The religion model offers more customization as well, and players can now better use the power of faith to spread their culture, or they can choose to have no state religion at all, boosting scientific endeavors. The tech tree remains the roadmap to scientific and industrial advancement, but there is now more than one path to milestone discoveries. Many of the most significant additions to the fourth version of Civilization involve customization.
Conveniently released alongside the game's second Beyond the Sword expansion pack, Sid Meier's Civilization IV includes the original game and its first add-on, Warlords.