Korsakovia. it's hard to speak. to spell and to put into words. to even find. and then to play. to actually run... to actually finish... but IMO its a very good hidden gem because of all these things. I would recommend it if you want a intense old school experience (game is creepy and unsettling)

this is one of the first games made by dan pinchbeck of thechineseroom. It hijacks half-life to tell a story about mental illness, which turns out to not be a story about mental illness at all but a story about a mental disease that hjjacks people to spread.

you have a lot of signature stuff here:
-very heavy handed narration
-impromptu/spontaneous dialogue (in the middle of banishing demons into the netherworld with the whack of almighty crowbar)
-puzzles based around gravity or perspective (getting out of fallen buildings)

tone is a pretty dark and triggering type of territory not fit for most people to venture through. you're basically going blind (and at times the screeen will flash white, near the end while you perform a jumping puzzles lol) and crazy at once. a doctor acts as the narrator and is speaking to you from the outside (kinda neat it was like inception) which basically is indistinguishable from hearing voices as you hallucinate an alternate reality. i thought that was a good premise but I absolutely loved the story arc in the last half of the game... (maybe i am a shitheel but i found it satisfying to climb atop my pile of wood boxes to go higher in my basement universe while hearing that the nurse is finally admitting to having the same delusions i have been telling her about, lol)

i found this mod was actually a real pleasure to play once i managed to get it work though. despite so many doors and paths i kept wandering and advancing the narration to the point it felt like stanley parable. the downside is the mod isn't stable and WILL crash and i suspect this is why there arent walkthroughs or let's plays of it (correct me if i'm wrong but i found abandoned attempts) it gets really good near the end but it also gets really hard and starts throwing jumping puzzles at you. (i actually DID do some classic jump crouches legit in the final inning of this madness but i dont want to be forced to do that in a platform FPS yo!)

to noclip add this to your episode 2 shortcut (starts with a space)

-steam -game korsakovia -dev

a shame its not more accessible because it still makes for a pretty good experience for us folks who like stuff like this... But man, the jumping puzzles (particularly the jump crouch bs) is understandably devisive!. i'd describe it as Hellblade: Senua's Sacrifice with a crowbar and invisible headcrabs. (pretty mental and spooky) the fact you actually are whacking monsters in this was a bit cheesy at first but i got into it. it both had this weird stanley feel to it as well as a kind of rebellious attitude about reality.