// 畫食物
            ctx.fillStyle = "red";
            ctx.fillRect(food.x, food.y, box, box);

            // 更新分數
            ctx.fillStyle = "black";
            ctx.font = "20px Arial";
            ctx.fillText("Score: " + score, box, box);

            // 移動蛇
            let snakeX = snake[0].x;
            let snakeY = snake[0].y;

            if (direction == "LEFT") snakeX -= box;
            if (direction == "UP") snakeY -= box;
            if (direction == "RIGHT") snakeX += box;
            if (direction == "DOWN") snakeY += box;

            // 如果蛇吃到食物
            if (snakeX == food.x && snakeY == food.y) {
                score++;
                food = {
                    x: Math.floor(Math.random() * 19 + 1) * box,
                    y: Math.floor(Math.random() * 19 + 1) * box
                };
            } else {
                snake.pop();
            }

            // 創建新的蛇頭
            const newHead = {
                x: snakeX,
                y: snakeY
            };

            // 遊戲結束條件：撞牆或撞到自己
            if (
                snakeX < 0 ||
                snakeX >= canvasSize ||
                snakeY < 0 ||
                snakeY >= canvasSize ||
                collision(newHead, snake)
            ) {
                clearInterval(game); // 遊戲結束
            }

            snake.unshift(newHead);
        }

        // 檢查蛇是否撞到自己
        function collision(head, array) {
            for (let i = 0; i < array.length; i++) {
                if (head.x == array[i].x && head.y == array[i].y) {
                    return true;
                }
            }
            return false;
        }

        // 每100毫秒更新一次遊戲
        let game = setInterval(draw, 100);
    </script>
</body>
</html>