anchor.diff:    
     num row, col;
     Piece piece;
  -  num dotCount;
  -  
  -  Tile(this.row, this.col, this.piece) {
  -    dotCount = piece.bugCount;
  -  }
  +
  +  Tile(this.row, this.col, this.piece);
     
     bool operator ==(other) {
       if (other is !Tile) { return false; }
  -    return row == other.row && col == other.col && dotCount == other.dotCount && piece == other.piece; 
  +    return row == other.row && col == other.col && piece == other.piece; 
     }
   
     int get hashCode {
  
positive.code: //    context.fillStyle = '#00f';
  //    context.fillRect(dotContainerRect.left, dotContainerRect.top, dotContainerRect.width, dotContainerRect.height);
  
      if (dotCount == 1) {
        _renderOneDot(context, dotContainerRect);
      } else if (dotCount == 2) {
        _renderTwoDots(context, dotContainerRect);
      } else if (dotCount == 3) {
        _renderThreeDots(context, dotContainerRect);
      }
    }
  
negative.code:     int result = 17;
      result = 37 * result + row.hashCode;
      result = 37 * result + col.hashCode;
      result = 37 * result + piece.hashCode;
      return result;
    }
  