Why did
that move lose?
Each Othello (reversi) move you play is compared with the best move in that position. How many discs it cost and why are written down move by move, and you can step back and compare the best line on the board. Free, no sign-up.
| # | You | Best | Loss | Grade |
|---|---|---|---|---|
| 47 | g2 | h2 | 4.0 | Inaccuracy |
| g2 is an X-square (diagonal to the empty corner h1). Playing it while the corner is empty often hands the corner over. | ||||
| 49 | g1 | g1 | 0.0 | Best |
| 51 | b7 | b1 | 16.0 | Blunder |
| b7 is an X-square (diagonal to the empty corner a8). Playing it while the corner is empty often hands the corner over. | ||||
| Parity: b7 is in a region of 6 empty squares (even); b1 is in a region of 1 (odd). In the endgame, playing first into an odd region usually lets you make the last move there. | ||||
The position at move 51. b7 is your move, b1 is the best move.
How it works
Play
Four strengths to choose from.
Get a grade
Weaker moves get a one-to-three line reason.
Compare
Step back to the position before your move and see the best move and the best line on the board. Take-backs are allowed.
Your records stay in this browser on this device. They do not carry over to other devices.
The grading scale
Loss is how many discs the final margin drops compared with the best move, estimated in the midgame and solved exactly in the endgame.
Dojos
New here? Start with Reversi or Endgames. Practice fills up once your games have turned up mistakes.
| Dojo | What it is | Link |
|---|---|---|
| Start playing | ||
| Reversi | Loss in discs for every move, with the reason. Endgames are solved to the last disc. Same rules as Othello. | Play → |
| Endgames | Positions solved exactly (new ones every week), each with a single best move. Wrong moves show the final margin and why they lose. | Solve → |
| Daily puzzle | One endgame puzzle a day. Keep a streak and share your result. | Today's puzzle → |
| Learn | ||
| Strategy | Corners, mobility, openness, parity, and openings such as the Tiger and Rabbit, on boards you can step through. | Read → |
| Practice | The positions where you made clear mistakes, asked again over the following days. | Practice → |
| Test yourself | ||
| Rank exam | Eleven computer opponents from 10 kyu to 5 dan. No hints, no take-backs. Win to earn the rank (Itte Dojo's own ranks, not official ones). | Take it → |
| One-minute rank check | Five endgame puzzles, 30 seconds each. Get a rank estimate and a title from how many you get right and how fast, and share the result card. | Check → |
| Play a friend | Send a link and play Othello or chess with a friend online, then review every move of your game. | Play → |
| Chess | ||
| Chess | Loss in centipawns for every move, plus hanging pieces and how the AI punishes mistakes. | Start → |