不到200行代码实现一个不断旋转的椭圆动画效果

源代码：
<html>
 <head>
     <script src="jQuery/jscex.jscexRequire.min.js" type="text/javascript"></script>
 </head>
 <body>
 
 <style type="text/css">

    input.css3btn
    {
        background: -moz-linear-gradient(270deg, #d2ebf8, #0c8ab5);

        background: -webkit-linear-gradient(top, #d2ebf8, #0c8ab5);

        background: -o-linear-gradient(top, #d2ebf8, #0c8ab5);

        filter: progid:DXImageTransform.Microsoft.Gradient(GradientType=0, StartColorStr='#000099CC', EndColorStr='#FF0087B4');

        border-top: 1px solid #38538c;

        border-right: 1px solid #1f2d4d;

        border-bottom: 1px solid #151e33;

        border-left: 1px solid #1f2d4d;

        border-radius: 4px;

        box-shadow: inset 0 1px 10px 1px #5c8bee, 0px 1px 0 #1d2c4d, 0 2px 0px #1f3053, 0 4px 4px 1px #111111;

        color: #f0f0f0;

        font: bold 20px "helvetica neue" , helvetica, arial, sans-serif;

        padding: 10px 0 10px 0;

        text-align: center;

        text-shadow: 0px -1px 1px #1e2d4d;

        width: 150px;

        background-clip: padding-box;

    }

    input.css3btn:hover

    {

        box-shadow: inset 0 0px 20px 1px #87adff, 0px 1px 0 #1d2c4d, 0 3px 0px #1f3053, 0 4px 4px 1px #111111;

        cursor: pointer;

    }

    input.css3btn:active

    {

        box-shadow: inset 0 1px 10px 1px #5c8bee, 0 1px 0 #1d2c4d, 0 2px 0 #1f3053, 0 4px 3px 0 #111111;

        margin-top: 1px;

    }

</style>
     <canvas id="myCanvas2" width="350" height="350" style="border: solid 15px #222; background-color: #111;

        color: #CCC;">
 Your browser does not support the canvas element.
 </canvas>
     <script>

        var canvas;

        var ctx;



        var px = 0;

        var py = 0;

        function init() {

            canvas = document.getElementById("myCanvas2");

            ctx = canvas.getContext("2d");

            ctx.strokeStyle = "#fff";

            ctx.translate(70, 70);

        }



        init();

        var i = 0;

        function drawEllipse(x, y, w, h) {
       ctx.clearRect(-canvas.width, -canvas.height, 2 * canvas.width, 2 * canvas.height);


            var k = 0.5522848;

            var ox = (w / 2) * k;

            var oy = (h / 2) * k;

            var xe = x + w;

            var ye = y + h;

            var xm = x + w / 2;

            var ym = y + h / 2;

            ctx.beginPath();

            ctx.moveTo(x, ym);

            ctx.bezierCurveTo(x, ym - oy, xm - ox, y, xm, y);

            ctx.bezierCurveTo(xm + ox, y, xe, ym - oy, xe, ym);

            ctx.bezierCurveTo(xe, ym + oy, xm + ox, ye, xm, ye);

            ctx.bezierCurveTo(xm - ox, ye, x, ym + oy, x, ym);

            ctx.stroke();

            ctx.translate(x + 70, y + 100);

            px = -70;

            py = -100;

            ctx.rotate(10 * Math.PI * 2 / 360);

        }

        var ct;
        var drawAsync = eval(Jscex.compile("async", function (ct) {
            while (true) {
                drawEllipse(px, py, 140, 200)
                $await(Jscex.Async.sleep(200, ct));
            }
        }))
        function Button1_onclick() {
            ct.cancel();
        }
        function Button2_onclick() {
            ct = new Jscex.Async.CancellationToken();
            drawAsync(ct).start();
        }
    </script>
     <br />
     <input id="Button2" class="css3btn" type="button" value="run" onclick="return Button2_onclick()" />
     <input id="Button1" class="css3btn" type="button" value="stop" onclick="return Button1_onclick()" />
 </body>
 </html>
效果：
点stop可以停止旋转的动画效果：
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不到200行代码实现一个不断旋转的椭圆动画效果

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