One example device includes a rotor platform that rotates about an axis of rotation. The device also includes a ring magnet mounted to the rotor platform to provide a rotor-platform magnetic field. The device also includes a stator platform that includes a planar mounting surface. The device also includes a plurality of conductive structures disposed along the planar mounting surface. The conductive structures remain within a predetermined distance to the ring magnet in response to rotation of the rotor platform about the axis of rotation. The conductive structures are electrically coupled to define an electrically conductive path that at least partially overlaps the ring magnet. The device also includes circuitry that causes an electrical current to flow through the conductive path. The electrical current generates a stator-platform magnetic field that interacts with the rotor-platform magnetic field such that the rotor platform rotates about the axis of rotation.