
 
     @Test
     fun `it always returns a move it is allowed to play`() {

app/src/test/java/org/prolibertate/games/game/pirates/PiratesAiProfileTest.kt

@@ -0,0 +1,45 @@
+package org.prolibertate.games.game.pirates
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.prolibertate.games.game.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+
+class PiratesAiProfileTest {
+
+    private fun playout(ai: PiratesAi, steps: Int): List<PiratesMove> {
+        var state = PiratesRules.initialState(PiratesOptions(level = PiratesLevel.CASUAL))
+        val chosen = mutableListOf<PiratesMove>()
+        repeat(steps) {
+            if (PiratesRules.isFinished(state)) return chosen
+            val seat = PiratesRules.currentSeat(state) ?: return chosen
+            val legal = PiratesRules.legalMoves(state, seat)
+            if (legal.isEmpty()) return chosen
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move", move in legal)
+            chosen += move
+            state = PiratesRules.applyMove(state, seat, move)
+        }
+        return chosen
+    }
+
+    @Test
+    fun everyLevelAndStyleReturnsLegalMoves() {
+        for (difficulty in listOf(AiDifficulty.EASY, AiDifficulty.MEDIUM, AiDifficulty.MIXED)) {
+            for (seed in 0L..5L) {
+                assertTrue(playout(PiratesAi(AiProfiles(difficulty, seed)), 12).isNotEmpty())
+            }
+        }
+        for (seed in 0L..3L) {
+            assertTrue(playout(PiratesAi(AiProfiles(AiDifficulty.HARD, seed)), 4).isNotEmpty())
+        }
+    }
+
+    @Test
+    fun defaultProfilePlaysAsBefore() {
+        val plain = playout(PiratesAi(), 10)
+        val medium = playout(PiratesAi(AiProfiles(AiDifficulty.MEDIUM, 77L)), 10)
+        assertEquals(plain, medium)
+    }
+}

app/src/test/java/org/prolibertate/games/game/president/PresidentAiProfileTest.kt

@@ -0,0 +1,71 @@
+package org.prolibertate.games.game.president
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class PresidentAiProfileTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(options: PresidentOptions, seed: Long) = TableConfig(
+        gameId = "president",
+        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 play(ai: PresidentAi, options: PresidentOptions, seed: Long): List<PresidentMove> {
+        var state = PresidentRules.initialState(config(options, seed))
+        val moves = mutableListOf<PresidentMove>()
+        var guard = 0
+        while (!PresidentRules.isFinished(state) && guard++ < 6000) {
+            val seat = PresidentRules.currentSeat(state)
+            if (seat == null) {
+                state = PresidentRules.nextRound(state)
+                continue
+            }
+            val legal = PresidentRules.legalMoves(state, seat)
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move", legal.contains(move))
+            moves += move
+            state = PresidentRules.applyMove(state, seat, move)
+        }
+        assertTrue("game did not finish", PresidentRules.isFinished(state))
+        return moves
+    }
+
+    @Test
+    fun `every difficulty and style plays complete games legally`() {
+        val variants = listOf(
+            PresidentOptions(playerCount = 4, roundsToPlay = 3),
+            PresidentOptions(playerCount = 5, roundsToPlay = 2, fourOfAKindBomb = true),
+            PresidentOptions(playerCount = 3, roundsToPlay = 2, twosClear = false),
+        )
+        for (difficulty in listOf(AiDifficulty.EASY, AiDifficulty.HARD, AiDifficulty.MIXED)) {
+            for (seed in 0L until 6L) {
+                val options = variants[(seed % variants.size).toInt()]
+                play(PresidentAi(AiProfiles(difficulty, seed)), options, 200L + seed)
+            }
+        }
+    }
+
+    @Test
+    fun `the default profile plays like a medium balanced seat`() {
+        val options = PresidentOptions(playerCount = 4, roundsToPlay = 2)
+        for (seed in 1L..3L) {
+            val default = play(PresidentAi(), options, seed)
+            val medium = play(PresidentAi(AiProfiles(AiDifficulty.MEDIUM, 55L + seed)), options, seed)
+            assertEquals(default, medium)
+        }
+    }
+}

app/src/test/java/org/prolibertate/games/game/sequence/SequenceAiLevelsTest.kt

@@ -0,0 +1,89 @@
+package org.prolibertate.games.game.sequence
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.AiStyle
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class SequenceAiLevelsTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(options: SequenceOptions, seed: Long) = TableConfig(
+        gameId = "sequence",
+        seats = (0 until options.playerCount).map {
+            PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it % options.teamCount)
+        },
+        optionsJson = json.encodeToString(options),
+        seed = seed,
+    )
+
+    /** Seeds that between them give some seat every style at this difficulty. */
+    private fun seedsCoveringStyles(difficulty: AiDifficulty, seats: Int): List<Long> {
+        // The standard opponent is balanced by definition, so there is no style to cover.
+        if (difficulty == AiDifficulty.MEDIUM) return listOf(0L, 1L, 2L)
+        val missing = AiStyle.entries.toMutableSet()
+        val seeds = mutableListOf<Long>()
+        var seed = 0L
+        while (missing.isNotEmpty() && seed < 500) {
+            val styles = (0 until seats).map { AiProfiles(difficulty, seed).of(it).style }
+            if (styles.any { it in missing }) {
+                seeds += seed
+                missing.removeAll(styles.toSet())
+            }
+            seed++
+        }
+        assertTrue("styles never covered: $missing", missing.isEmpty())
+        return seeds
+    }
+
+    private fun play(ai: SequenceAi, options: SequenceOptions, seed: Long): List<SequenceMove> {
+        var state = SequenceRules.initialState(config(options, seed))
+        val moves = mutableListOf<SequenceMove>()
+        var guard = 0
+        while (!SequenceRules.isFinished(state) && guard++ < 4000) {
+            val seat = SequenceRules.currentSeat(state) ?: break
+            val legal = SequenceRules.legalMoves(state, seat)
+            if (legal.isEmpty()) break
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move", legal.contains(move))
+            moves += move
+            state = SequenceRules.applyMove(state, seat, move)
+        }
+        assertTrue("game ran away", guard < 4000)
+        return moves
+    }
+
+    @Test
+    fun `every level and style plays a whole game legally`() {
+        val options = SequenceOptions(teamCount = 2, playersPerTeam = 1)
+        listOf(AiDifficulty.EASY, AiDifficulty.MEDIUM, AiDifficulty.HARD).forEach { difficulty ->
+            seedsCoveringStyles(difficulty, options.playerCount).forEach { seed ->
+                play(SequenceAi(AiProfiles(difficulty, seed)), options, 300L + seed)
+            }
+        }
+    }
+
+    @Test
+    fun `three teams play legally at every level`() {
+        val options = SequenceOptions(teamCount = 3, playersPerTeam = 1, sequencesToWin = 1)
+        listOf(AiDifficulty.EASY, AiDifficulty.HARD, AiDifficulty.MIXED).forEach { difficulty ->
+            play(SequenceAi(AiProfiles(difficulty, 4L)), options, 11L)
+        }
+    }
+
+    @Test
+    fun `the default profile plays as the standard opponent`() {
+        val options = SequenceOptions()
+        val standard = play(SequenceAi(), options, 21L)
+        val medium = play(SequenceAi(AiProfiles(AiDifficulty.MEDIUM, 6L)), options, 21L)
+        assertEquals(standard, medium)
+    }
+}

app/src/test/java/org/prolibertate/games/game/tayu/TayuAiLevelsTest.kt

@@ -0,0 +1,88 @@
+package org.prolibertate.games.game.tayu
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.AiStyle
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class TayuAiLevelsTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private val options = TayuOptions(tileCopies = 2)
+
+    private fun config(seed: Long) = TableConfig(
+        gameId = "tayu",
+        seats = (0 until options.playerCount).map {
+            PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it % 2)
+        },
+        optionsJson = json.encodeToString(options),
+        seed = seed,
+    )
+
+    /** Seeds that between them give some seat every style at this difficulty. */
+    private fun seedsCoveringStyles(difficulty: AiDifficulty, seats: Int): List<Long> {
+        // The standard opponent is balanced by definition, so there is no style to cover.
+        if (difficulty == AiDifficulty.MEDIUM) return listOf(0L, 1L, 2L)
+        val missing = AiStyle.entries.toMutableSet()
+        val seeds = mutableListOf<Long>()
+        var seed = 0L
+        while (missing.isNotEmpty() && seed < 500) {
+            val styles = (0 until seats).map { AiProfiles(difficulty, seed).of(it).style }
+            if (styles.any { it in missing }) {
+                seeds += seed
+                missing.removeAll(styles.toSet())
+            }
+            seed++
+        }
+        assertTrue("styles never covered: $missing", missing.isEmpty())
+        return seeds
+    }
+
+    private fun play(ai: TayuAi, seed: Long): List<TayuMove> {
+        var state = TayuRules.initialState(config(seed))
+        val moves = mutableListOf<TayuMove>()
+        var guard = 0
+        while (!TayuRules.isFinished(state) && guard++ < 500) {
+            val seat = TayuRules.currentSeat(state) ?: break
+            val legal = TayuRules.legalMoves(state, seat)
+            if (legal.isEmpty()) break
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move", legal.contains(move))
+            moves += move
+            state = TayuRules.applyMove(state, seat, move)
+        }
+        assertTrue("game ran away", guard < 500)
+        return moves
+    }
+
+    @Test
+    fun `every level and style plays a whole game legally`() {
+        listOf(AiDifficulty.EASY, AiDifficulty.MEDIUM, AiDifficulty.HARD).forEach { difficulty ->
+            seedsCoveringStyles(difficulty, options.playerCount).forEach { seed ->
+                play(TayuAi(AiProfiles(difficulty, seed)), 500L + seed)
+            }
+        }
+    }
+
+    @Test
+    fun `the gentle table setting is respected at every level`() {
+        listOf(AiDifficulty.EASY, AiDifficulty.HARD).forEach { difficulty ->
+            play(TayuAi(AiProfiles(difficulty, 2L), TayuLevel.GENTLE), 9L)
+        }
+    }
+
+    @Test
+    fun `the default profile plays as the standard opponent`() {
+        val standard = play(TayuAi(), 31L)
+        val medium = play(TayuAi(AiProfiles(AiDifficulty.MEDIUM, 8L)), 31L)
+        assertEquals(standard, medium)
+    }
+}

app/src/test/java/org/prolibertate/games/game/wizard/WizardAiProfilesTest.kt

@@ -0,0 +1,71 @@
+package org.prolibertate.games.game.wizard
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class WizardAiProfilesTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(seed: Long, options: WizardOptions) = TableConfig(
+        gameId = "wizard",
+        seats = (0 until options.playerCount).map {
+            PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it)
+        },
+        optionsJson = json.encodeToString(options),
+        seed = seed,
+    )
+
+    /** Plays a whole game with every seat on [ai], returning every move chosen. */
+    private fun playGame(ai: WizardAi, seed: Long, options: WizardOptions): List<WizardMove> {
+        val moves = mutableListOf<WizardMove>()
+        var state = WizardRules.initialState(config(seed, options))
+        var guard = 0
+        while (!WizardRules.isFinished(state) && guard++ < 5000) {
+            val seat = WizardRules.currentSeat(state)
+            if (seat == null) {
+                state = WizardRules.nextRound(state)
+                continue
+            }
+            val legal = WizardRules.legalMoves(state, seat)
+            val move = ai.chooseMove(state, seat, legal)
+            assertTrue("illegal move $move in ${state.phase}", legal.contains(move))
+            moves += move
+            state = WizardRules.applyMove(state, seat, move)
+        }
+        assertTrue("game with seed $seed did not finish", WizardRules.isFinished(state))
+        return moves
+    }
+
+    @Test
+    fun `every difficulty and style plays whole games legally`() {
+        for (difficulty in AiDifficulty.entries) {
+            for (seed in 1L..6L) {
+                val options = WizardOptions(
+                    playerCount = 3 + (seed % 4).toInt(),
+                    rounds = 6,
+                    screwTheDealer = seed % 2L == 0L,
+                )
+                playGame(WizardAi(AiProfiles(difficulty, seed)), seed, options)
+            }
+        }
+    }
+
+    @Test
+    fun `the default profile plays as a medium balanced seat`() {
+        val options = WizardOptions(playerCount = 4, rounds = 6)
+        for (seed in 1L..3L) {
+            val standard = playGame(WizardAi(), seed, options)
+            val explicit = playGame(WizardAi(AiProfiles(AiDifficulty.MEDIUM, 99L)), seed, options)
+            assertEquals(standard, explicit)
+        }
+    }
+}

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

@@ -0,0 +1,95 @@
+package org.prolibertate.games.game.yahtzee
+
+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.engine.AiDifficulty
+import org.prolibertate.games.game.engine.AiProfiles
+import org.prolibertate.games.game.engine.AiStyle
+import org.prolibertate.games.game.engine.PlayerKind
+import org.prolibertate.games.game.engine.PlayerSlot
+import org.prolibertate.games.game.engine.TableConfig
+
+class YahtzeeAiLevelsTest {
+
+    private val json = Json { encodeDefaults = true }
+
+    private fun config(options: YahtzeeOptions, seed: Long) = TableConfig(
+        gameId = "yahtzee",
+        seats = (0 until options.playerCount).map {
+            PlayerSlot(seat = it, name = "P$it", kind = PlayerKind.AI, team = it)
+        },
+        optionsJson = json.encodeToString(options),
+        seed = seed,
+    )
+
+    /** Seeds that between them give some seat every style at this difficulty. */
+    private fun seedsCoveringStyles(difficulty: AiDifficulty, seats: Int): List<Long> {
+        // The standard opponent is balanced by definition, so there is no style to cover.
+        if (difficulty == AiDifficulty.MEDIUM) return listOf(0L, 1L, 2L)
+        val missing = AiStyle.entries.toMutableSet()
+        val seeds = mutableListOf<Long>()
+        var seed = 0L
+        while (missing.isNotEmpty() && seed < 500) {
+            val styles = (0 until seats).map { AiProfiles(difficulty, seed).of(it).style }
+            if (styles.any { it in missing }) {
+                seeds += seed
+                missing.removeAll(styles.toSet())
+            }
+            seed++
+        }
+        assertTrue("styles never covered: $missing", missing.isEmpty())
+        return seeds
+    }
+
+    /** Plays a card out, returning the final state. */
+    private fun play(ai: YahtzeeAi, options: YahtzeeOptions, seed: Long): YahtzeeState {
+        var state = YahtzeeRules.initialState(config(options, seed))
+        var guard = 0
+        while (!YahtzeeRules.isFinished(state) && guard++ < 1000) {
+            val legal = YahtzeeRules.legalMoves(state, state.turn)
+            val move = ai.chooseMove(state, state.turn, legal)
+            assertTrue("illegal move $move", legal.contains(move))
+            state = YahtzeeRules.applyMove(state, state.turn, move)
+        }
+        assertTrue("game ran away", guard < 1000)
+        assertTrue(state.cards.all { it.isComplete })
+        return state
+    }
+
+    @Test
+    fun `every level and style fills a card legally`() {
+        val options = YahtzeeOptions(playerCount = 2)
+        listOf(AiDifficulty.EASY, AiDifficulty.MEDIUM, AiDifficulty.HARD).forEach { difficulty ->
+            seedsCoveringStyles(difficulty, options.playerCount).forEach { seed ->
+                play(YahtzeeAi(AiProfiles(difficulty, seed)), options, 40L + seed)
+            }
+        }
+    }
+
+    @Test
+    fun `the default profile plays as the standard opponent`() {
+        val options = YahtzeeOptions(playerCount = 2)
+        repeat(3) { i ->
+            val standard = play(YahtzeeAi(), options, 70L + i)
+            val medium = play(YahtzeeAi(AiProfiles(AiDifficulty.MEDIUM, 3L + i)), options, 70L + i)
+            assertEquals(standard.cards, medium.cards)
+        }
+    }
+
+    @Test
+    fun `hard scores clearly more than easy over a run of solo games`() {
+        val options = YahtzeeOptions(playerCount = 1)
+        fun average(difficulty: AiDifficulty): Double =
+            (1..12).map { i ->
+                play(YahtzeeAi(AiProfiles(difficulty, i.toLong())), options, 900L + i).totalFor(0)
+            }.average()
+
+        val easy = average(AiDifficulty.EASY)
+        val hard = average(AiDifficulty.HARD)
+        println("yahtzee solo average: easy $easy, hard $hard")
+        assertTrue("hard $hard did not beat easy $easy", hard > easy + 20)
+    }
+}

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

@@ -272,7 +272,7 @@ class YahtzeeRulesTest {
         var guard = 200
         while (!YahtzeeRules.isFinished(state) && guard-- > 0) {
             val legal = YahtzeeRules.legalMoves(state, state.turn)
-            state = YahtzeeRules.applyMove(state, state.turn, YahtzeeAi.chooseMove(state, state.turn, legal))
+            state = YahtzeeRules.applyMove(state, state.turn, YahtzeeAi().chooseMove(state, state.turn, legal))
         }
         assertTrue("the game should end on its own", guard > 0)
         assertTrue(YahtzeeRules.isFinished(state))
@@ -288,7 +288,7 @@ class YahtzeeRulesTest {
         var guard = 400
         while (!YahtzeeRules.isFinished(state) && guard-- > 0) {
             val legal = YahtzeeRules.legalMoves(state, state.turn)
-            state = YahtzeeRules.applyMove(state, state.turn, YahtzeeAi.chooseMove(state, state.turn, legal))
+            state = YahtzeeRules.applyMove(state, state.turn, YahtzeeAi().chooseMove(state, state.turn, legal))
         }
         assertTrue(guard > 0)
         assertTrue(state.cards.all { it.isComplete })

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

@@ -155,9 +155,9 @@ class SaveRoundTripAllGamesTest {
     @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 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 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()))
@@ -171,7 +171,7 @@ class SaveRoundTripAllGamesTest {
         GameCatalog.CATAN,
         CatanRules,
         CatanAi(),
-        opts(CatanOptions(3, 13, org.prolibertate.games.game.catan.CatanRuleSet.CITIES_AND_KNIGHTS)),
+        opts(CatanOptions(3, 13, setOf(org.prolibertate.games.game.catan.CatanExpansion.CITIES_AND_KNIGHTS))),
         steps = 600,
     )
 }

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

@@ -21,7 +21,7 @@ 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.CatanExpansion
 import org.prolibertate.games.game.catan.CatanRules
 import org.prolibertate.games.game.catan.CatanState
 import org.prolibertate.games.game.catan.ChaseRobber
@@ -69,7 +69,7 @@ class CatanCkInteractionTest {
         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),
+            CatanOptions(players, pointsToWin = 13, expansions = setOf(CatanExpansion.CITIES_AND_KNIGHTS)),
         ),
         seed = seed,
     )

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

@@ -8,7 +8,7 @@ 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.CatanExpansion
 import org.prolibertate.games.game.catan.CatanRules
 import org.prolibertate.games.game.catan.ProgressType
 import org.prolibertate.games.game.engine.PlayerKind
@@ -16,7 +16,7 @@ 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
+import org.prolibertate.games.ui.catanToggleExpansion
 
 class CatanCkTextTest {
 
@@ -28,7 +28,7 @@ class CatanCkTextTest {
             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),
+                CatanOptions(3, 13, setOf(CatanExpansion.CITIES_AND_KNIGHTS)),
             ),
             seed = 31L,
         )
@@ -56,20 +56,24 @@ class CatanCkTextTest {
 
     @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))
+        assertEquals(listOf(5, 8, 10, 12), catanPointsChoices(emptySet()))
+        assertEquals(listOf(8, 10, 13, 15), catanPointsChoices(setOf(CatanExpansion.CITIES_AND_KNIGHTS)))
+        assertEquals(10, catanDefaultPoints(emptySet()))
+        assertEquals(13, catanDefaultPoints(setOf(CatanExpansion.CITIES_AND_KNIGHTS)))
 
         val base = CatanOptions()
-        val ck = catanSwitchRules(base, CatanRuleSet.CITIES_AND_KNIGHTS)
-        assertEquals(CatanRuleSet.CITIES_AND_KNIGHTS, ck.ruleSet)
+        val ck = catanToggleExpansion(base, CatanExpansion.CITIES_AND_KNIGHTS, true)
+        assertEquals(setOf(CatanExpansion.CITIES_AND_KNIGHTS), ck.expansions)
         assertEquals("the published target for the new rules", 13, ck.pointsToWin)
-        assertEquals(10, catanSwitchRules(ck, CatanRuleSet.BASE).pointsToWin)
+        assertEquals(10, catanToggleExpansion(ck, CatanExpansion.CITIES_AND_KNIGHTS, false).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)
+        val short = catanToggleExpansion(base.copy(pointsToWin = 8), CatanExpansion.CITIES_AND_KNIGHTS, true)
         assertEquals(8, short.pointsToWin)
         assertEquals(3, ck.playerCount)
+
+        // Expansions cannot be combined yet: switching one on switches the other off.
+        val sea = catanToggleExpansion(ck, CatanExpansion.SEAFARERS, true)
+        assertEquals(setOf(CatanExpansion.SEAFARERS), sea.expansions)
     }
 }

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

@@ -28,7 +28,8 @@ internal object CatanFixtures {
 
     /** A fresh table, on the first setup placement. */
     fun start(players: Int = 3, seed: Long = 7L): CatanState =
-        CatanRules.initialState(config(players, seed))
+        // These tests are about the screen, not who starts: pin seat 0 first.
+        CatanRules.initialState(config(players, seed)).let { it.copy(firstSeat = 0, turn = 0) }
 
     /** A mid-game state on [turn]'s turn, then adjusted by [adjust]. */
     fun playing(

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

@@ -12,7 +12,7 @@ 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.CatanExpansion
 import org.prolibertate.games.game.catan.CatanRules
 import org.prolibertate.games.game.catan.CatanState
 import org.prolibertate.games.game.catan.MovePirate
@@ -29,7 +29,7 @@ import org.prolibertate.games.game.engine.TableConfig
 class CatanSeafarersInteractionTest {
 
     private fun fresh(): CatanState {
-        val options = CatanOptions(playerCount = 3, pointsToWin = 12, ruleSet = CatanRuleSet.SEAFARERS)
+        val options = CatanOptions(playerCount = 3, pointsToWin = 12, expansions = setOf(CatanExpansion.SEAFARERS))
         return CatanRules.initialState(
             TableConfig(
                 gameId = GameCatalog.CATAN,

docs/RULES-catan-seafarers.md

@@ -1,10 +1,10 @@
 # Katan: Seafarers
 
-The Seafarers rule set is chosen at setup next to *Base game* and *Cities & Knights*. It is the base
+Seafarers is an expansion switched on at setup (`CatanOptions.expansions`; the old single `ruleSet` in saves is still read) and its map is chosen beside it (`CatanOptions.scenario`). 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.
+(null in the other rule sets). It cannot yet be combined with Cities & Knights; the setup screen switches one off when the other is turned on.
 
 Where the published rules leave room, or where this game differs, it says so below.