$('.open-overlay').click(function() {

       $('.open-overlay').css('pointer-events', 'none');

       var overlay_navigation = $('.overlay-navigation'),

         top_bar = $('.bar-top'),

         middle_bar = $('.bar-middle'),

         bottom_bar = $('.bar-bottom');

​

       overlay_navigation.toggleClass('overlay-active');

       if (overlay_navigation.hasClass('overlay-active')) {

​

         top_bar.removeClass('animate-out-top-bar').addClass('animate-top-bar');

         middle_bar.removeClass('animate-out-middle-bar').addClass('animate-middle-bar');

         bottom_bar.removeClass('animate-out-bottom-bar').addClass('animate-bottom-bar');

         overlay_navigation.removeClass('overlay-slide-up').addClass('overlay-slide-down')

         overlay_navigation.velocity('transition.slideLeftIn', {

           duration: 300,

           delay: 0,

           begin: function() {

             $('nav ul li').velocity('transition.perspectiveLeftIn', {

               stagger: 150,