These three little guys belong to a class of puzzles called "take apart puzzles."
In each you must find the key piece that allows the puzzle to be taken apart.
Usually, it is a bigger challenge putting these back together again.
In this puzzle it is relatively easy to fit the pieces into the square shown.
There is a smaller square on the other side. This is the side you use to challenge
your friends to solve the puzzle. When they don't succeed, you deftly flip
the puzzle over and solve the easier version. Ha, ha, ha!
This requires more of a steady hand, than a steady intellect. But it is a challenge
to get all the balls to go to their proper place.