anchor.diff:  
     /**
      * Drehen des Tetris Steins um 90 Grad
  -   * Y Koordinate: row
  -   * x Koordinate: col
  +   * Y-Koordinate: row
  +   * X-Koordinate: col
      * Rotationsformal für 90 Grad:
      * x' = x * cos(90) - y * sin(90)
      * y' = x * sin(90) + y * cos(90)
      */
     void rotate(){
       var _rotate = [
  -      { 'row' : ~(_stone.elementAt(0)['col'] * sin(90) + _stone.elementAt(0)['row'] * cos(90)),  'col' : ~(_stone.elementAt(0)['col'] * cos(90) - _stone.elementAt(0)['row'] * sin(90)) },
  -      { 'row' : ~(_stone.elementAt(1)['col'] * sin(90) + _stone.elementAt(1)['row'] * cos(90)),  'col' : ~(_stone.elementAt(1)['col'] * cos(90) - _stone.elementAt(1)['row'] * sin(90)) },
  -      { 'row' : ~(_stone.elementAt(2)['col'] * sin(90) + _stone.elementAt(2)['row'] * cos(90)),  'col' : ~(_stone.elementAt(2)['col'] * cos(90) - _stone.elementAt(2)['row'] * sin(90)) },
  -      { 'row' : ~(_stone.elementAt(3)['col'] * sin(90) + _stone.elementAt(3)['row'] * cos(90)),  'col' : ~(_stone.elementAt(3)['col'] * cos(90) - _stone.elementAt(3)['row'] * sin(90)) }
  +      { 'row' : (_stone.elementAt(0)['col'] * sin(90).round() + _stone.elementAt(0)['row'] * cos(90).round()),  'col' : (_stone.elementAt(0)['col'] * cos(90).round() - _stone.elementAt(0)['row'] * sin(90).round()) },
  +      { 'row' : (_stone.elementAt(1)['col'] * sin(90).round() + _stone.elementAt(1)['row'] * cos(90).round()),  'col' : (_stone.elementAt(1)['col'] * cos(90).round() - _stone.elementAt(1)['row'] * sin(90).round()) },
  +      { 'row' : (_stone.elementAt(2)['col'] * sin(90).round() + _stone.elementAt(2)['row'] * cos(90).round()),  'col' : (_stone.elementAt(2)['col'] * cos(90).round() - _stone.elementAt(2)['row'] * sin(90).round()) },
  +      { 'row' : (_stone.elementAt(3)['col'] * sin(90).round() + _stone.elementAt(3)['row'] * cos(90).round()),  'col' : (_stone.elementAt(3)['col'] * cos(90).round() - _stone.elementAt(3)['row'] * sin(90).round()) }
       ];
   
       _stone = _rotate;
  
positive.code:         // Erzeugt ein Z Tetris Stein in der Farbe rot
          _tempColor = #red;
          temp = [
            { 'row' : height ~/ 2,       'col' : width ~/ 2 - 1  },
            { 'row' : height ~/ 2,       'col' : width ~/ 2      },
            { 'row' : height ~/ 2 + 1,   'col' : width ~/ 2      },
            { 'row' : height ~/ 2 + 1,   'col' : width ~/ 2 + 1  }
  
negative.code:    */
    void stop() { _gamestate = #stopped; }
  
  
    /**
     * Konstruktor um ein neues Tetris Spiel zu erzeugen
  