Add SnakePlay.reset to restore players and clear items

gameblocks/modules/gameplay/SnakePlay.js

@@ -33,9 +33,11 @@ function clonePlayer(player) {
 }
 
 function createPlayer({ playerId, segments }) {
+  const nextSegments = cloneCells(segments);
   return {
     playerId,
-    segments: cloneCells(segments),
+    segments: nextSegments,
+    initialSegments: cloneCells(nextSegments),
     alive: true,
   };
 }
@@ -63,6 +65,14 @@ export class SnakePlay {
     player.segments = cloneCells(segments);
   }
 
+  reset() {
+    this.items.clear();
+    for (const player of this.players.values()) {
+      player.segments = cloneCells(player.initialSegments);
+      player.alive = true;
+    }
+  }
+
   addItem({ cell, growth = 1 }) {
     const nextItem = {
       cell: cloneCell(cell),

gameblocks/modules/gameplay/SnakePlay.test.js

@@ -0,0 +1,36 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { SNAKE_DEATH_REASONS, SNAKE_PLAY_EVENTS, SnakePlay } from './SnakePlay.js';
+
+test('reset restores players and clears items', () => {
+  const play = new SnakePlay({ minRight: 0, maxRight: 7, minForward: 0, maxForward: 7 });
+  play.addPlayer({
+    playerId: 'a',
+    segments: [
+      { right: 2, forward: 2 },
+      { right: 2, forward: 1 },
+    ],
+  });
+  play.addItem({ cell: { right: 4, forward: 4 }, growth: 1 });
+  play.movePlayer({
+    playerId: 'a',
+    segments: [
+      { right: 9, forward: 2 },
+      { right: 2, forward: 2 },
+    ],
+  });
+  const events = play.step();
+  assert.equal(events[0].type, SNAKE_PLAY_EVENTS.PLAYER_DIED);
+  assert.equal(events[0].reason, SNAKE_DEATH_REASONS.WALL);
+  assert.equal(play.getPlayerState('a').alive, false);
+  assert.equal(play.getItemState().length, 1);
+
+  play.reset();
+  const restored = play.getPlayerState('a');
+  assert.equal(restored.alive, true);
+  assert.deepEqual(restored.segments, [
+    { right: 2, forward: 2 },
+    { right: 2, forward: 1 },
+  ]);
+  assert.equal(play.getItemState().length, 0);
+});