Good amount of feedback, it's fairly clear what you have to do.
It was a little too hard in the beginning, and I think it'd be nice to have some brief invincibility after getting hit so you can't get insta-killed haha.
Pretty addictive, but it makes it hard to concentrate when projectiles and background move in a smooth manner while the enemies move in a tick-based rythm.
The camera should perhaps be a little quicker to follow the player and I'd suggest making the spikes more obious. I fell on spikes that were outside of my monitor and sometimes the shooting particles covered them completely.