Thanks for you feedback. And first bug reports.
Yes, I think I tried to do something too unconventional here and it somewhat backfired. Next time I'll consider more intuitive mechanics that wouldn't require instructions.
Regarding the buttons - initially there was some logic associated with preconditioning whether a button can be pressed (like moving to next level only when reached a specific score) but decided to remove it so that player can observe all the levels and skip less interesting ones.