MyKana, a Japanese learning app I built for my own study

I built this for myself while trying to get serious about learning Japanese again:

https://mykana.app/

I studied a little Japanese more than 10 years ago, but only for a short time, so most of it didn't stick. Since then, I've been to Japan many times because my girlfriend is Japanese and my older brother lives there. More recently, with me and my girlfriend traveling back and forth to Japan quite a lot and both of us having family in Tokyo, I wanted a better way to rebuild my foundation and keep practicing consistently.

The app started around kana practice, but grew into something larger:

hiragana / katakana practice kanji and vocabulary study review-based learning AI chat for more natural practice some light gamification

The AI chat is free, but requires Google sign-in. That is mostly to prevent bot abuse, since it costs me money to run, and secondarily because it allows progress syncing across devices.

I'd appreciate honest feedback, especially on what would make this more genuinely useful for learning rather than just more feature-rich.