$(function() {
  var sections = $("#me,#work,#projects");
  var mainDiv = $('div#yui-main');

  sections.hide();

  $("#sidebar ul li").click(function (e) {
    if (mainDiv.attr('class') !== 'transitioning') {
      mainDiv.addClass('transitioning');
      var shownSection = $(this).find("a:first").attr("href");
      sections.hide();
      $(shownSection).slideDown("slow", function () {
        mainDiv.removeClass('transitioning');
      });
    }

    e.preventDefault();
  });
});