I like how you used the darkness effect + infinite enemy range to drive up the tension. It’s interesting that it really feels like a “complex” bullet hell despite all bullets spawning at near random positions.
Batteries are sadly extremely random. On my first playthrough I got to like, level 5 and found no batteries since wave 1. From my observations they seem to despawn after some time and, combined with darkness, are really hard to find. And even once you find them ,the extended vision doesn’t seem that much helpful. Would be cooler to get something else, maybe a super attack to destroy enemies effectively, since they have so much health.