Finally a game half open. You start with a small creature and when you make offspring you go to an editor to design them. At any time the game populates the system with creatures designed by other players. First 2d, then 3d water, then walk
M. Ageev, Q. Guo, D. Lagun, and E. Agichtein. Proceedings of the 34th international ACM SIGIR conference on Research and development in Information Retrieval, page 345--354. New York, NY, USA, ACM, (2011)