refactor(three-monks): Replace commands with phase wrappers

Rework task execution to be synchronous within a single tick.
Scheduling boundaries are now defined by `cycle` nodes, which
replace the previous `repeat` decorator.  All tasks are executed
immediately when scheduled, and parent/child propagation is
handled inline.

USAGE.md

@@ -10,12 +10,15 @@ Entity-Component-System with an observable-style API for TypeScript. Built for g
 - [API](#api)
   - [World](#world)
   - [Components](#components)
+  - [Singleton Components](#singleton-components)
   - [Queries](#queries)
   - [Observable Queries](#observable-queries)
   - [Change Tracking](#change-tracking)
   - [Relationships](#relationships)
   - [Events](#events)
   - [Serialization](#serialization)
+  - [Commands](#commands)
+  - [Behaviour Trees](#behaviour-trees)
 - [TypeScript Inference](#typescript-inference)
 
 ## Installation
@@ -132,6 +135,33 @@ Get returns a **live mutable reference** — no defensive copies. Mutations are
 
 ---
 
+### Singleton Components
+
+For global state (score, board, config) that doesn't need per-entity tracking. A single internal entity is created lazily and reused for all singleton components.
+
+```ts
+const Score = defineComponent("score", { points: 0, level: 1 });
+
+// Add (auto-creates the backing entity on first call)
+world.addSingleton(Score);
+
+// Get / set / check — no entity argument needed
+world.getSingleton(Score).points += 100;
+world.hasSingleton(Score);           // true
+world.setSingleton(Score, { points: 0, level: 2 });
+
+// Try-get
+const s = world.tryGetSingleton(Score); // Score | undefined
+
+// Mark dirty for change tracking
+world.markDirtySingleton(Score);
+
+// Remove (destroys the backing entity if it becomes bare)
+world.removeSingleton(Score);
+```
+
+---
+
 ### Queries
 
 Create filters with `query()`. Chain `.without()` to exclude components.
@@ -324,6 +354,142 @@ world2.get(e2, Health);                      // { current: 75, max: 100 }
 
 ---
 
+### Commands
+
+Decouple input from game logic. Define command components, register handlers, spawn command entities from input — the `CommandQueue` drains and dispatches them each frame.
+
+```ts
+import { CommandQueue } from "ecs-observable/commands";
+
+const MoveLeft  = defineComponent("moveLeft", {});
+const MoveRight = defineComponent("moveRight", {});
+
+const queue = new CommandQueue(world);
+
+// Register handlers
+queue.handle(MoveLeft, () => {
+  player.x -= 1;
+});
+
+queue.handle(MoveRight, () => {
+  player.x += 1;
+});
+
+// Input → spawn command entities
+onKey("ArrowLeft", () => {
+  const cmd = world.spawn();
+  world.add(cmd, MoveLeft);
+});
+
+// Each frame — drain and dispatch
+queue.execute();
+```
+
+Command entities are automatically destroyed after processing if they become bare.
+
+---
+
+### Behaviour Trees
+
+Behaviour trees control game flow by composing tasks into a tree. Each node in the tree is an ECS entity with a `Task` component. Parent-child relationships are `ChildOf` edges. This means you can query, observe, and serialize the tree just like any other ECS data.
+
+`buildTree()` takes a task entity definition and materializes it into entities, returning a fully-wired `TaskRunner`. Task definitions are created with factories, and non-task child entities can be mixed in as metadata; the runner ignores those non-task children during execution.
+
+```ts
+import { defineComponent, entity } from "ecs-observable";
+import { buildTree, Cancel, action, wait, parallel, cycle, whilst, sequential } from "ecs-observable/bt";
+```
+
+#### Task patterns
+
+**Action** — runs immediately. Normal return = success.
+```ts
+action(() => { doWork(); })
+```
+
+**Fail** — throw any error.
+```ts
+action(() => { throw new Error("bad"); })
+```
+
+**Cancel** — throw the `Cancel` symbol.
+```ts
+action(() => { throw Cancel; })
+```
+
+**Wait** — starts once and stays running until external code completes it.
+```ts
+wait((world, entity, task) => {
+  startAnimation(() => task.succeed());
+})
+```
+
+**Whilst** — runs its child while a condition is true, yielding at tick boundaries between successful iterations.
+```ts
+whilst(
+  () => true,
+  action((_world, _entity, dt) => {
+    timer.accumulator += dt;
+    if (timer.accumulator >= timer.interval) {
+      // ... act ...
+    }
+  }),
+)
+```
+
+#### Composite nodes
+
+```ts
+sequential([a, b, c])  // left-to-right, all must succeed
+selector([a, b, c])    // left-to-right, first success wins
+parallel([a, b, c])    // all at once, all must succeed
+random([a, b, c])      // pick one child each activation
+cycle(a)              // scheduling boundary — re-run child on future ticks
+whilst(test, a)       // conditional scheduling boundary
+```
+
+Non-task entity children are materialized but ignored by the runner:
+
+```ts
+const Label = defineComponent("label", { value: "" });
+
+sequential([
+  entity(Label, { value: "main sequence" }),
+  action(handleInput),
+  action(render),
+])
+```
+
+#### Full example
+
+```ts
+const runner = buildTree(
+  world,
+  parallel([
+    whilst(
+      () => true,
+      action((_world, _entity, dt) => {
+        updatePhysics(dt);
+      }),
+    ),
+    cycle(
+      sequential([
+        action(() => { handleInput(); }),
+        action(() => { render(); }),
+      ]),
+    ),
+  ]),
+);
+
+// Kick off
+runner.schedule(runner.root!);
+
+// Game loop
+setInterval(() => runner.tick(16), 16);
+```
+
+---
+
 ## TypeScript Inference
 
 Components infer their type from the defaults object — no separate type declaration needed.

examples/blackjack/commands.ts

@@ -0,0 +1,147 @@
+import { defineComponent } from "../../src/component";
+import type { World, Entity } from "../../src/index";
+import { query } from "../../src/query";
+import type { CommandQueue } from "../../src/commands/index";
+import {
+  Card,
+  InDeck,
+  InPlayerHand,
+  InDealerHand,
+  HoleHidden,
+  Score,
+  Bet,
+  GamePhase,
+} from "./components";
+import {
+  handValue,
+  isBust,
+  isBlackjack,
+  determineOutcome,
+  payout,
+} from "./game";
+
+// ── Command definitions ──────────────────────────────
+
+/** Player takes another card. */
+export const Hit = defineComponent("hit", {});
+
+/** Player stands (ends their turn). */
+export const Stand = defineComponent("stand", {});
+
+/** Start a new round. */
+export const NewRound = defineComponent("newRound", {});
+
+/** Increase the bet. */
+export const BetMore = defineComponent("betMore", {});
+
+/** Decrease the bet. */
+export const BetLess = defineComponent("betLess", {});
+
+// ── Command handlers ─────────────────────────────────
+
+export function registerCommands(
+  world: World,
+  commands: CommandQueue,
+  helpers: ReturnType<typeof import("./components").createCardHelpers>,
+): void {
+  commands.handle(Hit, () => {
+    const phase = world.getSingleton(GamePhase);
+    if (phase.phase !== "playerTurn") return;
+
+    const cardEntity = helpers.drawCard();
+    if (cardEntity) {
+      helpers.dealTo(cardEntity, InPlayerHand);
+    }
+
+    if (isBust(helpers.getHand(InPlayerHand))) {
+      world.removeSingleton(HoleHidden);
+      resolveRound(world, helpers);
+    }
+  });
+
+  commands.handle(Stand, () => {
+    const phase = world.getSingleton(GamePhase);
+    if (phase.phase !== "playerTurn") return;
+
+    world.removeSingleton(HoleHidden);
+    world.setSingleton(GamePhase, {
+      phase: "dealerTurn",
+      message: "Dealer's turn...",
+    });
+  });
+
+  commands.handle(NewRound, () => {
+    const phase = world.getSingleton(GamePhase);
+    if (phase.phase !== "roundOver" && phase.phase !== "betting") return;
+
+    const score = world.getSingleton(Score);
+    if (score.chips <= 0) {
+      world.setSingleton(GamePhase, {
+        phase: "roundOver",
+        message: "You're out of chips! Restart the program to play again.",
+      });
+      return;
+    }
+
+    helpers.startRound();
+  });
+
+  commands.handle(BetMore, () => {
+    const phase = world.getSingleton(GamePhase);
+    if (phase.phase !== "betting" && phase.phase !== "roundOver") return;
+
+    const bet = world.getSingleton(Bet);
+    const score = world.getSingleton(Score);
+    bet.amount = Math.min(bet.amount + 10, score.chips);
+  });
+
+  commands.handle(BetLess, () => {
+    const phase = world.getSingleton(GamePhase);
+    if (phase.phase !== "betting" && phase.phase !== "roundOver") return;
+
+    const bet = world.getSingleton(Bet);
+    bet.amount = Math.max(bet.amount - 10, 10);
+  });
+}
+
+// ── Internal ─────────────────────────────────────────
+
+export function resolveRound(
+  world: World,
+  helpers: ReturnType<typeof import("./components").createCardHelpers>,
+): void {
+  const playerCards = helpers.getHand(InPlayerHand);
+  const dealerCards = helpers.getHand(InDealerHand);
+  const score = world.getSingleton(Score);
+  const bet = world.getSingleton(Bet);
+
+  const outcome = determineOutcome(playerCards, dealerCards);
+  const winnings = payout(outcome, bet.amount);
+
+  score.chips += bet.amount + winnings;
+
+  switch (outcome) {
+    case "blackjack":
+    case "win":
+      score.wins++;
+      break;
+    case "lose":
+      score.losses++;
+      break;
+    case "push":
+      score.pushes++;
+      break;
+  }
+
+  const messages: Record<string, string> = {
+    win: "You win!",
+    lose: "Dealer wins.",
+    push: "Push — tie!",
+    blackjack: "Blackjack! You win 3:2!",
+  };
+
+  world.setSingleton(GamePhase, {
+    phase: "roundOver",
+    message: `${messages[outcome]} Press N for new round.`,
+  });
+}

examples/blackjack/components.ts

@@ -0,0 +1,203 @@
+import { defineComponent } from "../../src/component";
+import type { World, Entity } from "../../src/index";
+import { query } from "../../src/query";
+import { SUITS, RANKS, isBlackjack, type CardData } from "./game";
+
+// ── Component definitions ────────────────────────────
+
+/** Each card is its own entity. `order` tracks position within its collection. */
+export const Card = defineComponent("card", {
+  rank: "A",
+  suit: "♠",
+  order: 0,
+});
+
+// ── Tag components — mark which collection a card belongs to ─
+export const InDeck = defineComponent("inDeck", {});
+export const InPlayerHand = defineComponent("inPlayerHand", {});
+export const InDealerHand = defineComponent("inDealerHand", {});
+
+// ── Dealer state ─────────────────────────────────────
+/** When present (as singleton), the dealer's hole card is hidden. */
+export const HoleHidden = defineComponent("holeHidden", {});
+
+// ── Score / state ────────────────────────────────────
+export const Score = defineComponent("score", {
+  wins: 0,
+  losses: 0,
+  pushes: 0,
+  chips: 100,
+});
+
+export const Bet = defineComponent("bet", {
+  amount: 10,
+});
+
+/** Current phase of the game. */
+export type Phase = "betting" | "playerTurn" | "dealerTurn" | "roundOver";
+
+export const GamePhase = defineComponent("gamePhase", {
+  phase: "betting" as Phase,
+  message: "",
+});
+
+// ── Card helpers ─────────────────────────────────────
+
+export function createCardHelpers(world: World) {
+  return {
+    /** Create all 52 card entities with the InDeck tag. */
+    buildDeck(): void {
+      let order = 0;
+      for (const suit of SUITS) {
+        for (const rank of RANKS) {
+          const e = world.spawn();
+          world.add(e, Card, { rank, suit, order });
+          world.add(e, InDeck);
+          order++;
+        }
+      }
+    },
+
+    /** Shuffle the deck: collect all InDeck entities, shuffle, reassign order. */
+    shuffleDeck(): void {
+      const entities = [...world.query(query(Card, InDeck))];
+      for (let i = entities.length - 1; i > 0; i--) {
+        const j = Math.floor(Math.random() * (i + 1));
+        [entities[i], entities[j]] = [entities[j], entities[i]];
+      }
+      for (let i = 0; i < entities.length; i++) {
+        world.get(entities[i], Card).order = i;
+      }
+    },
+
+    /** Draw the top card from the deck (highest order). Returns entity or null. */
+    drawCard(): Entity | null {
+      const cards = [...world.query(query(Card, InDeck))];
+      if (cards.length === 0) return null;
+      let top = cards[0];
+      let topOrder = world.get(top, Card).order;
+      for (let i = 1; i < cards.length; i++) {
+        const o = world.get(cards[i], Card).order;
+        if (o > topOrder) {
+          top = cards[i];
+          topOrder = o;
+        }
+      }
+      world.remove(top, InDeck);
+      return top;
+    },
+
+    /** Move a card entity to a hand tag, assigning the next order. */
+    dealTo(cardEntity: Entity, tag: typeof InPlayerHand): void {
+      const existing = [...world.query(query(Card, tag))];
+      const nextOrder =
+        existing.length === 0
+          ? 0
+          : Math.max(...existing.map((e) => world.get(e, Card).order)) + 1;
+      world.add(cardEntity, tag);
+      world.get(cardEntity, Card).order = nextOrder;
+    },
+
+    /** Collect CardData from a hand tag, sorted by order. */
+    getHand(tag: typeof InPlayerHand): CardData[] {
+      return [...world.query(query(Card, tag))]
+        .map((e) => {
+          const c = world.get(e, Card);
+          return { rank: c.rank, suit: c.suit, order: c.order };
+        })
+        .sort((a, b) => a.order - b.order)
+        .map(({ rank, suit }) => ({ rank, suit }));
+    },
+
+    /** Remove all cards from a hand tag (destroy the card entities). */
+    clearHand(tag: typeof InPlayerHand): void {
+      for (const e of world.query(query(Card, tag))) {
+        world.destroy(e);
+      }
+    },
+
+    /** Count cards remaining in the deck. */
+    deckCount(): number {
+      return [...world.query(query(Card, InDeck))].length;
+    },
+
+    /** Deal initial 4 cards and start a round. */
+    startRound(): void {
+      const bet = world.getSingleton(Bet);
+      const score = world.getSingleton(Score);
+
+      score.chips -= bet.amount;
+
+      if (this.deckCount() < 15) {
+        const remaining = [...world.query(query(Card, InDeck))];
+        for (const e of remaining) {
+          world.remove(e, InDeck);
+        }
+        for (const e of remaining) {
+          world.add(e, InDeck);
+        }
+        this.shuffleDeck();
+      }
+
+      this.clearHand(InPlayerHand);
+      this.clearHand(InDealerHand);
+      world.removeSingleton(HoleHidden);
+
+      const c1 = this.drawCard();
+      const c2 = this.drawCard();
+      const c3 = this.drawCard();
+      const c4 = this.drawCard();
+      if (c1) this.dealTo(c1, InPlayerHand);
+      if (c2) this.dealTo(c2, InDealerHand);
+      if (c3) this.dealTo(c3, InPlayerHand);
+      if (c4) this.dealTo(c4, InDealerHand);
+
+      const playerCards = this.getHand(InPlayerHand);
+      const dealerCards = this.getHand(InDealerHand);
+
+      if (isBlackjack(playerCards)) {
+        world.removeSingleton(HoleHidden);
+
+        if (isBlackjack(dealerCards)) {
+          score.chips += bet.amount;
+          score.pushes++;
+          world.setSingleton(GamePhase, {
+            phase: "roundOver",
+            message: "Both have Blackjack — Push! Press N for new round.",
+          });
+        } else {
+          const winnings = payout("blackjack", bet.amount);
+          score.chips += bet.amount + winnings;
+          score.wins++;
+          world.setSingleton(GamePhase, {
+            phase: "roundOver",
+            message: "Blackjack! You win 3:2! Press N for new round.",
+          });
+        }
+      } else {
+        world.addSingleton(HoleHidden);
+        world.setSingleton(GamePhase, {
+          phase: "playerTurn",
+          message: "Your turn — H to hit, S to stand.",
+        });
+      }
+    },
+  };
+}
+
+// ── Internal ─────────────────────────────────────────
+
+function payout(outcome: string, bet: number): number {
+  switch (outcome) {
+    case "blackjack":
+      return Math.floor(bet * 1.5);
+    case "win":
+      return bet;
+    case "push":
+      return 0;
+    case "lose":
+      return -bet;
+    default:
+      return 0;
+  }
+}

examples/blackjack/game.ts

@@ -0,0 +1,104 @@
+// ── Blackjack game logic (pure functions, no ECS dependency) ──
+
+export const SUITS = ["♠", "♥", "♦", "♣"] as const;
+export const RANKS = [
+  "A",
+  "2",
+  "3",
+  "4",
+  "5",
+  "6",
+  "7",
+  "8",
+  "9",
+  "10",
+  "J",
+  "Q",
+  "K",
+] as const;
+
+export interface CardData {
+  rank: string;
+  suit: string;
+}
+
+// ── Hand evaluation ──────────────────────────────────
+/** Numeric value of a single card rank. */
+export function rankValue(rank: string): number {
+  if (rank === "A") return 11;
+  if (rank === "K" || rank === "Q" || rank === "J") return 10;
+  return parseInt(rank, 10);
+}
+
+/** Best total for a hand (aces count as 1 or 11). */
+export function handValue(cards: CardData[]): number {
+  let total = 0;
+  let aces = 0;
+  for (const c of cards) {
+    total += rankValue(c.rank);
+    if (c.rank === "A") aces++;
+  }
+  while (total > 21 && aces > 0) {
+    total -= 10;
+    aces--;
+  }
+  return total;
+}
+
+export function isBust(cards: CardData[]): boolean {
+  return handValue(cards) > 21;
+}
+
+export function isBlackjack(cards: CardData[]): boolean {
+  return cards.length === 2 && handValue(cards) === 21;
+}
+
+export function isSoft(cards: CardData[]): boolean {
+  let total = 0;
+  let aces = 0;
+  for (const c of cards) {
+    total += rankValue(c.rank);
+    if (c.rank === "A") aces++;
+  }
+  return aces > 0 && total <= 21;
+}
+
+// ── Dealer logic ─────────────────────────────────────
+/** Dealer must hit on soft 17 in this variant. */
+export function dealerShouldHit(cards: CardData[]): boolean {
+  const val = handValue(cards);
+  if (val < 17) return true;
+  if (val === 17 && isSoft(cards)) return true;
+  return false;
+}
+
+// ── Outcome ──────────────────────────────────────────
+export type Outcome = "win" | "lose" | "push" | "blackjack";
+
+export function determineOutcome(
+  playerCards: CardData[],
+  dealerCards: CardData[],
+): Outcome {
+  if (isBust(playerCards)) return "lose";
+  if (isBust(dealerCards)) return "win";
+  if (isBlackjack(playerCards) && !isBlackjack(dealerCards)) return "blackjack";
+  const pv = handValue(playerCards);
+  const dv = handValue(dealerCards);
+  if (pv > dv) return "win";
+  if (pv < dv) return "lose";
+  return "push";
+}
+
+/** Payout multiplier. Blackjack pays 3:2, win pays 1:1. */
+export function payout(outcome: Outcome, bet: number): number {
+  switch (outcome) {
+    case "blackjack":
+      return Math.floor(bet * 1.5);
+    case "win":
+      return bet;
+    case "push":
+      return 0;
+    case "lose":
+      return -bet;
+  }
+}

examples/blackjack/input.ts

@@ -0,0 +1,27 @@
+// ── Keyboard input via blessed ────────────────────────
+import type blessed from "blessed";
+
+export type Key =
+  | "h"
+  | "s"
+  | "n"
+  | "up"
+  | "down"
+  | "q";
+
+/** Wire blessed screen key events to a callback. */
+export function startInput(
+  screen: blessed.Widgets.Screen,
+  onKey: (key: Key) => void,
+): void {
+  screen.key(
+    ["h", "s", "n", "up", "down", "q", "C-c"],
+    (_ch, key) => {
+      if (key.name === "q" || key.name === "C-c") {
+        screen.destroy();
+        process.exit(0);
+      }
+      onKey(key.name as Key);
+    },
+  );
+}

examples/blackjack/main.ts

@@ -0,0 +1,141 @@
+// ── Blackjack: BT-driven game loop with command-based input ──
+//
+// Architecture:
+//   Behaviour Tree (buildTree) — controls game flow:
+//     parallel
+//       ├── dealerPlay (action)      — generator loop, auto-plays dealer hand
+//       └── cycle
+//             └── seq (sequential)
+//                   ├── handleInput (action)  — reads queued commands
+//                   └── render (action)       — draws via blessed
+//
+//   CommandQueue — processes input:
+//     Keyboard → spawn command entities → CommandQueue.execute()
+//     → handlers mutate game state
+//
+//   Cards as entities with tag components:
+//     Each card is an entity with a Card component ({ rank, suit, order }).
+//     Tag components (InDeck, InPlayerHand, InDealerHand) mark which
+//     collection the card belongs to. Queries find cards by tag.
+//     Order is tracked via the `order` field on Card.
+//
+// Usage:
+//   npx tsx examples/blackjack/main.ts
+
+import { World } from "../../src/index";
+import {
+  buildTree,
+  action,
+  parallel,
+  cycle,
+  sequential,
+  whilst,
+} from "../../src/bt/index";
+import { CommandQueue } from "../../src/commands/index";
+
+import {
+  Score,
+  Bet,
+  GamePhase,
+  InDealerHand,
+  createCardHelpers,
+} from "./components";
+
+import {
+  registerCommands,
+  resolveRound,
+  Hit,
+  Stand,
+  NewRound,
+  BetMore,
+  BetLess,
+} from "./commands";
+
+import { dealerShouldHit } from "./game";
+
+import { createUI, render } from "./render";
+import { startInput, type Key } from "./input";
+
+// ── Setup ────────────────────────────────────────────
+const world = new World();
+
+world.addSingleton(Score);
+world.addSingleton(Bet);
+world.addSingleton(GamePhase);
+
+const ui = createUI();
+const cards = createCardHelpers(world);
+const commands = new CommandQueue(world);
+
+registerCommands(world, commands, cards);
+
+// ── Behaviour Tree ───────────────────────────────────
+const runner = buildTree(
+  world,
+  parallel([
+    whilst(
+      () => true,
+      action(() => {
+        const phase = world.getSingleton(GamePhase);
+        if (phase.phase !== "dealerTurn") return;
+
+        if (dealerShouldHit(cards.getHand(InDealerHand))) {
+          const cardEntity = cards.drawCard();
+          if (cardEntity) {
+            cards.dealTo(cardEntity, InDealerHand);
+          }
+        } else {
+          resolveRound(world, cards);
+        }
+      }),
+    ),
+    cycle(
+      sequential([
+        action(() => {
+          commands.execute();
+        }),
+        action(() => {
+          render(world, ui);
+        }),
+      ]),
+    ),
+  ]),
+);
+
+// ── Input → Command mapping ──────────────────────────
+const keyToCommand: Partial<Record<Key, typeof Hit>> = {
+  h: Hit,
+  s: Stand,
+  n: NewRound,
+  up: BetMore,
+  down: BetLess,
+};
+
+startInput(ui.screen, (key) => {
+  const cmd = keyToCommand[key];
+  if (cmd) {
+    const cmdEntity = world.spawn();
+    world.add(cmdEntity, cmd);
+  }
+});
+
+// ── Game loop ────────────────────────────────────────
+world.setSingleton(GamePhase, {
+  phase: "betting",
+  message: "Welcome to Blackjack! Press N to start.",
+});
+
+cards.buildDeck();
+cards.shuffleDeck();
+runner.schedule((runner as any).root);
+
+const TICK_MS = 16;
+const interval = setInterval(() => {
+  runner.tick(TICK_MS);
+}, TICK_MS);
+
+process.on("SIGINT", () => {
+  clearInterval(interval);
+  ui.screen.destroy();
+  process.exit(0);
+});

examples/blackjack/render.ts

@@ -0,0 +1,173 @@
+// ── Terminal rendering via blessed ────────────────────
+import blessed from "blessed";
+import type { World } from "../../src/index";
+import { query } from "../../src/query";
+import {
+  Card,
+  InPlayerHand,
+  InDealerHand,
+  HoleHidden,
+  Score,
+  Bet,
+  GamePhase,
+} from "./components";
+import { handValue, isBust, isBlackjack } from "./game";
+
+const SUIT_SYMBOLS: Record<string, string> = {
+  "♠": "\x1b[37m♠\x1b[0m",
+  "♥": "\x1b[31m♥\x1b[0m",
+  "♦": "\x1b[31m♦\x1b[0m",
+  "♣": "\x1b[37m♣\x1b[0m",
+};
+
+export function createUI(): {
+  screen: blessed.Widgets.Screen;
+  dealerBox: blessed.Widgets.BoxElement;
+  playerBox: blessed.Widgets.BoxElement;
+  infoText: blessed.Widgets.TextElement;
+  controlsText: blessed.Widgets.TextElement;
+} {
+  const screen = blessed.screen({
+    smartCSR: true,
+    title: "Blackjack",
+  });
+
+  const dealerBox = blessed.box({
+    parent: screen,
+    top: 2,
+    left: "center",
+    width: 50,
+    height: 8,
+    border: { type: "line" },
+    label: " Dealer ",
+    style: { border: { fg: "white" } },
+  });
+
+  const playerBox = blessed.box({
+    parent: screen,
+    top: 12,
+    left: "center",
+    width: 50,
+    height: 8,
+    border: { type: "line" },
+    label: " Player ",
+    style: { border: { fg: "white" } },
+  });
+
+  const infoText = blessed.text({
+    parent: screen,
+    top: 22,
+    left: "center",
+    width: 50,
+    height: 5,
+    style: { fg: "white" },
+  });
+
+  const controlsText = blessed.text({
+    parent: screen,
+    bottom: 0,
+    left: "center",
+    width: 60,
+    height: 1,
+    style: { fg: "gray" },
+  });
+
+  return { screen, dealerBox, playerBox, infoText, controlsText };
+}
+
+function formatCard(rank: string, suit: string): string {
+  return `${rank}${SUIT_SYMBOLS[suit] ?? suit}`;
+}
+
+/** Collect cards from a hand tag, sorted by order. */
+function collectHand(
+  world: World,
+  tag: typeof InPlayerHand,
+): { rank: string; suit: string }[] {
+  return [...world.query(query(Card, tag))]
+    .map((e) => {
+      const c = world.get(e, Card);
+      return { rank: c.rank, suit: c.suit, order: c.order };
+    })
+    .sort((a, b) => a.order - b.order)
+    .map(({ rank, suit }) => ({ rank, suit }));
+}
+
+function formatHand(
+  cards: { rank: string; suit: string }[],
+  hideHole: boolean,
+): string {
+  if (cards.length === 0) return "  (empty)";
+
+  const lines: string[] = [];
+
+  if (hideHole && cards.length >= 2) {
+    lines.push(`  ${formatCard(cards[0].rank, cards[0].suit)}  ██`);
+    lines.push(`  Value: ${handValue([cards[0]])}`);
+  } else {
+    const cardStr = cards.map((c) => formatCard(c.rank, c.suit)).join("  ");
+    lines.push(`  ${cardStr}`);
+    const val = handValue(cards);
+    const extra = isBlackjack(cards)
+      ? " — BLACKJACK!"
+      : isBust(cards)
+        ? " — BUST!"
+        : "";
+    lines.push(`  Value: ${val}${extra}`);
+  }
+
+  return lines.join("\n");
+}
+
+/** Render the full game state into the blessed UI. */
+export function render(world: World, ui: ReturnType<typeof createUI>): void {
+  const score = world.tryGetSingleton(Score);
+  const bet = world.tryGetSingleton(Bet);
+  const phase = world.tryGetSingleton(GamePhase);
+  const holeHidden = world.hasSingleton(HoleHidden);
+
+  // Dealer
+  const dealerCards = collectHand(world, InDealerHand);
+  ui.dealerBox.setContent(formatHand(dealerCards, holeHidden));
+
+  // Player
+  const playerCards = collectHand(world, InPlayerHand);
+  ui.playerBox.setContent(formatHand(playerCards, false));
+
+  // Info
+  let info = "";
+  if (score) {
+    info += `Chips: ${score.chips}   Wins: ${score.wins}   Losses: ${score.losses}   Pushes: ${score.pushes}\n`;
+  }
+  if (bet) {
+    info += `Bet: ${bet.amount}\n`;
+  }
+  if (phase) {
+    info += `\n${phase.message}`;
+  }
+  ui.infoText.setContent(info);
+
+  // Dynamic controls based on phase
+  if (phase) {
+    switch (phase.phase) {
+      case "betting":
+        ui.controlsText.setContent(
+          "N : new round   ↑↓ : adjust bet   Q : quit",
+        );
+        break;
+      case "playerTurn":
+        ui.controlsText.setContent("H : hit   S : stand   Q : quit");
+        break;
+      case "dealerTurn":
+        ui.controlsText.setContent("Dealer is playing...");
+        break;
+      case "roundOver":
+        ui.controlsText.setContent(
+          "N : new round   ↑↓ : adjust bet   Q : quit",
+        );
+        break;
+    }
+  }
+
+  ui.screen.render();
+}

examples/tetris/commands.ts

@@ -1,4 +1,24 @@
 import { defineComponent } from "../../src/component";
+import type { World } from "../../src/index";
+import type { CommandQueue } from "../../src/commands/index";
+import {
+  Board,
+  Piece,
+  Score,
+  GameOver,
+  Paused,
+  TickTimer,
+  createPieceHelpers,
+} from "./components";
+import {
+  collides,
+  lockPiece,
+  clearLines,
+  scoreForLines,
+  tryRotate,
+} from "./game";
+
+// ── Command definitions ──────────────────────────────
 
 /** Move the active piece left. */
 export const MoveLeft = defineComponent("moveLeft", {});
@@ -20,3 +40,85 @@ export const TogglePause = defineComponent("togglePause", {});
 
 /** Restart after game over. */
 export const Restart = defineComponent("restart", {});
+
+// ── Command handlers ─────────────────────────────────
+
+export function registerCommands(
+  world: World,
+  commands: CommandQueue,
+  pieces: ReturnType<typeof createPieceHelpers>,
+): void {
+  const hasActivePiece = () => world.hasSingleton(Piece);
+  const isBlocked = () =>
+    world.hasSingleton(GameOver) || world.hasSingleton(Paused);
+
+  commands.handle(MoveLeft, () => {
+    if (!hasActivePiece() || isBlocked()) return;
+    const piece = world.getSingleton(Piece);
+    const board = world.getSingleton(Board);
+    if (!collides(board.grid, piece.shape, piece.x - 1, piece.y)) {
+      piece.x--;
+    }
+  });
+
+  commands.handle(MoveRight, () => {
+    if (!hasActivePiece() || isBlocked()) return;
+    const piece = world.getSingleton(Piece);
+    const board = world.getSingleton(Board);
+    if (!collides(board.grid, piece.shape, piece.x + 1, piece.y)) {
+      piece.x++;
+    }
+  });
+
+  commands.handle(Rotate, () => {
+    if (!hasActivePiece() || isBlocked()) return;
+    const piece = world.getSingleton(Piece);
+    const board = world.getSingleton(Board);
+    const result = tryRotate(board.grid, piece.shape, piece.x, piece.y);
+    if (result) {
+      piece.shape = result.shape;
+      piece.x = result.x;
+    }
+  });
+
+  commands.handle(SoftDrop, () => {
+    if (!hasActivePiece() || isBlocked()) return;
+    const piece = world.getSingleton(Piece);
+    const board = world.getSingleton(Board);
+    if (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
+      piece.y++;
+    }
+  });
+
+  commands.handle(HardDrop, () => {
+    if (!hasActivePiece() || isBlocked()) return;
+    const piece = world.getSingleton(Piece);
+    const board = world.getSingleton(Board);
+    while (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
+      piece.y++;
+    }
+    pieces.lockAndSpawn();
+  });
+
+  commands.handle(TogglePause, () => {
+    if (world.hasSingleton(GameOver)) return;
+    if (world.hasSingleton(Paused)) {
+      world.removeSingleton(Paused);
+    } else {
+      world.addSingleton(Paused);
+    }
+  });
+
+  commands.handle(Restart, () => {
+    if (!world.hasSingleton(GameOver)) return;
+    const board = world.getSingleton(Board);
+    for (let r = 0; r < board.grid.length; r++) {
+      board.grid[r].fill(0);
+    }
+    world.setSingleton(Score, { points: 0, lines: 0, level: 1 });
+    world.setSingleton(TickTimer, { accumulator: 0, interval: 800 });
+    world.removeSingleton(GameOver);
+    if (world.hasSingleton(Piece)) world.removeSingleton(Piece);
+    pieces.spawnPiece();
+  });
+}

examples/tetris/components.ts

@@ -1,6 +1,16 @@
 import { defineComponent } from "../../src/component";
+import type { World } from "../../src/index";
+import {
+  randomPiece,
+  collides,
+  lockPiece,
+  clearLines,
+  scoreForLines,
+  BOARD_W,
+} from "./game";
+
+// ── Component definitions ────────────────────────────
 
-// ── Board ────────────────────────────────────────────
 /** The playfield grid (20 rows × 10 cols). 0 = empty, non-zero = color index. */
 export const Board = defineComponent("board", {
   grid: Array.from({ length: 20 }, () => new Uint8Array(10)) as Uint8Array[],
@@ -29,3 +39,45 @@ export const TickTimer = defineComponent("tickTimer", {
   accumulator: 0,
   interval: 800, // ms between gravity ticks
 });
+
+// ── Piece helpers ────────────────────────────────────
+
+export function createPieceHelpers(world: World) {
+  return {
+    spawnPiece(): void {
+      const p = randomPiece();
+      world.addSingleton(Piece, {
+        shape: p.shape,
+        color: p.color,
+        x: Math.floor((BOARD_W - p.shape[0].length) / 2),
+        y: 0,
+      });
+    },
+
+    lockAndSpawn(): void {
+      const piece = world.getSingleton(Piece);
+      const board = world.getSingleton(Board);
+
+      lockPiece(board.grid, piece.shape, piece.color, piece.x, piece.y);
+      world.removeSingleton(Piece);
+
+      const cleared = clearLines(board.grid);
+      if (cleared > 0) {
+        const score = world.getSingleton(Score);
+        score.lines += cleared;
+        score.points += scoreForLines(cleared, score.level);
+        score.level = Math.floor(score.lines / 10) + 1;
+        const timer = world.getSingleton(TickTimer);
+        timer.interval = Math.max(100, 800 - (score.level - 1) * 70);
+      }
+
+      this.spawnPiece();
+
+      const newPiece = world.getSingleton(Piece);
+      if (collides(board.grid, newPiece.shape, newPiece.x, newPiece.y)) {
+        world.removeSingleton(Piece);
+        world.addSingleton(GameOver);
+      }
+    },
+  };
+}

examples/tetris/main.ts

@@ -1,26 +1,47 @@
 // ── Tetris: BT-driven game loop with command-based input ──
 //
 // Architecture:
-//   Behaviour Tree (TaskRunner) — controls game flow:
-//     root (sequential, repeat)
-//       ├── handleInput (leaf)     — reads queued commands, mutates state
-//       ├── gravityTick (leaf)     — auto-drop piece on timer
-//       └── render (leaf)          — draws via blessed
+//   Behaviour Tree (buildTree) — controls game flow:
+//     parallel
+//       ├── gravityTick (action)    — generator loop, auto-drop piece on timer
+//       └── cycle
+//             └── seq (sequential)
+//                   ├── handleInput (action)  — reads queued commands
+//                   └── render (action)       — draws via blessed
 //
 //   CommandQueue — processes input:
 //     Keyboard → spawn command entities → CommandQueue.execute()
 //     → handlers mutate game state
 //
+//   Singleton components — global state accessed via world.*Singleton():
+//     Board, Piece, Score, GameOver, Paused, TickTimer
+//
 // Usage:
 //   npx tsx examples/tetris/main.ts
 
 import { World } from "../../src/index";
-import { TaskRunner, Task, ChildOf } from "../../src/bt/index";
+import {
+  buildTree,
+  action,
+  parallel,
+  cycle,
+  sequential,
+  whilst,
+} from "../../src/bt/index";
 import { CommandQueue } from "../../src/commands/index";
 
-import { Board, Piece, Score, GameOver, Paused, TickTimer } from "./components";
+import {
+  Board,
+  Piece,
+  Score,
+  GameOver,
+  Paused,
+  TickTimer,
+  createPieceHelpers,
+} from "./components";
 
 import {
+  registerCommands,
   MoveLeft,
   MoveRight,
   Rotate,
@@ -30,15 +51,7 @@ import {
   Restart,
 } from "./commands";
 
-import {
-  randomPiece,
-  collides,
-  lockPiece,
-  clearLines,
-  scoreForLines,
-  tryRotate,
-  BOARD_W,
-} from "./game";
+import { collides } from "./game";
 
 import { createUI, render } from "./render";
 import { startInput, type Key } from "./input";
@@ -46,203 +59,55 @@ import { startInput, type Key } from "./input";
 // ── Setup ────────────────────────────────────────────
 const world = new World();
 
-// Create the singleton game entity
-const game = world.spawn();
-world.add(game, Board);
-world.add(game, Score);
-world.add(game, TickTimer);
+world.addSingleton(Board);
+world.addSingleton(Score);
+world.addSingleton(TickTimer);
 
-// Create blessed UI
 const ui = createUI();
-
-// Spawn the first piece
-spawnPiece();
-
-// ── Command handlers ─────────────────────────────────
+const pieces = createPieceHelpers(world);
 const commands = new CommandQueue(world);
 
-function spawnPiece(): void {
-  const p = randomPiece();
-  world.add(game, Piece, {
-    shape: p.shape,
-    color: p.color,
-    x: Math.floor((BOARD_W - p.shape[0].length) / 2),
-    y: 0,
-  });
-}
-
-function hasActivePiece(): boolean {
-  return world.has(game, Piece);
-}
-
-// Move left
-commands.handle(MoveLeft, () => {
-  if (!hasActivePiece() || world.has(game, GameOver) || world.has(game, Paused))
-    return;
-  const piece = world.get(game, Piece);
-  const board = world.get(game, Board);
-  if (!collides(board.grid, piece.shape, piece.x - 1, piece.y)) {
-    piece.x--;
-  }
-});
-
-// Move right
-commands.handle(MoveRight, () => {
-  if (!hasActivePiece() || world.has(game, GameOver) || world.has(game, Paused))
-    return;
-  const piece = world.get(game, Piece);
-  const board = world.get(game, Board);
-  if (!collides(board.grid, piece.shape, piece.x + 1, piece.y)) {
-    piece.x++;
-  }
-});
-
-// Rotate
-commands.handle(Rotate, () => {
-  if (!hasActivePiece() || world.has(game, GameOver) || world.has(game, Paused))
-    return;
-  const piece = world.get(game, Piece);
-  const board = world.get(game, Board);
-  const result = tryRotate(board.grid, piece.shape, piece.x, piece.y);
-  if (result) {
-    piece.shape = result.shape;
-    piece.x = result.x;
-  }
-});
-
-// Soft drop
-commands.handle(SoftDrop, () => {
-  if (!hasActivePiece() || world.has(game, GameOver) || world.has(game, Paused))
-    return;
-  const piece = world.get(game, Piece);
-  const board = world.get(game, Board);
-  if (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
-    piece.y++;
-  }
-});
-
-// Hard drop
-commands.handle(HardDrop, () => {
-  if (!hasActivePiece() || world.has(game, GameOver) || world.has(game, Paused))
-    return;
-  const piece = world.get(game, Piece);
-  const board = world.get(game, Board);
-  while (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
-    piece.y++;
-  }
-  lockAndSpawn();
-});
-
-// Toggle pause
-commands.handle(TogglePause, () => {
-  if (world.has(game, GameOver)) return;
-  if (world.has(game, Paused)) {
-    world.remove(game, Paused);
-  } else {
-    world.add(game, Paused);
-  }
-});
-
-// Restart
-commands.handle(Restart, () => {
-  if (!world.has(game, GameOver)) return;
-  const board = world.get(game, Board);
-  for (let r = 0; r < board.grid.length; r++) {
-    board.grid[r].fill(0);
-  }
-  world.set(game, Score, { points: 0, lines: 0, level: 1 });
-  world.set(game, TickTimer, { accumulator: 0, interval: 800 });
-  world.remove(game, GameOver);
-  if (world.has(game, Piece)) world.remove(game, Piece);
-  spawnPiece();
-});
-
-// ── Lock piece & spawn next ──────────────────────────
-function lockAndSpawn(): void {
-  const piece = world.get(game, Piece);
-  const board = world.get(game, Board);
-
-  lockPiece(board.grid, piece.shape, piece.color, piece.x, piece.y);
-  world.remove(game, Piece);
-
-  const cleared = clearLines(board.grid);
-  if (cleared > 0) {
-    const score = world.get(game, Score);
-    score.lines += cleared;
-    score.points += scoreForLines(cleared, score.level);
-    score.level = Math.floor(score.lines / 10) + 1;
-    const timer = world.get(game, TickTimer);
-    timer.interval = Math.max(100, 800 - (score.level - 1) * 70);
-  }
-
-  spawnPiece();
-
-  const newPiece = world.get(game, Piece);
-  if (collides(board.grid, newPiece.shape, newPiece.x, newPiece.y)) {
-    world.remove(game, Piece);
-    world.add(game, GameOver);
-  }
-}
+registerCommands(world, commands, pieces);
+pieces.spawnPiece();
 
 // ── Behaviour Tree ───────────────────────────────────
-const runner = new TaskRunner(world);
-
-// Build the BT structure:
-//   root (repeat)
-//     └── seq (sequential)
-//           ├── handleInput (leaf)
-//           ├── gravityTick (leaf)
-//           └── render (leaf)
-
-const root = world.spawn();
-world.add(root, Task, { kind: "repeat" });
-
-const seq = world.spawn();
-world.add(seq, Task, { kind: "sequential" });
-world.relate(seq, ChildOf, root);
-
-const handleInputTask = world.spawn();
-world.add(handleInputTask, Task, { kind: "leaf" });
-world.relate(handleInputTask, ChildOf, seq);
-
-const gravityTask = world.spawn();
-world.add(gravityTask, Task, { kind: "leaf" });
-world.relate(gravityTask, ChildOf, seq);
-
-const renderTask = world.spawn();
-world.add(renderTask, Task, { kind: "leaf" });
-world.relate(renderTask, ChildOf, seq);
-
-// ── Leaf handlers ────────────────────────────────────
-runner.onLeaf = (_w, entity) => {
-  if (entity === handleInputTask) {
-    commands.execute();
-    runner.succeed(entity);
-  } else if (entity === gravityTask) {
-    if (world.has(game, GameOver) || world.has(game, Paused)) {
-      runner.succeed(entity);
-      return;
-    }
-    const timer = world.get(game, TickTimer);
-    timer.accumulator += 16;
-    if (timer.accumulator >= timer.interval) {
-      timer.accumulator -= timer.interval;
-      if (hasActivePiece()) {
-        const piece = world.get(game, Piece);
-        const board = world.get(game, Board);
-        if (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
-          piece.y++;
-        } else {
-          lockAndSpawn();
+const runner = buildTree(
+  world,
+  parallel([
+    whilst(
+      () => true,
+      action((_world, _entity, dt) => {
+        if (world.hasSingleton(GameOver) || world.hasSingleton(Paused)) {
+          return;
         }
-      }
-    }
-    runner.succeed(entity);
-  } else if (entity === renderTask) {
-    render(world, game, ui);
-    runner.succeed(entity);
-  }
-};
+        const timer = world.getSingleton(TickTimer);
+        timer.accumulator += dt;
+        if (timer.accumulator >= timer.interval) {
+          timer.accumulator -= timer.interval;
+          if (world.hasSingleton(Piece)) {
+            const piece = world.getSingleton(Piece);
+            const board = world.getSingleton(Board);
+            if (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
+              piece.y++;
+            } else {
+              pieces.lockAndSpawn();
+            }
+          }
+        }
+      }),
+    ),
+    cycle(
+      sequential([
+        action(() => {
+          commands.execute();
+        }),
+        action(() => {
+          render(world, ui);
+        }),
+      ]),
+    ),
+  ]),
+);
 
 // ── Input → Command mapping ──────────────────────────
 const keyToCommand: Partial<Record<Key, typeof MoveLeft>> = {
@@ -264,14 +129,13 @@ startInput(ui.screen, (key) => {
 });
 
 // ── Game loop ────────────────────────────────────────
-runner.schedule(root);
+runner.schedule((runner as any).root);
 
 const TICK_MS = 16;
 const interval = setInterval(() => {
-  runner.tick();
+  runner.tick(TICK_MS);
 }, TICK_MS);
 
-// Cleanup on exit
 process.on("SIGINT", () => {
   clearInterval(interval);
   ui.screen.destroy();

examples/tetris/render.ts

@@ -1,6 +1,6 @@
 // ── Terminal rendering via blessed ────────────────────
 import blessed from "blessed";
-import type { World, Entity } from "../../src/index";
+import type { World } from "../../src/index";
 import { Board, Piece, Score, GameOver, Paused } from "./components";
 import { BOARD_W, BOARD_H, ghostY } from "./game";
 
@@ -91,16 +91,12 @@ export function createUI(): {
 }
 
 /** Render the full game state into the blessed UI. */
-export function render(
-  world: World,
-  gameEntity: Entity,
-  ui: ReturnType<typeof createUI>,
-): void {
-  const board = world.get(gameEntity, Board);
-  const piece = world.tryGet(gameEntity, Piece);
-  const score = world.tryGet(gameEntity, Score);
-  const isOver = world.has(gameEntity, GameOver);
-  const isPaused = world.has(gameEntity, Paused);
+export function render(world: World, ui: ReturnType<typeof createUI>): void {
+  const board = world.getSingleton(Board);
+  const piece = world.tryGetSingleton(Piece);
+  const score = world.tryGetSingleton(Score);
+  const isOver = world.hasSingleton(GameOver);
+  const isPaused = world.hasSingleton(Paused);
 
   // Build display grid
   const display = board.grid.map((row) => [...row]);

examples/three-monks/components.ts

@@ -0,0 +1,219 @@
+import { defineComponent } from "../../src/component";
+import type { Entity, World } from "../../src/index";
+import { query } from "../../src/query";
+
+export type ActionKind = "fetchWater" | "exchange" | "drink" | "chant" | "rest";
+export type ActionZone = "hand" | "selected" | "cooldown";
+
+export type ToolKind =
+  | "woodenFish"
+  | "bucket"
+  | "bottle"
+  | "woodenBucket"
+  | "bigBowl"
+  | "bigBucket"
+  | "mouse"
+  | "shoulderPole"
+  | "waterJar"
+  | "ladle";
+
+export type Phase = "setup" | "selecting" | "resolving" | "gameOver";
+
+export const ACTION_KINDS: readonly ActionKind[] = [
+  "fetchWater",
+  "exchange",
+  "drink",
+  "chant",
+  "rest",
+] as const;
+
+export const TOOL_KINDS: readonly ToolKind[] = [
+  "woodenFish",
+  "bucket",
+  "bottle",
+  "woodenBucket",
+  "bigBowl",
+  "bigBucket",
+  "mouse",
+  "shoulderPole",
+  "waterJar",
+  "ladle",
+] as const;
+
+export const CARRYING_TOOLS = new Set<ToolKind>([
+  "bucket",
+  "woodenBucket",
+  "bigBucket",
+  "shoulderPole",
+  "ladle",
+]);
+
+export const Player = defineComponent("threeMonks.player", {
+  seat: 0,
+  name: "",
+  water: 0,
+});
+
+export const ActionCard = defineComponent("threeMonks.actionCard", {
+  owner: 0 as Entity,
+  kind: "rest" as ActionKind,
+  zone: "hand" as ActionZone,
+});
+
+export const Tool = defineComponent("threeMonks.tool", {
+  owner: 0 as Entity,
+  kind: "bucket" as ToolKind,
+  water: 0,
+});
+
+export const Table = defineComponent("threeMonks.table", {
+  centralWater: 0,
+  round: 1,
+});
+
+export const WoodenFishMarker = defineComponent("threeMonks.woodenFishMarker", {
+  holder: 0 as Entity,
+});
+
+export const GameState = defineComponent("threeMonks.gameState", {
+  phase: "setup" as Phase,
+  winner: 0 as Entity | 0,
+  message: "",
+});
+
+export type RandomFn = () => number;
+
+export function setupGame(
+  world: World,
+  playerNames: readonly string[],
+  random: RandomFn = Math.random,
+): Entity[] {
+  if (playerNames.length < 3 || playerNames.length > 8) {
+    throw new Error("Three Monks requires 3-8 players");
+  }
+
+  const players: Entity[] = [];
+  for (let seat = 0; seat < playerNames.length; seat++) {
+    const player = world.spawn();
+    world.add(player, Player, { seat, name: playerNames[seat], water: 2 });
+    players.push(player);
+
+    for (const kind of ACTION_KINDS) {
+      const card = world.spawn();
+      world.add(card, ActionCard, { owner: player, kind, zone: "hand" });
+    }
+  }
+
+  const tools = dealBalancedTools(players.length, random);
+  for (let i = 0; i < players.length; i++) {
+    const tool = world.spawn();
+    world.add(tool, Tool, { owner: players[i], kind: tools[i], water: 0 });
+  }
+
+  const holder = players[Math.floor(random() * players.length)];
+  world.addSingleton(Table, { centralWater: 0, round: 1 });
+  world.addSingleton(WoodenFishMarker, { holder });
+  world.addSingleton(GameState, {
+    phase: "selecting",
+    winner: 0,
+    message: "Choose an action card.",
+  });
+
+  return players;
+}
+
+export function getPlayersInSeatOrder(world: World): Entity[] {
+  return [...world.query(query(Player))].sort(
+    (a, b) => world.get(a, Player).seat - world.get(b, Player).seat,
+  );
+}
+
+export function getPlayersFromMarker(world: World): Entity[] {
+  const players = getPlayersInSeatOrder(world);
+  if (players.length === 0) return [];
+
+  const holder = world.getSingleton(WoodenFishMarker).holder;
+  const index = Math.max(0, players.indexOf(holder));
+  return [...players.slice(index), ...players.slice(0, index)];
+}
+
+export function getLeftPlayer(world: World, player: Entity): Entity {
+  const players = getPlayersInSeatOrder(world);
+  const index = players.indexOf(player);
+  if (index < 0) throw new Error("Player is not seated");
+  return players[(index + 1) % players.length];
+}
+
+export function getRightPlayer(world: World, player: Entity): Entity {
+  const players = getPlayersInSeatOrder(world);
+  const index = players.indexOf(player);
+  if (index < 0) throw new Error("Player is not seated");
+  return players[(index - 1 + players.length) % players.length];
+}
+
+export function getToolOf(world: World, player: Entity): Entity {
+  for (const tool of world.query(query(Tool))) {
+    if (world.get(tool, Tool).owner === player) return tool;
+  }
+  throw new Error("Player does not have a tool");
+}
+
+export function getActionCard(
+  world: World,
+  player: Entity,
+  kind: ActionKind,
+): Entity | null {
+  for (const card of world.query(query(ActionCard))) {
+    const data = world.get(card, ActionCard);
+    if (data.owner === player && data.kind === kind) return card;
+  }
+  return null;
+}
+
+export function getSelectedAction(
+  world: World,
+  player: Entity,
+): ActionKind | null {
+  for (const card of world.query(query(ActionCard))) {
+    const data = world.get(card, ActionCard);
+    if (data.owner === player && data.zone === "selected") return data.kind;
+  }
+  return null;
+}
+
+export function allPlayersSelected(world: World): boolean {
+  return getPlayersInSeatOrder(world).every(
+    (player) => getSelectedAction(world, player) !== null,
+  );
+}
+
+export function hasWinner(world: World): boolean {
+  return world.getSingleton(GameState).winner !== 0;
+}
+
+function dealBalancedTools(playerCount: number, random: RandomFn): ToolKind[] {
+  const carrying = shuffle(
+    TOOL_KINDS.filter((kind) => CARRYING_TOOLS.has(kind)),
+    random,
+  );
+  const nonCarrying = shuffle(
+    TOOL_KINDS.filter((kind) => !CARRYING_TOOLS.has(kind)),
+    random,
+  );
+
+  const carryingCount = Math.ceil(playerCount / 2);
+  const tools = [
+    ...carrying.slice(0, carryingCount),
+    ...nonCarrying.slice(0, playerCount - carryingCount),
+  ];
+
+  return shuffle(tools, random);
+}
+
+function shuffle<T>(items: T[], random: RandomFn): T[] {
+  for (let i = items.length - 1; i > 0; i--) {
+    const j = Math.floor(random() * (i + 1));
+    [items[i], items[j]] = [items[j], items[i]];
+  }
+  return items;
+}

examples/three-monks/design.md

@@ -0,0 +1,78 @@
+# 三个和尚
+
+三个和尚是 3-8 人进行的卡牌游戏。
+
+玩家在游戏中扮演挑水生活的和尚。但是挑水的人越多，挑到的水却越少。
+
+首先喝到 10 口水的玩家赢得游戏胜利。
+
+## 游戏流程
+
+游戏按轮进行。
+
+每轮游戏进行以下阶段：
+- 出牌阶段：每名玩家各选择一张手牌扣下，同时翻开。将上一轮打出的牌收回手牌。
+- 行动阶段：依次进行有玩家提议进行的行动阶段。
+  - 念经阶段：
+    - 参与玩家：提议念经的玩家。
+    - 将木鱼标记交给最后一名念经的玩家。
+  - 挑水阶段：
+    - 参与玩家：持有挑水道具，且没有休息的玩家。
+    - 每名参与玩家将 2 个自己的水标记放在挑水道具上；若水不足，则不放。
+    - 从供应堆拿取玩家人数减去参与玩家数的水标记，放入桌面中央。
+  - 交换阶段：
+    - 参与玩家：没有提议念经的玩家。
+    - 每名参与玩家将自己的道具交换给左侧参与玩家。
+    - 道具上的水标记一同交换。
+  - 喝水阶段：
+    - 参与玩家：所有玩家。
+    - 每名参与玩家依次从桌面中央获得 1 个水标记。
+    - 喝水时，可以从自己面前的道具上获得最多 2 个水标记。
+
+游戏开始时，每名玩家获得 2 个水标记，然后随机挑选一名玩家获得木鱼标记。
+
+所有的结算从持有木鱼标记的玩家开始顺时针依次进行。
+
+## 规则细化
+
+- 行动阶段按固定顺序结算：念经 → 挑水 → 交换 → 喝水。只要任意玩家提议某阶段，该阶段本轮会结算一次。
+- 出牌时，上一轮打出的行动牌本轮不可选择；所有玩家完成本轮选择后，上一轮行动牌回到手牌，本轮行动牌成为下一轮不可选择的牌。
+- 游戏开始时洗混 10 张道具牌，每名玩家随机获得 1 张；未使用的道具牌不进入本局。发给玩家的道具牌中，挑水道具始终占一半；玩家人数为奇数时，挑水道具数量向上取整。
+- 喝水阶段中，玩家按木鱼标记开始的顺时针顺序逐个结算。玩家喝水后若达到 10 口水，立即获胜；若多人同阶段可能达到 10，结算顺序靠前者先胜利。
+- 木鱼道具在一轮结束时将木鱼标记交给其拥有者，会覆盖本轮念经阶段得到的木鱼标记。
+- 挑水时，水从参与玩家已喝到的水移动到其挑水道具上；若玩家的水不足以支付需要放置的数量，则本次不移动水，因此该玩家和其道具上的水总量不变。
+- 净瓶的水来自供应堆。
+- 老鼠在念经时总共移动 1 个水标记：从左右相邻玩家任一有水的道具上移动 1 个水到老鼠上。
+- 大碗在其拥有者喝水时，若本次没有从大碗上喝到水，则可从桌面中央将 1 个水标记放到大碗上。
+- 水缸拥有者只有自己提议喝水时才参与喝水阶段；参与时从供应堆额外获得 1 口水。
+
+## 游戏配件
+
+玩家配件（8 组）
+- 5x 行动牌：
+  - 提议挑水/交换/喝水/念经：若有任何玩家打出，本轮会进行此阶段。
+  - 休息：不参与挑水阶段。
+
+公共配件：
+- 若干水标记物
+- 木鱼标记
+- 10x 道具牌
+  - 木鱼：一轮结束时，获得木鱼标记。
+  - 水桶：挑水道具。挑水时只需将 1 个自己的水放在桶里。
+  - 净瓶：念经时，在净瓶上放一个水标记。
+  - 木桶：挑水道具。若有其他玩家参与挑水，无需将水放在桶里。
+  - 大碗：喝水时若未从大碗里喝到水，可从桌面中央将 1 个水标记放在大碗上。
+  - 大桶：挑水道具。喝水时可从桶里喝任意口水。
+  - 老鼠：念经时，可从两侧玩家的道具上将一个水移动到老鼠上。
+  - 扁担：挑水道具。被交换时，将扁担上的水放回桌面中央。
+  - 水缸：喝水时从供应堆额外获得一口水。必须自己提议喝水才能参与喝水。
+  - 水瓢：挑水道具。挑水后，从中央将一个水放在瓢里。
+
+## 设计实现
+
+- `components.ts`: 游戏数据与状态
+- `gameflow.ts`: 规则流程行为树
+- `rules.ts`: 规则引擎（阶段包装器 + 核心结算函数）
+- `logging.ts`: 日志输出
+- `simulate.ts`: 对局模拟与统计
+- `random-playthrough.ts`: 单局详细回放

examples/three-monks/gameflow.ts

@@ -0,0 +1,71 @@
+import type { World } from "../../src/index";
+import {
+  action,
+  buildTree,
+  sequential,
+  wait,
+  whilst,
+  type TaskControl,
+  type TaskRunner,
+} from "../../src/bt/index";
+import { allPlayersSelected, hasWinner } from "./components";
+import {
+  beginSelectionPhase,
+  chantPhase,
+  exchangePhase,
+  fetchWaterPhase,
+  drinkPhase,
+  endOfRoundPhase,
+  prepareNextRound,
+} from "./rules";
+
+export interface ThreeMonksFlow {
+  runner: TaskRunner;
+  start(): void;
+  notifySelectionChanged(): void;
+}
+
+export function createThreeMonksFlow(world: World): ThreeMonksFlow {
+  let selectionControl: TaskControl | null = null;
+
+  const completeSelectionIfReady = () => {
+    if (selectionControl && allPlayersSelected(world)) {
+      const control = selectionControl;
+      selectionControl = null;
+      control.succeed();
+    }
+  };
+
+  const runner = buildTree(
+    world,
+    whilst(
+      (world) => !hasWinner(world),
+      sequential([
+        action((world) => beginSelectionPhase(world)),
+        wait((world, _entity, control) => {
+          selectionControl = control;
+          if (allPlayersSelected(world)) {
+            selectionControl = null;
+            control.succeed();
+          }
+        }),
+        action((world) => chantPhase(world)),
+        action((world) => fetchWaterPhase(world)),
+        action((world) => exchangePhase(world)),
+        action((world) => drinkPhase(world)),
+        action((world) => endOfRoundPhase(world)),
+        action((world) => prepareNextRound(world)),
+      ]),
+    ),
+  );
+
+  return {
+    runner,
+    start() {
+      runner.schedule(runner.root!);
+    },
+    notifySelectionChanged() {
+      completeSelectionIfReady();
+    },
+  };
+}

examples/three-monks/logging.ts

@@ -0,0 +1,208 @@
+import { query, type Entity, type World } from "../../src/index";
+import {
+  ActionCard,
+  GameState,
+  Player,
+  Table,
+  Tool,
+  WoodenFishMarker,
+  getPlayersInSeatOrder,
+  getSelectedAction,
+  getToolOf,
+  type ActionKind,
+  type ToolKind,
+} from "./components";
+import type { RoundProposals } from "./rules";
+
+export const ACTION_LABELS: Record<ActionKind, string> = {
+  fetchWater: "挑水",
+  exchange: "交换",
+  drink: "喝水",
+  chant: "念经",
+  rest: "休息",
+};
+
+export const TOOL_LABELS: Record<ToolKind, string> = {
+  woodenFish: "木鱼",
+  bucket: "水桶",
+  bottle: "净瓶",
+  woodenBucket: "木桶",
+  bigBowl: "大碗",
+  bigBucket: "大桶",
+  mouse: "老鼠",
+  shoulderPole: "扁担",
+  waterJar: "水缸",
+  ladle: "水瓢",
+};
+
+export interface PlayerSnapshot {
+  entity: Entity;
+  name: string;
+  seat: number;
+  water: number;
+  action: ActionKind | null;
+  tool: ToolKind;
+  toolWater: number;
+  hasMarker: boolean;
+}
+
+export interface GameSnapshot {
+  round: number;
+  centralWater: number;
+  phase: string;
+  winner: Entity | 0;
+  players: PlayerSnapshot[];
+}
+
+export class GameLog {
+  private readonly lines: string[] = [];
+
+  add(line = ""): void {
+    this.lines.push(line);
+  }
+
+  section(title: string): void {
+    if (this.lines.length > 0) this.lines.push("");
+    this.lines.push(title);
+  }
+
+  entries(): readonly string[] {
+    return this.lines;
+  }
+
+  toString(): string {
+    return this.lines.join("\n");
+  }
+}
+
+export function snapshotGame(world: World): GameSnapshot {
+  const table = world.getSingleton(Table);
+  const marker = world.getSingleton(WoodenFishMarker).holder;
+  const state = world.getSingleton(GameState);
+
+  return {
+    round: table.round,
+    centralWater: table.centralWater,
+    phase: state.phase,
+    winner: state.winner,
+    players: getPlayersInSeatOrder(world).map((player) => {
+      const playerData = world.get(player, Player);
+      const toolData = world.get(getToolOf(world, player), Tool);
+      return {
+        entity: player,
+        name: playerData.name,
+        seat: playerData.seat,
+        water: playerData.water,
+        action: getSelectedAction(world, player),
+        tool: toolData.kind,
+        toolWater: toolData.water,
+        hasMarker: player === marker,
+      };
+    }),
+  };
+}
+
+export function formatSnapshot(snapshot: GameSnapshot): string[] {
+  return [
+    `第 ${snapshot.round} 轮 | 中央水=${snapshot.centralWater} | 阶段=${formatPhase(snapshot.phase)}`,
+    ...snapshot.players.map(formatPlayerSnapshot),
+  ];
+}
+
+export function formatPlayerSnapshot(player: PlayerSnapshot): string {
+  const marker = player.hasMarker ? " 🪵" : "";
+  const action = player.action ? ` | 行动=${ACTION_LABELS[player.action]}` : "";
+  return `${player.name}${marker}: 已喝=${player.water}, 道具=${TOOL_LABELS[player.tool]}(${player.toolWater})${action}`;
+}
+
+export function formatProposals(proposals: RoundProposals): string {
+  const phases: string[] = [];
+  if (proposals.chant) phases.push("念经");
+  if (proposals.fetchWater) phases.push("挑水");
+  if (proposals.exchange) phases.push("交换");
+  if (proposals.drink) phases.push("喝水");
+  return phases.length > 0 ? phases.join(" → ") : "无行动阶段";
+}
+
+export function formatAvailableActions(world: World, player: Entity): string {
+  const actions: ActionKind[] = [];
+  for (const card of world.query(query(ActionCard))) {
+    const data = world.get(card, ActionCard);
+    if (data.owner === player && data.zone === "hand") actions.push(data.kind);
+  }
+  return actions.map((action) => ACTION_LABELS[action]).join("、");
+}
+
+export function logSnapshot(log: GameLog, world: World): void {
+  for (const line of formatSnapshot(snapshotGame(world))) {
+    log.add(line);
+  }
+}
+
+export function logPhaseDelta(
+  log: GameLog,
+  label: string,
+  before: GameSnapshot,
+  after: GameSnapshot,
+): void {
+  const changes: string[] = [];
+
+  if (before.centralWater !== after.centralWater) {
+    changes.push(`中央水 ${before.centralWater}→${after.centralWater}`);
+  }
+
+  for (const beforePlayer of before.players) {
+    const afterPlayer = after.players.find(
+      (p) => p.entity === beforePlayer.entity,
+    )!;
+    const playerChanges: string[] = [];
+
+    if (beforePlayer.water !== afterPlayer.water) {
+      playerChanges.push(`已喝 ${beforePlayer.water}→${afterPlayer.water}`);
+    }
+    if (
+      beforePlayer.tool !== afterPlayer.tool ||
+      beforePlayer.toolWater !== afterPlayer.toolWater
+    ) {
+      playerChanges.push(
+        `道具 ${TOOL_LABELS[beforePlayer.tool]}(${beforePlayer.toolWater})→${TOOL_LABELS[afterPlayer.tool]}(${afterPlayer.toolWater})`,
+      );
+    }
+    if (beforePlayer.hasMarker !== afterPlayer.hasMarker) {
+      playerChanges.push(
+        afterPlayer.hasMarker ? "获得木鱼标记" : "失去木鱼标记",
+      );
+    }
+
+    if (playerChanges.length > 0) {
+      changes.push(`${afterPlayer.name}: ${playerChanges.join("，")}`);
+    }
+  }
+
+  if (changes.length === 0) {
+    log.add(`  ${label}: 无变化`);
+  } else {
+    log.add(`  ${label}: ${changes.join("；")}`);
+  }
+}
+
+export function formatPhase(phase: string): string {
+  switch (phase) {
+    case "setup":
+      return "设置";
+    case "selecting":
+      return "出牌";
+    case "resolving":
+      return "结算";
+    case "gameOver":
+      return "游戏结束";
+    default:
+      return phase;
+  }
+}
+
+export function winnerName(world: World): string | null {
+  const winner = world.getSingleton(GameState).winner;
+  if (winner === 0) return null;
+  return world.get(winner, Player).name;
+}

examples/three-monks/random-playthrough.log

@@ -0,0 +1,235 @@
+三个和尚随机对局（种子=20260701）
+玩家：慧空、明心、了尘、净远
+初始状态：
+第 1 轮 | 中央水=0 | 阶段=出牌
+慧空: 已喝=2, 道具=老鼠(0)
+明心: 已喝=2, 道具=水瓢(0)
+了尘: 已喝=2, 道具=木桶(0)
+净远 🪵: 已喝=2, 道具=水缸(0)
+
+第 1 轮
+  慧空 选择 挑水（可选：挑水、交换、喝水、念经、休息）
+  明心 选择 休息（可选：挑水、交换、喝水、念经、休息）
+  了尘 选择 交换（可选：挑水、交换、喝水、念经、休息）
+  净远 选择 喝水（可选：挑水、交换、喝水、念经、休息）
+  本轮行动阶段：挑水 → 交换 → 喝水
+  挑水: 中央水 0→3；了尘: 已喝 2→0，道具 木桶(0)→木桶(2)
+  交换: 慧空: 道具 老鼠(0)→水缸(0)；明心: 道具 水瓢(0)→老鼠(0)；了尘: 道具 木桶(2)→水瓢(0)；净远: 道具 水缸(0)→木桶(2)
+  喝水: 中央水 3→0；明心: 已喝 2→3；了尘: 已喝 0→1；净远: 已喝 2→5，道具 木桶(2)→木桶(0)
+  轮末道具: 无变化
+  轮末状态：
+第 2 轮 | 中央水=0 | 阶段=出牌
+慧空: 已喝=2, 道具=水缸(0)
+明心: 已喝=3, 道具=老鼠(0)
+了尘: 已喝=1, 道具=水瓢(0)
+净远 🪵: 已喝=5, 道具=木桶(0)
+
+第 2 轮
+  慧空 选择 念经（可选：交换、喝水、念经、休息）
+  明心 选择 交换（可选：挑水、交换、喝水、念经）
+  了尘 选择 休息（可选：挑水、喝水、念经、休息）
+  净远 选择 交换（可选：挑水、交换、念经、休息）
+  本轮行动阶段：念经 → 交换
+  念经: 慧空: 获得木鱼标记；净远: 失去木鱼标记
+  交换: 明心: 道具 老鼠(0)→木桶(0)；了尘: 道具 水瓢(0)→老鼠(0)；净远: 道具 木桶(0)→水瓢(0)
+  轮末道具: 无变化
+  轮末状态：
+第 3 轮 | 中央水=0 | 阶段=出牌
+慧空 🪵: 已喝=2, 道具=水缸(0)
+明心: 已喝=3, 道具=木桶(0)
+了尘: 已喝=1, 道具=老鼠(0)
+净远: 已喝=5, 道具=水瓢(0)
+
+第 3 轮
+  慧空 选择 交换（可选：挑水、交换、喝水、休息）
+  明心 选择 喝水（可选：挑水、喝水、念经、休息）
+  了尘 选择 交换（可选：挑水、交换、喝水、念经）
+  净远 选择 挑水（可选：挑水、喝水、念经、休息）
+  本轮行动阶段：挑水 → 交换 → 喝水
+  挑水: 中央水 0→1；净远: 已喝 5→3，道具 水瓢(0)→水瓢(3)
+  交换: 慧空: 道具 水缸(0)→水瓢(3)；明心: 道具 木桶(0)→水缸(0)；了尘: 道具 老鼠(0)→木桶(0)；净远: 道具 水瓢(3)→老鼠(0)
+  喝水: 中央水 1→0；慧空: 已喝 2→5，道具 水瓢(3)→水瓢(1)；明心: 已喝 3→4
+  轮末道具: 无变化
+  轮末状态：
+第 4 轮 | 中央水=0 | 阶段=出牌
+慧空 🪵: 已喝=5, 道具=水瓢(1)
+明心: 已喝=4, 道具=水缸(0)
+了尘: 已喝=1, 道具=木桶(0)
+净远: 已喝=3, 道具=老鼠(0)
+
+第 4 轮
+  慧空 选择 念经（可选：挑水、喝水、念经、休息）
+  明心 选择 挑水（可选：挑水、交换、念经、休息）
+  了尘 选择 休息（可选：挑水、喝水、念经、休息）
+  净远 选择 休息（可选：交换、喝水、念经、休息）
+  本轮行动阶段：念经 → 挑水
+  念经: 无变化
+  挑水: 中央水 0→2；慧空: 已喝 5→3，道具 水瓢(1)→水瓢(4)
+  轮末道具: 无变化
+  轮末状态：
+第 5 轮 | 中央水=2 | 阶段=出牌
+慧空 🪵: 已喝=3, 道具=水瓢(4)
+明心: 已喝=4, 道具=水缸(0)
+了尘: 已喝=1, 道具=木桶(0)
+净远: 已喝=3, 道具=老鼠(0)
+
+第 5 轮
+  慧空 选择 休息（可选：挑水、交换、喝水、休息）
+  明心 选择 喝水（可选：交换、喝水、念经、休息）
+  了尘 选择 挑水（可选：挑水、交换、喝水、念经）
+  净远 选择 念经（可选：挑水、交换、喝水、念经）
+  本轮行动阶段：念经 → 挑水 → 喝水
+  念经: 慧空: 道具 水瓢(4)→水瓢(3)，失去木鱼标记；净远: 道具 老鼠(0)→老鼠(1)，获得木鱼标记
+  挑水: 中央水 2→5
+  喝水: 中央水 5→1；慧空: 已喝 3→6，道具 水瓢(3)→水瓢(1)；明心: 已喝 4→6；了尘: 已喝 1→2；净远: 已喝 3→5，道具 老鼠(1)→老鼠(0)
+  轮末道具: 无变化
+  轮末状态：
+第 6 轮 | 中央水=1 | 阶段=出牌
+慧空: 已喝=6, 道具=水瓢(1)
+明心: 已喝=6, 道具=水缸(0)
+了尘: 已喝=2, 道具=木桶(0)
+净远 🪵: 已喝=5, 道具=老鼠(0)
+
+第 6 轮
+  慧空 选择 念经（可选：挑水、交换、喝水、念经）
+  明心 选择 挑水（可选：挑水、交换、念经、休息）
+  了尘 选择 交换（可选：交换、喝水、念经、休息）
+  净远 选择 挑水（可选：挑水、交换、喝水、休息）
+  本轮行动阶段：念经 → 挑水 → 交换
+  念经: 慧空: 获得木鱼标记；净远: 失去木鱼标记
+  挑水: 中央水 1→2；慧空: 已喝 6→4，道具 水瓢(1)→水瓢(4)
+  交换: 明心: 道具 水缸(0)→老鼠(0)；了尘: 道具 木桶(0)→水缸(0)；净远: 道具 老鼠(0)→木桶(0)
+  轮末道具: 无变化
+  轮末状态：
+第 7 轮 | 中央水=2 | 阶段=出牌
+慧空 🪵: 已喝=4, 道具=水瓢(4)
+明心: 已喝=6, 道具=老鼠(0)
+了尘: 已喝=2, 道具=水缸(0)
+净远: 已喝=5, 道具=木桶(0)
+
+第 7 轮
+  慧空 选择 喝水（可选：挑水、交换、喝水、休息）
+  明心 选择 休息（可选：交换、喝水、念经、休息）
+  了尘 选择 休息（可选：挑水、喝水、念经、休息）
+  净远 选择 休息（可选：交换、喝水、念经、休息）
+  本轮行动阶段：喝水
+  喝水: 中央水 2→0；慧空: 已喝 4→7，道具 水瓢(4)→水瓢(2)；明心: 已喝 6→7
+  轮末道具: 无变化
+  轮末状态：
+第 8 轮 | 中央水=0 | 阶段=出牌
+慧空 🪵: 已喝=7, 道具=水瓢(2)
+明心: 已喝=7, 道具=老鼠(0)
+了尘: 已喝=2, 道具=水缸(0)
+净远: 已喝=5, 道具=木桶(0)
+
+第 8 轮
+  慧空 选择 休息（可选：挑水、交换、念经、休息）
+  明心 选择 挑水（可选：挑水、交换、喝水、念经）
+  了尘 选择 挑水（可选：挑水、交换、喝水、念经）
+  净远 选择 挑水（可选：挑水、交换、喝水、念经）
+  本轮行动阶段：挑水
+  挑水: 中央水 0→3；净远: 已喝 5→3，道具 木桶(0)→木桶(2)
+  轮末道具: 无变化
+  轮末状态：
+第 9 轮 | 中央水=3 | 阶段=出牌
+慧空 🪵: 已喝=7, 道具=水瓢(2)
+明心: 已喝=7, 道具=老鼠(0)
+了尘: 已喝=2, 道具=水缸(0)
+净远: 已喝=3, 道具=木桶(2)
+
+第 9 轮
+  慧空 选择 交换（可选：挑水、交换、喝水、念经）
+  明心 选择 休息（可选：交换、喝水、念经、休息）
+  了尘 选择 交换（可选：交换、喝水、念经、休息）
+  净远 选择 交换（可选：交换、喝水、念经、休息）
+  本轮行动阶段：交换
+  交换: 慧空: 道具 水瓢(2)→木桶(2)；明心: 道具 老鼠(0)→水瓢(2)；了尘: 道具 水缸(0)→老鼠(0)；净远: 道具 木桶(2)→水缸(0)
+  轮末道具: 无变化
+  轮末状态：
+第 10 轮 | 中央水=3 | 阶段=出牌
+慧空 🪵: 已喝=7, 道具=木桶(2)
+明心: 已喝=7, 道具=水瓢(2)
+了尘: 已喝=2, 道具=老鼠(0)
+净远: 已喝=3, 道具=水缸(0)
+
+第 10 轮
+  慧空 选择 喝水（可选：挑水、喝水、念经、休息）
+  明心 选择 交换（可选：挑水、交换、喝水、念经）
+  了尘 选择 念经（可选：挑水、喝水、念经、休息）
+  净远 选择 挑水（可选：挑水、喝水、念经、休息）
+  本轮行动阶段：念经 → 挑水 → 交换 → 喝水
+  念经: 慧空: 失去木鱼标记；明心: 道具 水瓢(2)→水瓢(1)；了尘: 道具 老鼠(0)→老鼠(1)，获得木鱼标记
+  挑水: 中央水 3→4；明心: 已喝 7→5，道具 水瓢(1)→水瓢(4)
+  交换: 慧空: 道具 木桶(2)→水缸(0)；明心: 道具 水瓢(4)→木桶(2)；净远: 道具 水缸(0)→水瓢(4)
+  喝水: 中央水 4→0；慧空: 已喝 7→9；明心: 已喝 5→8，道具 木桶(2)→木桶(0)；了尘: 已喝 2→4，道具 老鼠(1)→老鼠(0)；净远: 已喝 3→6，道具 水瓢(4)→水瓢(2)
+  轮末道具: 无变化
+  轮末状态：
+第 11 轮 | 中央水=0 | 阶段=出牌
+慧空: 已喝=9, 道具=水缸(0)
+明心: 已喝=8, 道具=木桶(0)
+了尘 🪵: 已喝=4, 道具=老鼠(0)
+净远: 已喝=6, 道具=水瓢(2)
+
+第 11 轮
+  慧空 选择 挑水（可选：挑水、交换、念经、休息）
+  明心 选择 喝水（可选：挑水、喝水、念经、休息）
+  了尘 选择 休息（可选：挑水、交换、喝水、休息）
+  净远 选择 休息（可选：交换、喝水、念经、休息）
+  本轮行动阶段：挑水 → 喝水
+  挑水: 中央水 0→3；明心: 已喝 8→6，道具 木桶(0)→木桶(2)
+  喝水: 中央水 3→0；明心: 已喝 6→9，道具 木桶(2)→木桶(0)；了尘: 已喝 4→5；净远: 已喝 6→9，道具 水瓢(2)→水瓢(0)
+  轮末道具: 无变化
+  轮末状态：
+第 12 轮 | 中央水=0 | 阶段=出牌
+慧空: 已喝=9, 道具=水缸(0)
+明心: 已喝=9, 道具=木桶(0)
+了尘 🪵: 已喝=5, 道具=老鼠(0)
+净远: 已喝=9, 道具=水瓢(0)
+
+第 12 轮
+  慧空 选择 休息（可选：交换、喝水、念经、休息）
+  明心 选择 挑水（可选：挑水、交换、念经、休息）
+  了尘 选择 挑水（可选：挑水、交换、喝水、念经）
+  净远 选择 念经（可选：挑水、交换、喝水、念经）
+  本轮行动阶段：念经 → 挑水
+  念经: 了尘: 失去木鱼标记；净远: 获得木鱼标记
+  挑水: 中央水 0→1；净远: 已喝 9→7，道具 水瓢(0)→水瓢(3)
+  轮末道具: 无变化
+  轮末状态：
+第 13 轮 | 中央水=1 | 阶段=出牌
+慧空: 已喝=9, 道具=水缸(0)
+明心: 已喝=9, 道具=木桶(0)
+了尘: 已喝=5, 道具=老鼠(0)
+净远 🪵: 已喝=7, 道具=水瓢(3)
+
+第 13 轮
+  慧空 选择 交换（可选：挑水、交换、喝水、念经）
+  明心 选择 交换（可选：交换、喝水、念经、休息）
+  了尘 选择 念经（可选：交换、喝水、念经、休息）
+  净远 选择 交换（可选：挑水、交换、喝水、休息）
+  本轮行动阶段：念经 → 交换
+  念经: 了尘: 道具 老鼠(0)→老鼠(1)，获得木鱼标记；净远: 道具 水瓢(3)→水瓢(2)，失去木鱼标记
+  交换: 慧空: 道具 水缸(0)→水瓢(2)；明心: 道具 木桶(0)→水缸(0)；净远: 道具 水瓢(2)→木桶(0)
+  轮末道具: 无变化
+  轮末状态：
+第 14 轮 | 中央水=1 | 阶段=出牌
+慧空: 已喝=9, 道具=水瓢(2)
+明心: 已喝=9, 道具=水缸(0)
+了尘 🪵: 已喝=5, 道具=老鼠(1)
+净远: 已喝=7, 道具=木桶(0)
+
+第 14 轮
+  慧空 选择 喝水（可选：挑水、喝水、念经、休息）
+  明心 选择 喝水（可选：挑水、喝水、念经、休息）
+  了尘 选择 休息（可选：挑水、交换、喝水、休息）
+  净远 选择 休息（可选：挑水、喝水、念经、休息）
+  本轮行动阶段：喝水
+  喝水: 中央水 1→0；慧空: 已喝 9→11，道具 水瓢(2)→水瓢(0)；了尘: 已喝 5→7，道具 老鼠(1)→老鼠(0)
+
+游戏结束
+胜者：慧空
+第 14 轮 | 中央水=0 | 阶段=游戏结束
+慧空: 已喝=11, 道具=水瓢(0) | 行动=喝水
+明心: 已喝=9, 道具=水缸(0) | 行动=喝水
+了尘 🪵: 已喝=7, 道具=老鼠(0) | 行动=休息
+净远: 已喝=7, 道具=木桶(0) | 行动=休息

examples/three-monks/random-playthrough.ts

@@ -0,0 +1,151 @@
+import { World, query, type Entity } from "../../src/index";
+import {
+  ActionCard,
+  GameState,
+  Player,
+  Table,
+  setupGame,
+  type ActionKind,
+} from "./components";
+import {
+  beginSelectionPhase,
+  collectProposals,
+  prepareNextRound,
+  selectAction,
+  chantPhase,
+  fetchWaterPhase,
+  exchangePhase,
+  drinkPhase,
+  endOfRoundPhase,
+} from "./rules";
+import {
+  ACTION_LABELS,
+  GameLog,
+  formatAvailableActions,
+  formatProposals,
+  logPhaseDelta,
+  logSnapshot,
+  snapshotGame,
+  winnerName,
+} from "./logging";
+
+export interface RandomPlaythroughOptions {
+  seed?: number;
+  playerNames?: readonly string[];
+  maxRounds?: number;
+}
+
+export interface RandomPlaythroughResult {
+  world: World;
+  log: string;
+  roundsPlayed: number;
+}
+
+export function generateRandomPlayLog(
+  options: RandomPlaythroughOptions = {},
+): RandomPlaythroughResult {
+  const seed = options.seed ?? 20260701;
+  const random = mulberry32(seed);
+  const playerNames = options.playerNames ?? ["慧空", "明心", "了尘", "净远"];
+  const maxRounds = options.maxRounds ?? 200;
+
+  const world = new World();
+  const players = setupGame(world, playerNames, random);
+  const log = new GameLog();
+
+  log.section(`三个和尚随机对局（种子=${seed}）`);
+  log.add(`玩家：${playerNames.join("、")}`);
+  log.add("初始状态：");
+  logSnapshot(log, world);
+
+  let roundsPlayed = 0;
+
+  while (world.getSingleton(GameState).phase !== "gameOver") {
+    if (roundsPlayed >= maxRounds) {
+      throw new Error(`随机对局未能在 ${maxRounds} 轮内结束`);
+    }
+
+    const round = world.getSingleton(Table).round;
+    log.section(`第 ${round} 轮`);
+    beginSelectionPhase(world);
+
+    for (const player of players) {
+      const action = pickRandom(availableActions(world, player), random);
+      const playerName = world.get(player, Player).name;
+      log.add(
+        `  ${playerName} 选择 ${ACTION_LABELS[action]}（可选：${formatAvailableActions(world, player)}）`,
+      );
+      selectAction(world, player, action);
+    }
+
+    const proposals = collectProposals(world);
+    log.add(`  本轮行动阶段：${formatProposals(proposals)}`);
+
+    applyLoggedPhase(log, world, "念经", () => chantPhase(world));
+    applyLoggedPhase(log, world, "挑水", () => fetchWaterPhase(world));
+    applyLoggedPhase(log, world, "交换", () => exchangePhase(world));
+    applyLoggedPhase(log, world, "喝水", () => drinkPhase(world));
+    if (world.getSingleton(GameState).phase === "gameOver") break;
+
+    applyLoggedPhase(log, world, "轮末道具", () => endOfRoundPhase(world));
+    if (world.getSingleton(GameState).phase === "gameOver") break;
+
+    prepareNextRound(world);
+    log.add("  轮末状态：");
+    logSnapshot(log, world);
+    roundsPlayed++;
+  }
+
+  roundsPlayed++;
+  log.section("游戏结束");
+  log.add(`胜者：${winnerName(world)}`);
+  logSnapshot(log, world);
+
+  return { world, log: log.toString(), roundsPlayed };
+}
+
+function applyLoggedPhase(
+  log: GameLog,
+  world: World,
+  label: string,
+  phase: () => void,
+): void {
+  const before = snapshotGame(world);
+  phase();
+  const after = snapshotGame(world);
+  logPhaseDelta(log, label, before, after);
+}
+
+function availableActions(world: World, player: Entity): ActionKind[] {
+  const actions: ActionKind[] = [];
+  for (const card of world.query(query(ActionCard))) {
+    const data = world.get(card, ActionCard);
+    if (data.owner === player && data.zone === "hand") {
+      actions.push(data.kind);
+    }
+  }
+  if (actions.length === 0) {
+    throw new Error(`${world.get(player, Player).name} 没有可选行动牌`);
+  }
+  return actions;
+}
+
+function pickRandom<T>(items: readonly T[], random: () => number): T {
+  return items[Math.floor(random() * items.length)];
+}
+
+function mulberry32(seed: number): () => number {
+  let state = seed >>> 0;
+  return () => {
+    state += 0x6d2b79f5;
+    let t = state;
+    t = Math.imul(t ^ (t >>> 15), t | 1);
+    t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
+    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
+  };
+}
+
+if (process.argv[1]?.endsWith("random-playthrough.ts")) {
+  const result = generateRandomPlayLog();
+  console.log(result.log);
+}

examples/three-monks/rules.ts

@@ -0,0 +1,372 @@
+import type { Entity, World } from "../../src/index";
+import { query } from "../../src/query";
+import type { ToolEffectRecorder } from "./stats";
+import {
+  ActionCard,
+  CARRYING_TOOLS,
+  GameState,
+  Player,
+  Table,
+  Tool,
+  WoodenFishMarker,
+  allPlayersSelected,
+  getActionCard,
+  getLeftPlayer,
+  getPlayersFromMarker,
+  getPlayersInSeatOrder,
+  getRightPlayer,
+  getSelectedAction,
+  getToolOf,
+  type ActionKind,
+} from "./components";
+
+export interface RoundProposals {
+  fetchWater: boolean;
+  exchange: boolean;
+  drink: boolean;
+  chant: boolean;
+}
+
+export function beginSelectionPhase(world: World): void {
+  const state = world.getSingleton(GameState);
+  if (state.phase !== "gameOver") {
+    state.phase = "selecting";
+    state.message = `Round ${world.getSingleton(Table).round}: choose an action card.`;
+  }
+}
+
+export function selectAction(
+  world: World,
+  player: Entity,
+  kind: ActionKind,
+): void {
+  const state = world.getSingleton(GameState);
+  if (state.phase !== "selecting") return;
+  if (!world.has(player, Player)) throw new Error("Invalid player");
+
+  const card = getActionCard(world, player, kind);
+  if (!card) throw new Error("Player does not have that action card");
+
+  const cardData = world.get(card, ActionCard);
+  if (cardData.zone === "cooldown") {
+    throw new Error("Cannot select the action card played last round");
+  }
+
+  for (const other of world.query(query(ActionCard))) {
+    const data = world.get(other, ActionCard);
+    if (data.owner === player && data.zone === "selected") {
+      data.zone = "hand";
+    }
+  }
+
+  cardData.zone = "selected";
+
+  if (allPlayersSelected(world)) {
+    state.message = "All players selected. Resolving round.";
+  }
+}
+
+export function collectProposals(world: World): RoundProposals {
+  const proposals: RoundProposals = {
+    fetchWater: false,
+    exchange: false,
+    drink: false,
+    chant: false,
+  };
+
+  for (const player of getPlayersInSeatOrder(world)) {
+    const action = getSelectedAction(world, player);
+    if (!action || action === "rest") continue;
+    proposals[action] = true;
+  }
+
+  return proposals;
+}
+
+function isProposed(world: World, kind: ActionKind): boolean {
+  for (const player of getPlayersInSeatOrder(world)) {
+    if (getSelectedAction(world, player) === kind) return true;
+  }
+  return false;
+}
+
+function isGameOver(world: World): boolean {
+  return world.getSingleton(GameState).phase === "gameOver";
+}
+
+// ── Phase wrappers (each checks proposal + gameOver, then delegates) ──
+
+export function chantPhase(world: World, stats?: ToolEffectRecorder): void {
+  if (isGameOver(world) || !isProposed(world, "chant")) return;
+  resolveChant(world, stats);
+}
+
+export function fetchWaterPhase(
+  world: World,
+  stats?: ToolEffectRecorder,
+): void {
+  if (isGameOver(world) || !isProposed(world, "fetchWater")) return;
+  resolveFetchWater(world, stats);
+}
+
+export function exchangePhase(world: World, stats?: ToolEffectRecorder): void {
+  if (isGameOver(world) || !isProposed(world, "exchange")) return;
+  resolveExchange(world, stats);
+}
+
+export function drinkPhase(world: World, stats?: ToolEffectRecorder): void {
+  if (isGameOver(world) || !isProposed(world, "drink")) return;
+  resolveDrink(world, stats);
+}
+
+export function endOfRoundPhase(
+  world: World,
+  stats?: ToolEffectRecorder,
+): void {
+  if (isGameOver(world)) return;
+  resolveEndOfRoundTools(world, stats);
+  checkWinner(world);
+}
+
+export function prepareNextRound(world: World): void {
+  const state = world.getSingleton(GameState);
+  if (state.phase === "gameOver") return;
+
+  for (const card of world.query(query(ActionCard))) {
+    const data = world.get(card, ActionCard);
+    if (data.zone === "cooldown") data.zone = "hand";
+  }
+
+  for (const card of world.query(query(ActionCard))) {
+    const data = world.get(card, ActionCard);
+    if (data.zone === "selected") data.zone = "cooldown";
+  }
+
+  world.getSingleton(Table).round++;
+  state.phase = "selecting";
+  state.message = `Round ${world.getSingleton(Table).round}: choose an action card.`;
+}
+
+export function resolveFetchWater(
+  world: World,
+  stats?: ToolEffectRecorder,
+): void {
+  const table = world.getSingleton(Table);
+  const players = getPlayersInSeatOrder(world);
+  const participants = players.filter((player) => {
+    const action = getSelectedAction(world, player);
+    const tool = world.get(getToolOf(world, player), Tool);
+    return (
+      action !== null && action !== "rest" && CARRYING_TOOLS.has(tool.kind)
+    );
+  });
+
+  for (const player of participants) {
+    const toolEntity = getToolOf(world, player);
+    const tool = world.get(toolEntity, Tool);
+    let placed = 2;
+
+    if (tool.kind === "bucket") placed = 1;
+    if (tool.kind === "woodenBucket" && participants.length > 1) placed = 0;
+
+    const playerData = world.get(player, Player);
+    if (playerData.water >= placed) {
+      playerData.water -= placed;
+      tool.water += placed;
+      stats?.record(tool.kind, "挑水", {
+        playerWaterDelta: -placed,
+        ownToolWaterDelta: placed,
+      });
+    } else {
+      stats?.record(tool.kind, "挑水", {}, "水不足，未放水");
+    }
+  }
+
+  table.centralWater += players.length - participants.length;
+
+  for (const player of participants) {
+    const tool = world.get(getToolOf(world, player), Tool);
+    if (tool.kind === "ladle" && table.centralWater > 0) {
+      table.centralWater--;
+      tool.water++;
+      stats?.record(tool.kind, "挑水", {
+        ownToolWaterDelta: 1,
+        centralWaterDelta: -1,
+      });
+    }
+  }
+}
+
+export function resolveExchange(
+  world: World,
+  stats?: ToolEffectRecorder,
+): void {
+  const participants = getPlayersInSeatOrder(world).filter(
+    (player) => getSelectedAction(world, player) !== "chant",
+  );
+  if (participants.length <= 1) return;
+
+  const table = world.getSingleton(Table);
+  const tools = participants.map((player) => getToolOf(world, player));
+
+  for (const toolEntity of tools) {
+    const tool = world.get(toolEntity, Tool);
+    if (tool.kind === "shoulderPole" && tool.water > 0) {
+      const dumped = tool.water;
+      table.centralWater += dumped;
+      tool.water = 0;
+      stats?.record(tool.kind, "交换", {
+        ownToolWaterDelta: -dumped,
+        centralWaterDelta: dumped,
+      });
+    }
+  }
+
+  for (let i = 0; i < participants.length; i++) {
+    const giverTool = tools[i];
+    const receiver = participants[(i + 1) % participants.length];
+    world.get(giverTool, Tool).owner = receiver;
+  }
+}
+
+export function resolveDrink(world: World, stats?: ToolEffectRecorder): void {
+  for (const player of getPlayersFromMarker(world)) {
+    if (!canParticipateInDrink(world, player)) continue;
+
+    const table = world.getSingleton(Table);
+    const playerData = world.get(player, Player);
+    const tool = world.get(getToolOf(world, player), Tool);
+    let drankFromTool = 0;
+
+    if (table.centralWater > 0) {
+      table.centralWater--;
+      playerData.water++;
+    }
+
+    const maxFromTool =
+      tool.kind === "bigBucket" ? tool.water : Math.min(2, tool.water);
+    if (maxFromTool > 0) {
+      tool.water -= maxFromTool;
+      playerData.water += maxFromTool;
+      drankFromTool = maxFromTool;
+      stats?.record(tool.kind, "喝水", {
+        playerWaterDelta: maxFromTool,
+        ownToolWaterDelta: -maxFromTool,
+      });
+    }
+
+    if (tool.kind === "waterJar") {
+      playerData.water++;
+      stats?.record(tool.kind, "喝水", {
+        playerWaterDelta: 1,
+      });
+    }
+
+    if (
+      tool.kind === "bigBowl" &&
+      drankFromTool === 0 &&
+      table.centralWater > 0
+    ) {
+      table.centralWater--;
+      tool.water++;
+      stats?.record(tool.kind, "喝水", {
+        ownToolWaterDelta: 1,
+        centralWaterDelta: -1,
+      });
+    }
+
+    if (playerData.water >= 10) {
+      setWinner(world, player);
+      return;
+    }
+  }
+}
+
+export function resolveChant(world: World, stats?: ToolEffectRecorder): void {
+  const chanters = getPlayersFromMarker(world).filter(
+    (player) => getSelectedAction(world, player) === "chant",
+  );
+  if (chanters.length === 0) return;
+
+  world.getSingleton(WoodenFishMarker).holder = chanters[chanters.length - 1];
+
+  for (const player of chanters) {
+    const toolEntity = getToolOf(world, player);
+    const tool = world.get(toolEntity, Tool);
+
+    if (tool.kind === "bottle") {
+      tool.water++;
+      stats?.record(tool.kind, "念经", {
+        ownToolWaterDelta: 1,
+      });
+    } else if (tool.kind === "mouse") {
+      const moved = moveOneNeighborWaterTo(world, player, toolEntity);
+      if (moved) {
+        stats?.record(tool.kind, "念经", {
+          ownToolWaterDelta: 1,
+          otherToolWaterDelta: -1,
+        });
+      } else {
+        stats?.record(tool.kind, "念经", {}, "相邻道具无水可偷");
+      }
+    }
+  }
+}
+
+export function resolveEndOfRoundTools(
+  world: World,
+  stats?: ToolEffectRecorder,
+): void {
+  for (const toolEntity of world.query(query(Tool))) {
+    const tool = world.get(toolEntity, Tool);
+    if (tool.kind === "woodenFish") {
+      world.getSingleton(WoodenFishMarker).holder = tool.owner;
+      stats?.record(tool.kind, "轮末", {}, "获得木鱼标记");
+      return;
+    }
+  }
+}
+
+export function checkWinner(world: World): Entity | null {
+  for (const player of getPlayersFromMarker(world)) {
+    if (world.get(player, Player).water >= 10) {
+      setWinner(world, player);
+      return player;
+    }
+  }
+  return null;
+}
+
+function canParticipateInDrink(world: World, player: Entity): boolean {
+  const tool = world.get(getToolOf(world, player), Tool);
+  if (tool.kind !== "waterJar") return true;
+  return getSelectedAction(world, player) === "drink";
+}
+
+function moveOneNeighborWaterTo(
+  world: World,
+  player: Entity,
+  destinationTool: Entity,
+): boolean {
+  const neighbors = [
+    getLeftPlayer(world, player),
+    getRightPlayer(world, player),
+  ];
+  for (const neighbor of neighbors) {
+    const neighborToolEntity = getToolOf(world, neighbor);
+    const neighborTool = world.get(neighborToolEntity, Tool);
+    if (neighborTool.water > 0) {
+      neighborTool.water--;
+      world.get(destinationTool, Tool).water++;
+      return true;
+    }
+  }
+  return false;
+}
+
+function setWinner(world: World, player: Entity): void {
+  const state = world.getSingleton(GameState);
+  state.phase = "gameOver";
+  state.winner = player;
+  state.message = `${world.get(player, Player).name} wins!`;
+}

examples/three-monks/simulate.ts

@@ -0,0 +1,129 @@
+import { World, query, type Entity } from "../../src/index";
+import {
+  ActionCard,
+  GameState,
+  Player,
+  Table,
+  setupGame,
+  type ActionKind,
+} from "./components";
+import { ToolEffectStats, formatToolEffectSummaries } from "./stats";
+import {
+  beginSelectionPhase,
+  prepareNextRound,
+  selectAction,
+  chantPhase,
+  fetchWaterPhase,
+  exchangePhase,
+  drinkPhase,
+  endOfRoundPhase,
+} from "./rules";
+
+function mulberry32(seed: number): () => number {
+  let state = seed >>> 0;
+  return () => {
+    state += 0x6d2b79f5;
+    let t = state;
+    t = Math.imul(t ^ (t >>> 15), t | 1);
+    t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
+    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
+  };
+}
+
+function availableActions(world: World, player: Entity): ActionKind[] {
+  const actions: ActionKind[] = [];
+  for (const card of world.query(query(ActionCard))) {
+    const data = world.get(card, ActionCard);
+    if (data.owner === player && data.zone === "hand") {
+      actions.push(data.kind);
+    }
+  }
+  return actions;
+}
+
+function pickRandom<T>(items: readonly T[], random: () => number): T {
+  return items[Math.floor(random() * items.length)];
+}
+
+interface GameStats {
+  rounds: number;
+  waterDiff: number;
+}
+
+function runSingleGame(seed: number, stats?: ToolEffectStats): GameStats {
+  const random = mulberry32(seed);
+  const world = new World();
+  const playerNames = ["慧空", "明心", "了尘", "净远"];
+  const players = setupGame(world, playerNames, random);
+
+  let roundsPlayed = 0;
+  const maxRounds = 1000;
+
+  while (world.getSingleton(GameState).phase !== "gameOver") {
+    if (roundsPlayed >= maxRounds) {
+      throw new Error(`Game did not finish within ${maxRounds} rounds`);
+    }
+
+    beginSelectionPhase(world);
+
+    for (const player of players) {
+      const actions = availableActions(world, player);
+      const action = pickRandom(actions, random);
+      selectAction(world, player, action);
+    }
+
+    chantPhase(world, stats);
+    fetchWaterPhase(world, stats);
+    exchangePhase(world, stats);
+    drinkPhase(world, stats);
+    if (world.getSingleton(GameState).phase === "gameOver") break;
+
+    endOfRoundPhase(world, stats);
+    if (world.getSingleton(GameState).phase === "gameOver") break;
+
+    prepareNextRound(world);
+    roundsPlayed++;
+  }
+
+  const finalRound = world.getSingleton(Table).round;
+  const waterCounts = players.map((p) => world.get(p, Player).water);
+  const maxWater = Math.max(...waterCounts);
+  const minWater = Math.min(...waterCounts);
+
+  return {
+    rounds: finalRound,
+    waterDiff: maxWater - minWater,
+  };
+}
+
+export function runSimulation(gameCount = 100, startSeed = 20260701): void {
+  let totalRounds = 0;
+  let totalWaterDiff = 0;
+  const toolStats = new ToolEffectStats();
+
+  console.log(`开始模拟 ${gameCount} 局游戏...`);
+
+  for (let i = 0; i < gameCount; i++) {
+    const seed = startSeed + i;
+    const stats = runSingleGame(seed, toolStats);
+    totalRounds += stats.rounds;
+    totalWaterDiff += stats.waterDiff;
+  }
+
+  const avgRounds = totalRounds / gameCount;
+  const avgWaterDiff = totalWaterDiff / gameCount;
+
+  console.log("\n================ 统计结果 ================");
+  console.log(`模拟总局数: ${gameCount}`);
+  console.log(`结束时平均轮数: ${avgRounds.toFixed(2)} 轮`);
+  console.log(`结束时首尾玩家平均水差距: ${avgWaterDiff.toFixed(2)} 口水`);
+  console.log("==========================================");
+  console.log("\n道具效果统计（总变化量）:");
+  for (const line of formatToolEffectSummaries(toolStats)) {
+    console.log(line);
+  }
+}
+
+if (process.argv[1]?.endsWith("simulate.ts")) {
+  runSimulation();
+}

examples/three-monks/stats.ts

@@ -0,0 +1,94 @@
+import type { ToolKind } from "./components";
+import { TOOL_LABELS } from "./logging";
+
+export interface ToolEffectDelta {
+  playerWaterDelta?: number;
+  ownToolWaterDelta?: number;
+  otherToolWaterDelta?: number;
+  centralWaterDelta?: number;
+}
+
+export interface ToolEffectRecord extends Required<ToolEffectDelta> {
+  tool: ToolKind;
+  phase: string;
+  description?: string;
+}
+
+export interface ToolEffectSummary extends Required<ToolEffectDelta> {
+  tool: ToolKind;
+  activations: number;
+}
+
+export interface ToolEffectRecorder {
+  record(tool: ToolKind, phase: string, delta?: ToolEffectDelta, description?: string): void;
+}
+
+export class ToolEffectStats implements ToolEffectRecorder {
+  private readonly summaries = new Map<ToolKind, ToolEffectSummary>();
+  private readonly records: ToolEffectRecord[] = [];
+
+  record(
+    tool: ToolKind,
+    phase: string,
+    delta: ToolEffectDelta = {},
+    description?: string,
+  ): void {
+    const record: ToolEffectRecord = {
+      tool,
+      phase,
+      description,
+      playerWaterDelta: delta.playerWaterDelta ?? 0,
+      ownToolWaterDelta: delta.ownToolWaterDelta ?? 0,
+      otherToolWaterDelta: delta.otherToolWaterDelta ?? 0,
+      centralWaterDelta: delta.centralWaterDelta ?? 0,
+    };
+
+    this.records.push(record);
+
+    const summary = this.summaries.get(tool) ?? {
+      tool,
+      activations: 0,
+      playerWaterDelta: 0,
+      ownToolWaterDelta: 0,
+      otherToolWaterDelta: 0,
+      centralWaterDelta: 0,
+    };
+
+    summary.activations++;
+    summary.playerWaterDelta += record.playerWaterDelta;
+    summary.ownToolWaterDelta += record.ownToolWaterDelta;
+    summary.otherToolWaterDelta += record.otherToolWaterDelta;
+    summary.centralWaterDelta += record.centralWaterDelta;
+    this.summaries.set(tool, summary);
+  }
+
+  getRecords(): readonly ToolEffectRecord[] {
+    return this.records;
+  }
+
+  getSummaries(): ToolEffectSummary[] {
+    return [...this.summaries.values()].sort((a, b) =>
+      TOOL_LABELS[a.tool].localeCompare(TOOL_LABELS[b.tool], "zh-Hans-CN"),
+    );
+  }
+}
+
+export function formatToolEffectSummaries(stats: ToolEffectStats): string[] {
+  const summaries = stats.getSummaries();
+  if (summaries.length === 0) return ["无道具效果记录"];
+
+  return [
+    "道具 | 触发次数 | 玩家水变化 | 自身道具水变化 | 其他道具水变化 | 中央水变化",
+    "--- | ---: | ---: | ---: | ---: | ---:",
+    ...summaries.map((summary) =>
+      [
+        TOOL_LABELS[summary.tool],
+        summary.activations,
+        summary.playerWaterDelta,
+        summary.ownToolWaterDelta,
+        summary.otherToolWaterDelta,
+        summary.centralWaterDelta,
+      ].join(" | "),
+    ),
+  ];
+}

package.json

@@ -29,6 +29,7 @@
   "scripts": {
     "build": "tsup",
     "dev": "tsup --watch",
+    "typecheck": "tsc --noEmit",
     "test": "vitest run",
     "prepublishOnly": "npm run build"
   },

src/bt/index.ts

@@ -11,4 +11,31 @@ export {
 export type { TaskKind } from "./task";
 
 export { TaskRunner } from "./runner";
-export type { LeafHandler, TerminalHandler } from "./runner";
+export type {
+  ActionHandler,
+  WaitHandler,
+  ConditionHandler,
+  TaskControl,
+  TerminalHandler,
+} from "./runner";
+
+export {
+  buildTree,
+  Cancel,
+  action,
+  wait,
+  whilst,
+  sequential,
+  parallel,
+  selector,
+  random,
+  cycle,
+} from "./tree-def";
+export type {
+  TreeDef,
+  TaskEntityDef,
+  TaskMeta,
+  ActionFn,
+  WaitFn,
+  ConditionFn,
+} from "./tree-def";

src/bt/runner.ts

@@ -9,11 +9,34 @@ import {
   Cancelled,
   TERMINAL_TAGS,
   ChildOf,
+  Cancel,
 } from "./task";
 
 // ── Types ─────────────────────────────────────────────
-/** Callback invoked for each leaf task that becomes Scheduled. */
-export type LeafHandler = (world: World, entity: Entity) => void;
+/** Control object passed to wait tasks so they can complete themselves. */
+export interface TaskControl {
+  succeed(): void;
+  fail(): void;
+  cancel(): void;
+}
+
+/** Callback invoked when an action task starts executing. */
+export type ActionHandler = (world: World, entity: Entity, dt: number) => void;
+
+/** Callback invoked when a wait task starts executing. */
+export type WaitHandler = (
+  world: World,
+  entity: Entity,
+  control: TaskControl,
+  dt: number,
+) => void;
+
+/** Callback invoked by whilst tasks before each iteration. */
+export type ConditionHandler = (
+  world: World,
+  entity: Entity,
+  dt: number,
+) => boolean;
 
 /** Callback invoked when a task reaches a terminal status. */
 export type TerminalHandler = (
@@ -52,8 +75,12 @@ function clearSubtree(world: World, entity: Entity): void {
   }
 }
 
-function childrenOf(world: World, parent: Entity): Entity[] {
-  return world.getRelatedTo(parent, ChildOf);
+function* childrenOf(world: World, parent: Entity): IterableIterator<Entity> {
+  for (const child of world.getRelatedTo(parent, ChildOf)) {
+    if (world.has(child, Task)) {
+      yield child;
+    }
+  }
 }
 
 function parentOf(world: World, child: Entity): Entity | null {
@@ -64,31 +91,29 @@ function parentOf(world: World, child: Entity): Entity | null {
 /**
  * Push-based behaviour-tree runner.
  *
- * Only tasks tagged with `Scheduled` are processed each tick.
- * When a task finishes, it notifies its parent, which may schedule
- * the next child (sequential), aggregate results (parallel), or
- * propagate upward.
+ * Tasks tagged with `Scheduled` define tick boundaries. Once a scheduled
+ * task starts, child/parent propagation is immediate until a running wait task
+ * or an explicit scheduling boundary (`cycle`, `whilst`) yields to a future tick.
  *
- * Leaves are dispatched to a user-provided `onLeaf` callback.
- * Terminal results are dispatched to a user-provided `onTerminal` callback.
- *
- * @example
- * ```ts
- * const runner = new TaskRunner(world);
- * runner.onLeaf = (world, entity) => {
- *   // do the leaf's work, then call:
- *   runner.succeed(entity);
- * };
- *
- * // Each frame:
- * runner.tick();
- * ```
+ * Action, wait, and whilst condition callbacks are supplied by `buildTree` or
+ * assigned directly when using `TaskRunner` manually.
  */
 export class TaskRunner {
   private _world: World;
+  private _executing = new Set<Entity>();
+  private _currentDt = 0;
 
-  /** Called when a leaf task becomes Scheduled. */
-  onLeaf: LeafHandler = () => {};
+  /** Root task entity, set by `buildTree` for convenience. */
+  root?: Entity;
+
+  /** Called when an action task starts executing. */
+  onAction: ActionHandler = () => {};
+
+  /** Called when a wait task starts executing. */
+  onWait: WaitHandler = () => {};
+
+  /** Called by whilst tasks before each iteration. */
+  onCondition: ConditionHandler = () => false;
 
   /** Called when any task reaches a terminal status. */
   onTerminal: TerminalHandler = () => {};
@@ -100,34 +125,46 @@ export class TaskRunner {
   // ── Public API ────────────────────────────────────
 
   /**
-   * Process all Scheduled tasks.
+   * Process tasks scheduled for this tick.
    *
-   * Call once per frame. Only entities with `Scheduled` are touched.
+   * Call once per frame. Tasks scheduled while a tick is already in progress are
+   * deferred until the next tick boundary, but parent/child propagation caused
+   * by terminal status changes is immediate.
+   *
+   * @param dt Delta time in milliseconds since last tick.
    */
-  tick(): void {
-    const scheduled = [...this._world.query(query(Task, Scheduled))];
-    for (const entity of scheduled) {
-      this._world.remove(entity, Scheduled);
-      this._execute(entity);
+  tick(dt: number = 0): void {
+    const previousDt = this._currentDt;
+    this._currentDt = dt;
+
+    try {
+      const scheduled = [...this._world.query(query(Task, Scheduled))];
+      for (const entity of scheduled) {
+        if (!this._world.has(entity, Scheduled)) continue;
+        this._world.remove(entity, Scheduled);
+        this._execute(entity, dt);
+      }
+    } finally {
+      this._currentDt = previousDt;
     }
   }
 
-  /** Mark a leaf task as succeeded and propagate upward. */
+  /** Mark a task as succeeded and propagate upward. */
   succeed(entity: Entity): void {
     this._finish(entity, Succeeded);
   }
 
-  /** Mark a leaf task as failed and propagate upward. */
+  /** Mark a task as failed and propagate upward. */
   fail(entity: Entity): void {
     this._finish(entity, Failed);
   }
 
   /** Cancel a task and all its descendants. */
   cancel(entity: Entity): void {
-    this._cancelTree(entity);
+    this._cancelTree(entity, true);
   }
 
-  /** Schedule a task for execution next tick. */
+  /** Schedule a task for execution at the next tick boundary. */
   schedule(entity: Entity): void {
     if (this._world.has(entity, Task)) {
       this._world.add(entity, Scheduled);
@@ -142,84 +179,132 @@ export class TaskRunner {
 
   // ── Internal execution ────────────────────────────
 
-  private _execute(entity: Entity): void {
-    const t = this._world.get(entity, Task);
+  private _execute(entity: Entity, dt: number): void {
+    if (!this._world.has(entity, Task) || this._executing.has(entity)) return;
 
-    switch (t.kind) {
-      case "leaf":
-        this._executeLeaf(entity);
-        break;
-      case "sequential":
-        this._executeSequential(entity);
-        break;
-      case "parallel":
-        this._executeParallel(entity);
-        break;
-      case "random":
-        this._executeRandom(entity);
-        break;
-      case "repeat":
-        this._executeRepeat(entity);
-        break;
-      case "selector":
-        this._executeSelector(entity);
-        break;
+    const t = this._world.get(entity, Task);
+    this._executing.add(entity);
+
+    try {
+      switch (t.kind) {
+        case "action":
+          this._executeAction(entity, dt);
+          break;
+        case "wait":
+          this._executeWait(entity, dt);
+          break;
+        case "sequential":
+          this._executeSequential(entity, dt);
+          break;
+        case "parallel":
+          this._executeParallel(entity, dt);
+          break;
+        case "random":
+          this._executeRandom(entity, dt);
+          break;
+        case "cycle":
+          this._executeCycle(entity, dt);
+          break;
+        case "whilst":
+          this._executeWhilst(entity, dt);
+          break;
+        case "selector":
+          this._executeSelector(entity, dt);
+          break;
+      }
+    } finally {
+      this._executing.delete(entity);
     }
   }
 
-  private _executeLeaf(entity: Entity): void {
+  private _executeChild(entity: Entity, dt: number): void {
+    if (
+      !this._world.has(entity, Task) ||
+      isTerminal(this._world, entity) ||
+      this._world.has(entity, Running)
+    ) {
+      return;
+    }
+
+    if (this._world.has(entity, Scheduled)) {
+      this._world.remove(entity, Scheduled);
+    }
+
+    this._execute(entity, dt);
+  }
+
+  private _executeAction(entity: Entity, dt: number): void {
+    this._world.add(entity, Running);
+    try {
+      this.onAction(this._world, entity, dt);
+      if (!isTerminal(this._world, entity)) {
+        this.succeed(entity);
+      }
+    } catch (err) {
+      this._finishFromThrown(entity, err);
+    }
+  }
+
+  private _executeWait(entity: Entity, dt: number): void {
     this._world.add(entity, Running);
-    this.onLeaf(this._world, entity);
+    const control: TaskControl = {
+      succeed: () => this.succeed(entity),
+      fail: () => this.fail(entity),
+      cancel: () => this.cancel(entity),
+    };
+
+    try {
+      this.onWait(this._world, entity, control, dt);
+    } catch (err) {
+      this._finishFromThrown(entity, err);
+    }
   }
+
+  private _executeSequential(entity: Entity, dt: number): void {
+    for (const child of childrenOf(this._world, entity)) {
+      let status = terminalStatus(this._world, child);
+      if (status === "failed" || status === "cancelled") {
+        this._finish(entity, status === "cancelled" ? Cancelled : Failed);
+        return;
+      }
+      if (status === "succeeded") continue;
+
+      this._executeChild(child, dt);
 
-  private _executeSequential(entity: Entity): void {
-    const children = childrenOf(this._world, entity);
-
-    // Find the first non-terminal child
-    for (const child of children) {
-      if (isTerminal(this._world, child)) {
-        const status = terminalStatus(this._world, child)!;
-        if (status === "failed" || status === "cancelled") {
-          this._finish(entity, status === "cancelled" ? Cancelled : Failed);
-          return;
-        }
-        // succeeded — continue to next child
-        continue;
+      status = terminalStatus(this._world, child);
+      if (status === "failed" || status === "cancelled") {
+        this._finish(entity, status === "cancelled" ? Cancelled : Failed);
+        return;
       }
+      if (status === "succeeded") continue;
 
-      // Found a child that hasn't run yet — schedule it
-      this._world.add(child, Scheduled);
       return;
     }
 
-    // All children succeeded
     this._finish(entity, Succeeded);
   }
 
-  private _executeParallel(entity: Entity): void {
-    const children = childrenOf(this._world, entity);
+  private _executeParallel(entity: Entity, dt: number): void {
     let allDone = true;
 
-    for (const child of children) {
-      if (isTerminal(this._world, child)) {
-        const status = terminalStatus(this._world, child)!;
-        if (status === "failed" || status === "cancelled") {
-          this._finish(entity, status === "cancelled" ? Cancelled : Failed);
-          return;
-        }
-        // succeeded — this child is done
-        continue;
+    for (const child of childrenOf(this._world, entity)) {
+      let status = terminalStatus(this._world, child);
+      if (status === "failed" || status === "cancelled") {
+        this._finish(entity, status === "cancelled" ? Cancelled : Failed);
+        return;
       }
+      if (status === "succeeded") continue;
+
+      this._executeChild(child, dt);
+
+      status = terminalStatus(this._world, child);
+      if (status === "failed" || status === "cancelled") {
+        this._finish(entity, status === "cancelled" ? Cancelled : Failed);
+        return;
+      }
+      if (status === "succeeded") continue;
 
       allDone = false;
-
-      // Schedule if not already running or scheduled
-      if (
-        !this._world.has(child, Running) &&
-        !this._world.has(child, Scheduled)
-      ) {
-        this._world.add(child, Scheduled);
-      }
     }
 
     if (allDone) {
@@ -227,13 +312,12 @@ export class TaskRunner {
     }
   }
 
-  private _executeRandom(entity: Entity): void {
-    const children = childrenOf(this._world, entity);
+  private _executeRandom(entity: Entity, dt: number): void {
+    const eligible: Entity[] = [];
 
-    // Check if any child already reached a terminal
-    for (const child of children) {
-      if (isTerminal(this._world, child)) {
-        const status = terminalStatus(this._world, child)!;
+    for (const child of childrenOf(this._world, entity)) {
+      const status = terminalStatus(this._world, child);
+      if (status) {
         this._finish(
           entity,
           status === "succeeded"
@@ -244,72 +328,116 @@ export class TaskRunner {
         );
         return;
       }
+      if (!this._world.has(child, Running)) {
+        eligible.push(child);
+      }
     }
 
-    // Pick a random child that isn't already running
-    const eligible = children.filter(
-      (c) => !this._world.has(c, Running) && !this._world.has(c, Scheduled),
-    );
+    if (eligible.length === 0) return;
 
-    if (eligible.length > 0) {
-      const pick = eligible[Math.floor(Math.random() * eligible.length)];
-      this._world.add(pick, Scheduled);
+    const pick = eligible[Math.floor(Math.random() * eligible.length)];
+    this._executeChild(pick, dt);
+
+    const status = terminalStatus(this._world, pick);
+    if (status) {
+      this._finish(
+        entity,
+        status === "succeeded"
+          ? Succeeded
+          : status === "cancelled"
+            ? Cancelled
+            : Failed,
+      );
     }
-    // If no eligible children (all running), wait for one to finish
   }
 
-  private _executeRepeat(entity: Entity): void {
-    const children = childrenOf(this._world, entity);
+  private _executeCycle(entity: Entity, dt: number): void {
+    const child = this._firstTaskChild(entity);
+    if (!child) return;
 
-    // Repeat expects exactly one child
-    if (children.length === 0) return;
+    this._executeChild(child, dt);
 
-    const child = children[0];
-
-    // If child reached a terminal, reset the entire subtree and schedule again
     if (isTerminal(this._world, child)) {
       clearSubtree(this._world, child);
-      this._world.add(child, Scheduled);
-      return;
+      this._world.add(entity, Scheduled);
     }
-
-    // Schedule child if not already running or scheduled
-    if (
-      !this._world.has(child, Running) &&
-      !this._world.has(child, Scheduled)
-    ) {
-      this._world.add(child, Scheduled);
-    }
-    // Repeat itself never terminates — it just keeps the child going
+    // Cycle itself never terminates — it just creates tick-boundary cycles.
   }
 
-  private _executeSelector(entity: Entity): void {
-    const children = childrenOf(this._world, entity);
-
-    // Find the first non-terminal child
-    for (const child of children) {
-      if (isTerminal(this._world, child)) {
-        const status = terminalStatus(this._world, child)!;
-        if (status === "succeeded") {
-          // First success — selector succeeds
-          this._finish(entity, Succeeded);
-          return;
-        }
-        // failed or cancelled — continue to next child
-        continue;
+  private _executeWhilst(entity: Entity, dt: number): void {
+    let condition: boolean;
+    try {
+      condition = this.onCondition(this._world, entity, dt);
+    } catch (err) {
+      this._finishFromThrown(entity, err);
+      return;
+    }
+
+    if (!condition) {
+      this._finish(entity, Succeeded);
+      return;
+    }
+
+    const child = this._firstTaskChild(entity);
+    if (!child) {
+      this._finish(entity, Succeeded);
+      return;
+    }
+
+    this._executeChild(child, dt);
+
+    const status = terminalStatus(this._world, child);
+    if (status === "succeeded") {
+      clearSubtree(this._world, child);
+      this._world.add(entity, Scheduled);
+    } else if (status === "failed") {
+      this._finish(entity, Failed);
+    } else if (status === "cancelled") {
+      this._finish(entity, Cancelled);
+    }
+  }
+
+  private _executeSelector(entity: Entity, dt: number): void {
+    for (const child of childrenOf(this._world, entity)) {
+      let status = terminalStatus(this._world, child);
+      if (status === "succeeded") {
+        this._finish(entity, Succeeded);
+        return;
+      }
+      if (status === "failed" || status === "cancelled") continue;
+
+      this._executeChild(child, dt);
+
+      status = terminalStatus(this._world, child);
+      if (status === "succeeded") {
+        this._finish(entity, Succeeded);
+        return;
       }
+      if (status === "failed" || status === "cancelled") continue;
 
-      // Found a child that hasn't run yet — schedule it
-      this._world.add(child, Scheduled);
       return;
     }
 
-    // All children failed
     this._finish(entity, Failed);
   }
 
+  private _firstTaskChild(entity: Entity): Entity | null {
+    for (const child of childrenOf(this._world, entity)) {
+      return child;
+    }
+    return null;
+  }
+
   // ── Completion propagation ────────────────────────
 
+  private _finishFromThrown(entity: Entity, err: unknown): void {
+    if (err === Cancel) {
+      this.cancel(entity);
+    } else {
+      this.fail(entity);
+    }
+  }
+
   private _finish(
     entity: Entity,
     tag: typeof Succeeded | typeof Failed | typeof Cancelled,
@@ -322,30 +450,34 @@ export class TaskRunner {
     const status = terminalStatus(this._world, entity)!;
     this.onTerminal(this._world, entity, status);
 
-    // Notify parent
     const parent = parentOf(this._world, entity);
-    if (parent) {
-      this._world.add(parent, Scheduled);
+    if (parent && !this._executing.has(parent)) {
+      if (this._world.has(parent, Scheduled)) {
+        this._world.remove(parent, Scheduled);
+      }
+      this._execute(parent, this._currentDt);
     }
   }
 
-  private _cancelTree(entity: Entity): void {
+  private _cancelTree(entity: Entity, notifyParent: boolean): void {
     if (!this._world.has(entity, Task)) return;
 
-    // Cancel children first
+    // Cancel children first without repeatedly waking this node while its
+    // subtree is still being cancelled.
     for (const child of childrenOf(this._world, entity)) {
-      this._cancelTree(child);
+      this._cancelTree(child, false);
     }
 
-    // Cancel this node
     clearStatus(this._world, entity);
     this._world.add(entity, Cancelled);
     this.onTerminal(this._world, entity, "cancelled");
 
-    // Notify parent
     const parent = parentOf(this._world, entity);
-    if (parent) {
-      this._world.add(parent, Scheduled);
+    if (notifyParent && parent && !this._executing.has(parent)) {
+      if (this._world.has(parent, Scheduled)) {
+        this._world.remove(parent, Scheduled);
+      }
+      this._execute(parent, this._currentDt);
     }
   }
 }

src/bt/task.ts

@@ -1,30 +1,41 @@
 import { defineComponent } from "../component";
 import { defineRelationship } from "../relationship";
 
+// ── Cancel ────────────────────────────────────────────
+
+/** Throw from an action or wait starter to cancel that task and its subtree. */
+export const Cancel: unique symbol = Symbol("task.cancel");
+
 // ── Task component ────────────────────────────────────
 /**
  * Core component for behaviour-tree tasks.
  *
- * `kind` determines how the task evaluates its children:
- * - `"leaf"` — terminal node; external logic drives it to completion.
+ * `kind` determines how the task evaluates:
+ * - `"action"` — runs immediately and succeeds when its function returns.
+ * - `"wait"` — starts once and remains running until external code completes it.
  * - `"sequential"` — runs children one at a time, left to right.
  *   Succeeds when all children succeed; fails when any child fails.
- * - `"parallel"` — schedules all children at once.
+ * - `"parallel"` — starts all children at once.
  *   Succeeds when all children succeed; fails when any child fails.
- * - `"random"` — picks one child at random each time it's scheduled.
+ * - `"random"` — picks one child at random each time it runs.
  *   Succeeds/fails with that child's result.
- * - `"repeat"` — runs its single child. When the child finishes, resets it
- *   and runs again. Never terminates on its own (only via cancel).
+ * - `"cycle"` — runs its single child. When the child finishes, resets it
+ *   and schedules the next run for a future tick boundary. Never terminates
+ *   on its own (only via cancel).
+ * - `"whilst"` — runs its single child while its condition is true.
+ *   Succeeds when the condition becomes false; fails/cancels with its child.
  * - `"selector"` — runs children left to right. Succeeds on the first
  *   child that succeeds; fails only if all children fail.
  */
 export const Task = defineComponent("task", {
-  kind: "leaf" as
-    | "leaf"
+  kind: "action" as
+    | "action"
+    | "wait"
     | "sequential"
     | "parallel"
     | "random"
-    | "repeat"
+    | "cycle"
+    | "whilst"
     | "selector",
 });
 
@@ -34,7 +45,7 @@ export type TaskKind = (typeof Task.type)["kind"];
 /** A task that should be executed this tick. */
 export const Scheduled = defineComponent("scheduled", {});
 
-/** A task that is currently executing (multi-frame leaves). */
+/** A task that is currently executing or waiting for completion. */
 export const Running = defineComponent("running", {});
 
 /** The task completed successfully. */

src/bt/tree-def.ts

@@ -0,0 +1,231 @@
+import type { World, Entity } from "../index";
+import type { EntityDef, EntityDefChild } from "../entity-tree";
+import { Task, ChildOf, Cancel } from "./task";
+import { TaskRunner, type TaskControl } from "./runner";
+
+export { Cancel };
+
+// ── Task callback types ───────────────────────────────
+
+/** Runs immediately. Return = success, throw = failure, throw Cancel = cancel. */
+export type ActionFn = (world: World, entity: Entity, dt: number) => void;
+
+/** Starts a task that remains Running until completed by the supplied control. */
+export type WaitFn = (
+  world: World,
+  entity: Entity,
+  control: TaskControl,
+  dt: number,
+) => void;
+
+/** Controls a `whilst` task. False means the loop has completed successfully. */
+export type ConditionFn = (world: World, entity: Entity, dt: number) => boolean;
+
+export type TaskMeta =
+  | { readonly mode: "action"; readonly run: ActionFn }
+  | { readonly mode: "wait"; readonly start?: WaitFn }
+  | { readonly mode: "whilst"; readonly condition: ConditionFn };
+
+export type TaskEntityDef = EntityDef<typeof Task.type, TaskMeta | undefined>;
+
+/** Behaviour-tree definition accepted by `buildTree`. */
+export type TreeDef = TaskEntityDef;
+
+// ── Entity task factories ──────────────────────────────
+
+function compactChildren(children: readonly EntityDefChild[]): EntityDef[] {
+  return children.filter(Boolean) as EntityDef[];
+}
+
+function task(
+  kind: typeof Task.type.kind,
+  children: readonly EntityDefChild[] = [],
+  meta?: TaskMeta,
+): TaskEntityDef {
+  return {
+    kind: "entity",
+    component: Task,
+    value: { kind },
+    children: compactChildren(children),
+    meta,
+  };
+}
+
+/** Create an action task entity definition. */
+export function action(
+  run: ActionFn,
+  children: readonly EntityDefChild[] = [],
+): TaskEntityDef {
+  return task("action", children, { mode: "action", run });
+}
+
+/**
+ * Create a wait task entity definition.
+ *
+ * `wait()` creates a task that simply becomes Running. External systems can
+ * complete it with `runner.succeed(entity)`, `runner.fail(entity)`, or
+ * `runner.cancel(entity)`.
+ */
+export function wait(children?: readonly EntityDefChild[]): TaskEntityDef;
+export function wait(
+  start: WaitFn,
+  children?: readonly EntityDefChild[],
+): TaskEntityDef;
+export function wait(
+  startOrChildren?: WaitFn | readonly EntityDefChild[],
+  children: readonly EntityDefChild[] = [],
+): TaskEntityDef {
+  const hasChildrenAsFirstArg = Array.isArray(startOrChildren);
+  const start = hasChildrenAsFirstArg
+    ? undefined
+    : (startOrChildren as WaitFn | undefined);
+  return task("wait", hasChildrenAsFirstArg ? startOrChildren : children, {
+    mode: "wait",
+    start,
+  });
+}
+
+/** Create a sequential task entity definition. */
+export function sequential(
+  children: readonly EntityDefChild[] = [],
+): TaskEntityDef {
+  return task("sequential", children);
+}
+
+/** Create a parallel task entity definition. */
+export function parallel(
+  children: readonly EntityDefChild[] = [],
+): TaskEntityDef {
+  return task("parallel", children);
+}
+
+/** Create a selector task entity definition. */
+export function selector(
+  children: readonly EntityDefChild[] = [],
+): TaskEntityDef {
+  return task("selector", children);
+}
+
+/** Create a random task entity definition. */
+export function random(
+  children: readonly EntityDefChild[] = [],
+): TaskEntityDef {
+  return task("random", children);
+}
+
+/**
+ * Create a cycle task entity definition.
+ *
+ * `cycle(child)` and `cycle([child, metadataEntity])` are both supported.
+ * The runner operates only on child entities that have the `Task` component.
+ */
+export function cycle(child: EntityDef): TaskEntityDef;
+export function cycle(children?: readonly EntityDefChild[]): TaskEntityDef;
+export function cycle(
+  childOrChildren: EntityDef | readonly EntityDefChild[] = [],
+): TaskEntityDef {
+  return task(
+    "cycle",
+    Array.isArray(childOrChildren) ? childOrChildren : [childOrChildren],
+  );
+}
+
+/**
+ * Create a conditional loop task entity definition.
+ *
+ * Runs its child while `condition` returns true. When the child succeeds, the
+ * child subtree is reset and `whilst` schedules itself for the next tick
+ * boundary. When `condition` returns false, `whilst` succeeds.
+ */
+export function whilst(condition: ConditionFn, child: EntityDef): TaskEntityDef;
+export function whilst(
+  condition: ConditionFn,
+  children?: readonly EntityDefChild[],
+): TaskEntityDef;
+export function whilst(
+  condition: ConditionFn,
+  childOrChildren: EntityDef | readonly EntityDefChild[] = [],
+): TaskEntityDef {
+  return task(
+    "whilst",
+    Array.isArray(childOrChildren) ? childOrChildren : [childOrChildren],
+    { mode: "whilst", condition },
+  );
+}
+
+// ── Builder ───────────────────────────────────────────
+
+/**
+ * Materialize a behaviour-tree definition into ECS entities and return a
+ * fully-wired `TaskRunner`.
+ *
+ * Definitions are `EntityDef` trees produced by the task factories (`action`,
+ * `wait`, `sequential`, `parallel`, `selector`, `random`, `cycle`, `whilst`)
+ * and generic single-component entity factories. Non-task child entities are
+ * materialized into the ECS tree but ignored by `TaskRunner` execution.
+ */
+export function buildTree(world: World, def: TreeDef): TaskRunner {
+  const actions = new Map<Entity, ActionFn>();
+  const waits = new Map<Entity, WaitFn>();
+  const conditions = new Map<Entity, ConditionFn>();
+
+  function build(def: EntityDef, parent?: Entity): Entity {
+    const entity = world.spawn();
+    world.add(entity, def.component, def.value);
+
+    if (parent !== undefined) {
+      world.relate(entity, ChildOf, parent);
+    }
+
+    if (def.component === Task) {
+      const taskData = world.get(entity, Task);
+      const meta = def.meta as TaskMeta | undefined;
+
+      if (taskData.kind === "action") {
+        if (meta?.mode !== "action") {
+          throw new Error("Action task entity is missing an action function");
+        }
+        actions.set(entity, meta.run);
+      } else if (taskData.kind === "wait") {
+        if (meta?.mode === "wait" && meta.start) {
+          waits.set(entity, meta.start);
+        }
+      } else if (taskData.kind === "whilst") {
+        if (meta?.mode !== "whilst") {
+          throw new Error("Whilst task entity is missing a condition function");
+        }
+        conditions.set(entity, meta.condition);
+      }
+    }
+
+    for (const child of def.children) {
+      build(child, entity);
+    }
+
+    return entity;
+  }
+
+  const root = build(def);
+
+  if (!world.has(root, Task)) {
+    throw new Error("buildTree root must be a task entity");
+  }
+
+  const runner = new TaskRunner(world);
+  runner.root = root;
+
+  runner.onAction = (world, entity, dt) => {
+    actions.get(entity)?.(world, entity, dt);
+  };
+
+  runner.onWait = (world, entity, control, dt) => {
+    waits.get(entity)?.(world, entity, control, dt);
+  };
+
+  runner.onCondition = (world, entity, dt) => {
+    const condition = conditions.get(entity);
+    return condition ? condition(world, entity, dt) : false;
+  };
+
+  return runner;
+}

src/entity-tree.ts

@@ -0,0 +1,80 @@
+import type { ComponentDef } from "./component";
+import type { Entity } from "./entity";
+import type { RelationshipDef } from "./relationship";
+import type { World } from "./world";
+
+/**
+ * Declarative definition for one entity with one primary component.
+ *
+ * Children are materialized as entities and related to their parent by the
+ * relationship passed to `buildEntityTree`.
+ */
+export interface EntityDef<T extends Record<string, any> = any, M = unknown> {
+  readonly kind: "entity";
+  readonly component: ComponentDef<T>;
+  readonly value?: Partial<T>;
+  readonly children: readonly EntityDef[];
+  readonly meta?: M;
+}
+
+export type EntityDefChild = EntityDef | null | undefined | false;
+
+function compactChildren(children: readonly EntityDefChild[]): EntityDef[] {
+  return children.filter(Boolean) as EntityDef[];
+}
+
+/** Create a single-component entity definition. */
+export function entity<T extends Record<string, any>>(
+  component: ComponentDef<T>,
+  value?: Partial<T>,
+  children?: readonly EntityDefChild[],
+): EntityDef<T>;
+export function entity<T extends Record<string, any>>(
+  component: ComponentDef<T>,
+  children?: readonly EntityDefChild[],
+): EntityDef<T>;
+export function entity<T extends Record<string, any>>(
+  component: ComponentDef<T>,
+  valueOrChildren?: Partial<T> | readonly EntityDefChild[],
+  children: readonly EntityDefChild[] = [],
+): EntityDef<T> {
+  const hasChildrenAsSecondArg = Array.isArray(valueOrChildren);
+
+  const value = hasChildrenAsSecondArg
+    ? undefined
+    : (valueOrChildren as Partial<T> | undefined);
+  const childDefs = hasChildrenAsSecondArg ? valueOrChildren : children;
+
+  return {
+    kind: "entity",
+    component,
+    value,
+    children: compactChildren(childDefs),
+  };
+}
+
+/**
+ * Materialize an `EntityDef` tree into ECS entities.
+ *
+ * The supplied relationship connects child entities to their parent, which lets
+ * callers choose the semantic meaning of the tree edge.
+ */
+export function buildEntityTree(
+  world: World,
+  def: EntityDef,
+  childRelationship: RelationshipDef,
+  parent?: Entity,
+): Entity {
+  const entity = world.spawn();
+  world.add(entity, def.component, def.value);
+
+  if (parent !== undefined) {
+    world.relate(entity, childRelationship, parent);
+  }
+
+  for (const child of def.children) {
+    buildEntityTree(world, child, childRelationship, entity);
+  }
+
+  return entity;
+}

src/index.ts

@@ -8,6 +8,8 @@ export { query } from "./query";
 export { Query } from "./query";
 export type { Entity } from "./entity";
 export { makeEntity, entityIndex, entityGeneration } from "./entity";
+export { entity, buildEntityTree } from "./entity-tree";
+export type { EntityDef, EntityDefChild } from "./entity-tree";
 export { SparseSet } from "./storage/sparse-set";
 export type {
   WorldEvent,

src/relationship.ts

@@ -1,24 +1,55 @@
 // ── Relationship ─────────────────────────────────────
 /**
  * A relationship definition — like a component, but represents a directed
- * link between two entities.
+ * link between two entities. Every relationship carries an optional data
+ * payload (defaults to `{}` for bare edges).
  *
  * @example
  * ```ts
  * const ChildOf = defineRelationship('childOf');
- * world.relate(child, ChildOf, parent);
+ * const Health  = defineRelationship('health', { hp: 100 });
  * ```
  */
-export interface RelationshipDef {
+export interface RelationshipDef<T extends Record<string, any> = {}> {
   /** Unique symbol used as the storage key. */
   readonly _key: symbol;
   /** Human-readable name, used for serialization. */
   readonly name: string;
+  /** Default values used when no data override is provided. */
+  readonly defaults: T;
+  /** Phantom type for inference. */
+  readonly type: T;
 }
 
 /**
  * Define a named relationship between entities.
+ *
+ * When `defaults` is omitted the relationship is a bare edge (no data).
+ * When `defaults` is provided the relationship carries data accessible
+ * via `world.getRelData()` / `world.setRelData()`.
+ *
+ * @example
+ * ```ts
+ * // Bare edge
+ * const ChildOf = defineRelationship('childOf');
+ *
+ * // With data
+ * const Health = defineRelationship('health', { hp: 100 });
+ * ```
  */
-export function defineRelationship(name: string): RelationshipDef {
-  return { _key: Symbol(), name };
+export function defineRelationship(name: string): RelationshipDef<{}>;
+export function defineRelationship<T extends Record<string, any>>(
+  name: string,
+  defaults: T,
+): RelationshipDef<T>;
+export function defineRelationship<T extends Record<string, any>>(
+  name: string,
+  defaults?: T,
+): RelationshipDef<{}> | RelationshipDef<T> {
+  return {
+    _key: Symbol(),
+    name,
+    defaults: (defaults ?? {}) as any,
+    type: undefined as unknown as any,
+  };
 }

src/serialization.ts

@@ -5,6 +5,9 @@
 export interface WorldSnapshot {
   /** Entity stable ID → component map (component name → data). */
   entities: Record<string, Record<string, unknown>>;
-  /** Relationship name → (source ID → target ID). */
-  relationships: Record<string, Record<string, string>>;
+  /** Relationship name → (source ID → target ID or edge object). */
+  relationships: Record<
+    string,
+    Record<string, string | { target: string; data: unknown }>
+  >;
 }

src/world.ts

@@ -35,6 +35,8 @@ export class World {
   private _relReverse = new Map<symbol, Map<number, Set<number>>>();
   /** Key → RelationshipDef for event emission. */
   private _relKeyToDef = new Map<symbol, RelationshipDef>();
+  /** Relationship data: relationship._key → SparseSet<data> (keyed by source index). */
+  private _relData = new Map<symbol, SparseSet<any>>();
 
   // ── Change tracking ───────────────────────────────
   private _dirty = new Map<symbol, Set<number>>();
@@ -42,6 +44,9 @@ export class World {
   // ── Observable layer ──────────────────────────────
   private _observable = new ObservableLayer();
 
+  // ── Singleton entity ──────────────────────────────
+  private _singletonEntity: Entity | null = null;
+
   /** Global event stream. */
   get events$(): Observable<WorldEvent> {
     return this._observable.events$.asObservable();
@@ -90,6 +95,8 @@ export class World {
       if (fwd.has(idx)) {
         const target = fwd.get(idx);
         const rel = this._relKeyToDef.get(key)!;
+        // Clean up relationship data if applicable
+        this._relData.get(key)?.remove(idx);
         this._relRemoveEdge(entity, target, rel);
       }
 
@@ -250,14 +257,86 @@ export class World {
     }
   }
 
+  // ── Singleton component access ────────────────────
+
+  /**
+   * Add a singleton component to the world.
+   *
+   * A single shared entity is created lazily and reused for all singleton
+   * components.  Returns a mutable reference to the component data.
+   */
+  addSingleton<T extends Record<string, any>>(
+    def: ComponentDef<T>,
+    init?: Partial<T>,
+  ): T {
+    if (this._singletonEntity === null) {
+      this._singletonEntity = this.spawn();
+    }
+    return this.add(this._singletonEntity, def, init);
+  }
+
+  /** Remove a singleton component. Destroys the backing entity if it becomes bare. */
+  removeSingleton(def: ComponentDef<any>): void {
+    const e = this._singletonEntity;
+    if (e === null) return;
+    this.remove(e, def);
+    if (!this.hasAnyComponent(e)) {
+      this.destroy(e);
+      this._singletonEntity = null;
+    }
+  }
+
+  /** Get a mutable reference to a singleton component. Throws if missing. */
+  getSingleton<T extends Record<string, any>>(def: ComponentDef<T>): T {
+    return this.get(this._singletonEntity!, def);
+  }
+
+  /** Try-get a singleton component. Returns undefined if missing. */
+  tryGetSingleton<T extends Record<string, any>>(
+    def: ComponentDef<T>,
+  ): T | undefined {
+    const e = this._singletonEntity;
+    if (e === null) return undefined;
+    return this.tryGet(e, def);
+  }
+
+  /** Check whether a singleton component is present. */
+  hasSingleton(def: ComponentDef<any>): boolean {
+    const e = this._singletonEntity;
+    if (e === null) return false;
+    return this.has(e, def);
+  }
+
+  /** Bulk-replace a singleton component's data. Marks dirty. */
+  setSingleton<T extends Record<string, any>>(
+    def: ComponentDef<T>,
+    value: T,
+  ): void {
+    this.set(this._singletonEntity!, def, value);
+  }
+
+  /** Mark a singleton component as dirty for change tracking. */
+  markDirtySingleton(def: ComponentDef<any>): void {
+    this.markDirty(this._singletonEntity!, def);
+  }
+
   // ── Relationships ─────────────────────────────────
 
   /**
    * Create a directed relationship from `source` to `target`.
    * Each source can only have one target per relationship type.
    * If a relationship already exists, it is replaced.
+   *
+   * An optional `data` payload can be provided to store data along
+   * with the edge (accessible via `getRelData` / `setRelData`).
+   * Data is stored lazily — bare edges without data use no storage.
    */
-  relate(source: Entity, rel: RelationshipDef, target: Entity): void {
+  relate<T extends Record<string, any> = {}>(
+    source: Entity,
+    rel: RelationshipDef<T>,
+    target: Entity,
+    data?: Partial<T>,
+  ): void {
     const si = entityIndex(source);
     const ti = entityIndex(target);
     this._assertAlive(si, source);
@@ -285,6 +364,16 @@ export class World {
     this._relCounts[si]++;
     this._relCounts[ti]++;
 
+    // Lazy data storage — only allocate when data is provided
+    if (data !== undefined) {
+      let dataStore = this._relData.get(rel._key);
+      if (!dataStore) {
+        dataStore = new SparseSet<any>();
+        this._relData.set(rel._key, dataStore);
+      }
+      dataStore.set(si, { ...rel.defaults, ...data });
+    }
+
     this._emit({
       type: "relationshipAdded",
       source,
@@ -304,9 +393,48 @@ export class World {
     const target = this.getRelated(source, rel);
     if (target === undefined) return;
 
+    this._relData.get(rel._key)?.remove(si);
     this._relRemoveEdge(source, target, rel);
   }
 
+  /**
+   * Get the data stored alongside a relationship.
+   * Returns the relationship's defaults if no data was explicitly set.
+   */
+  getRelData<T extends Record<string, any> = {}>(
+    source: Entity,
+    rel: RelationshipDef<T>,
+  ): T {
+    const si = entityIndex(source);
+    this._assertAlive(si, source);
+
+    const store = this._relData.get(rel._key);
+    if (!store || !store.has(si)) {
+      return { ...rel.defaults };
+    }
+    return store.get(si);
+  }
+
+  /**
+   * Set the data for a relationship edge.
+   * Creates storage lazily if this is the first data set on this relationship type.
+   */
+  setRelData<T extends Record<string, any> = {}>(
+    source: Entity,
+    rel: RelationshipDef<T>,
+    data: T,
+  ): void {
+    const si = entityIndex(source);
+    this._assertAlive(si, source);
+
+    let store = this._relData.get(rel._key);
+    if (!store) {
+      store = new SparseSet<any>();
+      this._relData.set(rel._key, store);
+    }
+    store.set(si, data);
+  }
+
   /**
    * Get the target entity for a relationship, or undefined.
    */
@@ -322,17 +450,22 @@ export class World {
   /**
    * Get all source entities that point to `target` via this relationship.
    */
-  getRelatedTo(target: Entity, rel: RelationshipDef): Entity[] {
+  *getRelatedTo(
+    target: Entity,
+    rel: RelationshipDef,
+  ): IterableIterator<Entity> {
     const ti = entityIndex(target);
-    if (!this._isAlive(ti, target)) return [];
+    if (!this._isAlive(ti, target)) return;
 
     const rev = this._relReverse.get(rel._key);
-    if (!rev) return [];
+    if (!rev) return;
 
     const sources = rev.get(ti);
-    if (!sources) return [];
+    if (!sources) return;
 
-    return [...sources].map((si) => makeEntity(si, this._generations[si]));
+    for (const si of sources) {
+      yield makeEntity(si, this._generations[si]);
+    }
   }
 
   /**
@@ -434,14 +567,26 @@ export class World {
     }
 
     // Relationships
-    const relationships: Record<string, Record<string, string>> = {};
+    const relationships: Record<
+      string,
+      Record<string, string | { target: string; data: unknown }>
+    > = {};
     for (const [key, fwd] of this._relForward) {
       const rel = this._relKeyToDef.get(key)!;
-      const edges: Record<string, string> = {};
+      const edges: Record<string, string | { target: string; data: unknown }> =
+        {};
+      const dataStore = this._relData.get(key);
       for (const [si, target] of fwd.entries()) {
         const ti = entityIndex(target);
         if (ids[si] !== undefined && ids[ti] !== undefined) {
-          edges[ids[si]] = ids[ti];
+          if (dataStore?.has(si)) {
+            edges[ids[si]] = {
+              target: ids[ti],
+              data: dataStore.get(si),
+            };
+          } else {
+            edges[ids[si]] = ids[ti];
+          }
         }
       }
       if (Object.keys(edges).length > 0) {
@@ -501,11 +646,23 @@ export class World {
             `Pass it in the relationships array.`,
         );
       }
-      for (const [srcId, tgtId] of Object.entries(edges)) {
+      for (const [srcId, value] of Object.entries(edges)) {
         const source = idToEntity.get(srcId);
-        const target = idToEntity.get(tgtId);
-        if (source && target) {
-          world.relate(source, rel, target);
+        if (!source) continue;
+
+        if (typeof value === "string") {
+          // Pure edge (no data)
+          const target = idToEntity.get(value);
+          if (target) {
+            world.relate(source, rel, target);
+          }
+        } else if (typeof value === "object" && value !== null) {
+          // Edge with data
+          const edge = value as { target: string; data?: unknown };
+          const target = idToEntity.get(edge.target);
+          if (target) {
+            world.relate(source, rel, target, edge.data as any);
+          }
         }
       }
     }

test/bt.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect, beforeEach } from "vitest";
-import { World, type Entity } from "../src/index";
+import { World, defineComponent, entity, type Entity } from "../src/index";
 import {
   Task,
   Scheduled,
@@ -9,12 +9,19 @@ import {
   Cancelled,
   ChildOf,
   TaskRunner,
+  buildTree,
+  Cancel,
+  action,
+  wait,
+  cycle,
+  whilst,
+  sequential,
 } from "../src/bt/index";
 
 // ── Helpers ─────────────────────────────────────────
-function makeLeaf(world: World, parent?: Entity): Entity {
+function makeWait(world: World, parent?: Entity): Entity {
   const e = world.spawn();
-  world.add(e, Task, { kind: "leaf" });
+  world.add(e, Task, { kind: "wait" });
   if (parent) world.relate(e, ChildOf, parent);
   return e;
 }
@@ -40,9 +47,9 @@ function makeRandom(world: World, parent?: Entity): Entity {
   return e;
 }
 
-function makeRepeat(world: World, parent?: Entity): Entity {
+function makeCycle(world: World, parent?: Entity): Entity {
   const e = world.spawn();
-  world.add(e, Task, { kind: "repeat" });
+  world.add(e, Task, { kind: "cycle" });
   if (parent) world.relate(e, ChildOf, parent);
   return e;
 }
@@ -54,8 +61,178 @@ function makeSelector(world: World, parent?: Entity): Entity {
   return e;
 }
 
-// ── Leaf tasks ──────────────────────────────────────
-describe("Leaf tasks", () => {
+// ── Entity task factories ───────────────────────────
+describe("Entity task factories", () => {
+  it("materializes non-task child entities and ignores them during execution", () => {
+    const Label = defineComponent("testLabel", { value: "" });
+    const world = new World();
+    const calls: string[] = [];
+
+    const runner = buildTree(
+      world,
+      sequential([
+        entity(Label, { value: "sequence metadata" }),
+        action(() => calls.push("a")),
+        entity(Label, { value: "between leaves" }),
+        action(() => calls.push("b")),
+      ]),
+    );
+
+    const root = runner.root!;
+    const children = [...world.getRelatedTo(root, ChildOf)];
+    const labels = children
+      .filter((child) => world.has(child, Label))
+      .map((child) => world.get(child, Label).value);
+
+    expect(labels).toEqual(["sequence metadata", "between leaves"]);
+
+    runner.schedule(root);
+    for (let i = 0; i < 5; i++) runner.tick();
+
+    expect(calls).toEqual(["a", "b"]);
+    expect(world.has(root, Succeeded)).toBe(true);
+  });
+
+  it("action succeeds immediately when it returns", () => {
+    const world = new World();
+    let receivedDt = 0;
+    let receivedEntity: Entity | undefined;
+
+    const runner = buildTree(
+      world,
+      action((_world, entity, dt) => {
+        receivedEntity = entity;
+        receivedDt = dt;
+      }),
+    );
+
+    runner.schedule(runner.root!);
+    runner.tick(16);
+
+    expect(receivedEntity).toBe(runner.root);
+    expect(receivedDt).toBe(16);
+    expect(world.has(runner.root!, Succeeded)).toBe(true);
+  });
+
+  it("action fails or cancels when it throws", () => {
+    const world = new World();
+    const failed = buildTree(
+      world,
+      action(() => {
+        throw new Error("bad");
+      }),
+    );
+    const cancelled = buildTree(
+      world,
+      action(() => {
+        throw Cancel;
+      }),
+    );
+
+    failed.schedule(failed.root!);
+    failed.tick();
+    cancelled.schedule(cancelled.root!);
+    cancelled.tick();
+
+    expect(world.has(failed.root!, Failed)).toBe(true);
+    expect(world.has(cancelled.root!, Cancelled)).toBe(true);
+  });
+
+  it("wait can complete itself through task control", () => {
+    const world = new World();
+    const runner = buildTree(
+      world,
+      wait((_world, _entity, task) => {
+        task.succeed();
+      }),
+    );
+
+    runner.schedule(runner.root!);
+    runner.tick();
+
+    expect(world.has(runner.root!, Succeeded)).toBe(true);
+  });
+
+  it("wait without a starter remains running", () => {
+    const world = new World();
+    const runner = buildTree(world, wait());
+
+    runner.schedule(runner.root!);
+    runner.tick();
+
+    expect(world.has(runner.root!, Running)).toBe(true);
+  });
+
+  it("whilst loops at tick boundaries until its condition is false", () => {
+    const world = new World();
+    let count = 0;
+    const runner = buildTree(
+      world,
+      whilst(
+        () => count < 3,
+        action(() => {
+          count++;
+        }),
+      ),
+    );
+
+    runner.schedule(runner.root!);
+    runner.tick();
+    expect(count).toBe(1);
+    expect(world.has(runner.root!, Scheduled)).toBe(true);
+
+    runner.tick();
+    expect(count).toBe(2);
+
+    runner.tick();
+    expect(count).toBe(3);
+
+    runner.tick();
+    expect(world.has(runner.root!, Succeeded)).toBe(true);
+  });
+
+  it("whilst propagates child failure", () => {
+    const world = new World();
+    const runner = buildTree(
+      world,
+      whilst(
+        () => true,
+        action(() => {
+          throw new Error("bad");
+        }),
+      ),
+    );
+
+    runner.schedule(runner.root!);
+    runner.tick();
+
+    expect(world.has(runner.root!, Failed)).toBe(true);
+  });
+
+  it("cycle works with component child entities beside its task child", () => {
+    const Label = defineComponent("cycleLabel", { value: "" });
+    const world = new World();
+    let calls = 0;
+
+    const runner = buildTree(
+      world,
+      cycle([
+        entity(Label, { value: "cycle metadata" }),
+        action(() => {
+          calls++;
+        }),
+      ]),
+    );
+
+    runner.schedule(runner.root!);
+    for (let i = 0; i < 5; i++) runner.tick();
+
+    expect(calls).toBeGreaterThan(1);
+  });
+});
+
+// ── Wait tasks ──────────────────────────────────────
+describe("Wait tasks", () => {
   let world: World;
   let runner: TaskRunner;
 
@@ -64,79 +241,79 @@ describe("Leaf tasks", () => {
     runner = new TaskRunner(world);
   });
 
-  it("calls onLeaf when a leaf is scheduled and ticked", () => {
-    const leaf = makeLeaf(world);
+  it("calls onWait when a wait task is scheduled and ticked", () => {
+    const action = makeWait(world);
     const calls: Entity[] = [];
 
-    runner.onLeaf = (_w, e) => calls.push(e);
-    runner.schedule(leaf);
+    runner.onWait = (_w, e) => calls.push(e);
+    runner.schedule(action);
     runner.tick();
 
-    expect(calls).toEqual([leaf]);
+    expect(calls).toEqual([action]);
   });
 
-  it("marks leaf as Running after tick", () => {
-    const leaf = makeLeaf(world);
-    runner.schedule(leaf);
+  it("marks wait task as Running after tick", () => {
+    const action = makeWait(world);
+    runner.schedule(action);
     runner.tick();
 
-    expect(world.has(leaf, Running)).toBe(true);
-    expect(world.has(leaf, Scheduled)).toBe(false);
+    expect(world.has(action, Running)).toBe(true);
+    expect(world.has(action, Scheduled)).toBe(false);
   });
 
-  it("succeed() marks leaf as Succeeded", () => {
-    const leaf = makeLeaf(world);
-    runner.schedule(leaf);
+  it("succeed() marks wait task as Succeeded", () => {
+    const action = makeWait(world);
+    runner.schedule(action);
     runner.tick();
-    runner.succeed(leaf);
+    runner.succeed(action);
 
-    expect(world.has(leaf, Succeeded)).toBe(true);
-    expect(world.has(leaf, Running)).toBe(false);
+    expect(world.has(action, Succeeded)).toBe(true);
+    expect(world.has(action, Running)).toBe(false);
   });
 
-  it("fail() marks leaf as Failed", () => {
-    const leaf = makeLeaf(world);
-    runner.schedule(leaf);
+  it("fail() marks wait task as Failed", () => {
+    const action = makeWait(world);
+    runner.schedule(action);
     runner.tick();
-    runner.fail(leaf);
+    runner.fail(action);
 
-    expect(world.has(leaf, Failed)).toBe(true);
-    expect(world.has(leaf, Running)).toBe(false);
+    expect(world.has(action, Failed)).toBe(true);
+    expect(world.has(action, Running)).toBe(false);
   });
 
-  it("cancel() marks leaf as Cancelled", () => {
-    const leaf = makeLeaf(world);
-    runner.schedule(leaf);
+  it("cancel() marks wait task as Cancelled", () => {
+    const action = makeWait(world);
+    runner.schedule(action);
     runner.tick();
-    runner.cancel(leaf);
+    runner.cancel(action);
 
-    expect(world.has(leaf, Cancelled)).toBe(true);
-    expect(world.has(leaf, Running)).toBe(false);
+    expect(world.has(action, Cancelled)).toBe(true);
+    expect(world.has(action, Running)).toBe(false);
   });
 
-  it("onTerminal is called when leaf finishes", () => {
-    const leaf = makeLeaf(world);
+  it("onTerminal is called when wait task finishes", () => {
+    const action = makeWait(world);
     const terminals: { entity: Entity; status: string }[] = [];
 
     runner.onTerminal = (_w, e, s) => terminals.push({ entity: e, status: s });
-    runner.schedule(leaf);
+    runner.schedule(action);
     runner.tick();
-    runner.succeed(leaf);
+    runner.succeed(action);
 
-    expect(terminals).toEqual([{ entity: leaf, status: "succeeded" }]);
+    expect(terminals).toEqual([{ entity: action, status: "succeeded" }]);
   });
 
   it("reset() clears all status tags", () => {
-    const leaf = makeLeaf(world);
-    runner.schedule(leaf);
+    const action = makeWait(world);
+    runner.schedule(action);
     runner.tick();
-    runner.succeed(leaf);
+    runner.succeed(action);
 
-    runner.reset(leaf);
+    runner.reset(action);
 
-    expect(world.has(leaf, Succeeded)).toBe(false);
-    expect(world.has(leaf, Running)).toBe(false);
-    expect(world.has(leaf, Scheduled)).toBe(false);
+    expect(world.has(action, Succeeded)).toBe(false);
+    expect(world.has(action, Running)).toBe(false);
+    expect(world.has(action, Scheduled)).toBe(false);
   });
 });
 
@@ -152,44 +329,34 @@ describe("Sequential tasks", () => {
 
   it("runs children one at a time in order", () => {
     const seq = makeSequential(world);
-    const a = makeLeaf(world, seq);
-    const b = makeLeaf(world, seq);
-    const c = makeLeaf(world, seq);
+    const a = makeWait(world, seq);
+    const b = makeWait(world, seq);
+    const c = makeWait(world, seq);
 
     const leafCalls: Entity[] = [];
-    runner.onLeaf = (_w, e) => leafCalls.push(e);
+    runner.onWait = (_w, e) => leafCalls.push(e);
 
     runner.schedule(seq);
-    runner.tick(); // schedules first child
-    expect(world.has(a, Scheduled)).toBe(true);
-    expect(world.has(b, Scheduled)).toBe(false);
-    expect(world.has(c, Scheduled)).toBe(false);
-
-    runner.tick(); // runs a
-    runner.succeed(a);
-
-    // parent should be re-scheduled
-    runner.tick(); // schedules next child
-    expect(world.has(b, Scheduled)).toBe(true);
-
-    runner.tick(); // runs b
-    runner.succeed(b);
-
-    runner.tick(); // schedules c
-    expect(world.has(c, Scheduled)).toBe(true);
-
-    runner.tick(); // runs c
-    runner.succeed(c);
-
-    // parent should now be scheduled and succeed
     runner.tick();
+    expect(world.has(a, Running)).toBe(true);
+    expect(world.has(b, Running)).toBe(false);
+    expect(world.has(c, Running)).toBe(false);
+
+    runner.succeed(a);
+    expect(world.has(b, Running)).toBe(true);
+
+    runner.succeed(b);
+    expect(world.has(c, Running)).toBe(true);
+
+    runner.succeed(c);
     expect(world.has(seq, Succeeded)).toBe(true);
+    expect(leafCalls).toEqual([a, b, c]);
   });
 
   it("fails immediately when a child fails", () => {
     const seq = makeSequential(world);
-    const a = makeLeaf(world, seq);
-    const b = makeLeaf(world, seq);
+    const a = makeWait(world, seq);
+    const b = makeWait(world, seq);
 
     runner.schedule(seq);
     runner.tick(); // schedules a
@@ -206,8 +373,8 @@ describe("Sequential tasks", () => {
 
   it("succeeds when all children succeed", () => {
     const seq = makeSequential(world);
-    const a = makeLeaf(world, seq);
-    const b = makeLeaf(world, seq);
+    const a = makeWait(world, seq);
+    const b = makeWait(world, seq);
 
     runner.schedule(seq);
     runner.tick(); // schedules a
@@ -224,20 +391,20 @@ describe("Sequential tasks", () => {
   it("propagates terminal to grandparent", () => {
     const root = makeSequential(world);
     const child = makeSequential(world, root);
-    const leaf = makeLeaf(world, child);
+    const action = makeWait(world, child);
 
     const terminals: Entity[] = [];
     runner.onTerminal = (_w, e) => terminals.push(e);
 
     runner.schedule(root);
     runner.tick(); // schedules child
-    runner.tick(); // schedules leaf
-    runner.tick(); // runs leaf
-    runner.succeed(leaf);
+    runner.tick(); // schedules action
+    runner.tick(); // runs action
+    runner.succeed(action);
     runner.tick(); // child succeeds
     runner.tick(); // root succeeds
 
-    expect(terminals).toEqual([leaf, child, root]);
+    expect(terminals).toEqual([action, child, root]);
     expect(world.has(root, Succeeded)).toBe(true);
   });
 
@@ -261,24 +428,24 @@ describe("Parallel tasks", () => {
     runner = new TaskRunner(world);
   });
 
-  it("schedules all children at once", () => {
+  it("starts all children at once", () => {
     const par = makeParallel(world);
-    const a = makeLeaf(world, par);
-    const b = makeLeaf(world, par);
-    const c = makeLeaf(world, par);
+    const a = makeWait(world, par);
+    const b = makeWait(world, par);
+    const c = makeWait(world, par);
 
     runner.schedule(par);
     runner.tick();
 
-    expect(world.has(a, Scheduled)).toBe(true);
-    expect(world.has(b, Scheduled)).toBe(true);
-    expect(world.has(c, Scheduled)).toBe(true);
+    expect(world.has(a, Running)).toBe(true);
+    expect(world.has(b, Running)).toBe(true);
+    expect(world.has(c, Running)).toBe(true);
   });
 
   it("succeeds when all children succeed", () => {
     const par = makeParallel(world);
-    const a = makeLeaf(world, par);
-    const b = makeLeaf(world, par);
+    const a = makeWait(world, par);
+    const b = makeWait(world, par);
 
     runner.schedule(par);
     runner.tick(); // schedules both
@@ -307,8 +474,8 @@ describe("Parallel tasks", () => {
 
   it("fails immediately when any child fails", () => {
     const par = makeParallel(world);
-    const a = makeLeaf(world, par);
-    const b = makeLeaf(world, par);
+    const a = makeWait(world, par);
+    const b = makeWait(world, par);
 
     runner.schedule(par);
     runner.tick(); // schedules both
@@ -343,27 +510,25 @@ describe("Random tasks", () => {
 
   it("picks one child and succeeds/fails with it", () => {
     const rand = makeRandom(world);
-    const a = makeLeaf(world, rand);
-    const b = makeLeaf(world, rand);
+    const a = makeWait(world, rand);
+    const b = makeWait(world, rand);
 
     runner.schedule(rand);
     runner.tick();
 
-    // Exactly one child should be scheduled
-    const scheduled = [world.has(a, Scheduled), world.has(b, Scheduled)];
-    expect(scheduled.filter(Boolean)).toHaveLength(1);
+    // Exactly one child should be running
+    const running = [world.has(a, Running), world.has(b, Running)];
+    expect(running.filter(Boolean)).toHaveLength(1);
 
-    const picked = world.has(a, Scheduled) ? a : b;
-    runner.tick(); // runs picked leaf
+    const picked = world.has(a, Running) ? a : b;
     runner.succeed(picked);
 
-    runner.tick(); // random sees child done → succeeds
     expect(world.has(rand, Succeeded)).toBe(true);
   });
 
   it("fails when picked child fails", () => {
     const rand = makeRandom(world);
-    const a = makeLeaf(world, rand);
+    const a = makeWait(world, rand);
 
     runner.schedule(rand);
     runner.tick(); // schedules a (only child)
@@ -386,8 +551,8 @@ describe("Random tasks", () => {
   });
 });
 
-// ── Repeat ──────────────────────────────────────────
-describe("Repeat tasks", () => {
+// ── Cycle ──────────────────────────────────────────
+describe("Cycle tasks", () => {
   let world: World;
   let runner: TaskRunner;
 
@@ -397,110 +562,98 @@ describe("Repeat tasks", () => {
   });
 
   it("re-runs child after it succeeds", () => {
-    const rep = makeRepeat(world);
-    const leaf = makeLeaf(world, rep);
+    const cyc = makeCycle(world);
+    const action = makeWait(world, cyc);
 
-    let leafCount = 0;
-    runner.onLeaf = () => leafCount++;
+    let waitCount = 0;
+    runner.onWait = () => waitCount++;
 
-    runner.schedule(rep);
+    runner.schedule(cyc);
 
-    // First run
-    runner.tick(); // repeat schedules leaf
-    runner.tick(); // leaf runs
-    expect(leafCount).toBe(1);
-    runner.succeed(leaf);
+    runner.tick();
+    expect(waitCount).toBe(1);
+    runner.succeed(action);
 
-    // Repeat re-scheduled
-    runner.tick(); // repeat sees leaf done, resets and schedules again
-    runner.tick(); // leaf runs again
-    expect(leafCount).toBe(2);
-    runner.succeed(leaf);
+    // Completion schedules the cycle node at a tick boundary.
+    expect(world.has(cyc, Scheduled)).toBe(true);
+    runner.tick();
+    expect(waitCount).toBe(2);
+    runner.succeed(action);
 
-    // And again
-    runner.tick(); // repeat resets
-    runner.tick(); // leaf runs
-    expect(leafCount).toBe(3);
+    runner.tick();
+    expect(waitCount).toBe(3);
   });
 
   it("re-runs child after it fails", () => {
-    const rep = makeRepeat(world);
-    const leaf = makeLeaf(world, rep);
+    const cyc = makeCycle(world);
+    const action = makeWait(world, cyc);
 
-    let leafCount = 0;
-    runner.onLeaf = () => leafCount++;
+    let waitCount = 0;
+    runner.onWait = () => waitCount++;
 
-    runner.schedule(rep);
-    runner.tick(); // repeat schedules leaf
-    runner.tick(); // leaf runs
-    runner.fail(leaf);
+    runner.schedule(cyc);
+    runner.tick();
+    runner.fail(action);
 
-    // Repeat re-scheduled, resets leaf
-    runner.tick(); // repeat resets leaf
-    runner.tick(); // leaf runs again
-    expect(leafCount).toBe(2);
+    expect(world.has(cyc, Scheduled)).toBe(true);
+    runner.tick();
+    expect(waitCount).toBe(2);
   });
 
   it("never terminates on its own", () => {
-    const rep = makeRepeat(world);
-    const leaf = makeLeaf(world, rep);
+    const cyc = makeCycle(world);
+    const action = makeWait(world, cyc);
 
-    runner.schedule(rep);
-    runner.tick(); // schedules leaf
-    runner.tick(); // runs leaf
-    runner.succeed(leaf);
+    runner.schedule(cyc);
+    runner.tick();
+    runner.succeed(action);
 
-    // After many cycles, repeat is still not terminal
+    // After many cycles, cycle is still not terminal
     for (let i = 0; i < 5; i++) {
-      runner.tick(); // repeat resets + schedules leaf
-      runner.tick(); // leaf runs
-      runner.succeed(leaf);
+      runner.tick();
+      runner.succeed(action);
     }
 
-    expect(world.has(rep, Succeeded)).toBe(false);
-    expect(world.has(rep, Failed)).toBe(false);
-    expect(world.has(rep, Cancelled)).toBe(false);
+    expect(world.has(cyc, Succeeded)).toBe(false);
+    expect(world.has(cyc, Failed)).toBe(false);
+    expect(world.has(cyc, Cancelled)).toBe(false);
   });
 
   it("can be cancelled", () => {
-    const rep = makeRepeat(world);
-    const leaf = makeLeaf(world, rep);
+    const cyc = makeCycle(world);
+    const action = makeWait(world, cyc);
 
-    runner.schedule(rep);
-    runner.tick(); // schedules leaf
-    runner.tick(); // runs leaf
+    runner.schedule(cyc);
+    runner.tick();
 
-    runner.cancel(rep);
+    runner.cancel(cyc);
 
-    expect(world.has(rep, Cancelled)).toBe(true);
-    expect(world.has(leaf, Cancelled)).toBe(true);
+    expect(world.has(cyc, Cancelled)).toBe(true);
+    expect(world.has(action, Cancelled)).toBe(true);
   });
 
-  it("empty repeat does nothing", () => {
-    const rep = makeRepeat(world);
+  it("empty cycle does nothing", () => {
+    const cyc = makeCycle(world);
 
-    runner.schedule(rep);
+    runner.schedule(cyc);
     runner.tick();
 
     // No child, so nothing happens
-    expect(world.has(rep, Succeeded)).toBe(false);
-    expect(world.has(rep, Failed)).toBe(false);
+    expect(world.has(cyc, Succeeded)).toBe(false);
+    expect(world.has(cyc, Failed)).toBe(false);
   });
 
-  it("repeat inside sequential advances parent when cancelled", () => {
+  it("cycle inside sequential advances parent when cancelled", () => {
     const seq = makeSequential(world);
-    const rep = makeRepeat(world, seq);
-    const leaf = makeLeaf(world, rep);
-    const after = makeLeaf(world, seq);
+    const cyc = makeCycle(world, seq);
+    const action = makeWait(world, cyc);
+    const after = makeWait(world, seq);
 
     runner.schedule(seq);
-    runner.tick(); // seq schedules rep
-    runner.tick(); // rep schedules leaf
-    runner.tick(); // leaf runs
+    runner.tick();
 
-    // Cancel the repeat
-    runner.cancel(rep);
-    runner.tick(); // seq sees rep cancelled, seq becomes cancelled
+    // Cancel the cycle
+    runner.cancel(cyc);
 
     expect(world.has(seq, Cancelled)).toBe(true);
     expect(world.has(after, Scheduled)).toBe(false);
@@ -519,8 +672,8 @@ describe("Selector tasks", () => {
 
   it("succeeds on first child that succeeds", () => {
     const sel = makeSelector(world);
-    const a = makeLeaf(world, sel);
-    const b = makeLeaf(world, sel);
+    const a = makeWait(world, sel);
+    const b = makeWait(world, sel);
 
     runner.schedule(sel);
     runner.tick(); // schedules a
@@ -537,35 +690,28 @@ describe("Selector tasks", () => {
 
   it("tries next child when previous fails", () => {
     const sel = makeSelector(world);
-    const a = makeLeaf(world, sel);
-    const b = makeLeaf(world, sel);
-    const c = makeLeaf(world, sel);
+    const a = makeWait(world, sel);
+    const b = makeWait(world, sel);
+    const c = makeWait(world, sel);
 
     runner.schedule(sel);
     runner.tick(); // schedules a
     runner.tick(); // runs a
     runner.fail(a);
 
-    runner.tick(); // selector schedules b
-    expect(world.has(b, Scheduled)).toBe(true);
+    expect(world.has(b, Running)).toBe(true);
 
-    runner.tick(); // runs b
     runner.fail(b);
+    expect(world.has(c, Running)).toBe(true);
 
-    runner.tick(); // selector schedules c
-    expect(world.has(c, Scheduled)).toBe(true);
-
-    runner.tick(); // runs c
     runner.succeed(c);
-
-    runner.tick(); // selector succeeds
     expect(world.has(sel, Succeeded)).toBe(true);
   });
 
   it("fails when all children fail", () => {
     const sel = makeSelector(world);
-    const a = makeLeaf(world, sel);
-    const b = makeLeaf(world, sel);
+    const a = makeWait(world, sel);
+    const b = makeWait(world, sel);
 
     runner.schedule(sel);
     runner.tick(); // schedules a
@@ -590,16 +736,15 @@ describe("Selector tasks", () => {
 
   it("skips cancelled children and continues", () => {
     const sel = makeSelector(world);
-    const a = makeLeaf(world, sel);
-    const b = makeLeaf(world, sel);
+    const a = makeWait(world, sel);
+    const b = makeWait(world, sel);
 
     runner.schedule(sel);
     runner.tick(); // schedules a
     runner.tick(); // runs a
     runner.cancel(a);
 
-    runner.tick(); // selector sees a cancelled, tries b
-    expect(world.has(b, Scheduled)).toBe(true);
+    expect(world.has(b, Running)).toBe(true);
   });
 });
 
@@ -616,8 +761,8 @@ describe("Cancel", () => {
   it("cancels all descendants", () => {
     const root = makeSequential(world);
     const child = makeParallel(world, root);
-    const a = makeLeaf(world, child);
-    const b = makeLeaf(world, child);
+    const a = makeWait(world, child);
+    const b = makeWait(world, child);
 
     runner.schedule(root);
     runner.tick(); // schedules child
@@ -636,17 +781,17 @@ describe("Cancel", () => {
   it("cancel propagates to parent", () => {
     const root = makeSequential(world);
     const child = makeSequential(world, root);
-    const leaf = makeLeaf(world, child);
+    const action = makeWait(world, child);
 
     runner.schedule(root);
     runner.tick(); // schedules child
-    runner.tick(); // schedules leaf
-    runner.tick(); // runs leaf
+    runner.tick(); // schedules action
+    runner.tick(); // runs action
 
-    runner.cancel(leaf);
+    runner.cancel(action);
 
-    // leaf cancelled → child re-scheduled → child sees leaf cancelled → child cancelled
-    runner.tick(); // child processes cancelled leaf
+    // action cancelled → child re-scheduled → child sees action cancelled → child cancelled
+    runner.tick(); // child processes cancelled action
     expect(world.has(child, Cancelled)).toBe(true);
 
     // child cancelled → root re-scheduled → root sees child cancelled → root cancelled
@@ -655,8 +800,8 @@ describe("Cancel", () => {
   });
 });
 
-// ── Multi-frame leaves ──────────────────────────────
-describe("Multi-frame leaves", () => {
+// ── Multi-frame wait tasks ──────────────────────────────
+describe("Multi-frame wait tasks", () => {
   let world: World;
   let runner: TaskRunner;
 
@@ -665,28 +810,28 @@ describe("Multi-frame leaves", () => {
     runner = new TaskRunner(world);
   });
 
-  it("leaf stays Running across ticks until explicitly finished", () => {
-    const leaf = makeLeaf(world);
+  it("wait task stays Running across ticks until explicitly finished", () => {
+    const action = makeWait(world);
 
-    runner.schedule(leaf);
+    runner.schedule(action);
     runner.tick();
 
-    expect(world.has(leaf, Running)).toBe(true);
+    expect(world.has(action, Running)).toBe(true);
 
-    // Tick again — leaf is Running, not Scheduled, so nothing happens
+    // Tick again — action is Running, not Scheduled, so nothing happens
     runner.tick();
-    expect(world.has(leaf, Running)).toBe(true);
+    expect(world.has(action, Running)).toBe(true);
 
     // External system finishes it
-    runner.succeed(leaf);
-    expect(world.has(leaf, Succeeded)).toBe(true);
-    expect(world.has(leaf, Running)).toBe(false);
+    runner.succeed(action);
+    expect(world.has(action, Succeeded)).toBe(true);
+    expect(world.has(action, Running)).toBe(false);
   });
 
-  it("sequential waits for multi-frame leaf before advancing", () => {
+  it("sequential waits for multi-frame wait before advancing", () => {
     const seq = makeSequential(world);
-    const a = makeLeaf(world, seq);
-    const b = makeLeaf(world, seq);
+    const a = makeWait(world, seq);
+    const b = makeWait(world, seq);
 
     runner.schedule(seq);
     runner.tick(); // schedules a
@@ -698,10 +843,9 @@ describe("Multi-frame leaves", () => {
     expect(world.has(b, Scheduled)).toBe(false);
     expect(world.has(b, Running)).toBe(false);
 
-    // Finish a
+    // Finish a; parent propagation starts b immediately.
     runner.succeed(a);
-    runner.tick(); // seq schedules b
-    expect(world.has(b, Scheduled)).toBe(true);
+    expect(world.has(b, Running)).toBe(true);
   });
 });
 
@@ -729,11 +873,11 @@ describe("Edge cases", () => {
   it("tick is a no-op when nothing is scheduled", () => {
     const world = new World();
     const runner = new TaskRunner(world);
-    const leaf = makeLeaf(world);
+    const action = makeWait(world);
 
-    // Leaf exists but is not Scheduled
+    // Wait task exists but is not Scheduled
     expect(() => runner.tick()).not.toThrow();
-    expect(world.has(leaf, Running)).toBe(false);
+    expect(world.has(action, Running)).toBe(false);
   });
 
   it("deeply nested tree works correctly", () => {
@@ -742,29 +886,15 @@ describe("Edge cases", () => {
 
     const root = makeSequential(world);
     const mid = makeSequential(world, root);
-    const leaf = makeLeaf(world, mid);
+    const action = makeWait(world, mid);
 
     runner.schedule(root);
 
-    // Tick 1: root schedules mid
     runner.tick();
-    expect(world.has(mid, Scheduled)).toBe(true);
+    expect(world.has(action, Running)).toBe(true);
 
-    // Tick 2: mid schedules leaf
-    runner.tick();
-    expect(world.has(leaf, Scheduled)).toBe(true);
-
-    // Tick 3: leaf runs
-    runner.tick();
-    expect(world.has(leaf, Running)).toBe(true);
-
-    runner.succeed(leaf);
-    // leaf done → mid scheduled
-
-    runner.tick(); // mid sees leaf done → mid succeeds
+    runner.succeed(action);
     expect(world.has(mid, Succeeded)).toBe(true);
-
-    runner.tick(); // root sees mid done → root succeeds
     expect(world.has(root, Succeeded)).toBe(true);
   });
 });

test/relationships.test.ts

@@ -55,7 +55,7 @@ describe("Relationships", () => {
     world.relate(a, ChildOf, parent);
     world.relate(b, ChildOf, parent);
 
-    const children = world.getRelatedTo(parent, ChildOf);
+    const children = [...world.getRelatedTo(parent, ChildOf)];
     expect(children).toHaveLength(2);
     expect(children).toContain(a);
     expect(children).toContain(b);
@@ -63,7 +63,7 @@ describe("Relationships", () => {
 
   it("getRelatedTo returns empty when no edges", () => {
     const e = world.spawn();
-    expect(world.getRelatedTo(e, ChildOf)).toEqual([]);
+    expect([...world.getRelatedTo(e, ChildOf)]).toEqual([]);
   });
 
   it("unrelate removes the relationship", () => {
@@ -74,7 +74,7 @@ describe("Relationships", () => {
     world.unrelate(child, ChildOf);
 
     expect(world.getRelated(child, ChildOf)).toBeUndefined();
-    expect(world.getRelatedTo(parent, ChildOf)).toEqual([]);
+    expect([...world.getRelatedTo(parent, ChildOf)]).toEqual([]);
   });
 
   it("unrelate is idempotent", () => {
@@ -89,13 +89,13 @@ describe("Relationships", () => {
 
     world.relate(a, ChildOf, b);
     expect(world.getRelated(a, ChildOf)).toBe(b);
-    expect(world.getRelatedTo(b, ChildOf)).toContain(a);
+    expect([...world.getRelatedTo(b, ChildOf)]).toContain(a);
 
     world.relate(a, ChildOf, c);
     expect(world.getRelated(a, ChildOf)).toBe(c);
     // a should no longer point to b
-    expect(world.getRelatedTo(b, ChildOf)).toEqual([]);
-    expect(world.getRelatedTo(c, ChildOf)).toContain(a);
+    expect([...world.getRelatedTo(b, ChildOf)]).toEqual([]);
+    expect([...world.getRelatedTo(c, ChildOf)]).toContain(a);
   });
 });
 
@@ -243,7 +243,7 @@ describe("Destroy cleanup", () => {
 
     world.destroy(child);
     expect(world.getRelated(child, ChildOf)).toBeUndefined();
-    expect(world.getRelatedTo(parent, ChildOf)).toEqual([]);
+    expect([...world.getRelatedTo(parent, ChildOf)]).toEqual([]);
   });
 
   it("removes edges when target is destroyed", () => {
@@ -252,7 +252,7 @@ describe("Destroy cleanup", () => {
     world.relate(child, ChildOf, parent);
 
     world.destroy(parent);
-    expect(world.getRelatedTo(parent, ChildOf)).toEqual([]);
+    expect([...world.getRelatedTo(parent, ChildOf)]).toEqual([]);
     expect(world.getRelated(child, ChildOf)).toBeUndefined();
   });
 
@@ -376,6 +376,159 @@ describe("Dead entity safety", () => {
   it("getRelatedTo returns empty for dead entity", () => {
     const e = world.spawn();
     world.destroy(e);
-    expect(world.getRelatedTo(e, ChildOf)).toEqual([]);
+    expect([...world.getRelatedTo(e, ChildOf)]).toEqual([]);
+  });
+});
+
+// ── Data-carrying relationships ───────────────────────
+describe("Data-carrying relationships", () => {
+  let world: World;
+
+  beforeEach(() => {
+    world = new World();
+  });
+
+  it("defines a data-carrying relationship", () => {
+    const Health = defineRelationship("health", { hp: 100, maxHp: 100 });
+    expect(Health.name).toBe("health");
+    expect(Health.defaults).toEqual({ hp: 100, maxHp: 100 });
+  });
+
+  it("relate stores defaults as data", () => {
+    const Health = defineRelationship("health", { hp: 100 });
+    const player = world.spawn();
+    const game = world.spawn();
+
+    world.relate(player, Health, game);
+    const data = world.getRelData(player, Health);
+    expect(data).toEqual({ hp: 100 });
+  });
+
+  it("relate accepts data override", () => {
+    const Health = defineRelationship("health", { hp: 100 });
+    const player = world.spawn();
+    const game = world.spawn();
+
+    world.relate(player, Health, game, { hp: 50 });
+    const data = world.getRelData(player, Health);
+    expect(data).toEqual({ hp: 50 });
+  });
+
+  it("setRelData updates relationship data", () => {
+    const Health = defineRelationship("health", { hp: 100 });
+    const player = world.spawn();
+    const game = world.spawn();
+
+    world.relate(player, Health, game);
+    world.setRelData(player, Health, { hp: 75 });
+    expect(world.getRelData(player, Health)).toEqual({ hp: 75 });
+  });
+
+  it("getRelData returns defaults when no data was set", () => {
+    const Health = defineRelationship("health", { hp: 100 });
+    const player = world.spawn();
+
+    // Even without an edge, getRelData returns a copy of defaults
+    expect(world.getRelData(player, Health)).toEqual({ hp: 100 });
+  });
+
+  it("setRelData works even without prior relate", () => {
+    const Health = defineRelationship("health", { hp: 100 });
+    const player = world.spawn();
+
+    world.setRelData(player, Health, { hp: 50 });
+    expect(world.getRelData(player, Health)).toEqual({ hp: 50 });
+  });
+
+  it("data survives unrelate and re-relate", () => {
+    const Health = defineRelationship("health", { hp: 100 });
+    const player = world.spawn();
+    const game = world.spawn();
+
+    world.relate(player, Health, game, { hp: 50 });
+    world.unrelate(player, Health);
+
+    // After unrelate, stored data is gone, returns defaults
+    expect(world.getRelData(player, Health)).toEqual({ hp: 100 });
+
+    world.relate(player, Health, game, { hp: 80 });
+    // Note: this is a *new* relate with data, so stored data is { hp: 80 }
+    expect(world.getRelData(player, Health)).toEqual({ hp: 80 });
+  });
+
+  it("data is cleaned up on destroy", () => {
+    const Health = defineRelationship("health", { hp: 100 });
+    const player = world.spawn();
+    const game = world.spawn();
+
+    world.relate(player, Health, game, { hp: 50 });
+    world.destroy(player);
+
+    // After destroy the entity is dead — assertAlive throws, not the data lookup
+    expect(() => world.getRelData(player, Health)).toThrow("not alive");
+  });
+
+  it("setRelData with no prior edge stores data that getsRelated does not see", () => {
+    const Health = defineRelationship("health", { hp: 100 });
+    const player = world.spawn();
+
+    world.setRelData(player, Health, { hp: 50 });
+    // No edge exists yet
+    expect(world.getRelated(player, Health)).toBeUndefined();
+    // But data is stored (decoupled storage)
+    expect(world.getRelData(player, Health)).toEqual({ hp: 50 });
+  });
+
+  it("data-carrying relationships serialize and deserialize", () => {
+    const Health = defineRelationship("health", { hp: 100, maxHp: 100 });
+    const player = world.spawn();
+    const game = world.spawn();
+
+    world.relate(player, Health, game, { hp: 50, maxHp: 100 });
+
+    const snapshot = world.toJSON();
+
+    // Verify the snapshot has data in the relationship structure
+    const relSection = snapshot.relationships["health"];
+    expect(relSection).toBeDefined();
+
+    // Find the player source ID — it's the entity without components
+    const playerId = Object.keys(snapshot.entities).find(
+      (id) => Object.keys(snapshot.entities[id]).length === 0,
+    )!;
+    const edgeValue = relSection[playerId];
+    expect(typeof edgeValue).toBe("object");
+    expect((edgeValue as any).target).toBeDefined();
+    expect((edgeValue as any).data).toEqual({ hp: 50, maxHp: 100 });
+
+    // Check JSON round-trip preserves data
+    const parsed = JSON.parse(JSON.stringify(snapshot));
+    const world2 = World.fromJSON(parsed, [], [Health]);
+
+    const snap2 = world2.toJSON();
+    const playerId2 = Object.keys(snap2.entities).find(
+      (id) => Object.keys(snap2.entities[id]).length === 0,
+    )!;
+    expect(snap2.relationships["health"]).toBeDefined();
+    const edgeValue2 = snap2.relationships["health"][playerId2];
+    expect((edgeValue2 as any).data).toEqual({ hp: 50, maxHp: 100 });
+  });
+
+  it("pure edge-defined relationships still work alongside data relationships", () => {
+    const ChildOf2 = defineRelationship("childOf2");
+    const Score = defineRelationship("score", { points: 0 });
+
+    const parent = world.spawn();
+    const child = world.spawn();
+    const game = world.spawn();
+
+    world.relate(child, ChildOf2, parent);
+    world.relate(child, Score, game, { points: 42 });
+
+    // Pure edge still works
+    expect(world.getRelated(child, ChildOf2)).toBe(parent);
+
+    // Data edge still works
+    expect(world.getRelData(child, Score)).toEqual({ points: 42 });
   });
 });

test/serialization.test.ts

@@ -277,7 +277,9 @@ describe("Serialization — complex state", () => {
       const comps = snap.entities[id];
       return comps.position && comps.velocity && !comps.health;
     })!;
-    const playerId = snap.relationships.ownedBy[bulletId];
+    const playerEdge = snap.relationships.ownedBy[bulletId];
+    const playerId =
+      typeof playerEdge === "string" ? playerEdge : playerEdge.target;
 
     // Player should have a name
     const playerComps = snap.entities[playerId];

test/three-monks.test.ts

@@ -0,0 +1,268 @@
+import { describe, expect, it } from "vitest";
+import { World, query, type Entity } from "../src/index";
+import { generateRandomPlayLog } from "../examples/three-monks/random-playthrough";
+import {
+  ActionCard,
+  CARRYING_TOOLS,
+  GameState,
+  Player,
+  Table,
+  Tool,
+  WoodenFishMarker,
+  getActionCard,
+  getPlayersInSeatOrder,
+  getSelectedAction,
+  getToolOf,
+  setupGame,
+  type ActionKind,
+  type ToolKind,
+} from "../examples/three-monks/components";
+import { createThreeMonksFlow } from "../examples/three-monks/gameflow";
+import {
+  prepareNextRound,
+  resolveChant,
+  resolveEndOfRoundTools,
+  resolveDrink,
+  resolveExchange,
+  resolveFetchWater,
+  selectAction,
+} from "../examples/three-monks/rules";
+
+function setup(names = ["A", "B", "C"]): { world: World; players: Entity[] } {
+  const world = new World();
+  const players = setupGame(world, names);
+  return { world, players };
+}
+
+function setTool(
+  world: World,
+  player: Entity,
+  kind: ToolKind,
+  water = 0,
+): Entity {
+  const tool = getToolOf(world, player);
+  world.set(tool, Tool, { owner: player, kind, water });
+  return tool;
+}
+
+function selectAll(world: World, actions: readonly ActionKind[]): void {
+  const players = getPlayersInSeatOrder(world);
+  for (let i = 0; i < players.length; i++) {
+    selectAction(world, players[i], actions[i]);
+  }
+}
+
+describe("Three Monks random logging", () => {
+  it("generates a complete deterministic random playthrough log", () => {
+    const result = generateRandomPlayLog({ seed: 20260701 });
+
+    expect(result.log).toContain("三个和尚随机对局");
+    expect(result.log).toContain("游戏结束");
+    expect(result.log).toContain("胜者：慧空");
+    expect(result.roundsPlayed).toBe(14);
+  });
+});
+
+describe("Three Monks setup", () => {
+  it("requires 3-8 players", () => {
+    expect(() => setupGame(new World(), ["A", "B"])).toThrow();
+    expect(() =>
+      setupGame(new World(), ["1", "2", "3", "4", "5", "6", "7", "8", "9"]),
+    ).toThrow();
+  });
+
+  it("creates players, action cards, tools, table state, and wooden fish marker", () => {
+    const { world, players } = setup();
+
+    expect(players).toHaveLength(3);
+    expect([...world.query(query(Player))]).toHaveLength(3);
+    expect(players.map((player) => world.get(player, Player).water)).toEqual([
+      2, 2, 2,
+    ]);
+    expect([...world.query(query(ActionCard))]).toHaveLength(15);
+    const tools = [...world.query(query(Tool))].map(
+      (tool) => world.get(tool, Tool).kind,
+    );
+    expect(tools).toHaveLength(3);
+    expect(tools.filter((kind) => CARRYING_TOOLS.has(kind))).toHaveLength(2);
+    expect(world.hasSingleton(Table)).toBe(true);
+    expect(world.hasSingleton(GameState)).toBe(true);
+    expect(players).toContain(world.getSingleton(WoodenFishMarker).holder);
+  });
+});
+
+describe("Three Monks action selection", () => {
+  it("selects an available card and prevents selecting cooldown", () => {
+    const { world, players } = setup();
+
+    selectAction(world, players[0], "fetchWater");
+    expect(getSelectedAction(world, players[0])).toBe("fetchWater");
+
+    prepareNextRound(world);
+    const card = getActionCard(world, players[0], "fetchWater")!;
+    expect(world.get(card, ActionCard).zone).toBe("cooldown");
+    expect(() => selectAction(world, players[0], "fetchWater")).toThrow();
+
+    selectAction(world, players[0], "rest");
+    expect(getSelectedAction(world, players[0])).toBe("rest");
+  });
+
+  it("behavior tree completes a round after all players select", () => {
+    const { world, players } = setup();
+    const flow = createThreeMonksFlow(world);
+
+    flow.start();
+    flow.runner.tick();
+
+    for (const player of players) {
+      selectAction(world, player, "rest");
+      flow.notifySelectionChanged();
+      flow.runner.tick();
+    }
+
+    for (const player of players) {
+      const rest = getActionCard(world, player, "rest")!;
+      expect(world.get(rest, ActionCard).zone).toBe("cooldown");
+    }
+    expect(world.getSingleton(Table).round).toBe(2);
+  });
+});
+
+describe("Three Monks phase rules", () => {
+  it("fetch water moves player water to carrying tools and applies modifiers", () => {
+    const { world, players } = setup();
+    world.get(players[0], Player).water = 1;
+    setTool(world, players[0], "bucket");
+    setTool(world, players[1], "woodenBucket");
+    setTool(world, players[2], "ladle");
+    selectAll(world, ["fetchWater", "fetchWater", "rest"]);
+
+    resolveFetchWater(world);
+
+    expect(world.get(players[0], Player).water).toBe(0);
+    expect(world.get(getToolOf(world, players[0]), Tool).water).toBe(1);
+    expect(world.get(getToolOf(world, players[1]), Tool).water).toBe(0);
+    expect(world.get(getToolOf(world, players[2]), Tool).water).toBe(0);
+    expect(world.getSingleton(Table).centralWater).toBe(1);
+  });
+
+  it("fetch water does not move water when the player cannot pay", () => {
+    const { world, players } = setup();
+    world.get(players[0], Player).water = 0;
+    setTool(world, players[0], "bucket");
+    selectAll(world, ["fetchWater", "rest", "rest"]);
+
+    resolveFetchWater(world);
+
+    expect(world.get(players[0], Player).water).toBe(0);
+    expect(world.get(getToolOf(world, players[0]), Tool).water).toBe(0);
+    expect(world.getSingleton(Table).centralWater).toBe(2);
+  });
+
+  it("ladle moves one central water after fetching", () => {
+    const { world, players } = setup();
+    world.get(players[0], Player).water = 2;
+    setTool(world, players[0], "ladle");
+    setTool(world, players[1], "woodenFish");
+    setTool(world, players[2], "bottle");
+    selectAll(world, ["fetchWater", "rest", "rest"]);
+
+    resolveFetchWater(world);
+
+    expect(world.get(players[0], Player).water).toBe(0);
+    expect(world.get(getToolOf(world, players[0]), Tool).water).toBe(3);
+    expect(world.getSingleton(Table).centralWater).toBe(1);
+  });
+
+  it("exchange excludes chant proposers and shoulder pole dumps water", () => {
+    const { world, players } = setup();
+    const shoulderPole = setTool(world, players[0], "shoulderPole", 3);
+    const bottle = setTool(world, players[1], "bottle");
+    const bucket = setTool(world, players[2], "bucket");
+    selectAll(world, ["exchange", "chant", "exchange"]);
+
+    resolveExchange(world);
+
+    expect(world.getSingleton(Table).centralWater).toBe(3);
+    expect(world.get(shoulderPole, Tool).water).toBe(0);
+    expect(world.get(shoulderPole, Tool).owner).toBe(players[2]);
+    expect(world.get(bucket, Tool).owner).toBe(players[0]);
+    expect(world.get(bottle, Tool).owner).toBe(players[1]);
+  });
+
+  it("drink resolves in wooden fish order and first player to 10 wins immediately", () => {
+    const { world, players } = setup();
+    world.setSingleton(WoodenFishMarker, { holder: players[1] });
+    world.getSingleton(Table).centralWater = 3;
+    world.get(players[1], Player).water = 9;
+    setTool(world, players[0], "bucket");
+    setTool(world, players[1], "bucket");
+    setTool(world, players[2], "bucket");
+    selectAll(world, ["drink", "drink", "drink"]);
+
+    resolveDrink(world);
+
+    expect(world.getSingleton(GameState).winner).toBe(players[1]);
+    expect(world.get(players[2], Player).water).toBe(2);
+  });
+
+  it("water jar participates in drink only when its owner proposed drink", () => {
+    const { world, players } = setup();
+    world.getSingleton(Table).centralWater = 3;
+    setTool(world, players[0], "waterJar");
+    setTool(world, players[1], "bucket");
+    setTool(world, players[2], "bucket");
+    selectAll(world, ["rest", "drink", "drink"]);
+
+    resolveDrink(world);
+
+    expect(world.get(players[0], Player).water).toBe(2);
+    expect(world.get(players[1], Player).water).toBe(3);
+  });
+
+  it("big bowl stores central water if the owner did not drink from it", () => {
+    const { world, players } = setup();
+    world.setSingleton(WoodenFishMarker, { holder: players[0] });
+    world.getSingleton(Table).centralWater = 2;
+    setTool(world, players[0], "bigBowl", 0);
+    setTool(world, players[1], "bucket");
+    setTool(world, players[2], "bucket");
+    selectAll(world, ["drink", "drink", "drink"]);
+
+    resolveDrink(world);
+
+    expect(world.get(players[0], Player).water).toBe(3);
+    expect(world.get(getToolOf(world, players[0]), Tool).water).toBe(1);
+    expect(world.getSingleton(Table).centralWater).toBe(0);
+  });
+
+  it("chant gives marker to last chanter and applies bottle/mouse effects", () => {
+    const { world, players } = setup(["A", "B", "C", "D"]);
+    world.setSingleton(WoodenFishMarker, { holder: players[0] });
+    setTool(world, players[0], "bucket", 1);
+    setTool(world, players[1], "bottle", 0);
+    const mouse = setTool(world, players[2], "mouse", 0);
+    setTool(world, players[3], "bucket", 1);
+    selectAll(world, ["rest", "chant", "chant", "rest"]);
+
+    resolveChant(world);
+
+    expect(world.getSingleton(WoodenFishMarker).holder).toBe(players[2]);
+    expect(world.get(getToolOf(world, players[1]), Tool).water).toBe(1);
+    expect(world.get(mouse, Tool).water).toBe(1);
+  });
+
+  it("wooden fish tool overrides chant marker at end of round", () => {
+    const { world, players } = setup();
+    setTool(world, players[0], "woodenFish");
+    setTool(world, players[1], "bottle");
+    setTool(world, players[2], "bucket");
+    selectAll(world, ["rest", "chant", "rest"]);
+
+    resolveChant(world);
+    expect(world.getSingleton(WoodenFishMarker).holder).toBe(players[1]);
+
+    resolveEndOfRoundTools(world);
+    expect(world.getSingleton(WoodenFishMarker).holder).toBe(players[0]);
+  });
+});

tsconfig.json

@@ -11,8 +11,7 @@
     "declarationMap": true,
     "sourceMap": true,
     "outDir": "./dist",
-    "rootDir": "./src"
   },
-  "include": ["src"],
-  "exclude": ["node_modules", "dist"]
+  "include": ["src", "test", "examples"],
+  "exclude": ["node_modules", "dist"],
 }