Thank you for this notebook. This is a new topic to me, and I found the statement in bold somewhat confusing. Thinking of a chess board, I would imagine that rook contiguity would imply that each square is only contiguous with squares of the opposite color, e.g., a white square is only rook contiguity neighbors with black squares, which made me confused about the statement "black squares would count as neighbors with other black squares under the rook criterion".
Best,
Evan