Explanation
Open the explanation (shows the answer)
The answer is b1. With best play to the end: +8 (a win by 8).
Best line: b1 h8 h3 d1 h4 h6 g2 f1 h7 h2
Other moves
| Move | Result | Why |
|---|---|---|
| h2 | -4 (a loss by 4) | h2 is in an even region (6 empties); b1 is in an odd one (1). Opponent's moves: 7 after this move, 3 after b1. Openness: 3 for this move (flips 1), 0 for b1 (flips 5). The opponent's best answer is b1 (then h3 h4 h6). |
| h3 | -4 (a loss by 4) | h3 is in an even region (6 empties); b1 is in an odd one (1). Opponent's moves: 7 after this move, 3 after b1. Openness: 3 for this move (flips 6), 0 for b1 (flips 5). The opponent's best answer is b1 (then d1 f1 h6). |
| h6 | -6 (a loss by 6) | Openness: 2 for this move (flips 5), 0 for b1 (flips 5). The opponent's best answer is b1 (then h4 h8 h7). |
| h7 | -8 (a loss by 8) | h7 is a C-square (next to the corner h8). In this shape it lets the corner be taken. The opponent's best answer is h6 (then b1 d1 h3). |
| h4 | -8 (a loss by 8) | h4 is in an even region (6 empties); b1 is in an odd one (1). Opponent's moves: 5 after this move, 3 after b1. Openness: 2 for this move (flips 3), 0 for b1 (flips 5). The opponent's best answer is b1 (then d1 f1 h3). |
| f1 | -12 (a loss by 12) | After this move the opponent can play the corner h1. f1 is in an even region (6 empties); b1 is in an odd one (1). Opponent's moves: 6 after this move, 3 after b1. The opponent's best answer is b1 (then d1 h1 h3). |
| g2 | -20 (a loss by 20) | g2 is an X-square (diagonal to the corner h1). While the corner is empty it tends to give the corner away. g2 is in an even region (6 empties); b1 is in an odd one (1). Opponent's moves: 9 after this move, 3 after b1. The opponent's best answer is b1 (then pass h6 h7). |
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.