04-16-2015, 10:23 PM
Rewatching the video, I think it's an overgrown Sphero on the bottom, and a balancing bot on the top. The top can move around w/o pushing the bottom around, but when the bottom gets too far over, the top starts climbing back up to the top.
I build in Lego! Blogs at:
http://L3-G0.blogspot.com (or http://L3-G0.com for short)
http://MCK-Y.blogspot.com and
http://BB-8.blogspot.com
http://L3-G0.blogspot.com (or http://L3-G0.com for short)
http://MCK-Y.blogspot.com and
http://BB-8.blogspot.com