You know... Maybe the attack from the boss of the 2nd world is a little bit too fast... Only if you know the boss well you can dodge it.
Very easy to learn, very hard to master game. I think it is really cool how putting the order of notes in a specific way can generate new sounds and patterns. Love your game and will probably buy it when it is Early Access on Steam.
I think that having a checkpoint is kinda not the point in these games.