SimEarth, is a simulation game that lets you explore and experiment with the development of planets, the evolution of life, and the rise of civilization. You can adjust a planet's geological properties, atmospheric properties, life endurance properties, and civilization properties as it develops, or you can experiment with an existing planet such as Mars, Venus, or Earth. You can unleash disasters on a planet such as meteors, earthquakes, fires, or even nukes, to either hurt or help a planet along.