var SlideList = new Class({
 initialize: function(menu, options) {
 this.setOptions(this.getOptions(), options);
 
 this.menu = $(menu), this.current = this.menu.getElement('li.current');
  
 this.menu.getElements('li').each(function(item){
 item.addEvent('mouseover', function(){ this.moveBg(item); }.bind(this));
 item.addEvent('mouseout', function(){ this.moveBg(this.current); }.bind(this));
 item.addEvent('click', function(event){ this.clickItem(event, item); }.bind(this));
 }.bind(this));
   
 this.back = new Element('li').addClass('background').adopt(new Element('div').addClass('left')).injectInside(this.menu);
 this.back.fx = this.back.effects(this.options);
 if(this.current) this.setCurrent(this.current);
 },
   
 setCurrent: function(el, effect){
 this.back.setStyles({left: (el.offsetLeft)+'px', width: (el.offsetWidth)+'px'});
 (effect) ? this.back.effect('opacity').set(0).start(1) : this.back.setOpacity(1);
 this.current = el;
 },
   
 getOptions: function(){
 return {
 transition: Fx.Transitions.sineInOut,
 duration: 500, wait: false,
 onClick: Class.empty
 };
 },
  
 clickItem: function(event, item) {
 if(!this.current) this.setCurrent(item, true);
 this.current = item;
 this.options.onClick(new Event(event), item);
 },
  
 moveBg: function(to) {
 if(!this.current) return;
 this.back.fx.custom({
 left: [this.back.offsetLeft, to.offsetLeft],
 width: [this.back.offsetWidth, to.offsetWidth]
 });
 }
 });
  
 SlideList.implement(new Options);