Wikipedia
Colobot (Colonize with Bots) is an educational real-time strategy video game featuring 3D graphics. The objective of the game is to find a planet for colonization by the human race by establishing a basic infrastructure on the surface and eliminating any alien life forms endangering the expedition. The game takes place on the Earth, Moon, and 7 fictional planets. The main feature of the game which makes it educational is the ability of the player to program his or her robots using a programming language similar to C++ or Java.
The game has been recommended by the Polish Ministry of National Education as a teaching aid for learning the basics of algorithms and object-oriented programming.
Epsitec has released the games' source code under GNU GPL v3 after being contacted by PPC (Recently rebranded to ICC & TerranovaTeam).