<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
body{
background:black;
overflow:hidden;
margin:0;
}
canvas{
background:#000;
}
</style>
</head>
<body>
<div>
<canvas id="canvas"></canvas>
</div>
</body>
<script type="text/javascript">
window.addEventListener("resize", resizeCanvas, false);
window.addEventListener("DOMContentLoaded", onLoad, false);
window.requestAnimationFrame =
window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function (callback) {
window.setTimeout(callback, 1000/60);
};
var canvas, ctx, w, h, particles = [], probability = 0.04,
xPoint, yPoint;
function onLoad() {
canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
resizeCanvas();
window.requestAnimationFrame(updateWorld);
}
function resizeCanvas() {
if (!!canvas) {
w = canvas.width = window.innerWidth;
h = canvas.height = window.innerHeight;
}
}
function updateWorld() {
update();
paint();
window.requestAnimationFrame(updateWorld);
}
function update() {
if (particles.length < 500 && Math.random() < probability) {
createFirework();
}
var alive = [];
for (var i=0; i<particles.length; i++) {
if (particles[i].move()) {
alive.push(particles[i]);
}
}
particles = alive;
}
function paint() {
ctx.globalCompositeOperation = 'source-over';
ctx.fillStyle = "rgba(0,0,0,0.2)";
ctx.fillRect(0, 0, w, h);
ctx.globalCompositeOperation = 'lighter';
for (var i=0; i<particles.length; i++) {
particles[i].draw(ctx);
}
}
function createFirework() {
xPoint = Math.random()*(w-200)+100;
yPoint = Math.random()*(h-200)+100;
var nFire = Math.random()*50+100;
var c = "rgb("+(~~(Math.random()*200+55))+","
+(~~(Math.random()*200+55))+","+(~~(Math.random()*200+55))+")";
for (var i=0; i<nFire; i++) {
var particle = new Particle();
particle.color = c;
var vy = Math.sqrt(25-particle.vx*particle.vx);
if (Math.abs(particle.vy) > vy) {
particle.vy = particle.vy>0 ? vy: -vy;
}
particles.push(particle);
}
}
function Particle() {
this.w = this.h = Math.random()*4+1;
this.x = xPoint-this.w/2;
this.y = yPoint-this.h/2;
this.vx = (Math.random()-0.5)*10;
this.vy = (Math.random()-0.5)*10;
this.alpha = Math.random()*.5+.5;
this.color;
}
Particle.prototype = {
gravity: 0.05,
move: function () {
this.x += this.vx;
this.vy += this.gravity;
this.y += this.vy;
this.alpha -= 0.01;
if (this.x <= -this.w || this.x >= screen.width ||
this.y >= screen.height ||
this.alpha <= 0) {
return false;
}
return true;
},
draw: function (c) {
c.save();
c.beginPath();
c.translate(this.x+this.w/2, this.y+this.h/2);
c.arc(0, 0, this.w, 0, Math.PI*2);
c.fillStyle = this.color;
c.globalAlpha = this.alpha;
c.closePath();
c.fill();
c.restore();
}
}
</script>
</html>
