anchor.diff:      final m = game.field.mineCount;
       final duration = game.duration.inMilliseconds;
   
  -    final key = "w$w-h$h-m$m";
  +    final key = _getKey(w, h, m);
   
       final currentScore = _getIntValue(key, null);
       if(currentScore == null || currentScore > duration) {
         _setIntValue(key, duration);
  +      _highScoreUpdated.fireEvent(null);
         return true;
       } else {
         return false;
       }
  +  }
  +
  +  int getHighScore(int width, int height, int mineCount) {
  +    final key = _getKey(width, height, mineCount);
  +    return _getIntValue(key, null);
     }
   
     void reset() {
  
positive.code:     _setIntValue(key, value + 1);
    }
  
  }
  
negative.code: class GameStorage {
    static final _gameCountKey = 'gameCount';
    final dartlib.EventHandle _highScoreUpdated;
  
    final Storage _storage;
  
    GameStorage() :
      _storage = window.localStorage,
      _highScoreUpdated = new dartlib.EventHandle();
  
    int get gameCount => _getIntValue(_gameCountKey);
  
    dartlib.EventRoot get highScoreUpdated => _highScoreUpdated;
  
    void recordState(GameState state) {
      assert(state != null);
  