Amazing buildup and atmosphere, that's just like... obvious. Almost not worth commenting on for how good it is; really speaks for itself. The game makes one of the best cases for "fixed camera can be good actually" because of how well it's used... mostly. I like how the shots are framed in order to make the most sense when descending the tower, it adds tension to going back up, feeling like you're pushing up against the unknown even though you've just been there. However, some shots seem overly cruel or just straight up oversights - one or two times enemies are placed, invisibly, on the other side of camera transitions. There's at least one point I can think of where you can't see the lower half of your body when you're trying to get onto some stairs, and it's unreasonably easy to get caught on the environment. This specific example (second combat room after the blue pool checkpoint) is especially bad because it's clearly a room you're meant to run instead of fight through. This wouldn't be so bad without some of the issues that exist with the movement, though. Movement feels floaty with little start or endlag as far as I can tell. The light in front of the player is pretty insufficient to show which direction you're facing due to its splotchy vagueness. A narrower cone of light with harder edges would be much more useful. Combat is expectedly simple but suffers from the above problems, as well as some others. Poor movement/turning feedback is compounded by the inconsistent auto-aim that's especially bad at close range. At point-blank range, bullets will pass straight through enemies, combined with (as far as I can tell) the lack of recovery i-frames, death can feel frustrating. It would go a long way to give the player a shove move or just... fix the ghost bullet issue.
If I wanted to nitpick I could say that the descent down the spire doesn't feel very... down-ful, somehow. The main reason is probably that you aren't given very many good views of the swamp from above, and you never get a good idea of your progression relative to the height of the trees. When you get to the bottom, the swamp is disappointingly small. The atmosphere established there is great but you never really feel like the setup has been fully paid off. It would've been much better to take time and resources away from the many redundant rooms of the spire to let the swamp reach its full potential. There are enough setpieces throughout the Spire, it wouldn't have hurt to cut one or two (my vote goes to the CLEARLY UNFAIR mukbang room near the top).
Another random suggestion that might help the experience is imposing an ammo limit, where you can't pick up any more till you shoot some off. It would make going up the Spire a bit more engaging and force the player to conserve ammo, paradoxically making the game easier for those who were both good scavengers and overly trigger-happy.
Overall a good experience that's easy to recommend. I don't know how much I'll add to the world by going off on this game that's so obscure the backloggd page isn't even set up properly. I kinda have to hope the dev(s?) see this cause I think there's a lot of good here. Keep it up.