A game idea starts to form

Saturday, 11 a.m. (8 hours in):

Thinking about the game while trying to sleep proved to be a very good idea. So even though I woke up one hour later than planned, and also went to the super market, I’m not entirely out of schedule.
Compared to others, the theme is suiting me a lot. It means that I can get away with minimal graphics and consider that even a bonus (if done right, of course). My first idea while laying in bed was to have minimalistic controls, but I didn’t really want to make an endless runner aka Canabalt. I then thought about what minimalism is – a reduction of the information we receive, distilled to only the essential bits. So how about reducing the player’s information by limiting his senses?
Somehow, I remembered a game called Batcave or something like that, which I had seen at a previous Ludum Dare, which lets you control a bat in the dark using its sonar. I liked the idea back then, and it fits quite well into Minimalism. Of course, I can’t just redo something somebody else did, not on purpose at least – that would take the whole imagination part out of the contest. So, what other places are dark and have animals?
The depths of the ocean are pretty dark – like, really dark. And I guess there’s an animal operating with sound waves or similar (or I could just make one up). But this would mean that I’d have to draw fish, which far surpasses my artistic skills. Maybe something simpler in form?
How about the universe? Except the various stars, the universe is dark, and most planets are round. Great, I have the setting – and also the gameplay. But more on that when I actually get it to work.

Timeplan: 1 hour behind.