Gravity Wells
Just finished Build 01. I added a big planet object that exerts mass on the player using Newton’s Law of Gravitation with an arbitrary G:

(Source: Wikipedia)
I also implemented collisions with the planets: when you hit a planet, the large planet disappears.
This gave me a lot of trouble, because I haven’t tried to detect collisions in Unity before (not counting cases where a trigger object detects if another object enters it). For example, I couldn’t get the OnCollisionEnter function to register any collisions at all, regardless of whether I attempted to perform collisions between rigid bodies or sphere colliders. Eventually, I just told the player script to send messages to any objects that it hit via the OnControllerColliderHit function.
You can try out my latest build here: http://jceipek.github.com/LudumDare23/
I think it’s time to go to sleep for a bit.
Livestream: www.twitch.tv/jceipek
Screencast: http://students.olin.edu/2012/czwiebel/webcam/

One of my ideas this evening was about steering the planet earth around and crashing into asteroids, attempting to become bigger… ultimately realizing that it would never be as big as the giant stars.
Given my toolchain this didn’t seem like much fun to implement. Unity would be a great tool for this sort of thing, I think.
I was trying to avoid making my game too much like Osmos, but it definitely served as part of the inspiration for my idea.
I definitely think that Unity could be used to tackle something like that, though.