Action Script Snow

[prignibus]

Salve a tutti, ho questo codice che mi da l'effetto neve.
Visto che ho un sito per palloncini vorrei che alcune immagini si alternassero
cioè si visualizzassero palloncini di più tipo.

Ultima cosa, se potete per caso farmi capire come posso fare per
invertire l'effetto?

Grazie anticipatamente per il vostro aiuto.
Saluti

<script type="text/javascript">

/******************************************
* Snow Effect Script- By Altan d.o.o. (http://www.altan.hr/snow/index.html)
* Visit Dynamic Drive DHTML code library (http://www.dynamicdrive.com/) for full source code
* Last updated Nov 9th, 05' by DD. This notice must stay intact for use
******************************************/
  
  //Configure below to change URL path to the snow image
  var snowsrc="snow.gif"
  // Configure below to change number of snow to render
  var no = 10;
  // Configure whether snow should disappear after x seconds (0=never):
  var hidesnowtime = 0;
  // Configure how much snow should drop down before fading ("windowheight" or "pageheight")
  var snowdistance = "pageheight";

///////////Stop Config//////////////////////////////////

  var ie4up = (document.all) ? 1 : 0;
  var ns6up = (document.getElementById&&!document.all) ? 1 : 0;

	function iecompattest(){
	return (document.compatMode && document.compatMode!="BackCompat")? document.documentElement : document.body
	}

  var dx, xp, yp;    // coordinate and position variables
  var am, stx, sty;  // amplitude and step variables
  var i, doc_width = 800, doc_height = 600; 
  
  if (ns6up) {
    doc_width = self.innerWidth;
    doc_height = self.innerHeight;
  } else if (ie4up) {
    doc_width = iecompattest().clientWidth;
    doc_height = iecompattest().clientHeight;
  }

  dx = new Array();
  xp = new Array();
  yp = new Array();
  am = new Array();
  stx = new Array();
  sty = new Array();
  snowsrc=(snowsrc.indexOf("dynamicdrive.com")!=-1)? "snow.gif" : snowsrc
  for (i = 0; i < no; ++ i) {  
    dx[i] = 0;                        // set coordinate variables
    xp[i] = Math.random()*(doc_width-50);  // set position variables
    yp[i] = Math.random()*doc_height;
    am[i] = Math.random()*20;         // set amplitude variables
    stx[i] = 0.02 + Math.random()/10; // set step variables
    sty[i] = 0.7 + Math.random();     // set step variables
		if (ie4up||ns6up) {
      if (i == 0) {
        document.write("<div id=\"dot"+ i +"\" style=\"POSITION: absolute; Z-INDEX: "+ i +"; VISIBILITY: visible; TOP: 15px; LEFT: 15px;\"><a href=\"http://dynamicdrive.com\">[img]"+snowsrc+"[/img]<\/a><\/div>");
      } else {
        document.write("<div id=\"dot"+ i +"\" style=\"POSITION: absolute; Z-INDEX: "+ i +"; VISIBILITY: visible; TOP: 15px; LEFT: 15px;\">[img]"+snowsrc+"[/img]<\/div>");
      }
    }
  }

  function snowIE_NS6() {  // IE and NS6 main animation function
    doc_width = ns6up?window.innerWidth-10 : iecompattest().clientWidth-10;
		doc_height=(window.innerHeight && snowdistance=="windowheight")? window.innerHeight : (ie4up && snowdistance=="windowheight")?  iecompattest().clientHeight : (ie4up && !window.opera && snowdistance=="pageheight")? iecompattest().scrollHeight : iecompattest().offsetHeight;
    for (i = 0; i < no; ++ i) {  // iterate for every dot
      yp[i] += sty[i];
      if (yp[i] > doc_height-50) {
        xp[i] = Math.random()*(doc_width-am[i]-30);
        yp[i] = 0;
        stx[i] = 0.02 + Math.random()/10;
        sty[i] = 0.7 + Math.random();
      }
      dx[i] += stx[i];
      document.getElementById("dot"+i).style.top=yp[i]+"px";
      document.getElementById("dot"+i).style.left=xp[i] + am[i]*Math.sin(dx[i])+"px";  
    }
    snowtimer=setTimeout("snowIE_NS6()", 10);
  }

	function hidesnow(){
		if (window.snowtimer) clearTimeout(snowtimer)
		for (i=0; i<no; i++) document.getElementById("dot"+i).style.visibility="hidden"
	}
		

if (ie4up||ns6up){
    snowIE_NS6();
		if (hidesnowtime>0)
		setTimeout("hidesnow()", hidesnowtime*1000)
		}

</script>