var bdover = Class.create({
	initialize: function(el,yto) {
		this.el=el;
		this.yto=yto;
	},
	
	corsoup_: function (){
		
		t=parseInt($(this.el).getStyle("top"));
		if(t>-this.yto){
			t-=3
			$(this.el).setStyle({top:t+"px"})
		}else{
			clearInterval(this.intup)
		}
	},
	corsoup: function (){
		clearInterval(this.intdw)
		this.intup=setInterval((this.corsoup_).bind(this),10);
	},
	corsodw: function (){
		clearInterval(this.intup)
		this.intdw=setInterval((this.corsodw_).bind(this),10);
	},
	corsodw_: function(){
		t=parseInt($(this.el).getStyle("top"));
		if(t<0){
			t+=3
			$(this.el).setStyle({top:t+"px"})
		}else{
			clearInterval(this.intdw)
		}
		
	}
});