An exercise device is described which includes a platform having a first end and a second end opposite the first end; first and second wheels, wherein the first wheel is positioned proximate the first end and the second wheel is positioned proximate the second end and the first and second wheels are configured to roll across a surface as the exercise device is displaced along the surface; a first motor configured to apply a first torque to the first wheel where the magnitude of the first torque is related to the distance of the exercise device from a zero position and the direction of the first torque urges movement of the exercise device toward the zero position. Versions are also described with more wheels and more motors.