This robotic turret is described in Chapter 8 of the Discovery Book. It is used to illustrate the concept of how sensors can be used on autonomous robots.
In one configuration, Shot-Roller rolls around while looking for objects to fire zamor spheres at. In another program, the robot can be remote controlled with Touch Sensors as inputs.
Building and Programming this Robot
Instructions for building and programming this robot are included in The LEGO MINDSTORMS NXT 2.0 Discovery Book.