var SlideList = new Class({
    initialize: function(menu, options) {
        this.setOptions(this.getOptions(), options);
 
        this.menu = $(menu), this.current = this.menu.getElement('.wyr a');
        var tab = this.menu.getElements('li');
        tab.unshift($('menu_gt').getElements('h1')[0]);
        tab.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('span').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);