<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>贪吃蛇</title>
</head>
<body>
<canvas id="game" width="450" height="450" style="border:1px solid red;margin:30px auto;display:
block;"></canvas>
<script type="text/javascript">
var canvas = document.getElementById("game");
//拿到上下文，画图工具
var cxt = canvas.getContext("2d");
//每个格子的宽度
var width = 15;
//面向对象，蛇的身体是一节一节的
/*
定义一个Cell类，具备x和y还具备f
x和y代表格子的坐标，f代表方向
f方向
1代表左，-1代表右
2代表下，-2代表上
*/
function Cell(x,y,f){
this.x=x;
this.y=y;
this.f=f;
}
function Food(x,y){
this.x=x;
this.y=y;
}
//蛇的对象 蛇是由Cell组成的
var snake =[];
var length = 2;//蛇的长度
var speed = 100;//100毫秒移动一个单元格
var food= new Food(15,15);
//初始化蛇的身体
for(var i=0;i<length;i++){
snake[i] = new Cell(i, 0, -1)
}
for(var i = 0;i<snake.length;i++){
var cell= snake[i];
cxt.fillStyle = "gray";
if(i==snake.length-1){
cxt.fillStyle="red";
}
cxt.beginPath();
cxt.rect(cell.x*width ,cell.y*width,width,width);
cxt.closePath();
cxt.fill();
}
cxt.fillStyle = "green";
cxt.beginPath();
cxt.rect(food.x*width ,food.y*width,width,width);
cxt.closePath();
cxt.fill();
//怎么让蛇头跟着键盘动，监听键盘事件
document.onkeydown = function(e){
var code = e.keyCode;
var direction = 0;
switch(code){
case 37:direction = 1;break;
case 38:direction = 2;break;
case 39:direction = -1;break;
case 40:direction = -2;break;
case 87:direction = 2;break;
case 65:direction = 1;break;
case 83:direction = -2;break;
case 68:direction = -1;break;
}//switch
var head = snake[snake.length-1];
if(direction!=0&&(head.f+direction)!=0){
//调用蛇的移动方法
moveSnake(direction);
}//if(direction)
}//function(e)
function moveSnake(direction){
var head = snake[snake.length-1];//蛇头
if(!direction){
direction=head.f;
}
var newSnake = [];
var newHead = new Cell(head.x, head.y, head.f);
for(var i = 1;i<snake.length;i++){
newSnake[i-1] = snake[i];
}
newHead.f=direction;
//修改x和y的值
switch(direction){
case 1:newHead.x-- ;break;
case 2:newHead.y-- ;break;
case -1:newHead.x++ ;break;
case -2:newHead.y++ ;break;
}
newSnake[newSnake.length]=newHead
snake=newSnake;
gameOver();
draw();
}
function gameOver(){
//检查撞到游戏的边框
var head = snake[snake.length-1];
if(head.x>=30||head.y>=30||head.x<0||head.y<0){
alert("撞墙,游戏结束");
window.location.reload();
}
//不能咬到自己
for(var i=0;i < snake.length-1;i++){
if(snake[i].x == head.x && snake[i].y == head.y){
alert("撞到自己了,游戏结束");
window.location.reload();
}
}
}
function draw(){
cxt.clearRect(0, 0, 450, 450);
cxt.fillStyle = "green";
cxt.beginPath();
cxt.rect(food.x*width ,food.y*width,width,width);
cxt.closePath();
cxt.fill();
//判断蛇的蛇头是不是和食物的坐标重合
var head = snake[snake.length-1];
if(head.x==food.x&&head.y==food.y){
var newHead = new Cell(head.x, head.y, head.f);
//修改x和y的值
switch(newHead.f){
case 1:newHead.x-- ;break;
case 2:newHead.y-- ;break;
case -1:newHead.x++ ;break;
case -2:newHead.y++ ;break;
}
snake[snake.length] = newHead;
randFood();
}
for(var i = 0;i<snake.length;i++){
var cell= snake[i];
cxt.fillStyle = "gray";
if(i==snake.length-1){
cxt.fillStyle="red";
}
cxt.beginPath();
cxt.rect(cell.x*width ,cell.y*width,width,width);
cxt.closePath();
cxt.fill();
}
}
function randFood(){
food.x=Math.ceil(Math.random()*28)+1;
food.y=Math.ceil(Math.random()*28)+1;
}
var autoRun = setInterval(moveSnake,speed);
</script>
</body>
</html>
