帮我改成wasd网页代码

苏洛萱

const canvas = document.getElementById("gameCanvas");
const context = canvas.getContext("2d");
const startButton = document.getElementById("startButton");

const gridSize = 20;
let snake = [{x: 200, y: 200}];
let food = {x: 0, y: 0};
let dx = gridSize;
let dy = 0;
let score = 0;

function drawSnake() {
    context.clearRect(0, 0, canvas.width, canvas.height);
    snake.forEach(part => {
        context.fillStyle = "green";
        context.fillRect(part.x, part.y, gridSize, gridSize);
    });
}

function generateFood() {
    food.x = Math.floor(Math.random() * canvas.width / gridSize) * gridSize;
    food.y = Math.floor(Math.random() * canvas.height / gridSize) * gridSize;
}

function drawFood() {
    context.fillStyle = "red";
    context.fillRect(food.x, food.y, gridSize, gridSize);
}

function moveSnake() {
    const head = {x: snake[0].x + dx, y: snake[0].y + dy};
    snake.unshift(head);
    if (head.x === food.x && head.y === food.y) {
        score++;
        generateFood();
    } else {
        snake.pop();
    }
}

function changeDirection(event) {
    const keyPressed = event.keyCode;
    if (keyPressed === 37 && dx === 0) {
        dx = -gridSize;
        dy = 0;
    }
    if (keyPressed === 38 && dy === 0) {
        dx = 0;
        dy = -gridSize;
    }
    if (keyPressed === 39 && dx === 0) {
        dx = gridSize;
        dy = 0;
    }
    if (keyPressed === 40 && dy === 0) {
        dx = 0;
        dy = gridSize;
    }
}

function gameLoop() {
    moveSnake();
    drawSnake();
    drawFood();
    if (snake[0].x < 0 || snake[0].x >= canvas.width || snake[0].y < 0 || snake[0].y >= canvas.height) {
        clearInterval(game);
        alert("Game Over! Your score is " + score);
    }
}

startButton.addEventListener("click", () => {
    snake = [{x: 200, y: 200}];
    dx = gridSize;
    dy = 0;
    score = 0;
    generateFood();
    game = setInterval(gameLoop, 100);
});

document.addEventListener("keydown", changeDirection);

kaia

好的！我来帮你把按键控制改成用 WASD 键。原来的代码是用上下左右箭头（keyCode 37、38、39、40）来控制方向的，我们改成用 W (上)、A (左)、S (下)、D (右) 四个键。

同时，我帮你修正了一些小错误，比如：

- 蛇身 `snake` 应该是一个数组，初始时蛇头可以放在画布中央；
- `moveSnake` 函数里获取蛇头的位置应该用 `snake[0]` 而不是 `snake.x`；
- 游戏结束检测也要根据蛇头位置判断。

下面是修改后的完整代码，注意我用注释标出了修改按键的部分，你可以看一下：

1. const canvas = document.getElementById("gameCanvas");
   
2. const context = canvas.getContext("2d");
   
3. const startButton = document.getElementById("startButton");
   
4. 
   
5. const gridSize = 20;
   
6. let snake = [];
   
7. let food = {x: 0, y: 0};
   
8. let dx = gridSize;
   
9. let dy = 0;
   
10. let score = 0;
    
11. let game;
    
12. 
    
13. function drawSnake() {
    
14.     context.clearRect(0, 0, canvas.width, canvas.height);
    
15.     snake.forEach(part => {
    
16.         context.fillStyle = "green";
    
17.         context.fillRect(part.x, part.y, gridSize, gridSize);
    
18.     });
    
19. }
    
20. 
    
21. function generateFood() {
    
22.     food.x = Math.floor(Math.random() * canvas.width / gridSize) * gridSize;
    
23.     food.y = Math.floor(Math.random() * canvas.height / gridSize) * gridSize;
    
24. }
    
25. 
    
26. function drawFood() {
    
27.     context.fillStyle = "red";
    
28.     context.fillRect(food.x, food.y, gridSize, gridSize);
    
29. }
    
30. 
    
31. function moveSnake() {
    
32.     const head = {x: snake[0].x + dx, y: snake[0].y + dy};
    
33.     snake.unshift(head); // 把新头加到蛇身前面
    
34. 
    
35.     // 如果吃到食物了
    
36.     if (head.x === food.x && head.y === food.y) {
    
37.         score++;
    
38.         generateFood();
    
39.     } else {
    
40.         snake.pop(); // 没吃到食物，尾巴去掉
    
41.     }
    
42. }
    
43. 
    
44. function changeDirection(event) {
    
45.     const keyPressed = event.key.toLowerCase(); // 获取按键的小写字母
    
46. 
    
47.     // 用 WASD 控制方向
    
48.     if (keyPressed === 'a' && dx === 0) { // A 向左
    
49.         dx = -gridSize;
    
50.         dy = 0;
    
51.     }
    
52.     if (keyPressed === 'w' && dy === 0) { // W 向上
    
53.         dx = 0;
    
54.         dy = -gridSize;
    
55.     }
    
56.     if (keyPressed === 'd' && dx === 0) { // D 向右
    
57.         dx = gridSize;
    
58.         dy = 0;
    
59.     }
    
60.     if (keyPressed === 's' && dy === 0) { // S 向下
    
61.         dx = 0;
    
62.         dy = gridSize;
    
63.     }
    
64. }
    
65. 
    
66. function gameLoop() {
    
67.     moveSnake();
    
68.     drawSnake();
    
69.     drawFood();
    
70. 
    
71.     const head = snake[0];
    
72.     // 碰壁就结束游戏
    
73.     if (
    
74.         head.x < 0 || head.x >= canvas.width ||
    
75.         head.y < 0 || head.y >= canvas.height
    
76.     ) {
    
77.         clearInterval(game);
    
78.         alert("Game Over! Your score is " + score);
    
79.     }
    
80. }
    
81. 
    
82. startButton.addEventListener("click", () => {
    
83.     // 初始化蛇的起点在画布中心
    
84.     snake = [
    
85.         {x: canvas.width / 2, y: canvas.height / 2}
    
86.     ];
    
87.     dx = gridSize;
    
88.     dy = 0;
    
89.     score = 0;
    
90.     generateFood();
    
91.     game = setInterval(gameLoop, 100);
    
92. });
    
93. 
    
94. document.addEventListener("keydown", changeDirection);

复制代码

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**简单解释一下怎么用 WASD 控制：**

- 按下 W 键，蛇头往上移动；
- 按下 A 键，蛇头往左移动；
- 按下 S 键，蛇头往下移动；
- 按下 D 键，蛇头往右移动；

记得蛇不能直接往反方向走哦，比如当前往右时，不能马上按 A 往左，否则蛇会撞到自己。

如果你还有不懂的地方，随时问我！????