Biggest thing seems to be writing non-trivial GraphQL + Rails backend. It was quite interesting work: there is still not really much best practices for this combination, so just to make it work in a Rails way did take some time and trial and error. At the end I am happy with results and I hope to find some time to publish blog post on it.

Other than that: I did some face lift for my side project http://notationtraining.com and implemented new MIDI API to connect midi (piano) keyboard directly to web app.