Pretty fun, although yeah, there's a lot of mechanics you clearly didn't have time to actually make use of. I only used the rifle/SMG after already beating the game pistol-only, I never needed to turn the NVGs off, the keypad doesn't seem to have a code anywhere, and the ammo pickups are useless since there's only like ten enemies.
But hey, it was fun enough that I went back and tried to beat it again, pacifist, so you did something right.
Was the "our base is under attack" scripted when you got past a certain point? It seemed to trigger even though no enemies should have seen me, and they went in a completely wrong direction.