You just never ever feel safe in this game. Clearing out hallways so you can walk through safely will end up fucking you over in a few minutes when zombies get up as crimson heads. A safe hallway you thought that was void of any enemies soon becomes overrun by zombies and dogs. Because ammunition is low, it's also important to know which hallways to clear up and to waste precious kerosene on.
Ammo conservation is a must. Knowing when to use ammunition is a daunting task. You always feel like it may have been unnecessary, but were left with no other choice. In addition, the tradeoffs between using healing and ammunition is something the player must be aware of. Sometimes it might just be better to get bit by a zombie and heal up instead of wasting ammunition. Sometimes it might also be better to waste ammunition on zombies for healing. The point is that the game forces you to have a balance of the two and you feel dreadfully uneasy if this balance isn't in place.
Even saving is unnerving. Not knowing if you're saving at the correct time and frivolously wasting ink cartridges. But because a lot of this game is about exploration and puzzle solving, it isn't that huge of a set-back if you do end up dying because you'll immediately know what to do.
The fixed camera angles and tank controls also greatly enhance the horror. Entering a new room only to find your camera jumbled and a new zombie slowly creeping on you shoots your adrenaline way the fuck up.
There's way more to talk about what this game does right like inventory management, metroidvania exploration, chilling music, enemy variety, dense atmospheric environments, and much more.
It's a huge shame what modern horror games have turned into. They're either glorified shooters or incredibly atmospheric but lack the gameplay to truly make the player feel unease.
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https://imgur.com/fsYJcFn https://imgur.com/SZie71I
Starcraft 2 Username = Gears