<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
* {
margin: 0;
padding: 0;
}
html, body {
width: 100%;
height: 100%;
background-color: black;
overflow: hidden;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
<script>
var canvas = document.getElementById("canvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
var content2d = canvas.getContext("2d");
var balls = []; //存储对象
//小球的基本属性
function ball() {
this.x = null;
this.y = null;
this.angle = null;
this.vx=null;
this.vy=null;
this.r = null;
this.color = null;
this.init = function (x, y) {
//初始化属性值
this.x = x;
this.y = y;
//随机角度
this.angle = Math.random() * Math.PI * 2;
//随机小球的大小
this.r = this.randomNum(10,25);
this.vx=(this.randomNum(6,12)+Math.random()*0.5)*Math.cos(this.angle);
this.vy=(this.randomNum(6,12)+Math.random()*0.5)*Math.sin(this.angle);
this.color = this.randomColor();
};
//随机小球颜色
this.randomColor = function () {
return "#" + parseInt(Math.random() * 16777216).toString(16);
};
//随机大小
this.randomNum = function (min, max) {
return Math.random() * max + min;
};
//重绘时需移动
this.move=function(){
this.x+=this.vx;
this.y+=this.vy;
this.r-=0.3;
this.vx*=0.93;
this.vy*=0.93;
}
}
//创建小球
function createBall(x, y) {
var count = parseInt(Math.random() * 30 + 10);
for (var i = 0; i < count; i++) {
var b = new ball();
b.init(x, y);
balls.push(b);
}
}
//画小球
function Draw(){
for(var i=0;i<balls.length;i++){
var circle=balls[i];
circle.move();
content2d.beginPath();
content2d.fillStyle=circle.color;
content2d.arc(circle.x,circle.y,circle.r,0,Math.PI*2);
content2d.fill();
content2d.closePath();
}
}
//移除小球
function removeBall(){
for(var i=0;i<balls.length;i++){
var circle=balls[i];
if(circle.r<0.3){
balls.splice(i,1);
i--;
}
}
}
//计时器，即重绘
loop();
function loop(){
//清除整个canvas
content2d.clearRect(0,0,canvas.width,canvas.height);
Draw();
removeBall();
window.requestAnimationFrame(loop);
}
canvas.onmouseup = function (e) {
var x = e.pageX;
var y = e.pageY;
createBall(x, y);
}
</script>
</body>
</html>
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