public void userOpenTile(int aX, int aY)
	{
		MaskValue mask = mField.getMaskValue(aX, aY);
		if (mask.isNothing())
		{
			TileValue tile = mField.getTileValue(aX, aY);
			openTile(aX, aY);
			if (tile.isBomb()) mSweeper.die(aX, aY);
			if (won()) mSweeper.win();
		}
	}