Wow! Roman is not short on superlatives for this one! First he shows you several positions where the discussion is whether a bishop is good or bad, then you get to see both sides' misunderstanding of this concept. But our author saves his highest opprobrium for a simple pawn move. "This is the worst move I've seen in months." One side clearly wasn't thinking about squares gained and taken away - it turns out to be the pivotal mistake. Enjoy the lesson!