Explanation
Open the explanation (shows the answer)
The answer is b8. With best play to the end: +4 (a win by 4).
Best line: b8 g2 h1 b2 h3 c8 b1 f8 h5 a1
Other moves
| Move | Result | Why |
|---|---|---|
| b2 | -4 (a loss by 4) | 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 f8 (then c8 b7 a8). |
| h3 | -4 (a loss by 4) | After this move the opponent can play the corner h1. The opponent's best answer is h1 (then g2 b2 h5). |
| b1 | -12 (a loss by 12) | b1 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 b2 a8 b7). |
| c8 | -12 (a loss by 12) | The opponent's best answer is f8 (then b1 a1 b2). |
| b7 | -16 (a loss by 16) | 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 h7 (then h5 a8 b8). |
| h5 | -18 (a loss by 18) | The opponent's best answer is h3 (then g2 h1 b1). |
| g2 | -22 (a loss by 22) | g2 is an X-square (diagonal to the corner h1). While the corner is empty it tends to give the corner away. After this move the opponent can play the corner h1. The opponent's best answer is h1 (then b1 f8 b2). |
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.