Firaxis Games. (2005). Sid Meier's Civilization IV [Video game]. 2K Games.

Sid Meier's Civilization IV is a 4X turn-based strategy game developed by Firaxis Games and released by 2K Games in 2005. As the fourth installment in the Civilization series, it challenges players to build an empire from the ground up, starting in 4000 BC and advancing through various historical eras.

The core gameplay revolves around the "4X" principles: eXplore, eXpand, eXploit, and eXterminate. Players begin with a settler unit to establish their first city, initiating the growth of their civilization. The game offers multiple victory conditions, including military conquest, cultural dominance, space race achievements, and diplomatic success through the United Nations. This variety allows players to adopt diverse strategies tailored to their preferred playstyle.

A significant enhancement in Civilization IV is its fully 3D graphics engine, a departure from the 2D visuals of its predecessors. This upgrade provides a more immersive and detailed representation of the game world. The game also introduces a refined religion system, enabling players to found and spread religions, influencing diplomatic relations and internal cultural development. Additionally, the government civic options have been expanded, offering more flexibility in shaping the political and social structures of one's civilization.

The game's soundtrack has been widely acclaimed, with the title song, "Baba Yetu," composed by Christopher Tin, earning the distinction of being the first piece of video game music to win a Grammy Award.

Civilization IV received critical acclaim for its depth, replayability, and improvements over previous entries in the series. It has been listed among the best video games of all time and sold over 3 million copies by 2008. The game also spawned several expansions, including Warlords and Beyond the Sword, each adding new content and features that further enriched the gameplay experience.