<!DOCTYPE html>
<html>
<head>
<title>星空</title>
<script type="text/javascript">
function draw() {
var canvas=document.getElementById("canvas");
var context=canvas.getContext("2d");
context.fillStyle="black";
context.fillRect(0,0,canvas.width,canvas.height);
for(var i=0;i<20;i++){
var r=Math.random()*10+10;
var x=Math.random()*canvas.width;
var y=Math.random()*canvas.height;
var a=Math.random()*360;
drawStar(context,x,y,r,r/2.3,a)
}
}
function drawStar(cxt,x,y,r,R,rot) {
cxt.beginPath();
for(var i=0;i<5;i++){
cxt.lineTo(Math.cos((18+i*72-rot)/180*Math.PI)*R+x,-
Math.sin((18+i*72-rot)/180*Math.PI)*R+y);
cxt.lineTo(Math.cos((54+i*72-rot)/180*Math.PI)*r+x,-
Math.sin((54+i*72-rot)/180*Math.PI)*r+y);
}
cxt.fillStyle="yellow"
cxt.closePath();
cxt.fill();
}
</script>
<style type="text/css">
</style>
</head>
<body onload="draw()";>
<canvas id="canvas" width="800" height="400">
</canvas>
</body>
</html>
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