The idea of no jumping is really interesting concept and I feel it was implemented fairly well. I can tell what you wanted to achieve with this game, but I do think there are a couple things I want to point out.
- I don't see how the theme comes into play other than I die in one hit. If that was the intention, I'm not sure I feel good about that. In general, I personally find 1 hit deaths to be discouraging and unhelpful for the player. I think the player should take at least 3 hits. This gives the player a hit to realize they're going to have to be a little more careful, think things through, etc and 2 more attempts to get it right.
- I can tell that you wanted this very atmospheric feel to it and dim lightning, but with the rest of the mechanics, I think its causes some issues. Lighting was very critical and I don't mind it being something you have to replenish, but I do think that your enemies need to be more visible. Even with full lighting I couldn't see dangers, which isn't great, especially with 1 hit.
- The reticle for the gun probably should only turn a color if its hitting something interactable. Red for enemies, some friendly color or whatever to highlight that it can interact, but youre not in danger. Also, normally I'm not a fan of the reticles being smoothed in their movement, but it does work for this game, so kudos there.
- I had some issues with the shoot jump mechanic not working all the time which eventually led to me bugging out at some point near the power up and locking myself into a wall :'(
Overall, I feel like I know what you were aiming to accomplish in this project and it was ambitious and a bit unique, so congrats on going for it!