This is a really nice game, and the bullet hell desing is on point! As criticism, besides the checkpoints (I know other comments have brought up the issue. sorry for being repetitive), I would have swapped the order of some bosses, because bosses 2 and 3 I have defeated first try both the times I got to them, but I had a harder time fighting the first boss. The fourth boss I could not defeat and gave up :P
Congratulations to the team!