In the Middle size league, two teams of up to 5 robots play soccer on an 18x12 meter indoor field. Each robot is equipped with sensors and an on-board computer to analyze the current game situation and successfully play soccer.
Through wireless communication they can establish inter-team cooperation and receive all referee commands. But no external intervention by humans is allowed, except substitutions.
In recent years research made good progress. Until 2007, the robots were only able to distinguish their own goal from the opponent goal by the goal color (the goals were colored yellow and blue respectively). Since the RoboCup 2008 tournament all teams were able to play with net goals only. The ball is the only item that is still color-marked. The color of the ball is decided by the technical committee and is announced sometime before the competitions.
Changes in the tournaments regulation like this will bring us eventually to the overall RoboCup goal:
By the year 2050,
develop a team of fully autonomous humanoid robots
that can win against the human world soccer champion team.