text: var panels = function(panels, jQuery) {
      var visible = {};
      
  ////// visible ///////////////////////////////////////////////////////////
      visible.showCenter = function() {
          if ($(".center.panel").hasClass("hide-left")) {
              rotate(RIGHT_TO_CENTER);
          } else if ($(".center.panel").hasClass("hide-right")) {
              rotate(LEFT_TO_CENTER);
          }
      };
      
      visible.showLeft = function() {
          rotate(CENTER_TO_LEFT);
      };
      
      visible.showRight = function(panel) {
          rotate(CENTER_TO_RIGHT, panel);
      };
      
      
  ////// hidden ////////////////////////////////////////////////////////////
      var CENTER_TO_LEFT = 0;
      var CENTER_TO_RIGHT = 1;
      var LEFT_TO_CENTER = 2;
      var RIGHT_TO_CENTER = 3;
      
      
      function rotate(direction, panel) {
          var panel = panel ? "#" + panel : "";
          
          /*
           * No arbitrary movement, only continuous rotation -- as if the
           * three panels were drawn on the same sheet of paper.
           */
          switch(direction) {
              case CENTER_TO_LEFT:
                  $(".right.panel").addClass("hide-right");
                  $(".center.panel").addClass("hide-right");
                  $(".left.panel").removeClass("hide-left");
                  break;
              case LEFT_TO_CENTER:
                  $(".right.panel").addClass("hide-right");
                  $(".left.panel").addClass("hide-left");
                  $(".center.panel").removeClass("hide-left hide-right");
                  break;
              case CENTER_TO_RIGHT:
                  $(".left.panel").addClass("hide-left");
                  $(".center.panel").addClass("hide-left");
                  
                  // multiple right panels exist
                  if (panel) {
                      $(panel).parent(".right.panel")
                              .removeClass("hide-right");
                  } else {
                      $(".right.panel").removeClass("hide-right");
                  }
                  break;
              case RIGHT_TO_CENTER:
                  $(".right.panel").addClass("hide-right");
                  $(".left.panel").addClass("hide-left");
                  $(".center.panel").removeClass("hide-left hide-right");
                  break;
          }
      }
      
      
      // expose interface //////////////////////////////////////////////////
      return visible;
  }(window.panels = window.panels || {}, $, undefined);
  