Looks good so far. It's also cool the way you had the enemies coming out of the vent in the ceiling. I realize it's not a finished game yet, and some of these you might have already thought about, but here's a few things to consider:
1) Some people were having problems with it being too dark. I had this problem all the time with my old monitor, which was way too dark. I always had to run games like Half-Life 2 and Doom 3 in a window and use the brightness control in windows or modify the config file to make it brighter. So maybe put some kind of brightness or gamma control in.
2) I noticed in the beginning that you could stand on the bed and jump through the ceiling. This means you could probably end up walking through the bottoms of ramps.
3) A gun flash would really add to the graphics, and having to reload the gun would be more realistic.
4) You said you were going to add more enemy types, and my suggestion is to have one shoot back with some kind of plasma or energy weapon that you can also use.
Just some ideas
Windows XP Service Pack 2 -- Pentium 4 HT 3.0 ghz
1 GB DUAL DDR RAM -- NVIDIA GeForce 6600 GT 128 MB (PCI Express)
