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Reversi lessons · Advanced · Step 7
Parity: Getting the Last Move
Late in the game, when the empty squares split into separate regions, whoever plays last in each region has the edge — the last move can't be flipped back. If you play first in a region with an odd number of empty squares, you're more likely to get the last move there (parity). White also responds with its best moves, so keep playing the best move until the end.
Puzzle 1
The empty squares are split into several regions. Play the best moves to the end. (Black to move)
Show answer and explanation
The yellow circle marks the answer. The empty regions have 3, 1, 2, 2, 1, and 1 squares. Start in an odd region and secure the last moves, and Black wins by 52. Starting with the biggest-flipping move wins by only 6.
Puzzle 2
Pay attention to the isolated empty square. Play your best to the end! (Black to move)
Show answer and explanation
The yellow circle marks the answer. The empty regions have 3, 6, and 1 squares. Start with the answer and play your best to the end, and Black wins by 48. Starting with the biggest-flipping move wins by 10.