old_contents: $(document).ready(function () {
    var h = $('.full-page-jumbotron').height();
    $(window).on('wheel', function (e) {
      if ($(window).scrollTop() > 0) {
        $('.navbar-fixed nav').css('background', '#607d8b');
        $('.navbar-fixed nav *').css('text-shadow', 'none');
        $('.full-page-jumbotron *').slideUp();
        $('.full-page-jumbotron').height(h/2);
      } else {
        $('.navbar-fixed nav').css('background', 'transparent');
        $('.navbar-fixed nav *').css('text-shadow', '1px 1px black');
        $('.full-page-jumbotron *').fadeIn();
        $('.full-page-jumbotron').height(h);
      }
    });
  });
  
new_contents: $(document).ready(function () {
    var h = $('.full-page-jumbotron').height();
    $(window).on('scroll', function (e) {
      if ($(window).scrollTop() > 0) {
        $('.navbar-fixed nav').css('background', '#607d8b');
        $('.navbar-fixed nav *').css('text-shadow', 'none');
        $('.full-page-jumbotron *').slideUp();
        $('.full-page-jumbotron').height(h/2);
      } else {
        $('.navbar-fixed nav').css('background', 'transparent');
        $('.navbar-fixed nav *').css('text-shadow', '1px 1px black');
        $('.full-page-jumbotron *').fadeIn();
        $('.full-page-jumbotron').height(h);
      }
    });
  });
  
subject: fix #12, change event listener from wheel to scroll in dynamic_navbar.js