I played around with this a bit tonight and have a few suggestions:
1 - Volume control slider for the music. I'd like to be turn this down so I can hear ambient sounds instead -- would make the game even more relaxing for me.
2 - Native controller support would be nice. There's some in there already for steering, but no take off / land button support yet. This would me specifically as I have a dual monitor set up and the mouse cursor soon leaves the window and starts pulling up the task bar, etc. Even in full screen, as the mouse does not lock to the screen, it drifts to the second monitor. Also, flying with the keyboard is pretty difficult for me, ring races are more frustrating than enjoyable else.
3 - Option to turn off the timer in ring races. As part of the idea of a chill experience and playing any way we want, and option to remove failure from this challenge would be nice. At the least it could allow us to practice better times without the rings vanishing after an unknown length of time.
4 - A proper exit game menu item. I could not find one and am currently using Alt F4 when playing full screen to exit the game, but a menu item for this would be appreciated.
On the whole, liking what I've seen so far, and looking forward to future builds.