Explanation
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The answer is d1. With best play to the end: +8 (a win by 8).
Best line: d1 g4 g1 b6 f1 b1 c1 b8 a7 h1
Other moves
| Move | Result | Why |
|---|---|---|
| c1 | -2 (a loss by 2) | The opponent's best answer is b6 (then a7 a8 a6). |
| b1 | -6 (a loss by 6) | The opponent's best answer is b6 (then g1 h1 h2). |
| a7 | -6 (a loss by 6) | a7 is a C-square (next to the corner a8). In this shape it lets the corner be taken. Openness: 4 for this move (flips 1), 2 for d1 (flips 2). The opponent's best answer is a8 (then d1 g4 a6). |
| g1 | -14 (a loss by 14) | g1 is a C-square (next to the corner h1). In this shape it lets the corner be taken. g1 is in an even region (4 empties); d1 is in an odd one (3). Opponent's moves: 9 after this move, 7 after d1. The opponent's best answer is f1 (then a8 d1 a6). |
| f1 | -18 (a loss by 18) | After this move the opponent can play the corner h1. f1 is in an even region (4 empties); d1 is in an odd one (3). Openness: 5 for this move (flips 4), 2 for d1 (flips 2). The opponent's best answer is d1 (then a8 g1 a6). |
| a6 | -18 (a loss by 18) | After this move the opponent can play the corner a8. Openness: 4 for this move (flips 2), 2 for d1 (flips 2). The opponent's best answer is a7 (then h1 d1 b1). |
| h2 | -20 (a loss by 20) | h2 is a C-square (next to the corner h1). In this shape it lets the corner be taken. h2 is in an even region (4 empties); d1 is in an odd one (3). Openness: 4 for this move (flips 3), 2 for d1 (flips 2). The opponent's best answer is g4 (then c1 g1 f1). |
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.