Pen_Walker is made of Arduino, Light Sensors and Servo Motors. We use the arduino which called "Japanino" from the Japan Magazine-Adult's Science
check it out from its website otonanokagaku.net/japanino/
The differneces between Arduino and Japaniuno is
the connector of Jappanino is USB and its power supply are connect to the AAA batteries.Trying to make this project without connect to the power by adaptar, we use three AA batteries to support the 3 Servo Motors.
The three Light sensors of the Pen_Walker are its three big eyes which are photovaristors. The eyes(photovaristors) control three legs of the Pen_Walker and the color of the LED light in the center