Personally, I\'m a fan of the cubic worlds. Discworlds, or oreos, always seem to have the issue of walking off the edge, and while I\'m interested in suggestions, I\'ve yet to see any elegant way of dealing with that. If you use a cube based world, with gravity transitions at the \"corners,\" as mentioned before, it seems to give a lot more flexibility. If you really have issues with the transitions, you build near the center of the faces and avoid the edges, something you essentially already have to do with a discworld for fear of falling off. It just doesn\'t make sense to me to have a hard set up and down in a game based around space.
Secondly, I\'m curious why it seems to be assumed that the center of gravity has to be a set point. What if it were to be made dynamic, so major changes to a planet actually had an effect? Make it so the center actually lies where the center of mass for the planet is (possibly requiring something like 1% of the planet\'s blocks to be edited to trigger recalculation, to save on cpu), so that mining away a large portion of a planet would actually cause changes.