Mega-Monster offers its choice

"Doubles the existing life-points OR movement rate" — the engine
always took the OR's left side because the client never asked. With
Mega-Monster selected, the hint bar now offers the choice (hit points
lit by default), and the pick rides the cast as params.boost — its
own field, freeing params.cardId for the name-a-card spells it
belongs to. Both halves of the OR are pinned in the creature suite.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/engine/src/game.ts

@@ -199,6 +199,8 @@ export interface CastParams {
   cardId?: string;
   points?: number;
   clockwise?: boolean;
+  /** MEGA-MONSTER: which stat doubles. */
+  boost?: "life" | "movement";
 }
 
 export interface GameConfig {
@@ -1465,7 +1467,7 @@ const CARD_EFFECTS: Record<string, AttackEffect | NeutralEffect | CounterEffect>
       if (!creature) return "no such monster";
       if (creature.kind === "shadow" || creature.kind === "alter-ego") return "that is no monster";
       if (!gameLos(state, caster.position, creature.position)) return "no line of sight";
-      const boost = cmd.params?.cardId === "movement" ? "movement" : "life";
+      const boost = cmd.params?.boost === "movement" ? "movement" : "life";
       if (boost === "movement") creature.movesPerTurn *= 2;
       else creature.maxDamage *= 2;
       events.push({ type: "monsterBoosted", creatureId: creature.id, boost });

packages/engine/test/creatures.test.ts

@@ -205,6 +205,16 @@ describe("monsters", () => {
     });
     expect(state.creatures[0]!.maxDamage).toBe(8);
 
+    // "Doubles the existing life-points OR movement rate" — the other choice.
+    const movesBefore = state.creatures[0]!.movesPerTurn;
+    const mm2 = giveCard(state, me, "mega-monster", "MM2", 3);
+    state = must(state, me, {
+      type: "cast", instanceId: mm2.instanceId, target: { kind: "creature", creatureId: id },
+      params: { boost: "movement" },
+    });
+    expect(state.creatures[0]!.movesPerTurn).toBe(movesBefore * 2);
+    expect(state.creatures[0]!.maxDamage).toBe(8);
+
     const dc = giveCard(state, me, "dispel-creation", "DC", 2);
     state = must(state, me, {
       type: "cast", instanceId: dc.instanceId, target: { kind: "cell", cell: state.creatures[0]!.position },