The game was so dark I could barely play. Maybe it was because of the glare on my monitor, but at max brightness I couldn't see anything. This was really bad when I lost my gun. If I missed a target I thought the gun was lost forever. I couldn't see the gun on the ground, so I thought it dissappeared. I had to look at the comments here to realize how to pick the gun back up.
Other than that, I thought having to pick up the gun after throwing it was annoying. If I missed an enemy, I would have to walk right up to it and die to pick up my gun again (depending on where the gun dropped) and the final door switches took a while because missing a switch meant I to walk up and get it and try the sequence again. I feel like something more interesting could have been done maybe instead.
The music and lighting did come together for a nice game feel though, and I liked that the particle effects of dust were there in front of the exit door as if the player was barely making it out.