var clouds1pos = 0;
var clouds2pos = 0;
var clouds1posy = 300;
var clouds2posy = 500;

function getElementObject(elementName)
{
  obj = null;
  if(document.getElementById){
	if(document.getElementById(elementName)){
	  obj = document.getElementById(elementName);
	}
  } else {
	if(document.getElementByName(elementName)){
	  obj = document.getElementByName(elementName);
	}
  }
 
  return obj;
}
		
function updateClouds()
{
	//alert(clouds1pos);
	clouds1pos = clouds1pos-1;
	clouds2pos = clouds2pos-2;
	
	clouds1posy = Math.floor(clouds1posy - clouds1posy/10);
	clouds2posy = Math.floor(clouds2posy - clouds2posy/10);
	
	var clouds1 = document.getElementById("clouds1");
	var clouds2 = document.getElementById("clouds2");
	var buildings = document.getElementById("buildings");
	
	clouds1.style.backgroundPosition = "" + clouds1pos + "px "+clouds1posy+"px";
	clouds2.style.backgroundPosition = "" + clouds2pos + "px "+clouds2posy+"px";
	//buildings.style.backgroundPosition = "0px "+clouds2posy+"px";
	
	setTimeout(updateClouds, 30);	
}