anchor.diff:          _setState(GameState.won);
         }
       }
  +    _update();
     }
  +
  +  void _update() => _updatedEvent.fireEvent(EventArgs.empty);
   
     void _setState(GameState value) {
       if(_state != value) {
  
positive.code: 
    Game(this.field) :
      _state = GameState.notStarted,
      _states = new List<SquareState>() {
      assert(field != null);
      _minesLeft = field.mineCount;
      _revealsLeft = field.size - field.mineCount;
  
negative.code: class Game {
    final Field field;
    final List<SquareState> _states;
    final EventHandle<EventArgs> _updatedEvent;
  
    GameState _state;
    int _minesLeft;
  