I 'spose I'll use this to start my first venture documented on TIGSource. I don't really know when I got this idea, but I found myself starting work on this game earlier today, and so far it's been going pretty well.
I haven't done any research to see if this has ever been done before, but to my knowledge it hasn't. In simple terms, I'm creating a platform game that takes place entirely in the dark (aka a completely black screen, and the player must rely solely on sounds to guide themselves through the level.
Right now, I'm developing "lights on" and just closing my eyes to experience how the real gameplay will go. Below is a "lights up" screenshot of my test level (not that it explains much) and a "lights down" screenshot of what it would look like eventually (which explains even less).
Although the level I've made has WAY too steep a learning curve, I'm going to try to turn it into an accessible demo soon and I'll put it up for folks to play. I also need to think about a good plot to put with the game to fit in with the darkness.