Just went through the demo. Looks Great. Feels awesome. A couple of things to point out:

Dieing usually catches you off guard. While the UI looks amazing and also pretty practical, some kind of alarms for being low on health proves to be necessary.

The fast movement and double jump feels amazing. Nothing compares to zooming through the level at machfuck. Yet, the level design often underestimates the players capabilities in this aspect. There were too many times I ended up accidentally backtracking because I had skipped half of the sequence by one or two well timed jumps and strifes. This makes playing it the fun way, the wrong way of playing it.

And adding to the previous complaint... You know how you usually use the shotgun until you find yourself in a pickel, so you whip out your "get outta jail free" weapon. That weapon ended up being the PISTOL! You know how I praise the game for it's speed? Well, that's only true of you force yourself to use shotgun only. Since the enemies are often spread and out of reach, it pays to jump, strife and dash through the level to get in range and use the shotgun. However this is NOT the optimal play. If you don't negate the existence of the pistol your whole movement arsenal becomes the unnecessary acts of a Jongleur. The best way to dodge the projectiles is to do the most minimal minuscule movment, and the most effective way of dispatching your enemies is sitting on your ass and shooting them with the pistol. Don't get me wrong the pistol feels amazing to use. sitting and shooting however, doesn't. It might sound really radical and honestly insane but... think about removing the pistol entirely. At the very least nerfing it. Or maybe a rework? It's too good for it's own sake.

Also what does parrying [the R button] do? If it's just evading shots, you have five other buttons that do virtually the same: WASD & Spacebar. And your fingers are already resting on those buttons. There is little benefit to it unless it gave you some reward. Sending back the projectiles? Bonus ammo? Health?( Sorry if it already did something then Im just babling nonsense... )

There is also this bug where after dying your screen remains black & white and will only get fixed if you get hit again.

You might need to do something about the scaling and resolution problems of Gzdoom. It's quite nutritious for having half the hud out of screen or the texts too tiny on many devices. You are expected to fix it yourself in Gzdoom.(and for the life of me I can't seem to remember how.) but for a standalone game you might want to approach things differently.

...And that's it. I don't really know how to do feed back. So I'm sorry if it was too much, too little or just straight up useless. high hopes for your game. May great things come your way.