In this paper the design of the CMU Hammerhead middle-size robot soccer team is presented. The team consisted of 4 fully autonomous robots with wireless communication and color vision. The robots’ color segmentation algorithm, CMVision, provided reliable, real-time ball tracking and was tolerant to changes in lighting conditions. The robots’ software architecture was implemented using TeamBots, a Java-based environment for behavior based robot control, and Clay, a TeamBots module for creating motor-schema based control systems. The use of behavior-based control allowed to the robots to react quickly to the dynamic environment despite non-holonomic platforms. The team included some team- work by sharing information about the ball’s location and the states of other team members. The CMU Hammerheads made it to the quarter finals of the competition.