"Steerable Mass" is the concept behind this orb-robot. It was realized by Nils Völker and I really recommend a look at his beautiful and well-balanced website, also with lots of technical explanations of his bot. This is meanwhile his third exploration of a NXT bot, and the works all have its unique charm.

Another, but similar robot (not made by Nils) is the "Rotundus-groundbot". Same technique, but much more spooky!

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