code: function watchFocus() {
    var _blurred = false;
    window.addEventListener('focus', function() {
      if (_blurred) {
        _blurred = false;
        // startAnimating();
        // controls.freeze = false;
      }
    });
    window.addEventListener('blur', function() {
      // stopAnimating();
      _blurred = true;
      controls.freeze = true;
    });
  }
docs: Stop animating if the window is out of focus