JavaScript 实现网页背景烟花特效

<html>
<head>
<title>背景的烟花效果</title>
<style type="text/css">
<!--
body {
background-color: #000000;
}
-->
</style></head>
<body>
<script language="JavaScript">
var col = new Array('#ffffff','#fff000','#ffa000','#ff00ff','#00ff00','#0000ff','#ff0000');
var p='<div id="rearDiv" style="position:absolute;top:0px;left:0px">';
var n=0;
for (i=0;i<14;++i){
 n++;
 if (n=(col.length-1)) n=0;
 p=p+'<div style="position:relative;width:1px;height:1px;background:'+col[n]+';font-size:3px">.</div>';
}
p=p+"</div>";
document.write(p);
var Clrs = new Array('ff0000','00ff00','000aff','ff00ff','ffa500','ffff00','00ff00','ffffff','fffff0');
var sClrs = new Array('ffa500','55ff66','AC9DFC','fff000','fffff0');
var peepY;
var peepX;
var step = 5;
var tallyStep = 0;
var backColor = 'ffa000';
var Mtop = 250;
var Mleft = 250;
function dissilient() {
 peepY = window.document.body.clientHeight/3;
 peepX = window.document.body.clientWidth/8;
 enlarge();
 tallyStep+= step;
 reduce();
 T=setTimeout("dissilient()",20);
}
function enlarge(){
 for ( i = 0 ; i < rearDiv.all.length ; i++ ) {
  var c=Math.round(Math.random()*(Clrs.length-1));
  if (tallyStep < 90)
   rearDiv.all[i].style.background=backColor;
  if (tallyStep > 90)
   rearDiv.all[i].style.background=Clrs[c];
  rearDiv.all[i].style.top = Mtop + peepY*Math.sin((tallyStep+i*5)/3)*Math.sin(550+tallyStep/100);
  rearDiv.all[i].style.left = Mleft + peepY*Math.cos((tallyStep+i*5)/3)*Math.sin(550+tallyStep/100);
 }
}
function reduce(){
 if (tallyStep == 220) {
  tallyStep = -10;
  var k=Math.round(Math.random()*(sClrs.length-1));
  backColor = sClrs[k];
  Dtop = window.document.body.clientHeight - 250;
  Dleft = peepX * 3.5;
  Mtop = Math.round(Math.random()*Dtop);
  Mleft = Math.round(Math.random()*Dleft);
  document.all.rearDiv.style.top = Mtop+document.body.scrollTop;
  document.all.rearDiv.style.left = Mleft+document.body.scrollLeft;
  if ((Mtop < 20) || (Mleft < 20)) {
  Mtop += 90;
  Mleft += 90;
 }
 }
}
dissilient();
</script>
</body>
</html>