Starting from the oppresive and cold facilities of Mars before everything takes clear form as the body horror-esque nightmares of hell paints the walls and floors that we navigate, it's the ultimate power fantasy.
Not only a great actioner, but also very uncomfortable in its progression and occacionally anxious when it gets closer to the horror of the concept. Looking at the lamented souls and visceras of our fallen allies complemented with the carnage that we produce creates a sort of unpleasantness that (intentional or not) tells us the kind of character we are making in the process. We are as much fighting evil as we are becoming one with it. And wether by lack of vision (the darkness in some sections of "The Shores of Hell" that channel Ridley Scott's Alien) or the direct result of faicing flesh and metal as one manifestation of the militaristic desire of being the savior of the universe, one thing is clear to me: the demented face of Doomguy pleased after finding another powerful weapon is my sleep paralysis demon.