Explanation
Open the explanation (shows the answer)
The answer is a5. With best play to the end: ±0 (a draw).
Best line: a5 d1 f2 g3 e1 f3 g2 h1 h2 g1
Other moves
| Move | Result | Why |
|---|---|---|
| d1 | -22 (a loss by 22) | d1 is in an even region (10 empties); a5 is in an odd one (1). The opponent's best answer is a5 (then f2 g1 f3). |
| f3 | -22 (a loss by 22) | f3 is in an even region (10 empties); a5 is in an odd one (1). Opponent's moves: 5 after this move, 3 after a5. The opponent's best answer is a5 (then f1 d1 e1). |
| f1 | -22 (a loss by 22) | f1 is in an even region (10 empties); a5 is in an odd one (1). Opponent's moves: 6 after this move, 3 after a5. Openness: 4 for this move (flips 2), 0 for a5 (flips 3). The opponent's best answer is a5 (then f3 d1 e1). |
| e1 | -28 (a loss by 28) | e1 is in an even region (10 empties); a5 is in an odd one (1). Opponent's moves: 6 after this move, 3 after a5. Openness: 4 for this move (flips 5), 0 for a5 (flips 3). The opponent's best answer is a5 (then d1 g3 f3). |
| f2 | -38 (a loss by 38) | f2 is in an even region (10 empties); a5 is in an odd one (1). Opponent's moves: 7 after this move, 3 after a5. Openness: 4 for this move (flips 4), 0 for a5 (flips 3). The opponent's best answer is a5 (then f3 g3 h2). |
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.