This is a game called Devil's Tuning Fork, named after something also known as a blivet. It's a puzzle game, sort of in the line of Portal in that you have a tool that helps you move around dangerous/unnavigable rooms, with one major difference: your character is in absolute darkness at all times. Move in any direction, look wherever you want, but with few exceptions, you can't see a thing. The only way you're able to get around is by observing sound waves you make with your tuning fork. Despite it being an easy game, it's an extremely frustrating play, which should surprise no one.
When I'm playing a vidya, if the screen starts fading to black, I automatically assume something is about to happen. A cutscene? A map change? Did I enter an area I was supposed to avoid and get sent back to start? No, my tuning fork just stopped resonating. I kept sitting back like “okay what's going on” only to realize the answer was a resounding (ha) nothing. It took a minute to get used to it, but I did feel like an idiot for that full minute. How dare you, game.
As you can see in the .gif, the sound waves move pretty slowly, enough so that you can absorb the layout. It's also slow enough that when you're trying to jump over a ledge and have lost your orientation and need to be able to see right now goddamnit it can get pretty frustrating. And then sometimes you're taking aim, and you think your cursor is still pointed at that bell, but no, you'd be wrong—just a twitch to the left means missing by a wide margin when you're playing in first person and damn it you can't see. Also: vertigo. Lord almighty. You'll be standing in one place and because of the way the sound waves illuminate the room everything feels like it's moving, you included, right off the side of that ledge—wow nope you were actually moving and now you're dead.
As far as I know, the premise was purposely left pretty vague. A bunch of children have fallen into comas, their souls trapped in stuffed animals that you need to rescue. While trying to figure out how to get to them, you'll hear things like “I'm scared!” “Save me too!” “Please don't hurt me!” and an adult male voice growling threatening things.
If you're interested, you can download it for free from the site!