var viewer=new Class(
	{
		mode:'rand', 
		modes:['top','right','bottom','left','alpha'], 
		sizes:{w:480,h:240},
		fxOptions:{duration:1000},
		interval:5000,
		
		initialize:function(a,b){
			if(b) for(var o in b) this[o]=b[o];
			
			if(this.buttons){
				this.buttons.previous.addEvent('click',this.previous.bind(this,[true]));
				this.buttons.next.addEvent('click',this.next.bind(this,[true]))
			}

			this._current=0;
			this._previous=null;
			this.items=a.setStyle('display','none');
			
			try{this.items[this._current].setStyle('display','block');}
			catch(e){e=null;}			
		
			this.disabled=false;
			this.attrs={left:['left',-this.sizes.w,0,'px'],top:['top',-this.sizes.h,0,'px'],right:['left',this.sizes.w,0,'px'],bottom:['top',this.sizes.h,0,'px'],alpha:['opacity',0,1,'']};
			this.rand=this.mode=='rand';
			this.sequence=typeof(this.mode)=='object'?this.mode:false;
			this.curseq=0;
			this.timer=null
		},
		
		walk:function(n,b){
			if(this._current!==n&&!this.disabled){
				this.disabled=true;
				if(b){this.stop()}
			
				if(this.rand){this.mode=this.modes.getRandom()}
				else if(this.sequence){
					this.mode=this.sequence[this.curseq];
					this.curseq+=this.curseq+1<this.sequence.length?1:-this.curseq
				}
				this._previous=this._current;
				this._current=n;
				var a=this.attrs[this.mode].associate(['p','f','t','u']);
				for(var i=0;i<this.items.length;i++){
					if(this._current===i){
						this.items[i].setStyles($extend({'display':'block','z-index':'2'},JSON.decode('{"'+a.p+'":"'+a.f+a.u+'"}')))
						}
					else if(this._previous===i){
						this.items[i].setStyles({'z-index':'1'})
					}
					else{this.items[i].setStyles({'display':'none','z-index':'0'})}
				}
				//che fa qua?
				this.items[n].set('tween',{onComplete:this.onComplete.bind(this)}).tween(a.p,a.f,a.t)
			}
		},
		
		play:function(a){
			this.stop();
			if(!a){this.next()}
			this.timer=this.next.periodical(this.interval,this,[false])
		},
		
		stop:function(){
			$clear(this.timer)
		},
		
		next:function(a){
			this.walk(this._current+1<this.items.length?this._current+1:0,a)
		},
		
		previous:function(a){
			this.walk(this._current>0?this._current-1:this.items.length-1,a)
		},
		
		onComplete:function(){
			this.disabled=false;
			this.items[this._previous].setStyle('display','none');
			if(this.onWalk)this.onWalk(this._current)
		}
	}
);