by 222doc » Mon Jun 07, 2010 1:55 pmX2.1 is my long going project now. A articulating Biped. Since the new Mindstorms NXT Mmux has came out it has helped simplified and lighten this project. X2 climbed its first step in a autonomous state do to the new Mmux. It is a quality part as well, easy on battery life, compact, light. I am using two Mmux at this point anf the new battery box.