Not bad but has a lot of mistakes.

Graphics: Almost all graphics are ripped, a lot of them look kinda bad, paper thin walls. Those are all to be expected for a first FPS though.

Sound: Most of the sound fits well and doesn't clash with the game but the shrieking bushes are really annoying...

Gameplay: The GamePlay has a lot of things that could be improved but its certainly not bad. The gameplay is very repetitive, every level is about the same, and it doesn't seem to get much harder.
Sometimes when I drop through a hole an enemy kills me instantly and there is nothing I can do.
A lot of passage ways are the same size as you so you get stuck a lot.
While there are many different enemies they all seem to behave the same way, it would make a world of difference to what you have now if they had different abilities and stuff. Another thing that isn't a problem but could make the game a lot more fun is your gun, sure pistols are great and all but if you had a rapid fire rifle and the enemies had health it would make it a lot more fun.

Story: There isn't much to say about this, classic mutated monsters that have to be eliminated. In a game like this the story doesn't have much effect on the gameplay so it doesn't matter too much.

Interface: Mouse looking would make this game a lot better. Apart from that the controls work fine.

Overall: This game is about what you would expect for a first FPS, slightly better in some aspects. Most of the cons I mentioned were mainly suggestions for the future as they are all common for a game like this. This game is certainly not bad, but it could be improved a lot.