The legs are retractable and are actuated by tiny servo motors inside the body. [Greg06] even included an ultrasonic distance sensor for the obstacle avoidance mechanism.

The code includes two Arduino libraries: one for the servo and another for the ultrasonic sensors. The main code is a simple 14-line piece with a simple if-else statement you can readily modify.

Awesome mechDOG 12-servo quadruped robot. ... Each leg has 3x ST1 servos or Lynxmotion Smart Servos and they are controlled by an Arduino Uno and a Lynxmotion LSS Adapter ... ultrasonic sensors, ...