Explanation
Open the explanation (shows the answer)
The answer is a5. With best play to the end: +2 (a win by 2).
Best line: a5 a4 a3 b3 c3 a2 b2 a1 b8 c8
Other moves
| Move | Result | Why |
|---|---|---|
| a3 | -2 (a loss by 2) | Openness: 4 for this move (flips 1), 0 for a5 (flips 1). The opponent's best answer is b3 (then a5 a4 c3). |
| b8 | -2 (a loss by 2) | The opponent's best answer is c8 (then a3 a5 c3). |
| b3 | -4 (a loss by 4) | Opponent's moves: 7 after this move, 4 after a5. Openness: 5 for this move (flips 2), 0 for a5 (flips 1). The opponent's best answer is c3 (then a5 a4 a3). |
| c3 | -6 (a loss by 6) | Opponent's moves: 6 after this move, 4 after a5. Openness: 2 for this move (flips 4), 0 for a5 (flips 1). The opponent's best answer is b2 (then b8 c8 a3). |
| a4 | -12 (a loss by 12) | Openness: 4 for this move (flips 1), 0 for a5 (flips 1). The opponent's best answer is a5 (then b3 c3 b8). |
| c8 | -14 (a loss by 14) | The opponent's best answer is c3 (then a5 b2 a3). |
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.