/* BUTTON MOUSE DOWN EFFECT */
$(document).ready(function() {
	   $(".btn_down").mousedown(function(){
	     bgDown($(this));
     });
     
	   $(".btn_down").mouseout(function(){
	     bgNormal($(this));
     });
     
	   $(".btn_down").mouseup(function(){
	     bgHover($(this));
     });
     
	   $(".btn_down").mouseover(function(){
	     bgHover($(this));
     });
     
     function bgNormal(elem) {
	     elem.css("background-position","0 0");
     }
     
     function bgHover(elem) {
	     var elemHeight = elem.height();
	     elem.css("background-position","0 -"+ elemHeight +"px");
     }
     
     function bgDown(elem) {
	     var elemHeight = elem.height() * 2;
	     elem.css("background-position","0 -"+ elemHeight +"px");
     }
     
   });