The WallsBot is built from the Lego Spike Essential educational kit. The movement is achieved by running of motors. There is a special roller In the front part of the Bot. That roller detects a collision with an obstacle (wall), slides along the wall, and the built-in gyroscope reacts to this and activates the wall avoidance algorithm.
The set includes step-by-step building instruction and an example of program (in Spike environment).