C-evo

C-evo (a.k.a. Civilization-Evolution) is a free turn-based strategy computer game written in Delphi, with the majority of design and programming done by Steffen Gerlach. The source code is in the public domain, but the graphics are freeware. C-evo is based on Sid Meier's Civilization II, but with the aim of correcting design mistakes by implementing six design principles which correct the game itself and strengthen its weak artificial intelligence.

Gameplay
C-evo (a.k.a. Civilization-Evolution) is an empire building game, dealing with the history of humans from antiquity into the future. This includes aspects of exploration and expansion, war and diplomacy, cultivation and pollution, industry and agriculture, research and administration. Players must constantly make decisions such as whether and where to build cities, roads, irrigation, fortresses, and whether to form an alliance with a neighboring country or risk attacking it, and whether to devote scarce resources to education/research/production, warfare, or the well-being of the populace. A successful player manages to find a balance among these choices. The game starts with the development of the wheel, and ends when the first player has successfully constructed the first off-planet spaceship headed to the Solar System. As the game progresses, the player finds that the building of factories, for example, leads to increased pollution, which must be cleared up and could be eliminated through development of cleaner technologies.

The game can be played in Single or Multiplayer (hotseat) or Supervisor mode against 1 to 15 computer-controlled players, human players, or both. It does have a limited client–server architecture, and can be played easily over either a LAN or the WWW using Microsoft's Remote Desktop Protocol when the game is run from a game server.

Resources
On the webpage, the game, its source code, AI modules, player contributions such as many additional nations, maps, mods, and utilities are available.

The game has an open AI interface, which means the player can replace the standard AI contained in the package with other AI algorithms, either for all nations or for individual nations. The documentation of the AI's DLL-interface is available from the project homepage. There is also an AI development kit.

Reception
C-evo has been praised as one of the best freeware strategy games, particularly for its strong artificial intelligence opponents.

At the 2005 International Joint Conference on Artificial Intelligence, Rubén Sánchez-Pelegrín and Belén Díaz-Agudo presented a paper entitled "An Intelligent Decision Module based on CBR for C-evo" which discusses using C-evo as a platform to perform artificial intelligence research.