Korsakovia

Christopher thinks the world has ended.
His neurologist is starting to believe he may be right.

Korsakovia is a game mod for the game Half-Life 2 made by thechineseroom, maker of Dear Esther.

In the St. Clements Neurological Clinic is a man named Christopher, who suffers from Korsakoff's psychosis, a mental disorder that has caused him to fabricate false memories while unable to form new ones. He also had a long history of self-harm, and his latest episode has left him blind and burnt. In the nightmare world he has constructed, the world has come to an end, and he is under attack by a race of monsters called "The Collectors". His neurologist, Dr. Grayson, attempts to help Christopher come to grips with reality, but as time goes on and Christopher delve deeper into his lucid fantasies, Dr. Grayson finds herself being dragged down with him...

..at least, that's ONE way of looking at it.

Download it for free here. (Requires Orange Box version of Half-Life 2 to play; will not work with original retail Half-Life 2.)

Tropes used in Korsakovia include:

Abandoned Hospital: The first level. It's a Retraux of how Christopher perceives the hospital he is in, with very minimal lighting.
Apocalyptic Log: Christopher believes the world has ended, and recounts the days before and after it had happened. Whether or not it actually DID happen is open for interpretation.
Battle in the Center of the Mind: The Game. Trying to figure what's going on in the game while knowing that you're playing as a person with Korsakoff's Syndrome will get you nowhere. AT ALL.
Booby Trap: One way to deal with the Collectors is to lure them into a room (or even a storage crate in the second chapter), then quickly run out and shut the door behind you.
Captain Ersatz/Name's the Same: The Collectors are all the same but in form.
Dark Is Not Evil: The only enemies in the game are these faceless clouds of black smoke called "The Collectors". Though they attack you, Christopher insists that they are only doing what has to be done.

Christopher:I guess that none of us are supposed to be here now, now we're all dead, they are just collecting it all up. You can't blame them for that.

Eldritch Abomination: The Collectors are simply large, featureless clouds of black smoke.
The End of the World as We Know It
Eye Scream/First Episode Spoiler: Christopher gouged out his eyes. which is why the game has very minimal lighting
Gainax Ending: So we've got Dr. Grayson rambling about a needle, Christopher talking about hiding his eyes in the Sun and then it ends with someone (Grayson again?) shouting "WAKE UP!". And that's it. Borders on No Ending.
HUD: Subverted- there is no health meter or sprint meter onscreen, probably to make the game more frantic and realistic. Note however that yes, you can die.
Hearing Voices: The entire mod is narrated by disembodied voices. The characters themselves are never seen (unless you count your own hand holding the crowbar).
Meaningful Name: The game's name is derived from Korsakoff's Syndrome, which is what Christopher has. In short, the game plays through his perceived ideas while under the effects of the psychosis.
Mind Screw: The game starts to make less and less sense as you traverse through the mind of Christopher. Then the TV's start to show up. And then...well...The End of the World as We Know It???
Mind Rape: Due to the nature of Korsakoff's Syndrome.
Oh Crap: You thought Christopher was simply insane and that this whole idea about the world having ended was just a delusion, and Dr. Grayson was simply tending to him. Then the title of chapter 3 reads: The Assimilation of Dr. Grayson.
Painting the Fourth Wall: Instead of a health meter, your screen becomes cracked.
Platform Hell: Since you can't see your feet, a lot of the platforming can frustrating.
Room Full of Crazy: Well, his mind is acting even more delusional...
Self-Inflicted Hell: It's implied that Christopher brought this whole delusion on himself after wrapping his hands in copper wire and punching them through his television screen.
Snowy Screen of Death: Quite literally: one part of the level has you jumping between floating platforms, each with a pair of floating television sets spinning around between them with a deadly electric arc between them.
Surreal Horror: If David Lynch or Stanley Kubrick made a video game, this would be it.
With This Herring: Your one and only weapon in the game is a crowbar, and it's not a very good one.
What Could Have Been: Originally, the plot was to have been about an actual apocalypse, with the Collectors coming from television screens and inflicting Korsakoff's Syndrome on viewers, trapping them in a Hell like what's in the final game.