private boolean isClear(int direction) {
		Coordinate c = getWallCoordinate(direction);

		switch (direction) {
			case Display.NORTH:
			case Display.SOUTH:
				return !WorldBackend.getCurrent()
				       .checkWall(c.x, c.y, Display.HORIZONTAL);
			case Display.EAST:
			case Display.WEST:
			default:
				return !WorldBackend.getCurrent()
				       .checkWall(c.x, c.y, Display.VERTICAL);
		}
	}