var ns4up = (document.layers) ? 1 : 0;
var ie4up = (document.all) ? 1 : 0;

var pathImg = new Array;
var posImg = new Array;
var colorImg = new Array;
var nPapers=40;
var docWidth=800;
var docHeight=600;


if (ie4up){
  docWidth=document.body.clientWidth;
  docHeight=document.body.clientHeight;
}else{
  if (ns4up){
    docWidth=window.innerWidth;
    docHeight=window.innerHeight;
  }  
}

var incr = 6;
var delay = 50;
var cantImg = 5;

for (i=0; i < nPapers; i++){
  posImg[i]=Math.round(Math.random()*docHeight);
  r=Math.random();
  if (r<0.33) colorImg[i]=0;
  else if (r<0.66) colorImg[i]=1;
       else colorImg[i]=2;
}

pathImg[0]=new Array;
pathImg[0][0] = "images/red_paper0000.gif";
pathImg[0][1] = "images/red_paper0001.gif";
pathImg[0][2] = "images/red_paper0002.gif";
pathImg[0][3] = "images/red_paper0003.gif";
pathImg[0][4] = "images/red_paper0004.gif";

pathImg[1]=new Array;
pathImg[1][0] = "images/blue_paper0000.gif";
pathImg[1][1] = "images/blue_paper0001.gif";
pathImg[1][2] = "images/blue_paper0002.gif";
pathImg[1][3] = "images/blue_paper0003.gif";
pathImg[1][4] = "images/blue_paper0004.gif";

pathImg[2]=new Array;
pathImg[2][0] = "images/green_paper0000.gif";
pathImg[2][1] = "images/green_paper0001.gif";
pathImg[2][2] = "images/green_paper0002.gif";
pathImg[2][3] = "images/green_paper0003.gif";
pathImg[2][4] = "images/green_paper0004.gif";

if (ns4up)
  for (i=0;i<nPapers;i++)
    document.write("<layer name=\"LImg"+i+"\" left="+Math.random()*docWidth+" top=\""+posImg[i]+"\" visibility=\"show\"><img name=\"papel"+i+"\" src=\""+pathImg[colorImg[i]][posImg[i] % cantImg]+"\" border=\"0\"></layer>");
else
  if (ie4up)
    for (i=0;i<nPapers;i++)
      document.write("<div id='DImg"+i+"' style='position:absolute;top:"+posImg[i]+"px;left:"+Math.random()*docWidth+"px;width:20px;height:20px;z-index:50'><img name='papel"+i+"' src='"+pathImg[colorImg[i]][posImg[i] % cantImg]+"'></div>");

function mover(){

  if (ns4up){
    for (i=0; i<nPapers; i++){
      if (posImg[i] > docHeight) posImg[i]=0;
      else posImg[i]+=incr;
      document.layers["LImg"+i].top = posImg[i]+window.pageYOffset;
      document.layers["LImg"+i].document.images["papel"+i].src = pathImg[colorImg[i]][posImg[i] % cantImg];
    }
  }else{
    if (ie4up){
      for (i=0; i<nPapers; i++){
        if (posImg[i] > docHeight) posImg[i]=0;
        else posImg[i]+=incr;

        document.all["DImg"+i].style.top=posImg[i]+document.body.scrollTop;
        document.all["papel"+i].src=pathImg[colorImg[i]][posImg[i] % cantImg];
      }
    }
  }
  setTimeout("mover()", delay);
}

function init(){

  mover();
}

init();