Initial pass at unicorn pack.

internal/ai/ai.go

@@ -35,12 +35,12 @@ import (
 
 // Action is one move the bot wants to make, mirroring the client protocol.
 type Action struct {
-	Type   string   // buy | buyAvocado | sell | trade | tradeChoose | pass | arrange | ready | revealChoose
+	Type   string   // buy | buyAvocado | sell | trade | tradeChoose | pass | arrange | ready | revealChoose | sacrificeChoose
 	Row    int      // buy / buyAvocado
 	Cards  []string // sell / trade
 	Pick   int      // tradeChoose
 	Order  []string // arrange
-	CardID string   // revealChoose (Cockatoo): the pet to reveal
+	CardID string   // revealChoose (Cockatoo) / sacrificeChoose (Water of Youth): the pet
 }
 
 // Bot is a computer player at a fixed difficulty level.
@@ -62,6 +62,12 @@ func (b *Bot) Act(v *game.View, mem *Memory) *Action {
 	me := &v.Players[v.YouSeat]
 	switch v.Phase {
 	case game.PhaseShop:
+		if v.PendingSacrifice != nil {
+			if v.PendingSacrifice.PlayerID == me.ID {
+				return b.decideSacrifice(v)
+			}
+			return nil
+		}
 		if v.PendingReveal != nil {
 			if v.PendingReveal.PlayerID == me.ID {
 				return b.decideReveal(v)
@@ -107,6 +113,26 @@ func (b *Bot) decideReveal(v *game.View) *Action {
 	return &Action{Type: "revealChoose", CardID: best}
 }
 
+// decideSacrifice resolves Water of Youth (Unicorn pack): give up the
+// lowest-value eligible pet to upgrade into a next-tier card.
+func (b *Bot) decideSacrifice(v *game.View) *Action {
+	me := &v.Players[v.YouSeat]
+	worst, worstVal := "", math.Inf(1)
+	for _, id := range v.PendingSacrifice.Options {
+		for _, c := range me.Deck {
+			if c.ID == id {
+				if val := keepValue(c); val < worstVal {
+					worst, worstVal = id, val
+				}
+			}
+		}
+	}
+	if worst == "" && len(v.PendingSacrifice.Options) > 0 {
+		worst = v.PendingSacrifice.Options[0]
+	}
+	return &Action{Type: "sacrificeChoose", CardID: worst}
+}
+
 // Pending reports whether the seat owes the game an action right now — the
 // server uses it to decide when to schedule a bot move.
 func Pending(v *game.View) bool {
@@ -116,6 +142,9 @@ func Pending(v *game.View) bool {
 	me := &v.Players[v.YouSeat]
 	switch v.Phase {
 	case game.PhaseShop:
+		if v.PendingSacrifice != nil {
+			return v.PendingSacrifice.PlayerID == me.ID
+		}
 		if v.PendingReveal != nil {
 			return v.PendingReveal.PlayerID == me.ID
 		}

internal/ai/ai_test.go

@@ -102,6 +102,8 @@ func applyAction(g *game.Game, playerID string, a *Action) error {
 		return g.TradeChoose(playerID, a.Pick)
 	case "revealChoose":
 		return g.RevealChoose(playerID, a.CardID)
+	case "sacrificeChoose":
+		return g.SacrificeChoose(playerID, a.CardID)
 	case "pass":
 		return g.Pass(playerID)
 	case "arrange":
@@ -139,6 +141,20 @@ func TestBotsFinishGoldenGame(t *testing.T) {
 	}
 }
 
+// TestBotsFinishUnicornGame plays complete games on the Unicorn pack (tiers
+// 1-3 printed; 4-6 still in progress, so late shops are barren but battles
+// still resolve). It exercises the Mana and Ailment mechanics via
+// SimulateBattle rollouts plus the new shop effects (Water of Youth's sacrifice
+// choice, Bigfoot), and fails on any illegal or missing bot action.
+func TestBotsFinishUnicornGame(t *testing.T) {
+	for range 5 {
+		g := playBotGamePack(t, "unicorn", 1, 0.6)
+		if g.Round != game.MaxRounds {
+			t.Errorf("unicorn game ended on round %d, want %d", g.Round, game.MaxRounds)
+		}
+	}
+}
+
 // TestObserveTracksOpponentDeck checks the memory's opponent model against
 // the opponent's real deck after known public actions. The model may only
 // contain information a human spectator would have.

internal/ai/shop.go

@@ -52,6 +52,20 @@ func (cx *ctx) applyTemplateShopEffects(deck []game.Card, c game.Card, trigger g
 			for range best {
 				deck = append(deck, cx.simApple())
 			}
+		case game.ActionRevealTierForApples:
+			// Quetzalcoatl: a fixed apple reward if a low-tier pet can be revealed.
+			eligible := false
+			for _, d := range deck {
+				if d.IsPet() && d.ID != c.ID && (e.Cap <= 0 || d.Tier <= e.Cap) {
+					eligible = true
+					break
+				}
+			}
+			if eligible {
+				for range max(e.Count, 1) {
+					deck = append(deck, cx.simApple())
+				}
+			}
 		case game.ActionDoubleApples:
 			apples := 0
 			for _, dc := range deck {
@@ -87,6 +101,39 @@ func (cx *ctx) applyTemplateShopEffects(deck []game.Card, c game.Card, trigger g
 			if i := slices.IndexFunc(deck, func(d game.Card) bool { return d.ID == c.ID }); i >= 0 {
 				deck = slices.Delete(deck, i, i+1)
 			}
+		case game.ActionUpgradeNextTier:
+			// Unicorn pack (Water of Youth): discard this food and the lowest-value
+			// pet, then gain a sampled top card of the next tier for free.
+			nextTier := cx.v.Round + 1
+			if nextTier > game.MaxRounds {
+				continue
+			}
+			if i := slices.IndexFunc(deck, func(d game.Card) bool { return d.ID == c.ID }); i >= 0 {
+				deck = slices.Delete(deck, i, i+1)
+			}
+			worst, worstVal := -1, 0.0
+			for i, d := range deck {
+				if !d.IsPet() {
+					continue
+				}
+				if v := keepValue(d); worst < 0 || v < worstVal {
+					worst, worstVal = i, v
+				}
+			}
+			if worst < 0 {
+				continue // no pet to sacrifice; the food is wasted
+			}
+			deck = slices.Delete(deck, worst, worst+1)
+			pool := cx.unseenPool(nextTier)
+			if len(pool) == 0 {
+				pool = game.TierContentsForPack(cx.v.Pack, nextTier)
+			}
+			if len(pool) > 0 {
+				rc := pool[rand.IntN(len(pool))]
+				rc.ID = cx.nextSimID()
+				deck = append(deck, rc)
+				deck = cx.applyTemplateShopEffects(deck, rc, game.TriggerBuy)
+			}
 		}
 	}
 	return deck