貪吃蛇是一款經典的游戲，現在可以用HTML和JavaScript來編寫貪吃蛇代碼。HTML用于創建游戲畫面，JavaScript用于實現游戲邏輯。

<canvas id="canvas" width="400" height="400"></canvas>
<script>
// 定義常量
const COLS = 20; // 列數
const ROWS = 20; // 行數
const SNAKE_SIZE = 20; // 蛇塊大小
// 定義變量
var canvas, ctx, snake;
// 初始化函數
function init() {
canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
snake = new Snake();
}
// 繪制函數
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
snake.move();
snake.draw();
setTimeout(draw, 100);
}
// 蛇類
function Snake() {
this.body = [{ x: 10, y: 10 }, { x: 9, y: 10 }, { x: 8, y: 10 }];
this.direction = "right";
this.draw = function() {
ctx.fillStyle = "green";
for (var i = 0; i< this.body.length; i++) {
var bodyPart = this.body[i];
ctx.fillRect(bodyPart.x * SNAKE_SIZE, bodyPart.y * SNAKE_SIZE, SNAKE_SIZE, SNAKE_SIZE);
}
};
this.move = function() {
var newHead = { x: this.body[0].x, y: this.body[0].y };
if (this.direction === "right") {
newHead.x++;
} else if (this.direction === "left") {
newHead.x--;
} else if (this.direction === "up") {
newHead.y--;
} else if (this.direction === "down") {
newHead.y++;
}
this.body.unshift(newHead);
this.body.pop();
};
}
// 監聽鍵盤事件
document.addEventListener("keydown", function(event) {
if (event.key === "ArrowRight") {
snake.direction = "right";
} else if (event.key === "ArrowLeft") {
snake.direction = "left";
} else if (event.key === "ArrowUp") {
snake.direction = "up";
} else if (event.key === "ArrowDown") {
snake.direction = "down";
}
});
// 初始化并開始游戲
init();
draw();
</script>

以上是一個簡單的貪吃蛇代碼示例，其中創建了一個Snake類，用于表示貪吃蛇，包含了蛇的身體、方向、移動、繪制等屬性和方法。監聽了鍵盤事件，用于改變蛇的方向。通過不斷調用繪制函數，實現了蛇的不斷運動和重新繪制。