I started taking music theory classes in my local community college (I can now highly recommend this for self-thought musicians) and created a quite a few exercises to help me along the way. E.g. I couldn’t trust myself with stuff like interval identification and needed a computer to tell me if something’s wrong. These exercises are mostly of the flashcard type. I hope people find them helpful https://www.onlinemusictools.com/

The code is quickly hacked create-react-app mini apps. Since I mostly wrote them while preparing for tests. Some of them are even on github. One of these days I’ll sit down and refactor the disparate little apps into a coherent whole. One day.