 After the Stratagus example, other real time strategy games were developed, such as "Globulation 2", which experiments with game management mechanics, "0 A.D.", a former freeware project, and the 3D projects Spring and Glest.In addition, the more economically driven strategy game "Widelands" bases itself upon the proprietary "Settlers" franchise.Racing games, another uncommon Linux commercial genre, has also seen development with "TORCS" and "VDrift", as well as the "Mario Kart"-inspired "SuperTuxKart".