Downloaded and played. This is going to sound harsh - I don't want to rate it, I've compliled a list of problems instead.
Universal. Changes gloves when changing weapons. Rooms are to big and square. I'd like to be built out of bones that can survive a shot from a Desert eagle!
Level 1. He keeps scoped pistol in his room? Holes between segments, mixs sifi+modernday+ww2, door with no walls next to 2xpistols, bathroom should have different segments from corridors. First chair is half inside the 'desk'.
Level 2. Having lots of enemies spawning at the same time lagged my PC, I can stand in the spawn point and whenever they shoot my health goes back up, enemies at back stand there watching me kill the other ones, skeletons have ww2 colt pistols - changes from gloves to invisible hands. Doors need walls around them!
Level 3. Square rooms, again. Segments have the same texture, again. Random sifi lifts?
Big skeleton level. Random door floating next to boss door, the base is magically suspended over lava... Skeletons dont all shoot you - easy to do one at a time. Big guy gets trapped in door which means he can't shoot back
Level after boss. WTH there's billions of health packs? Lava sounds like squishy mud, I can easily walk off map, managed to skip last room by jumping over stairs
Level after that... Big skeleton can't hit me, only the roof, I shot one of the smaller skelentons and the ''encountered a problam and needed to close'.
After all that, I couldn't be bothered going through it again to do a few more levels.
Sounds harsh, I know, I kinda felt bad focusing on the downsides but theres not much else, did you actually play through it properly before posting?