canvas ribbon background effect

Awesome HTML5 Ribbon Background Effect
Use the canvas ribbon effect generated by HTML5, and use the native canvas to generate the final effect
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Ribbon</title>
    <style type="text/css">
        body{
            width:100%;
            margin:0;
            overflow:hidden;
            user-select:none;

        }
        #info {
            border-radius: 3px;
            margin: 0;
            position: fixed;
            top: 0;
            right: 0;
            width:25em;
            padding:1em;
            text-align:center;
            line-height:1.3em;
            transition: right 0.3s cubic-bezier(.65,.18,.79,.3);
            font-family: 'microsoft yahei',Arial,sans-serif;
            color: orange;
            font-size:14px;
        }
    </style>
</head>
<body>
<canvas id = 'canv'></canvas>
<div id = 'info'>
    Click on the screen to change the background color~~~
</div>



<script>
    window.requestAnimFrame = (function() {
        return window.requestAnimationFrame ||
                window.webkitRequestAnimationFrame ||
                window.mozRequestAnimationFrame ||
                window.oRequestAnimationFrame ||
                window.msRequestAnimationFrame ||
                function(callback) {
                    window.setTimeout(callback, 1000 / 60);
                };
    })();

    var c = document.getElementById ('canv'),
            $ = c.getContext('2d'),
            w = c.width = window.innerWidth,
            h = c.height = window.innerHeight,
            arr = [],
            u = 0;
    o = 0,

            $.fillStyle = '#FEFAE6';
    $.fillRect(0,0,w,h);
    $.globalCompositeOperation = "source-over";

    var inv = function () {
        $.restore();
        $.fillStyle = "#" + (o ? "FEFAE6" : "000000");
        $.fillRect(0, 0, w, h);
        $.fillStyle = "#" + (o ? "000000" : "FEFAE6");
        $.save()
    };
    window.addEventListener("touchstart", function(e){
        e.preventDefault();
        o =! o;
        inv()
    }, false);

    window.addEventListener("mousedown", function(e){
        o =! o;
        inv()
    }, false);

    window.addEventListener("keydown", function(keydn) {
        if (keydn.keyCode == 32) {
            o =! o;
            inv()
        }
    }, false);

    window.addEventListener('resize', function(){
        c.width = window.innerWidth;
        c.height = window.innerHeight;
    }, false);

    var ready = function() {
        arr = [];
        for (var i = 0; i < 20; i++) {
            set();
        }
    }

    var set = function() {
        arr.push({
            x1: w,
            y1: h,
            _x1: w - Math.random() * w,
            _y1: h - Math.random() * h,
            _x2: w - Math.random() * w,
            _y2: h - Math.random() * h,
            x2: -w + Math.random() * w,
            y2: -h + Math.random() * h,
            rot: Math.random() * 180,
            a1: Math.random() * 10,
            a2: Math.random() * 10,
            a3: Math.random() * 10
        });
    }

    var pretty = function() {
        u - = .2;
        for (var i in arr) {
            var b = arr[i];
            b._x1 *= Math.sin(b.a1 -= 0.001);
            b._y1 *= Math.sin(b.a1);
            b._x2 -= Math.sin(b.a2 += 0.001);
            b._y1 += Math.sin(b.a2);
            b.x1 -= Math.sin(b.a3 += 0.001);
            b.y1 += Math.sin(b.a3);
            b.x2 -= Math.sin(b.a3 -= 0.001);
            b.y2 += Math.sin(b.a3);
            $.save();
            $.globalAlpha = 0.03;
            $.beginPath();
            $.strokeStyle = 'hsla('+ u + ', 85%, 60%, .7)';
            $.moveTo(b.x1, b.y1);
            $.bezierCurveTo(b._x1, b._y1, b._x2, b._y2, b.x2, b.y2);
            $.stroke();
            $.restore();
        }
        window.requestAnimFrame(pretty);
    }
    ready();
    pretty();

    setTimeout(function() {
        var info= document.getElementById('info');
        info.style.right = '-500px';
    }, 5500);

</script>
</body>
</html>
canvas ribbon background effect

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