This vehicle is very very insteresting: It allows you to do robotics only with mecanics elements (engine excluded). The "programm" is saved over a black chain with red connectors and white rods which let turn the left or the right or both white connector with eight green rods. A clever [engrenage] systeme allows to do turn one of the two yellow wheels each time its white connector turns. See the machine in action. The forward wheel is multi-directionnal: it's a ball over which knex are installed.