Explanation
Open the explanation (shows the answer)
The answer is e1. With best play to the end: +6 (a win by 6).
Best line: e1 g1 f1 a5 b8 b7 a8 a2 a6 b2
Other moves
| Move | Result | Why |
|---|---|---|
| b8 | -12 (a loss by 12) | b8 is in an even region (6 empties); e1 is in an odd one (3). The opponent's best answer is e1 (then b7 a6 a5). |
| b7 | -12 (a loss by 12) | 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. b7 is in an even region (6 empties); e1 is in an odd one (3). The opponent's best answer is b8 (then e1 g1 f1). |
| b1 | -20 (a loss by 20) | b1 is a C-square (next to the corner a1). In this shape it lets the corner be taken. b1 is in an even region (4 empties); e1 is in an odd one (3). Opponent's moves: 9 after this move, 7 after e1. The opponent's best answer is a1 (then b7 g1 b8). |
| b2 | -30 (a loss by 30) | b2 is an X-square (diagonal to the corner a1). While the corner is empty it tends to give the corner away. After this move the opponent can play the corner a1. b2 is in an even region (4 empties); e1 is in an odd one (3). The opponent's best answer is g1 (then b8 a7 a5). |
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.