Full disclosure: I made this app. I’m posting because getting a strong engine to play weak in a believable way turned out to be the interesting part, and I’d like feedback from stronger players.
Background
My son started Go at 7. His class is once a week and he wanted to play at home, but I couldn’t find an app I was comfortable handing a 7-year-old: sign-ins, ads, upsell pop-ups, or chat with strangers. So I built one.
It runs KataGo as a native module on the phone. Moves are computed on the device, not on a server, so it works in airplane mode, and there’s no account.
The hard part: playing weak like a human
My first try was just cutting visits. It didn’t feel like a beginner; it felt like a strong engine holding back. Even with 1–3 visits the policy net picks reasonable moves, so it never makes the mistakes a real beginner makes. My son was confused: “it’s playing randomly, so why am I losing?”
What worked better:
- At the weakest levels, with some probability the app skips KataGo entirely and plays a move from a simple built-in MCTS bot. That probability is 75% at 18k and tapers to zero by about 6k. Only bypassing KataGo gives you a genuinely bad move; randomness inside KataGo still picks moves it likes.
- Then KataGo’s Human SL model, which imitates players of a given rank. That’s now the default for new players.
It’s 22 levels from 18 kyu to amateur 4 dan.
What else is in it
- 10,000+ problems grouped by theme (liberties, ladders, nets, snapback, semeai, life and death…), with hints and explanations
- 9x9, 13x13 and 19x19; Chinese or Japanese/Korean rules
- a free beginner course, from captures up to territory on 9x9
- after a game, review with a win-rate graph, plus an explanation that picks up to 5 of your moves worth another look and roughly how many points each lost
What it isn’t
- No online play, by design: no account means no strangers.
- The main net is small (b6c96) so it runs on a phone. For deep analysis, use KaTrain or Lizzie on a desktop.
- It sends anonymous usage stats (Firebase) to help me improve it; you can turn that off in Settings. Game records stay on the phone.
- Free to try with daily limits; a one-time purchase removes them. No subscription.
What I’d like feedback on
I’m about 8 kyu, so I can’t judge the top of the range. If you try the 1k–4d levels, do they feel roughly right?
Search “Go AI KataGo” on the App Store or Google Play. Happy to answer questions here.