canvas特效星空.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        html,body {
            margin:0;
            overflow:hidden;
            width:100%;
            height:100%;
            cursor:none;
            background:black;
        }
    </style>
</head>
<body>

<canvas id="canvas"></canvas>

<script>
    var ctx = document.getElementById('canvas'),
        content = ctx.getContext('2d'),
        round = [],
        WIDTH,
        HEIGHT,
        initRoundPopulation = 80;

    WIDTH = document.documentElement.clientWidth;
    HEIGHT = document.documentElement.clientHeight;

    ctx.width = WIDTH;
    ctx.height = HEIGHT;

    function Round_item(index, x, y) {
        this.index = index
        this.x = x
        this.y = y
        this.r = Math.random() * 2 + 1
        var alpha = (Math.floor(Math.random() * 10) + 1) / 10 / 2
        this.color = "rgba(255, 255, 255," + alpha + ")"
    }

    function animate() {
        content.clearRect(0, 0, WIDTH, HEIGHT)
        for (var i in round) {
            round[i].move()
        }
        requestAnimationFrame(animate)
    }


    Round_item.prototype.draw = function () {
        content.fillStyle = this.color
        content.shadowBlur = this.r * 2
        content.beginPath()
        content.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false)
        content.closePath()
        content.fill()
    }

    Round_item.prototype.move = function () {
        this.y -= 0.15
        if (this.y <= -10) {
            this.y = HEIGHT + 10
        }
        this.draw()
    }

    function init () {
        for (var i= 0; i < initRoundPopulation; i++) {
            round[i] = new Round_item(i,Math.random() * WIDTH,Math.random() * HEIGHT);
            round[i].draw();
        }
        animate();
    }

    init();
</script>
</body>
</html>