BUG (BTS Unaltered Gameplay) is a game modification (mod) that vastly improves the interface of Civilization IV : Beyond the Sword by Firaxis. It adds new screens, a better scoreboard, alerts and reminders, a strategy layer, and more. Everything is user-configurable via an organized, tabbed dialog.
It is built on top of an application framework akin to Spring for Java that provides component configuration via simple XML files. It has extensive utility modules for modders to build upon and developer documentation. The BUG Team actively supports developers wishing to use BUG as a base for their own mods via the BUG forum at www.civfanatics.com.