The Lego Mindstorms Robotics Invention System was introduced in 1998, and quickly became Lego's best-selling kit. From its surveys, Lego found that the median purchasing age for the Mindstorms kit is 23. The Mindstorms Programmable Brick, called the RCX, contains a microcomputer that enables those who build the robots to then program their movement. Sensors and motors can be attached to the RCX and an ordinary Lego model can move, sense and respond to its environment. The Mindstorms kit does include basic instructions and sample robots, but these are not comprehensive. This book includes a variety of new robots, explanations for readers, and theory behind the practice of building robots.