Crossroads Game Position all 4 balls To the inside then to the outside

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About the item

A fun and clever puzzle. You should find it fairly easy to manipulate the balls to the center positions
but the outside may be more of a challenge?.
whatever way you tilt the puzzle seems to cause at least one of the balls to move away from the outside?
But, there is a very elegant and quick solution that involves using a scientific principal. Can you find it?

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