function Snow(tag, fallrate)
{
	this.x = 0;
	this.y = 0;
	this.fallrate = fallrate;
	this.tag = tag;
	this.move = function() {
	  this.x = this.x + Math.floor(Math.random()*60)-30;
	  this.y = this.y + this.fallrate;
	  var backPositionString = this.x + 'px ' + this.y + 'px';
	  $(this.tag).animate({backgroundPosition: backPositionString},3000,'linear');
	};
	this.start = function() {
	  this.move();
		var self = this;
		this.interval = setInterval( function(){self.move()}, 3000 );
	};
}

$(document).ready(function() {
var snow1 = new Snow('#snow1',30).start();
var snow2 = new Snow('#snow2',40).start();
});