Very nice experience overall.
The graphics are okay, but the very barren. Nonetheless, what is there is not bad, by any means.
The music and sounds effects are okay as well, nothing really stands out, but not out of place.
Gameplay wise, it's good. The movement is a bit floaty, and a bit of a nuisance in very precise platforming, but it's not bothersome for most of the time. The upgrades feel and control nice.
One gripe I have about the level design, or camera system, is that you encounter "leap of faith" situations quite often.
I did manage to cheese the first boss, since it broke the walls of it's area, followed me to another screen, fell down bellow in a spike trap and died. But it did not break anything and I got the intended upgrades, so hats of for making a bulletproof event system.
The Buff Slime enemy, and the Dash "Boss" got a chuckle out of me :)
Nice entry!