Kento: Video, Scan & Review Go

I made Kento so that a game played on a real Go board doesn't vanish when the stones go back in the bowls. Prop your phone in front of the board and film the game. When you're done, hand Kento the video. It finds the board, waits for each stone to settle, reads the moves in order and writes the SGF. The rules of Go check every move on the way, so an illegal move never ends up in the record. Afterwards you can check the record against the video: each move sits next to the frame it came from, and anything misread is fixed with a tap.

If you'd rather not wait for the end, record live and the phone writes the moves down while you play. For a single position, one photo is enough. Kento finds the corners itself and works out whether the board is 9x9, 13x13 or 19x19. When it isn't sure, it puts the handles close and you nudge them.

You can also enter a game by voice. Say "D four" or "pass" and the stone goes down, which helps when you're replaying a game from a book and your hands are busy with the stones. Recognition runs on the phone and takes English commands. It's off until you turn it on in Settings.

If you play online, type your OGS username and your games come into the library.

Then comes the review. Mistakes are measured in points, so you read "this move lost 5 points" rather than a win percentage, and one tap takes you to the biggest one. A score graph shows where the game turned. You can branch off at any move to try what you should have played, and the engine analyses your line as you go. The positions you got wrong stay under My Mistakes, sorted by opening, middle game and endgame, so you can come back and practise them. Each day one of them comes back as the daily problem. To show a game to a friend, export it as an MP4 or a GIF.

The board reader and the KataGo engine both run on the phone. Your photos and videos stay on the device, and everything works without a signal, at a club table or on a plane.

Kento also comes with about 70,000 professional games, from Dosaku and Shusaku to Go Seigen and Cho Chikun, plus every AlphaGo game. Around 3,000 are in the app and the rest are in packs you download when you want them. Any of them can get the same review you run on your own games.

Three full reviews a day are free, and reopening a game you've already reviewed doesn't use one up. A single purchase removes the limit for good. There's no subscription and there are no ads. You only sign in if you want cloud backup.

One tip: for video and live recording, keep the phone still and the board well lit.