if you realy want to simulate it, play OMNI IV.
But onmi doesn't have [simple] collisions, or even things that orbit, if you could put US and Omni together... AWESOME!!
More: Evolving LifeBut, I still think just life that is pixels as cities, only large ones, and a spaceship that you and them can actually fly. Since the chances are so small... You can choose to make them larger, and go quicker (not time, just evolution), or to just get spaceships going around to kill or fly yourself there should be a button to just pop it on a habitable planet. If there is none:
Sometimes, make a new planet and it gives you terrestrial planets to chose from, and it asks you to upload or make a new map (new idea), or it pops on the closes terrestrial planet or moon.
QuestionDo you have words (like in a box over a button almost anywhere on the computer) pop up when you mouse over a "new object".
Texture MakerSimple, an in game texture maker. You can see it as a globe and edit, or as a map, and it saves it in some map folder.