It’s a puzzle ball consisting of a twenty-sided icosahedron base, twelve numbered pegs, and twenty triangular tiles with different combinations of pips at the corners.

To start, remove all of the tiles and all of the pegs from the icosahedron. Place the numbered pegs wherever you wish on the puzzle ball. Then, you must figure out how to arrange the triangular tiles on the puzzle ball.

This is tougher than it seems. Each triangular tile has a different combination of pips in its corners. Some corners have none, while others have one, two, or three pips. And each corner neighbors a different numbered peg. Each numbered peg is surrounded by five corners, and the pips on each corner, when added together, should total the number on the peg.

And with numbers ranging from 1 to 12, you have to be both clever and careful in your tile placement. That peg labeled “1” can only have a single pip neighboring it, meaning that the other four tiles surrounding that peg should have empty corners.