The Empire Earth series is a franchise of real-time strategy computer games developed by Stainless Steel Studios and Mad Doc Software, and published by Sierra Entertainment, Activision, and Vivendi. The games in the series are historical RTS games that are similar to Age of Empires. Rick Goodman, who designed Empire Earth and Empires: Dawn of the Modern World, was one of the lead designers of Age of Empires. The games use the Titan and Titan 2.0 engine, which was sold after Stainless Steel Studios closed.