先看效果图：
直接上代码（直接用）：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
body {
overflow: hidden;
margin: 0;
padding: 0;
background: hsla(242, 30%, 5%, 1);
}
canvas {
width: 100%;
}
</style>
</head>
<body>
<canvas id='canv'></canvas>
<script>
/*
(Book REF) HTML5 Canvas Ch. 5: Math, Physics, and Animation ::: Uniform Circular Motion
By Steve Fulton and Jeff Fulton
*/
window.requestAnimFrame = (function () {
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function (callback) {
window.setTimeout(callback, 1000 / 60);
};
})();
window.addEventListener('load', start, false);
var c,
$,
w,
h,
msX,
msY,
midX,
midY,
num = 650,
parts = [],
begin = 50,
repeat = 20,
end = Math.PI * 2,
force = null,
msdn = false;
function start() {
c = document.getElementById('canv');
$ = c.getContext('2d');
w = c.width = window.innerWidth;
h = c.height = window.innerHeight;
midX = w / 2;
midY = h / 2;
force = Math.max(w, h) * 0.09;
flow = begin;
window.requestAnimFrame(create);
run();
}
function run() {
window.requestAnimFrame(run);
go();
}
function Part() {
this.deg = 0;
this.rad = 0;
this.x = 0;
this.y = 0;
this.distX = 0;
this.distY = 0;
this.color = 'rgb(' + Math.floor(Math.random() * 130) + ',' + Math.floor(Math.random() * 50) + ',' + Math.floor(Math.random() * 100) + ')';
this.size;
}
function create() {
var n = num;
while (n--) {
var p = new Part();
p.deg = Math.floor(Math.random() * 360);
p.rad = Math.floor(Math.random() * w * 0.5);
p.x = p.distX = Math.floor(Math.random() * w);
p.y = p.distY = Math.floor(Math.random() * h);
p.size = 1 + Math.floor(Math.random() * (p.rad * 0.055));
parts[n] = p;
}
c.onmousemove = msmv;
c.onmousedown = msdn;
c.onmouseup = msup;
var int = setInterval(function () {
flow--;
if (flow === repeat) clearInterval(int);
}, 20);
}
function go() {
$.globalCompositeOperation = 'source-over';
$.fillStyle = 'hsla(242, 30%, 5%, .55)';
$.fillRect(0, 0, w, h);
$.globalCompositeOperation = 'lighter';
var mx = msX;
var my = msY;
var bounds = force;
if (msdn) {
bounds = force * 2;
}
var n = num;
while (n--) {
var p = parts[n];
var radi = Math.PI / 180 * p.deg;
p.distX = midX + p.rad * Math.cos(radi);
p.distY = midY + p.rad * Math.sin(radi) * 0.4;
if (mx && my) {
var react = Math.floor((bounds * 0.5) + Math.random() * (bounds * 0.9));
if (p.distX - mx > 0 &&
p.distX - mx < bounds &&
p.distY - my > 0 &&
p.distY - my < bounds) {
p.distX += react;
p.distY += react;
} else if (p.distX - mx > 0 &&
p.distX - mx < bounds &&
p.distY - my < 0 &&
p.distY - my > -bounds) {
p.distX += react;
p.distY -= react;
} else if (p.distX - mx < 0 &&
p.distX - mx > -bounds &&
p.distY - my > 0 &&
p.distY - my < bounds) {
p.distX -= react;
p.distY += react;
} else if (p.distX - mx < 0 &&
p.distX - mx > -bounds &&
p.distY - my < 0 &&
p.distY - my > -bounds) {
p.distY -= react;
p.distY -= react;
}
}
p.x += ((p.distX - p.x) / flow);
p.y += ((p.distY - p.y) / flow);
var x = p.x;
var y = p.y;
var s = p.size * (p.y * 1.5 / h);
if (s < 0.1) {
s = 0;
}
$.beginPath();
$.fillStyle = p.color;
$.arc(x, y, s, 0, end, true);
$.fill();
$.closePath();
var vary;
if (p.size < 2) {
vary = 4;
} else if (p.size < 3) {
vary = 3;
} else if (p.size < 4) {
vary = 2;
} else {
vary = 1;
}
vary *= (p.y / (h * 0.9));
p.deg += vary;
p.deg = p.deg % 360;
}
}
function msmv(e) {
var p = getPos(e.target);
var sX = window.pageXOffset;
var sY = window.pageYOffset;
msX = e.clientX - p.x + sX;
msY = e.clientY - p.y + sY;
}
function msdn(e) {
msdn = true;
}
function msup(e) {
msdn = false;
}
function getPos(el) {
var cosmo = {
};
cosmo.x = el.offsetLeft;
cosmo.y = el.offsetTop;
while (el.offsetParent) {
el = el.offsetParent;
cosmo.x += el.offsetLeft;
cosmo.y += el.offsetTop;
}
return cosmo;
}
</script>
</body>
</html>
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