Explanation
Open the explanation (shows the answer)
The answer is b1. With best play to the end: +2 (a win by 2).
Best line: b1 g1 b2 b7 a8 g8 e8 a1 a2 b6
Other moves
| Move | Result | Why |
|---|---|---|
| a8 | -4 (a loss by 4) | The opponent's best answer is g1 (then a2 a1 b6). |
| b6 | -6 (a loss by 6) | The opponent's best answer is b7 (then a8 g1 b1). |
| b7 | -10 (a loss by 10) | b7 is an X-square (diagonal to the corner a8). While the corner is empty it tends to give the corner away. After this move the opponent can play the corner a8. The opponent's best answer is a8 (then b1 g1 a2). |
| a2 | -14 (a loss by 14) | a2 is a C-square (next to the corner a1). In this shape it lets the corner be taken. The opponent's best answer is a1 (then a8 b6 b7). |
| b2 | -16 (a loss by 16) | b2 is an X-square (diagonal to the corner a1). While the corner is empty it tends to give the corner away. The opponent's best answer is b7 (then a8 g1 b6). |
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.