Civilization IV is a major reinvention of the previous Civilization games. All the basic concepts from Civilization are still here, but many of the more troublesome features have been greatly improved. The presentation has also been improved with a powerful new 3D engine and great new soundtrack. Gameplay was optimized for a faster and more compelling experience. The user interface is very familiar to anyone that's played RTS games before and is really easy to learn for those that have not. The tech tree has been expanded over previous games to allow greater flexibility and more strategic options for developing your own perfect world.