gistfile1.js

$(document).ready(function(e) {
    //hide menu
    var lastScrollTop, incr = 0;
    var menuSpace = 20; startsOn = 80;
    $(window).scroll(function(event) {
        var st = $(this).scrollTop();
        if (st > startsOn) {
            if (st > lastScrollTop) {
                incr += 1;
                if (incr >= menuSpace) {
                    $(".topMenu").addClass("hide");
                    incr = menuSpace;
                }
            } else {
                incr -= 1;
                if (incr <= 5) {
                    $(".topMenu").removeClass("hide");
                    incr = 0;
                }
            }
        } else {
            $(".topMenu").removeClass("hide");
        }
        lastScrollTop = st;
    });
});