text: var fullscreenButton = document.getElementById('fullscreen');
  if (fullscreenButton && (document.exitFullscreen||document.webkitExitFullscreen||document.webkitExitFullScreen||document.mozCancelFullScreen||document.msExitFullscreen)) {
      fullscreenButton.onclick = function() {
  	var d = document;
  	if (d.fullscreenElement||d.webkitFullscreenElement||d.webkitFullScreenElement||d.mozFullScreenElement||d.msFullscreenElement) {
  	    (d.exitFullscreen||d.webkitExitFullscreen||d.webkitExitFullScreen||d.mozCancelFullScreen||d.msExitFullscreen).call(d);
  	} else {
  	    var e = document.body;
  	    (e.requestFullscreen||e.webkitRequestFullscreen||e.webkitRequestFullScreen||e.mozRequestFullScreen||e.msRequestFullscreen).call(e);
  	}
      }
      if (window.navigator.standalone === true) {
  	fullscreenButton.style.opacity = '0';
      }
  } else if (fullscreenButton) {
      fullscreenButton.style.opacity = '0';
  }
  