anchor.diff:    final Field field;
     final Array2d<SquareState> _states;
     final EventHandle<EventArgs> _updatedEvent;
  +  final EventHandle<GameState> _gameStateEvent;
   
     GameState _state;
     int _minesLeft;
  
positive.code:       } else if(gameEnded) {
          _endTime = new Date.now();
        }
      }
    }
  
  
negative.code:     this.field = field,
      _state = GameState.reset,
      _states = new Array2d<SquareState>(field.width, field.height, SquareState.hidden),
      _updatedEvent = new EventHandle<EventArgs>(),
      _gameStateEvent = new EventHandle<GameState>() {
      assert(field != null);
      _minesLeft = field.mineCount;
      _revealsLeft = field.length - field.mineCount;
  