Extending the self [balancing robot] (https://github.com/laurensvalk/segway) to higher dimensions...
2DOF: On a [small plastic ball] (https://www.youtube.com/watch?v=PX7RNmyJgEs)
3DOF: Can also turn the longitudinal axis, [BB8 style] (https://youtu.be/3GlxzoE0jcg)