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

	var portal = $$('#portal div img');
	portal.addEvents({
		mouseenter: function() {
			this.set('tween', {duration: '600'});
			this.tween('opacity', 0.25);
		},
		mouseleave: function() {
			this.set('tween', {duration: '600'});
			this.tween('opacity', 1.0);
		}
	});
});