<!DOCTYPE html>
<html>
<head>
<title>聪明的子弹完整版</title>
<script type="text/javascript" src="jquery-1.8.3.js"></script>
<script type="text/javascript">
var x = 225;
var y=450;
var mousex, mousey;
var canvas;
var ctx;
var c=0;
var zidan=new Object();
$(document).ready(function () {
canvas = $(document).get(0).getElementById("MyCanvas");
if (canvas.getContext) {
ctx = canvas.getContext("2d");
zidan.x = 245;
zidan.y = 10;
zidan.jiaodu = Math.PI * 0.5;
zidan.sudu = 10;
zidan.dadao = 0;//0代表没打到，1代表打到
animate();
}
});
zidan.move = function () {
if(y - zidan.y>0)
{
zidan.y = zidan.y + Math.abs(zidan.sudu * Math.cos(zidan.jiaodu));
}
else
{
zidan.y = zidan.y - Math.abs(zidan.sudu * Math.cos(zidan.jiaodu));
}
if(x - zidan.x>0)
{
zidan.x = zidan.x + Math.abs(zidan.sudu * Math.sin(zidan.jiaodu));
}
else
{
zidan.x = zidan.x - Math.abs(zidan.sudu * Math.sin(zidan.jiaodu));
}
//超出下边界 www.2cto.com
if (zidan.y > 500)
zidan.y = 10;
//请添加超出上左右边界的判断
//if (zidan.y == 10)
zidan.jiaodu = Math.atan((x - zidan.x) / (y - zidan.y));
};
function animate()
{
ctx.clearRect(0, 0, 500, 500);
//由键盘控制的方块
if (zidan.dadao == 1)
ctx.fillStyle = "red";
ctx.fillRect(x, y, 50, 50);
ctx.fillStyle = "black";
ctx.beginPath();
ctx.arc(zidan.x, zidan.y, 10, 0, Math.PI * 2, false);
ctx.closePath();
ctx.fill();
if(zidan.dadao==0)
setTimeout(animate, 100);
//动画的逻辑,子弹直线运动，超出范围，则重新设置为10
zidan.move();
//碰撞检测,如果打到，则方块变成红色，游戏停止
if((zidan.y>y)&&(zidan.y<y+50)&&(zidan.x>x)&&(zidan.x<x+50))
{
zidan.dadao = 1;
alert(c/10);
}
c=c+1;
};
</script>
</head>
<body >
<div>
<canvas id="MyCanvas" width="500" height="500" > </canvas>
</div>
</body>
<script type="text/javascript">
//注意这里是document，canvas应该也能捕获keydown事件，留以后试吧
$(document).keydown(function (e) {
var k = e.keyCode;
//如果不知道按键的代码，用alert输出看
//alert(k);
if (k == 37)
x = x - 10;
if (k == 39)
x = x + 10;
if (k == 38)
y = y - 10;
if (k == 40)
y = y + 10;
});
</script>
</html>
