First off this is not a FPS. It's a sneak and peek game. Your weapons are weak, you can find little ammo. You creep around trying not to be detected. If you get detected and hide, an alien yanks the door off and kills you anyway.
Important objects can be missed and never made available again.
Then there's the inability to save game except for a few places on each level. You complete a difficult sequence and get killed before you can save game. FRUSTRATING! Why do devs do that? No one likes it.
Overall, the game could have been fun. Images and sound are good. Levels are challenging, but with no quick save, the game just sucks. I didn't pay much for this game, but I feel like I wasted 10 hours.