window.addEvent('domready', function(){

  $('menu').getElements('li').each( function( elem ) {

    var list = elem.getElement('ul');

    elem.addEvents({
      'mouseenter' : function(){
        elem.addClass('on');
      },
      'mouseleave' : function(){
        elem.removeClass('on');
      }
    });  
  
    if(list) {
      var myFx = new Fx.Slide(list).hide();
      elem.addEvents({
        'mouseenter' : function(){
            elem.addClass('on');
            myFx.cancel();
            myFx.slideIn();
        },
        'mouseleave' : function(){
          elem.removeClass('on');
          myFx.cancel();
          myFx.slideOut();
        }
      });
    }
  });
});