About the analyzer
The position analyzer lets you set up any reversi (Othello) position and see the disc margin of every legal move. Open a position you were unsure about in an endgame puzzle or in the review of a game, and check it.
Reading the numbers
The margin is the final disc difference from the side to move. With 18 or fewer empty squares the computer tries to read to the very end (exact search). When it finishes in time, the result says "Solved exactly" and the margin is the exact final result. With more empty squares, or when a hard position cannot be read to the end in time, it is an estimate at the search depth shown, marked with ≈, and every move is compared at that same depth.
The number on each square is how many discs the move loses against the best move. The list grades each loss on the same five steps as the dojo.
- Bestloss up to 0.5 discs
- Goodup to 2 discs
- Inaccuracyup to 5 discs
- Mistakeup to 10 discs
- Blundermore than 10 discs
Where it runs
Everything is computed in your browser on this device; the position is never sent to the server. It lives only in the page link (after the #) and is not stored in this browser either. To improve the site, only the number of times Analyze is pressed is sent, as an anonymous count (never the position or the result).
If setting up discs by hand is slow, play a game in the reversi dojo and open any move of its review with "Analyze this position".