diff --git a/src/samples/tic-tac-toe.ts b/src/samples/tic-tac-toe.ts
index 6f1f73b..add32eb 100644
--- a/src/samples/tic-tac-toe.ts
+++ b/src/samples/tic-tac-toe.ts
@@ -24,7 +24,7 @@ export function createInitialState() {
             { name: 'x', min: 0, max: BOARD_SIZE - 1 },
             { name: 'y', min: 0, max: BOARD_SIZE - 1 },
         ]),
-        parts: [] as TicTacToePart[],
+        parts: {} as Record<string, TicTacToePart>,
         currentPlayer: 'X' as PlayerType,
         winner: null as WinnerType,
         turn: 0,
@@ -104,7 +104,7 @@ export function hasWinningLine(positions: number[][]): boolean {
 }
 
 export function checkWinner(host: Entity<TicTacToeState>): WinnerType {
-    const parts = host.value.parts;
+    const parts = Object.values(host.value.parts);
 
     const xPositions = parts.filter((p: TicTacToePart) => p.player === 'X').map((p: TicTacToePart) => p.position);
     const oPositions = parts.filter((p: TicTacToePart) => p.player === 'O').map((p: TicTacToePart) => p.position);
@@ -118,7 +118,7 @@ export function checkWinner(host: Entity<TicTacToeState>): WinnerType {
 
 export function placePiece(host: Entity<TicTacToeState>, row: number, col: number, player: PlayerType) {
     const board = host.value.board;
-    const moveNumber = host.value.parts.length + 1;
+    const moveNumber = Object.keys(host.value.parts).length + 1;
     const piece: TicTacToePart = {
         id: `piece-${player}-${moveNumber}`,
         regionId: 'board',
@@ -126,7 +126,7 @@ export function placePiece(host: Entity<TicTacToeState>, row: number, col: numbe
         player,
     };
     host.produce(state => {
-        state.parts.push(piece);
+        state.parts[piece.id] = piece;
         board.childIds.push(piece.id);
         board.partMap[`${row},${col}`] = piece.id;
     });
diff --git a/tests/samples/tic-tac-toe.test.ts b/tests/samples/tic-tac-toe.test.ts
index 150ea0e..1051c76 100644
--- a/tests/samples/tic-tac-toe.test.ts
+++ b/tests/samples/tic-tac-toe.test.ts
@@ -163,9 +163,9 @@ describe('TicTacToe - helper functions', () => {
             const state = getState(ctx);
             placePiece(state, 1, 1, 'X');
 
-            expect(state.value.parts.length).toBe(1);
-            expect(state.value.parts[0].position).toEqual([1, 1]);
-            expect(state.value.parts[0].player).toBe('X');
+            expect(Object.keys(state.value.parts).length).toBe(1);
+            expect(state.value.parts['piece-X-1'].position).toEqual([1, 1]);
+            expect(state.value.parts['piece-X-1'].player).toBe('X');
         });
 
         it('should add piece to board region children', () => {
@@ -183,7 +183,7 @@ describe('TicTacToe - helper functions', () => {
             placePiece(state, 0, 0, 'X');
             placePiece(state, 0, 1, 'O');
 
-            const ids = state.value.parts.map(p => p.id);
+            const ids = Object.keys(state.value.parts);
             expect(new Set(ids).size).toBe(2);
         });
     });
@@ -229,8 +229,8 @@ describe('TicTacToe - game flow', () => {
         const result = await runPromise;
         expect(result.success).toBe(true);
         if (result.success) expect(result.result.winner).toBeNull();
-        expect(ctx.state.value.parts.length).toBe(1);
-        expect(ctx.state.value.parts[0].position).toEqual([1, 1]);
+        expect(Object.keys(ctx.state.value.parts).length).toBe(1);
+        expect(ctx.state.value.parts['piece-X-1'].position).toEqual([1, 1]);
     });
 
     it('should reject move for wrong player and re-prompt', async () => {