I really like the idea, but imho I think that keeping track of the terrain and the enemies and the rule, all that in a fast pace it's too much (for me at least), I'd suggest to start easy and make it harder as the game progresses, either speeding it up or adding keys one at a time (eg starting with A and S, then add D, and finally F).
I see what you did with the name of the game. I also liked the aesthetics, specially the color palette, very retro like