I didn't get the camera vector thing exactly, this seem to be tied to the camera angle, this make me a little bit crazy, but I have no doubt this could be cool to figure this out once and for all.

Ok, but I don't see exactly how your thing occur, if you're jumping or just using a stair. Personally, I just use 1 simple event for ceiling collision. Even if I think you are a better programmer than me, I can show you this in DM if you want, maybe you could integrate this in your system :)

You seem to work on very ambitious projects.
I also get stuck on some walls, depending of player angle. About stairs, it's all about Z sorting/picking the right 3DObj.
Camera tilt is a good idea, but true hell for me.
I must admit this is real C3 blackmagic we have done right here, and without JS.

I think your the one who hide the more stuff here ! ; )
I used "Sine" on the camera Zelev for head bobbing, the jump & fall speed are not constant, it accelerate. And jumping while moving make the player accelerate on multiple axis instead of just Z one. All of that give a more aggressive feeling.

I'm really happy to see that someone else made his own FPS system on C3.

Here's mine, with sprint, jump, crouch, wallride, stairs, ladders, elevators, and basic physics. All running at 60fps in FullHD for the cost of... 160 events.

BTW, did you work on some kind of immersive sim ala "Thief" ? 👀