Makeblock mBot Ranger: 3-in-1 Robotics Kit for Building Robots from Scratch

My kid tore through the tank build in one afternoon, then spent the whole weekend testing it on gravel and grass in the backyard. The all-terrain wheels actually grip on sand, which surprised me since I figured it'd just spin out. Wiring up the motors himself was the part he was proudest of.

The self-balancing form took my son a solid afternoon to get right, and watching it finally stay upright on the gravel driveway was worth every minute. It handles grass and sand way better than I expected for something this size.

The self-balancing mode genuinely surprised me—it wobbles for a second then just locks in and follows you around the room. Took the tank version out on gravel and grass and it never got stuck once.