簡單實用好看的小球碰碰碰

標(biāo)簽：

Html5

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>小球</title>
        <style type="text/css">
            *{
                margin: 0;
                padding: 0;
            }
            #myCanvas{
                border: 1px solid dodgerblue;
                box-shadow: 10px 10px 10px gray;
                background: lightblue;
            }
        </style>
    </head>
    <body>
        <canvas id="myCanvas" width="700" height="600"></canvas>
    </body>
    <script type="text/javascript">
        var canvas = document.getElementById('myCanvas');
        //获取上下文(获取对象)
        var a = canvas.getContext('2d');
        //创建随机函数 随机半径
        function randomR (m,n) {
            return Math.floor(Math.random()*(n-m+1)+m);
        }
        //创建随机函数 随机颜色
        function randomC () {
            var r=randomR(0,250);
            var g=randomR(0,250);
            var b=randomR(0,250);
            var strcolor='rgb('+r+','+g+','+b+')';
            return strcolor;
        }
        //小球的构造函数
        function balls () {
            //半径
            this.r=randomR(5,50);
            this.x=randomR(this.r,canvas.width-this.r);
            this.y=randomR(this.r,canvas.height-this.r);
            //速度
            this.speedX=randomR(-20,20);
            this.speedY=randomR(-20,20);
            //颜色
            this.color=randomC();
        }
        //实例化
        var arr=[];
        for (var i=0;i<100;i++) {
            var ball=new balls();
            arr.push(ball);
        }
        //添加画
        balls.prototype.draw=function  () {
            a.beginPath();
            a.arc(this.x,this.y,this.r,0,Math.PI*2,false);
            a.fillStyle=this.color;
            a.fill();
        }
        //添加动
        balls.prototype.move=function  () {
            this.x+=this.speedX;
            this.y+=this.speedY;
            if (this.x>=canvas.width-this.r) {
                this.speedX*=-1;
                //碰撞的时候小球变色
                this.color=randomC();
                //碰撞的时候背景变色
//              canvas.style.backgroundColor=randomC();
            }
            if (this.x<=this.r) {
                this.speedX*=-1;
                this.color=randomC();
//              canvas.style.backgroundColor=randomC();
            }
            if (this.y>=canvas.height-this.r) {
                this.speedY*=-1;
                this.color=randomC();
//              canvas.style.backgroundColor=randomC();
            }
            if (this.y<=this.r) {
                this.speedY*=-1;
                this.color=randomC();
//              canvas.style.backgroundColor=randomC();
            }   
        }
        //定时器
        setInterval(function  () {
            a.clearRect(0,0,canvas.width,canvas.height);
            for (var i=0;i<arr.length;i++) {
                arr[i].draw();
                arr[i].move();
            }
        },100)
    </script>
</html>

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