最近看到一个很漂亮的曲线，研究了一下。
从圆心画一条线匀速转动，终点再画一条线转动，2条线转速不同，会画出很漂亮的花纹。
一个周期
完整周期
<html>
<style>
body { background:black; }
p { text-align:center; color:white; }
canvas { display:block; margin:auto; }
</style>
<body>
<p><input type="checkbox" id="check">轨迹</p>
<canvas id="canvas"></canvas>
<script>
canvas.width = 800;
canvas.height = 800;
var ctx = canvas.getContext('2d');
ctx.strokeStyle = 'white';var R = 200;
var q1 = 0, q2 = 0;
var x0 = canvas.width/2;
var y0 = canvas.height/2;function draw() {if (!check.checked) {ctx.beginPath();ctx.clearRect(0, 0, canvas.width, canvas.height);} x1 = R * Math.cos(q1) + x0;y1 = -R * Math.sin(q1) + y0;if (!check.checked) { ctx.moveTo(x0, y0);ctx.lineTo(x1, y1);}x2 = R * Math.cos(q2) + x1;y2 = -R * Math.sin(q2) + y1;ctx.lineTo(x2, y2);ctx.stroke();q1 += 0.1;q2 += 0.21;
}function cls() {ctx.beginPath();ctx.clearRect(0, 0, canvas.width, canvas.height);
}check.onchange = function(){ cls(); };setInterval(draw, 50);
</script>
</body>
</html>
