responsive-training-sep27-snippet1.css

#navigation #main-menu li {
  -webkit-border-radius: 7px
  -moz-border-radius: 7px;
  border-radius: 7px;
  background: green;
  box-sizing: border-box;
  width: 45%;
  float: left;
  margin: 5px;
  padding: 10px 0;
  text-align: center;
}

script.js

(function ($, Drupal, window, document, undefined) {
  Drupal.behaviors.toggleMenu = {
    attach: function(context) {
      // $("#navigation #main-menu").tinyNav();
      var menu_toggle = $('<div class="menu-toggle" />');
      $("#navigation").prepend(menu_toggle);
      $("#navigation .menu-toggle").click(function() {
        $("#navigation #main-menu").slideToggle();
      });
      $(window).resize(function() {
        if ($(this).width() < 480) {
          $('#navigation #main-menu').hide();
        }
        else {
          $('#navigation #main-menu').show();
        }
      });
    }
  }
}) (jQuery, Drupal, this, this.document);