Its Fun, Level is good. Found I think 2 of the 3 Secrets, and the Looparound through the Projector-Window was a nice touch to avoid Backtracking and have the Level feel less Linear-ly.
Music could have been heavier I think, And you need more Environment Props and/or different Textures and Areas, it feels a bit empty as it is now.
Some of the Encounters are nice, others feel like just a bunch of Enemies or the same Enemy mashed into a small Area.
It needs a tiny Intro, something non-intrusive that makes it clear why you're there and why you're on an empty Balcony with that other Guy and why you're shooting everything up. Nothing long and winded, just something short and quick.
Gameplay feels great, didn't encounter any Bugs, getting a second Pistol to dualwield instead of just getting more Ammo was a nice surprise. I'm assuming Enemies and their Sounds are Placeholders, as are most other Graphics.
As for Balancing, sometimes Enemies felt a little Bullet sponge-y and there's no Headshotting or anything, or at least none that I felt. But I'm not good at shooting anyways, so I probably wouldn't have noticed even if it were there.