Gonna take a guess here. I would say each of the cups has a ball in it and the mechanism moves so that only one is left down when the cups are lifted and the other two balls are held in the cups in some way
@The next plague, no, no, is magic
@ Abnormal Fiber, thank you, Consuela.
@The next plague, small clasps in the cups most likely with a shafts running the length on the arm
@The next plague, no that's waaaay too simple. It's actually a machine comprised of three tiny particle accelerators that can create extremely short-lived, marble-sized black holes.
@The next plague, invisible string that's pulled tight on 2 and released on the others? Could run along the arms and be connected to a mechanism inside deciding
@The next plague, The cup that the ball is in moves a little before lifting up. Maybe you are right?
@TheWhiteWolf, or magnets in the cups and stronger magnets hidden in the table
@mas2de, that was my first thought as well but any electromagnet that would be present in that system would have to be immensely powerful to lift a ball that size or tuned finely with a light ball that it's consistency couldn't be guaranteed and it would require more wiring and circuitry than I think is present there
@TheWhiteWolf, just regular magnets. Those balls could be magnets themselves and just have a piece of iron on top and a single movable strong magnet below. Easy peasy
@ Abnormal Fiber, I like your answer better *wingardium leviosa*
@The next plague, magnets brah
@Apathetic Husk, I feel compelled to comment just because of my username
@TheWhiteWolf, magnets would be my guess
@The next plague, In the wise words of Jesse Pinkman
I love how he wears sunglass like he thinks he's so cool for outsmarting us humans
@TriangleTesticles, nah, he wears the glasses cause he's shady 😎
This is how Skynet began.
what is this and do i want it
I'm going to guess that there's an elaborate matrix of hoses in the arms through which the ball is sucked.