…and since it is designed to work on mobile, that’s a problem 
Typical problems linked to a slow network connection include…
- MIDI chords taking a long time to load, breaking the immersion. That’s mostly a problem in Randomized mode, which I find better when it comes to learning chords rather than specific MIDI samples of chords.
- Youtube videos taking time to start and either skipping or losing sync with the chord progression. (By the way, it is unfair that the Youtube video loading time is accounted by the exercise timer in Level Up bonus levels)
Things you could try to make the situation better include…
- Keeping MIDI chords in some longer-lived local cache so that they need to be downloaded less often (there is obviously some caching in place as I don’t see the loading screen all the time, but I still see the “loading XXX” for the same XXX multiple times in a session, so it seems you could try harder).
- Loading all the resources you need before an exercise starts (I know this one can be very hard for youtube videos though. Maybe you’ll eventually need to move away from them in favor of storing small audio snippets yourself, if the citation laws of the country you’re hosted in allow for that?)