While it's not what you're asking for, you might be interested in Robocode: http://robocode.sourceforge.net/ It has been around long enough to be 'balanced', and even the most advanced strategies are documented by the community and available for you to improve upon. The community has also developed a way for people to submit their robots and have them run against all of the other robots via a distributed tournament client.
The description, from the website: "Robocode is a programming game, where the goal is to develop a robot battle tank to battle against other tanks in Java or .NET. The robot battles are running in real-time and on-screen."
The description, from the website: "Robocode is a programming game, where the goal is to develop a robot battle tank to battle against other tanks in Java or .NET. The robot battles are running in real-time and on-screen."