Fun game!
I think it's a little to punishing when it resets you back to the start of the game, feels like it defeats the purpose of the checkpoints. Also, having a little more feedback when you die - having a second or two to process how you died, and having a clear respawn timer would both be really nice.
Also, having some feedback on enemies getting hit would be great. It wasn't clear to me at first that the moonknives were damaging the spiders, I thought maybe I just had to jump /around/ then, since there was no indication that the knives were actually damaging them.
Overall, though, I enjoyed playing your game. Great job!