Okay, I just played Enigma. (I know it's a little late in the thread but, hey, I may as well, right?) First impressions are:
Gameplay: 9/10, I thought the contrast of the AK to the MP5 was good, the lack of AK ammo was also realistic and good. If you can make each gun in the full game as distinct as this, it'll be cracking.
One problem I had was that there was one point (where you meet the first soldier) where I think he shot me through a wall or doorframe, which meant I was much less interested in peeking round corners (since I figured, corner or no corner, they could hit me.) Probably a FPSC bug, though.
Atmosphere: 8/10, it was very moody, very dark and contrasting, you felt like something was wrong, like normal life had stopped. This was mainly due to the lighting and placeables. However, one thing I will say about the lighting: There were places where I simply could not see my hand in front of my face! I know the place is enclosed, but even so, it would be nice if there were no spots where there was no lighting, unless it's done for effect (you know, "Oh, should I go down that nasty, dark tunnel? Oh, I have to... *shivers*") The feel from the lighting was good, but impacted the gameplay negatively at times. Not all the time, it should be said. Also, some creepy sounds at places would have really added to the atmosphere (although Guards swearing was very immersive and made it feel more real).
Your placeables are all nice, especially as they're mainly (if not all) custom. The HUD is OK, although the bland box for ammo and health looked rather normal. Also, consider making the crosshair semi-transparent: at times, I had to aim away from where I thought a guard would be as I crept round a corner, so that I could see whether or not there was a guard there.
But overall it has a lot of promise, the extreme difficulty is hard to get used to but well-balanced (especially since it's quite short) and, with an over-arching storyline provided by Gone and more enemies and weapons, I think you're on to a winner!
@AaronG: wow, that's nice...
3D game making is a combination of pc crashes, yelling and coffee.
I'm not actually a Kiwi, I just randomly thought it up one day.