window.addEvent('domready',function() {
    var topbar = $('header').set('tween', { duration: 200 }), topDistance = 10, fadeTo = 0.5;
    var topbarME = function() { topbar.tween('opacity', 1); }, topbarML = function() { topbar.tween('opacity', fadeTo); };
    var events = {
        mouseenter: topbarME,
        mouseleave: topbarML
    };
    new ScrollSpy({
        min: topDistance,
        onLeave: function() {
            topbarME();
            topbar.removeEvents(events);
        },
        onEnter: function() {
            topbarML();
            topbar.addEvents(events);
        }
    });
});