anchor.diff:    set y(int y) {
       super.y = y;
       buttonText.y = y;
  +  }
  +
  +  /**
  +   * Put the pivot point into the center of the button.
  +   */
  +  void centerPivot() {
  +    pivotX = bitmapData.width / 2;
  +    pivotY = bitmapData.height / 2;
     }
   
     /**
  
positive.code: 
  /**
   * Represents a simple Button.
   * 
   * Example:
   *      Button button = new Button(this, "resourceName", "buttonText")
   *        ..setCoordinates(300, 400)
  
negative.code: 
    /**
     * Create a Button from [StageXL.BitmapData ].
     *
     * * stateContext: current state you are in
     * * text: label of the button
     * * addToWorld: add the button to the world?
  