Cool game, really reminded me of nuclear throne with the setting. The enemies are a bit unbalanced, such as the red ones, whose bullets are big and too fast to dodge in close range, enemy bullet speeds need to be lowered since the player only has 5 HP. Maybe health pickups would have made the game less punishing.
But the best part of the game is the stealth mechanic, since its the best way to kill enemies, I found myself creeping next to enemies and the enemies noticing me before I made the kill, which led to intense firefights. I think you can expand on this gameplay style of stealth first then run and gun.