You should have the up arrow also jump and Z fire too
I liked the death stuff
Running into an enemy should just kill them
Overall it just seemed too bland and unchanging to keep me interested. Maybe gray isn't the best choice of background?
From what I researched, between QWERTY, AZERTY and QWERTZ keyboards the Z key is in very odd places, while the X and C are always on the same spot, which is why I chose them. I don't see why I should also make Z fire, and most people have issues with using UP for jumping, and since I feel little difference I just used another key for it.
The aesthetics will remain unchanged throughout the game. I want to focus on making the levels be different of a gameplay and design front.
Running into an enemy will never kill them.