Empire Earth Retail Add-ons v2.0.0.0.... Sierra has released new patches for Empire Earth, bringing the 3D real-time strategy game by Stainless Steel Studios to version 2.0.0.0. This Difficulty Setting and Multiplayer Lobby Add-On is available in English and international editions, and as the name indicates they add the single-player difficulty options and multiplayer lobby created for The Art of Conquest expansion back into the original game.