A quick break from the semi-rigorous robotics discussion… Hex Bugs (officially HEXBUG) were cool. Not just the tiny ones that were only bristles and a vibromotor, but the slightly larger toys.
Specifically I had (have) two larvae and one of their scarabs.
Hex Bugs: Larva (green), Scarab (orange), and Larva (blue)
They really are ingenious mechanical contraptions. The scarab is just a motor, but via body and gearbox design it produces interesting movement behavior over slightly bumpy terrain. The scarab was designed to be fast, and it delivers, but at the cost of only moving in a single direction. The larva can only move slowly, but it’s equipped with a proximity sensor that allows it to detect a collision and turn. And all with a single motor, no less. The mechanism depends on the direction the motor is spinning to engage a clutch gear. If only one of the wheels has the clutch, the robot turns while it’s reversing. It may not turn the right way, but if that’s the case, it will just keep on turning.
I think these simple toys highlight a key principle for robotics: we don’t necessarily need sophisticated software/control if we choose an elegant mechanical design that fits our desired behavior goals.
Side note: my dog, a Chihuahua terrier mix, also loves these things, though less as robots and more as prey. No amount of elegant mechanical design survives an enthusiastic terrier.