html+canvas star background case

Without further ado, here is the complete code:
<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>星空背景</title>
		<style>
		/*css reset */
		body,p,div,ol,ul,li,dl,dt,dd,h1,h2,h3,h4,h5,h6,form,input,iframe,nav {
		    margin: 0;
		    padding: 0;
		}
		html,body {
		    width: 100%;
		    height: 100%;
		}
		body {
		    font: 14px Microsoft YaHei;
		    -webkit-text-size-adjust:100%;
		    -moz-user-select: none;
		    -webkit-user-select: none;
		    user-select: none;
		    position: relative;
		    background: #000;
		}
		
		#canvas {
		    width: 100%;
		    height: 100%;
		    display: block;
		    opacity: .8;
		}

		</style>
	</head>
	<body>
		<canvas id="canvas"></canvas>
<script>
// 音量大小,0.01-1


//宇宙特效
var canvas = document.getElementById('canvas'),
ctx = canvas.getContext('2d'),
w = canvas.width = window.innerWidth,
h = canvas.height = window.innerHeight,

hue = 217,
stars = [],
count = 0,
maxStars = 1100;                //星星数量,默认1300
var canvas2 = document.createElement('canvas'),
ctx2 = canvas2.getContext('2d');
canvas2.width = 100;
canvas2.height = 100;
var half = canvas2.width / 2,
gradient2 = ctx2.createRadialGradient(half, half, 0, half, half, half);
gradient2.addColorStop(0.025, '#CCC');
gradient2.addColorStop(0.1, 'hsl(' + hue + ', 61%, 33%)');
gradient2.addColorStop(0.25, 'hsl(' + hue + ', 64%, 6%)');
gradient2.addColorStop(1, 'transparent');

ctx2.fillStyle = gradient2;
ctx2.beginPath();
ctx2.arc(half, half, half, 0, Math.PI * 2);
ctx2.fill();

// End cache
function random(min, max) {
    if (arguments.length < 2) {
        max = min;
        min = 0;
    }

    if (min > max) {
        var hold = max;
        max = min;
        min = hold;
    }

    return Math.floor(Math.random() * (max - min + 1)) + min;
}

function maxOrbit(x, y) {
    var max = Math.max(x, y),
    diameter = Math.round(Math.sqrt(max * max + max * max));
    return diameter / 2;
    //星星移动范围，值越大范围越小，
}

var Star = function() {

    this.orbitRadius = random(maxOrbit(w, h));
    this.radius = random(60, this.orbitRadius) / 10;       //星星大小,值越大星星越小,默认8
    
    this.orbitX = w / 2;
    this.orbitY = h / 2;
    this.timePassed = random(0, maxStars);
    this.speed = random(this.orbitRadius) / 80000;        //星星移动速度,值越大越慢,默认5W
    
    this.alpha = random(2, 10) / 10;

    count++;
    stars[count] = this;
}

Star.prototype.draw = function() {
    var x = Math.sin(this.timePassed) * this.orbitRadius + this.orbitX,
    y = Math.cos(this.timePassed) * this.orbitRadius + this.orbitY,
    twinkle = random(10);

    if (twinkle === 1 && this.alpha > 0) {
        this.alpha -= 0.05;
    } else if (twinkle === 2 && this.alpha < 1) {
        this.alpha += 0.05;
    }

    ctx.globalAlpha = this.alpha;
    ctx.drawImage(canvas2, x - this.radius / 2, y - this.radius / 2, this.radius, this.radius);
    this.timePassed += this.speed;
}

for (var i = 0; i < maxStars; i++) {
    new Star();
}

function animation() {
    ctx.globalCompositeOperation = 'source-over';
    ctx.globalAlpha = 0.5;                                 //尾巴
    ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 2)';
    ctx.fillRect(0, 0, w, h)

    ctx.globalCompositeOperation = 'lighter';
    for (var i = 1,
    l = stars.length; i < l; i++) {
        stars[i].draw();
    };

    window.requestAnimationFrame(animation);
}

animation();
</script>
</body>
</html>
Rendering: (actually moving, not static)
html+canvas star background case

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