in public/js/learn.js [233:243]
    jQuery(document).keydown(function(e) {
      // prev links - left arrow key
      if(e.which == '37') {
        jQuery('.nav.nav-prev').click();
      }
      // next links - right arrow key
      if(e.which == '39') {
        jQuery('.nav.nav-next').click();
      }
    });