Amazing fun :D
Like other people said, this is probably the most competent top-down shooter I've played online in a looong time. Weapon variety kept it fresh, and the level design was fantastic and very well detailed. You managed great pacing (something that few games seem to get), between the unsettling industrial-looking areas, well-lit desecrated offices, and that glorious "holy shit" night vision level. I'm really glad you didn't overuse that night-vision thing, btw.
I would have appreciated more than 4 "small" enemies and 2 "boss" enemies, though. Just a suggestion, but if you had a way for the corpses to rise again like in Dead Space, I am absolutely positive that you could make many people actually scream out loud ;)
Pistol would have been nice to upgrade, and i think an upgrade for the Vulcan would be great, because it seems to lack that "final weapon" feeling of power. Personal upgrades like health bar or speed would be nice, like maybe a sprint bar? With a faster character, the exploration would be more fun. The terminals were well placed, though, and the interface worked well with the game.
The music was incredibly well placed, with a lonely sountrack of sound effects on most of the levels, and some fast-paced music during some tense moments. As far as the sound goes, it reminds me exactly of Half-Life 2.
When I zoom in on the Explorer window, the game won't scale, but I can see outside the intended field of vision. I guess if you're having trouble, or don't like the tense feeling that you get with a small field of vision, that's a good way to make things easier.
When I used this zoom in the first swarm level, when I fired the China Lake, it seemed to hit everything on the map. I fired it to what should have been "offscreen" (but i could see it when zoomed in), and I could see EBE's from all over the map disappearing like they got hit. The "notice" bar would confirm that I got the exp. from all of them. Idk if you intended it like that, but it certainly takes a lot of the tension off of the Swarm mode.
There's nothing to actually complain about, but it's got a bit of room for improvement. But that just means it has even more potential :P I'm really looking forward to what you guys are going to come up with for the next game :D