window.addEvent('domready', function() {
			/* example a:  top down */
			$$('#a a').each(function(el) {
				//fx
				var fx = new Fx.Tween(el,{
					duration: 750,
					link: 'cancel'
				});
				
				//css & events
				el.setStyle('background-position','0px 75px').addEvents({
					'mouseenter': function(e) {
						e.stop();
						fx.start('background-position','0px 189px');
					},
					'mouseleave': function(e) {
						e.stop();
						fx.start('background-position','0px 75px');
					}
				});
			});
			
			/* example b:  right left */
			$$('#b a').each(function(el) {
				//css
				var reset = false;
				var fx = new Fx.Tween(el,{
					duration: 500,
					link: 'cancel',
					onComplete:function() {
						if(reset) {
							el.setStyle('background-position','0 0');
						}
					}
				});
				//events
				el.setStyle('background-position','0 0').addEvents({
					'mouseenter': function(e) {
						e.stop();
						fx.start('background-position','-10px 0');
						reset = false;
					},
					'mouseleave': function(e) {
						reset = true;
						fx.start('background-position','-10px 0');
					}
				});
			});
			
		});