Hey, this is really good! I had lots of fun playing through the demo. I also wanted to report three bugs (no pun intended? unless...) that I found during my playthrough.
When you go through the door in which you have to use the 1F key, there's a long hallway with two enemies. I got too close to the horizontal wooden boards on the right side, and my character collided with them and started floating. This bug actually softlocked me, enemies couldn't attack me (they'd just roam below me) but I also couldn't use the doors, and the camera triggers wouldn't work. I didn't find any fix for it so I just restarted my playthrough.
In my second playthrough I avoided the wooden boards, but one of the enemies (the one that is not on this screenshot) spawned behind the wall and it was stuck outside of the room until I went out and gone inside the room again.
The third bug that I found is that when you pick up objects you get a little message that says what you got. I could still move and interact with stuff while seeing this message (I'm not sure if it's supposed to freeze the game while it's shown?), but enemies were frozen until I pressed the interact button to hide the message. So basically I could still play after picking up objects while the message was onscreen, but enemies were stuck and couldn't do anything to me.
Aside from that, I had lots of fun playing! This has so much potential and the setting is quite interesting. I also appreciate all the options that you implemented, like disabling the dithering and the color limits, along with a speedrun timer. The analog movement is also really good, I prefer tank controls personally and used them through the demo, but analog movement is a nice option for people who are not too comfortable with the tank movement style.
Overall, I really enjoyed the demo, it's very well done. Looking forward to the full release!