Empire Earth, also known as EE, is a real-time strategy computer game developed by Stainless Steel Studios and released on November 23, 2001. It is the first game in the Empire Earth series. It has been described as very similar to the Age of Empires series, and received positive reviews. The game requires players to collect resources to construct buildings, produce citizens, and conquer opposing civilizations. Empire Earth spans 500,000 years of world history, which is divided into 14 epochs, beginning with the prehistoric age, and ending with the nano age. An expansion pack was developed by Mad Doc Software called Empire Earth: The Art of Conquest, which was released on September 17, 2002. It added new features such as a special power for each civilization, and a new 15th epoch, entitled the Space Age, which focuses on the colonization of space planets.