Do you sleep with the light(s) on or off?

I'm not really picky either way, I can sleep with the lights on or off, with a little bit of sound, no sound, or a lot of sound. As long as it isn't like, BLARING music or something like that, I can sleep just fine. The one thing I'm REALLY picky about though, is my sleeping position... can never sleep unless I'm on my side in juuuuust the right way.