Very fun and quick game.
The incremental difficulty is very good, the music and bosses are nice to deal with, I just have some notes:
- The sound effects of the 3rd boss are a bit too loud even with loud music
- Against the final boss I was more often hit by the fact of having made contact with the boss rather than being hit by him.
- I don't know if it's just me, but I didn't use the slide mechanic, I found it particularly uncomfortable as well as using the Z jump, I found it more intuitive to use the up arrow. (In the case of this note it's more of a feeling I have, I don't consider it a flaw.)
Final result 8,5/10, I hope also in future works :)