private boolean canHaveAsWall(List<Position> positions, boolean recursive) {
		if (positions == null)
			return false;

		for (Position pos : positions) {
			if (!grid.getElementsOnPosition(pos).isEmpty())
				return false;

			if (recursive && !canHaveAsWall(grid.getPositionsAround(pos), false))
				return false;
		}

		return true;
	}