Wow, getting some great retro shooter vibes from this one! Dunno what this one is doing buried underneath everything else as for the most part it hits all of the important pillars for a good shooter to me: nice gore and feedback for shooting, nice enemy variety, good combat telegraphs, a great old-school shotgun, interesting levels with all sorts of enemy formations, secrets, and so on and so forth! Found myself easily getting addicted to blasting through the demons!
If I had to point out some parts I feel could be worked on:
Jump felt really bad: not only is it incredibly short, it also screws up if you try to jump too close to a stair, making you awkwardly have to step back to jump.
Weird that you don't carry over anything between levels: yes, some games do allow you to start fresh upon death, but usually that's only if you die in the level and restart instead of load, not if you just got into the level from a previous one, no?
No way to restart after dying apart from going to the menu and selecting restart level? I know that makes some sense, but that extra step feels unnecessary: feels like you should be able to just click fire and have you restart the level right there.
No save/load feature? I don't mind it so much as I always try to beat levels without save scumming, but still, I'd like to be able to save my progress in general if I want to take a break.
Picking up items is kind of lackluster and uninformative due to the same sound effects being used for everything: maybe use different sounds and flashes of color to signify what you're picking up?
And the big one: while I think it's great overall and that the aesthetic is kind of unique, it is perhaps lacking a unique hook (or gameplay that feels so good that it doesn't need a hook). There's just so many boomer shooters out nowadays that I can easily see this one getting shunted to the bottom of the pile despite being good: just feels like another Doom conversion mod. Dunno exactly what the best approach would be: maybe more wacky weapons akin to something like Blood or Heretic instead of the more standard shotgun and rifles? I did feel like the initial slow-orb-fire pistol and melee combo was pretty neat, only for it to get overshadowed. Maybe play up the story angle more with dialogue and objectives and events? It did feel like apart from quips at the start of the level, everything was quiet and directionless. Maybe some sort of unique combat ability like glory kills that adds some spice and strategy to the combat? Up to you in the end.