This is pretty fun! Gameplay is nice, art is simple but fun and fits, procedurally generated terrain is random but still fair (no "big" dead ends as far as I could see), movement and shooting fells good. It even has giant spam space worms (didn't paid much attention to the screenshots, nice surprise as I encountered one). Only real possibility for refinement is enemy AI, I think they just stand around, waiting for you and shooting as soon as you are close. Giving them movement and maybe line of sight would also make it a bit more challenging (if you play it safe and don't encounter a worm I see no real dangers).