Exciting shooter, but still makes me think.
I enjoyed this game quite a bit. The gameplay suggests a retro feel, but the graphics suggest something more modern. The attention to detail in this game was very clear. As other reviewers have said, the music was a bit... limited, but it still served its purpose.
Even though it was a rather fast-paced shooter, I still found myself employing tactics like running for cover, prioritizing targets based on how threatened I was by them, and (as expected) experimenting with the different weapon types and upgrades.
Oddly enough, even though keys are an overused game mechanism, I found them to work quite well here. I was also pleasantly surprised to find doors didn't relock themselves if I died.
Resetting a few random rooms when the player dies is a very effective measure that adds quite a bit of spice to gameplay, particularly if you return to a room from a different direction than when you first cleared it out.
In short, it's not a terribly long or deep game, but it definitely makes my favorites list. Excellent work.