Awesome! I don't know how to play the piano, so I built a little midi piano app[0] and then realized I didn't know how to make the app teach me how to play. I've been looking through other "how to play" apps, and got some interesting ideas, but I love how straightforward your approach is. I'm definitely at the level where simply practicing and reinforcing scales would help a lot, so I'd love to add a similar type of functionality to my app. Thanks for putting this together!