Nice concept!
Gameplay feels pretty nice, visuals are pretty fun (really like those pico-8 aesthetics).
Unfortunately I feel like the game can be rushed through by just damage boosting, if you had a more puzzle game approach i think you could do a lot more with the concept. For example needing certain blocks to open doors or needing to shoot an ennemi on the way with the green ones.
Overall the concept is pretty fun, hope this can help you improve the game :)