diff --git a/examples/blackjack/commands.ts b/examples/blackjack/commands.ts
index 84b257f..3090d69 100644
--- a/examples/blackjack/commands.ts
+++ b/examples/blackjack/commands.ts
@@ -1,4 +1,26 @@
 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", {});
@@ -14,3 +36,112 @@ 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.`,
+  });
+}
diff --git a/examples/blackjack/components.ts b/examples/blackjack/components.ts
index c4f7008..720c446 100644
--- a/examples/blackjack/components.ts
+++ b/examples/blackjack/components.ts
@@ -1,6 +1,10 @@
 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 ────────────────────────────
 
-// ── Card ─────────────────────────────────────────────
 /** Each card is its own entity. `order` tracks position within its collection. */
 export const Card = defineComponent("card", {
   rank: "A",
@@ -36,3 +40,164 @@ 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(0, "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;
+  }
+}
diff --git a/examples/blackjack/main.ts b/examples/blackjack/main.ts
index 4242d9a..8f1a2d1 100644
--- a/examples/blackjack/main.ts
+++ b/examples/blackjack/main.ts
@@ -2,11 +2,12 @@
 //
 // Architecture:
 //   Behaviour Tree (buildTree) — controls game flow:
-//     root (repeat)
-//       └── seq (sequential)
-//             ├── handleInput (leaf)     — reads queued commands, mutates state
-//             ├── dealerPlay (leaf)      — auto-plays dealer hand on dealerTurn
-//             └── render (leaf)          — draws via blessed
+//     parallel
+//       ├── dealerPlay (leaf)      — generator loop, auto-plays dealer hand
+//       └── repeat
+//             └── seq (sequential)
+//                   ├── handleInput (leaf)  — reads queued commands
+//                   └── render (leaf)       — draws via blessed
 //
 //   CommandQueue — processes input:
 //     Keyboard → spawn command entities → CommandQueue.execute()
@@ -22,34 +23,28 @@
 //   npx tsx examples/blackjack/main.ts
 
 import { World } from "../../src/index";
-import { query } from "../../src/query";
 import { buildTree } from "../../src/bt/index";
 import { CommandQueue } from "../../src/commands/index";
 
 import {
-  Card,
-  InDeck,
-  InPlayerHand,
-  InDealerHand,
-  HoleHidden,
   Score,
   Bet,
   GamePhase,
+  InDealerHand,
+  createCardHelpers,
 } from "./components";
 
-import { Hit, Stand, NewRound, BetMore, BetLess } from "./commands";
-
 import {
-  SUITS,
-  RANKS,
-  handValue,
-  isBust,
-  isBlackjack,
-  dealerShouldHit,
-  determineOutcome,
-  payout,
-  type CardData,
-} from "./game";
+  registerCommands,
+  resolveRound,
+  Hit,
+  Stand,
+  NewRound,
+  BetMore,
+  BetLess,
+} from "./commands";
+
+import { dealerShouldHit } from "./game";
 
 import { createUI, render } from "./render";
 import { startInput, type Key } from "./input";
@@ -57,305 +52,60 @@ import { startInput, type Key } from "./input";
 // ── Setup ────────────────────────────────────────────
 const world = new World();
 
-// Singleton game state
 world.addSingleton(Score);
 world.addSingleton(Bet);
 world.addSingleton(GamePhase);
 
-// Create blessed UI
 const ui = createUI();
-
-// ── Card helpers (tag-based) ─────────────────────────
-
-/** Create all 52 card entities with the InDeck tag. */
-function 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. */
-function shuffleDeck(): void {
-  const entities = [...world.query(query(Card, InDeck))];
-  // Fisher-Yates shuffle
-  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]];
-  }
-  // Reassign order to match shuffled position
-  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. */
-function drawCard(): number | null {
-  const cards = [...world.query(query(Card, InDeck))];
-  if (cards.length === 0) return null;
-  // Find the one with the highest order
-  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. */
-function dealTo(cardEntity: number, 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. */
-function 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). */
-function clearHand(tag: typeof InPlayerHand): void {
-  for (const e of world.query(query(Card, tag))) {
-    world.destroy(e);
-  }
-}
-
-/** Count cards remaining in the deck. */
-function deckCount(): number {
-  return [...world.query(query(Card, InDeck))].length;
-}
-
-// ── Game flow ────────────────────────────────────────
-
-function dealInitial(): void {
-  const c1 = drawCard();
-  const c2 = drawCard();
-  const c3 = drawCard();
-  const c4 = drawCard();
-  if (c1) dealTo(c1, InPlayerHand);
-  if (c2) dealTo(c2, InDealerHand);
-  if (c3) dealTo(c3, InPlayerHand);
-  if (c4) dealTo(c4, InDealerHand);
-}
-
-function startRound(): void {
-  const bet = world.getSingleton(Bet);
-  const score = world.getSingleton(Score);
-
-  // Deduct bet
-  score.chips -= bet.amount;
-
-  // Re-shuffle if deck is low
-  if (deckCount() < 15) {
-    // Move all remaining InDeck cards back, then shuffle
-    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);
-    }
-    shuffleDeck();
-  }
-
-  // Clear old hands
-  clearHand(InPlayerHand);
-  clearHand(InDealerHand);
-  world.removeSingleton(HoleHidden);
-
-  dealInitial();
-
-  // Check for natural blackjack
-  const playerCards = getHand(InPlayerHand);
-  const dealerCards = 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.",
-    });
-  }
-}
-
-function resolveRound(): void {
-  const playerCards = getHand(InPlayerHand);
-  const dealerCards = 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.`,
-  });
-}
-
-// ── Command handlers ─────────────────────────────────
+const cards = createCardHelpers(world);
 const commands = new CommandQueue(world);
 
-commands.handle(Hit, () => {
-  const phase = world.getSingleton(GamePhase);
-  if (phase.phase !== "playerTurn") return;
-
-  const cardEntity = drawCard();
-  if (cardEntity) {
-    dealTo(cardEntity, InPlayerHand);
-  }
-
-  if (isBust(getHand(InPlayerHand))) {
-    world.removeSingleton(HoleHidden);
-    resolveRound();
-  }
-});
-
-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;
-  }
-
-  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);
-});
+registerCommands(world, commands, cards);
 
 // ── Behaviour Tree ───────────────────────────────────
 const runner = buildTree(world, {
-  kind: "repeat",
-  child: {
-    kind: "sequential",
-    children: [
-      {
-        kind: "leaf",
-        run: () => {
-          commands.execute();
-        },
-      },
-      {
-        kind: "leaf",
-        *run() {
-          while (true) {
-            const dt: number = yield;
-            const phase = world.getSingleton(GamePhase);
-            if (phase.phase !== "dealerTurn") continue;
+  kind: "parallel",
+  children: [
+    {
+      kind: "leaf",
+      *run() {
+        while (true) {
+          const dt: number = yield;
+          const phase = world.getSingleton(GamePhase);
+          if (phase.phase !== "dealerTurn") continue;
 
-            if (dealerShouldHit(getHand(InDealerHand))) {
-              const cardEntity = drawCard();
-              if (cardEntity) {
-                dealTo(cardEntity, InDealerHand);
-              }
-            } else {
-              resolveRound();
+          if (dealerShouldHit(cards.getHand(InDealerHand))) {
+            const cardEntity = cards.drawCard();
+            if (cardEntity) {
+              cards.dealTo(cardEntity, InDealerHand);
             }
+          } else {
+            resolveRound(world, cards);
           }
-        },
+        }
       },
-      {
-        kind: "leaf",
-        run: () => {
-          render(world, ui);
-        },
+    },
+    {
+      kind: "repeat",
+      child: {
+        kind: "sequential",
+        children: [
+          {
+            kind: "leaf",
+            run: () => {
+              commands.execute();
+            },
+          },
+          {
+            kind: "leaf",
+            run: () => {
+              render(world, ui);
+            },
+          },
+        ],
       },
-    ],
-  },
+    },
+  ],
 });
 
 // ── Input → Command mapping ──────────────────────────
@@ -381,8 +131,8 @@ world.setSingleton(GamePhase, {
   message: "Welcome to Blackjack! Press N to start.",
 });
 
-buildDeck();
-shuffleDeck();
+cards.buildDeck();
+cards.shuffleDeck();
 runner.schedule((runner as any).root);
 
 const TICK_MS = 16;
diff --git a/examples/tetris/commands.ts b/examples/tetris/commands.ts
index 68e0321..5ddc9d7 100644
--- a/examples/tetris/commands.ts
+++ b/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();
+  });
+}
diff --git a/examples/tetris/components.ts b/examples/tetris/components.ts
index c382203..fc75942 100644
--- a/examples/tetris/components.ts
+++ b/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);
+      }
+    },
+  };
+}
diff --git a/examples/tetris/main.ts b/examples/tetris/main.ts
index 0c3dddf..4648147 100644
--- a/examples/tetris/main.ts
+++ b/examples/tetris/main.ts
@@ -2,11 +2,12 @@
 //
 // Architecture:
 //   Behaviour Tree (buildTree) — controls game flow:
-//     root (repeat)
-//       └── seq (sequential)
-//             ├── handleInput (leaf)     — reads queued commands, mutates state
-//             ├── gravityTick (leaf)     — auto-drop piece on timer
-//             └── render (leaf)          — draws via blessed
+//     parallel
+//       ├── gravityTick (leaf)    — generator loop, auto-drop piece on timer
+//       └── repeat
+//             └── seq (sequential)
+//                   ├── handleInput (leaf)  — reads queued commands
+//                   └── render (leaf)       — draws via blessed
 //
 //   CommandQueue — processes input:
 //     Keyboard → spawn command entities → CommandQueue.execute()
@@ -22,9 +23,18 @@ import { World } from "../../src/index";
 import { buildTree } 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,
@@ -34,15 +44,7 @@ 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";
@@ -50,208 +52,67 @@ import { startInput, type Key } from "./input";
 // ── Setup ────────────────────────────────────────────
 const world = new World();
 
-// Singleton game state — one entity holds all of these
 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.addSingleton(Piece, {
-    shape: p.shape,
-    color: p.color,
-    x: Math.floor((BOARD_W - p.shape[0].length) / 2),
-    y: 0,
-  });
-}
-
-function hasActivePiece(): boolean {
-  return world.hasSingleton(Piece);
-}
-
-// Move left
-commands.handle(MoveLeft, () => {
-  if (
-    !hasActivePiece() ||
-    world.hasSingleton(GameOver) ||
-    world.hasSingleton(Paused)
-  )
-    return;
-  const piece = world.getSingleton(Piece);
-  const board = world.getSingleton(Board);
-  if (!collides(board.grid, piece.shape, piece.x - 1, piece.y)) {
-    piece.x--;
-  }
-});
-
-// Move right
-commands.handle(MoveRight, () => {
-  if (
-    !hasActivePiece() ||
-    world.hasSingleton(GameOver) ||
-    world.hasSingleton(Paused)
-  )
-    return;
-  const piece = world.getSingleton(Piece);
-  const board = world.getSingleton(Board);
-  if (!collides(board.grid, piece.shape, piece.x + 1, piece.y)) {
-    piece.x++;
-  }
-});
-
-// Rotate
-commands.handle(Rotate, () => {
-  if (
-    !hasActivePiece() ||
-    world.hasSingleton(GameOver) ||
-    world.hasSingleton(Paused)
-  )
-    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;
-  }
-});
-
-// Soft drop
-commands.handle(SoftDrop, () => {
-  if (
-    !hasActivePiece() ||
-    world.hasSingleton(GameOver) ||
-    world.hasSingleton(Paused)
-  )
-    return;
-  const piece = world.getSingleton(Piece);
-  const board = world.getSingleton(Board);
-  if (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
-    piece.y++;
-  }
-});
-
-// Hard drop
-commands.handle(HardDrop, () => {
-  if (
-    !hasActivePiece() ||
-    world.hasSingleton(GameOver) ||
-    world.hasSingleton(Paused)
-  )
-    return;
-  const piece = world.getSingleton(Piece);
-  const board = world.getSingleton(Board);
-  while (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
-    piece.y++;
-  }
-  lockAndSpawn();
-});
-
-// Toggle pause
-commands.handle(TogglePause, () => {
-  if (world.hasSingleton(GameOver)) return;
-  if (world.hasSingleton(Paused)) {
-    world.removeSingleton(Paused);
-  } else {
-    world.addSingleton(Paused);
-  }
-});
-
-// Restart
-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);
-  spawnPiece();
-});
-
-// ── Lock piece & spawn next ──────────────────────────
-function 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);
-  }
-
-  spawnPiece();
-
-  const newPiece = world.getSingleton(Piece);
-  if (collides(board.grid, newPiece.shape, newPiece.x, newPiece.y)) {
-    world.removeSingleton(Piece);
-    world.addSingleton(GameOver);
-  }
-}
+registerCommands(world, commands, pieces);
+pieces.spawnPiece();
 
 // ── Behaviour Tree ───────────────────────────────────
 const runner = buildTree(world, {
-  kind: "repeat",
-  child: {
-    kind: "sequential",
-    children: [
-      {
-        kind: "leaf",
-        run: () => {
-          commands.execute();
-        },
-      },
-      {
-        kind: "leaf",
-        *run() {
-          while (true) {
-            const dt: number = yield;
-            if (world.hasSingleton(GameOver) || world.hasSingleton(Paused)) {
-              continue;
-            }
-            const timer = world.getSingleton(TickTimer);
-            timer.accumulator += dt;
-            if (timer.accumulator >= timer.interval) {
-              timer.accumulator -= timer.interval;
-              if (hasActivePiece()) {
-                const piece = world.getSingleton(Piece);
-                const board = world.getSingleton(Board);
-                if (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
-                  piece.y++;
-                } else {
-                  lockAndSpawn();
-                }
+  kind: "parallel",
+  children: [
+    {
+      kind: "leaf",
+      *run() {
+        while (true) {
+          const dt: number = yield;
+          if (world.hasSingleton(GameOver) || world.hasSingleton(Paused)) {
+            continue;
+          }
+          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();
               }
             }
           }
-        },
+        }
       },
-      {
-        kind: "leaf",
-        run: () => {
-          render(world, ui);
-        },
+    },
+    {
+      kind: "repeat",
+      child: {
+        kind: "sequential",
+        children: [
+          {
+            kind: "leaf",
+            run: () => {
+              commands.execute();
+            },
+          },
+          {
+            kind: "leaf",
+            run: () => {
+              render(world, ui);
+            },
+          },
+        ],
       },
-    ],
-  },
+    },
+  ],
 });
 
 // ── Input → Command mapping ──────────────────────────
@@ -281,7 +142,6 @@ const interval = setInterval(() => {
   runner.tick(TICK_MS);
 }, TICK_MS);
 
-// Cleanup on exit
 process.on("SIGINT", () => {
   clearInterval(interval);
   ui.screen.destroy();