Pretty good retro-style FPS. But instead of being dynamic and crazy like it's many counterparts, it's more tactical and moody. You move slower, enemies are very deadly, your health restricted by hunger meter (which acts as a kind of second health bar - I found this mechanic rather underdeveloped, but it's still interesting idea, and it does not get in the way of action), you can lean, aim down sight, crouch to reduce sight jitter, and this game even have realistic, relatively complex reload mechanic. There are almost no saves throughout the levels, which gives weight and consequences to death. Citadel encourages you to play very carefully and tactically, and I very much enjoyed this tense gameplay. Game feel in this game is also incredible, every weapon bangs and clangs magnificently.

Guns look, sound and twitch in an incredibly impactful way. Every burst of shots is accompanied by a barrage of shell casings clanking very satisfyingly, and every kill is accompanied by an explosion of gibs. Gibs system is very thoughtfully done, and it makes killing enemies incredibly enjoyable.

The world around you is an abstract, greenish metal hellscape under heavy scarlet sky, populated with your former comrades who have gone insane. Heavily featured gore punctuates not only how fun it is to spray walls with their guts, but also how pitiful it would be to be in their place - you often see ripped faces of your enemies, full of regret and sorrow amidst the wreckage you just caused.

Citadel can feel very amateurish at times - visual design of maps is always the same and too monotonous, enemy design is far too boring compared to main character and bosses, a couple of music tracks do not fit the mood, and the game becomes too easy in later levels. But even amateurish elements of this game form a strangely alluring atmosphere.

Also, this game has the most disturbing yet satisfying flamethrower kill effects.