shooting star/comet mf2fm

<script type="text/javascript">
// <![CDATA[
var speed=25; // how fast - smaller is faster
var how_often=10; // average time between re-appearances of a comet (in seconds)
var how_many=10; // maximum number of comets in flight
var colours=new Array("#ff0", "#f93", "#f60", "#e93", "#e94", "#da5", "#da6", "#cb7", "#cb8", "#cc9", "#dcb", "#ddd");
// above line lists colours for the comet and its tail (can be as long or short as you like)

/****************************
* Shooting Star/Comet Effect*
*(c)2008-13 mf2fm web-design*
*  http://www.mf2fm.com/rv  *
* DON'T EDIT BELOW THIS BOX *
****************************/

var dx=new Array();
var dy=new Array();
var xpos=new Array();
var ypos=new Array();
var comets=new Array();
var swide=800;
var shigh=600;
var tail=colours.length;
var boddie=false;

function addLoadEvent(funky) {
  var oldonload=window.onload;
  if (typeof(oldonload)!='function') window.onload=funky;
  else window.onload=function() {
    if (oldonload) oldonload();
    funky();
  }
}

addLoadEvent(whooosh);

function whooosh() { if (document.getElementById) {
  var i;
  boddie=document.createElement("div");
  boddie.style.position="fixed";
  boddie.style.top="0px";
  boddie.style.left="0px";
  boddie.style.overflow="visible";
  boddie.style.width="1px";
  boddie.style.height="1px";
  boddie.style.backgroundColor="transparent";
  document.body.appendChild(boddie);
  set_width();
  for (i=0; i<how_many; i++) {
    write_comet(i*tail);
	setTimeout('launch('+(i*tail)+')', Math.max(1000*i));
  }
}}

function write_comet(a) {
  var i, s;
  for (i=0; i<tail; i++) {
    s=2+(i<tail/4)+2*!i;
	comets[i+a]=div(s, s);
	comets[i+a].style.backgroundColor=colours[i];
	boddie.appendChild(comets[i+a]);
  }
}

function div(w, h) {
  var d=document.createElement("div");
  d.style.position="absolute";
  d.style.overflow="hidden";
  d.style.width=w+"px";
  d.style.height=h+"px";
  return (d);
}

function stepthrough(a) {
  var i;
  if (Math.random()<0.008||ypos[a]+dy[a]<5||xpos[a]+dx[a]<5||xpos[a]+dx[a]>=swide-5||ypos[a]+dy[a]>=shigh-5) {
	for (i=0; i<tail; i++) setTimeout('comets['+(i+a)+'].style.visibility="hidden"', speed*(tail-i));
	setTimeout('launch('+a+')', Math.max(1000, 2000*Math.random()*how_often));
  }
  else setTimeout('stepthrough('+a+')', speed);
  for (i=tail-1; i>=0; i--) {
	if (i) {
      xpos[i+a]=xpos[i+a-1];
      ypos[i+a]=ypos[i+a-1];
	}
	else {
	  xpos[i+a]+=dx[a];
      ypos[i+a]+=dy[a];
	}
    comets[i+a].style.left=xpos[i+a]+"px";
    comets[i+a].style.top=ypos[i+a]+"px";
  }
}

function launch(a) {
  var i;
  dx[a]=(Math.random()>0.5?1:-1)*(1+Math.random()*3);
  dy[a]=(Math.random()>0.5?1:-1)*((7-dx[a])/3+Math.random()*(dx[a]+5)/3);
  xpos[a]=2*tail*dx[a]+Math.round(Math.random()*(swide-4*tail*dx[a]));
  ypos[a]=2*tail*dy[a]+Math.round(Math.random()*(shigh-4*tail*dy[a]));
  for (i=0; i<tail; i++) {
    xpos[i+a]=xpos[a];
    ypos[i+a]=ypos[a];
	comets[i+a].style.visibility="visible";
  }
  stepthrough(a);
}

window.onresize=set_width;
function set_width() {
  var sw_min=999999;
  var sh_min=999999;
  if (document.documentElement && document.documentElement.clientWidth) {
    if (document.documentElement.clientWidth>0) sw_min=document.documentElement.clientWidth;
    if (document.documentElement.clientHeight>0) sh_min=document.documentElement.clientHeight;
  }
  if (typeof(self.innerWidth)!="undefined" && self.innerWidth) {
    if (self.innerWidth>0 && self.innerWidth<sw_min) sw_min=self.innerWidth;
    if (self.innerHeight>0 && self.innerHeight<sh_min) sh_min=self.innerHeight;
  }
  if (document.body.clientWidth) {
    if (document.body.clientWidth>0 && document.body.clientWidth<sw_min) sw_min=document.body.clientWidth;
    if (document.body.clientHeight>0 && document.body.clientHeight<sh_min) sh_min=document.body.clientHeight;
  }
  if (sw_min==999999 || sh_min==999999) {
    sw_min=800;
    sh_min=600;
  }
  swide=sw_min;
  shigh=sh_min;
}
// ]]>
</script>