For the record, Stephenson's skateboard smartwheels used a bunch of little pads mounted on telescoping spokes instead of a solid wheel. The board had a terrain-

For the record, Stephenson's skateboard smartwheels used a bunch of little pads mounted on telescoping spokes instead of a solid wheel. The board had a terrain-scanning laser mounted in the nose, and pulled the spokes in and out so that the wheel was perfectly shaped for the contours of whatever it was about to roll over; you can ride a smartwheel board down stairs as smoothly as you would a ramp. But they were still very much wheels. There was no walking motion involved.