window.addEvent("domready", function() {
    var slideItems = $$("#prod_sobremesa li img");
    var tracking = 0;
    var pageSize = 4;

    var scroll = new Fx.Scroll($$('.logos')[0],
	{
	    wait: false,
	    duration: 450,
	    transition: Fx.Transitions.Cubic.easeInOut
	});
    $$('img.prev').addEvent('click', function(e) {
        e = new Event(e).stop();
        if (tracking == Math.floor(slideItems.length / pageSize)) {
            scroll.toElement(slideItems[0]);
            tracking = 0;
        }
        else {
            scroll.toElement(slideItems[pageSize * (tracking + 1)]);
            tracking++;
        }
    });
    $$('.next').addEvent('click', function(e) {
        e = new Event(e).stop();
        if (tracking == 0) {
            tracking = Math.floor(slideItems.length / pageSize);
            scroll.toElement(slideItems[slideItems.length - 1]);
        }
        else {
            scroll.toElement(slideItems[pageSize * (tracking - 1)]);
            tracking--;
        }
    });

});