Explanation
Open the explanation (shows the answer)
The answer is b5. With best play to the end: +8 (a win by 8).
Best line: b5 b8 g2 g7 h8 g1 f8 d8 f1 a1
Other moves
| Move | Result | Why |
|---|---|---|
| g2 | -4 (a loss by 4) | The opponent's best answer is a1 (then d7 a2 b5). |
| d7 | -4 (a loss by 4) | d7 is in an even region (4 empties); b5 is in an odd one (1). The opponent's best answer is a1 (then g2 a2 b5). |
| f8 | -4 (a loss by 4) | Openness: 3 for this move (flips 2), 0 for b5 (flips 1). The opponent's best answer is a1 (then g2 a2 b5). |
| d8 | -6 (a loss by 6) | d8 is in an even region (4 empties); b5 is in an odd one (1). Openness: 2 for this move (flips 1), 0 for b5 (flips 1). The opponent's best answer is a1 (then f8 a2 b5). |
| f1 | -10 (a loss by 10) | The opponent's best answer is a1 (then a2 b5 g2). |
About these puzzles
Each position comes from a real game. The engine solved it to the end (perfect play by both sides) and only positions with a single best move, clearly better than the second-best move, were kept. "Best play wins by N" is the final disc margin when both sides play perfectly.
If you play a different move, you see the final margin your move leads to with perfect play afterwards, and how much it gave up. Results are stored only in this browser.
To be graded during a full game, go to the Reversi dojo.