code: function updateAreLoading(that, update) {
          that.areLoading = that.areLoading + update;
          return that.areLoading === 0;
      }
docs: ### updateAreLoading
  
  Updates the counter of loading frames
  
  @param {GameWindow} that A reference to the GameWindow instance
  @param {number} update The number to add to the counter
  
  @see GameWindow.lockedUpdate
  
  @api private