I had hard time getting it work in full screen (2 buttons for full screen, but one of them makes it super tiny).
I know that controls are explained on the page, but I think more interactive tutorial is needed for players like me that are bit slower to understand the game.
Now on second play I realized that "song progress" is on top. That part is really hard to see on 4k Display, so if anyone else has issues, its better to set your resolution to 1080p
When you are able to read things it is actually really fun :)