It was scary at the start then it kinda fell stale due to repetition. It's not a bad concept but I do feel like there could be more done with it. How about an upgrade shop for the tesla coils where you can spend points to upgrade your devices? Then mix up the enemies so that the crab people are not the only scary thing on this ship. I would also fix a few of those dead ends, even if they might be there for the enemy spawning (in fact you can make these doorways you can enter to get to other levels of the ship). I would say though, you are on the right track!!