An inverting or tippe top is a classic physics toy: a spinning top that spontaneously inverts itself to spin on its handle at high speed, then rolls back over onto its base when it stops. Turns out, four spheres joined in a close-packed tetrahedron will do the same thing, and this quick video tutorial from YouTuber VTK9990 shows one made from four marbles and some epoxy. [via The Automata / Automaton Blog]

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