Hey ! It was a bit hard to understand what to do and how the shooting worked at first. The concept is quite interesting though !
I didn't see the wall ! As cool as diegetic UI is, there are caveats where people tend to miss some info. I was more attracted by the cool props etc :)
The part that was a bit confusing was the "reload" mechanic, I could only shoot once every few seconds, which was a bit frustrating at first ! You may want to add a "reload progress" bar on the gun, + a feedback when you try to shoot with no ammo left for example !