Korsakovia is a strange beast... It is one of the most atmospheric and easily the scariest game I have ever played. It uses 99% HL2 props, has only one type of enemy and only the crowbar to defend against them.
As you move through the game, you hear a discussion between a psychiatric patient and his therapist, permeated by sound bites of others recounting your injuries from a previous event.
The game continues as you delve deeper into this personification of your own madness.
Graphics, style and new visual content:
Korsakovia takes a ton of random props from HL2, and adds very little of it's own. The enemies are the only prop I could perceive as 'custom' or 'new', and even then, they simply remind me of HL2 headcrabs with a new skin. I won't go into details of their new appearance. That's easily a sight worth the first 10 minutes of play.
This isn't a bad thing though, as Korsakovia's story is built around the content available and manages to create an amazingly dense and gritty atmosphere. I've never been so scared of HL2's television props before. Seriously.
Mapping, level design:
The game starts out with familiar surroundings. Familiar as in roofs are held up by walls, walls stand on a floor, and the floor is usually connected to the ground in some way. Televisions also don't kill you.
As the game progresses, the walls are slowly torn away and physics starts to lose any grip it had on the game.
The maps are heavily cluttered and often confusing to navigate, but that's all a part of the game's charm. You're meant to wander, always wary of the next door as an enemy could be behind it.
You begin with large open buildings, warehouses and a few courtyards, but then move to almost claustrophobic hallways riddled with an abundance of interconnected rooms and dead ends before finally moving to a point where doors, walls, roofs and floors no longer exist, and you're jumping between moving props. The orientation doesn't stay solid either, as you're often moving through rooms that are so slanted, any more of a tilt would cause you to fall upwards.
The enemies have a seemingly random placement, but their numbers are never certain. You may come across a lone enemy in an entire warehouse, then three of them in a tiny room.
Shocks are pretty constant, but it's the time spent in between that scares you the most.
There is no set path for you to take and the maps can often lead you around in circles. The sound clips continually enlighten you as to your character's sanity, with the occasional clue hidden within the discussion to help you progress with the game. A long drawn out discussion with his therapist about a particular subject will often have a clue hidden in the subtext. If they mention blood and walls, pull out your flashlight and start looking for messages.
The maps mirror the discussions, and the discussions mirror your mind. As your character slowly regresses into their own hellish delusions, the discussions become more forced until you can no longer be sure that the therapist is even real, or just another hallucination.
I would reveal some of the story here, but I have to say that experiencing it cold-turkey is so much better.
There is only one weapon in the game, and you can't kill with it. It's only use is to remove locks from doors. Your only defense against your shadowy foes is to lock them in other rooms. The game can get amazingly tense as you may lock an enemy in a room only to find you have to backtrack through it again. There are a number of environmental hazards and platforming areas, with the jumps getting harder and at some points near impossible.
You will find yourself sneaking around more than in Metal Gear Solid, and making more acrobatic runs and jumps than in Mirror's Edge once the enemies spot you. Fear will push you forward until you hit a dead end, and fear will make you uncertain of the way back. My first encounter with an enemy resulted in my jumping out a third story window to escape. This is horror as it should be.
There are a number of ways in which this game could be improved, but they're mostly just graphical. Take a look at the charts on the hospital beds at the start and you'll know what I mean.