The American Mathematical Monthly 1989 seems to have a difficult math problem: the picture below shows a regular hexagonal chessboard composed of small triangles. Now please fill the whole chessboard with the three kinds of diamonds on the right (only a part is put in the picture) to prove that when you fill the whole chessboard, you use every diamond.

At the end of the article, a handsome "proof" is provided. Color each diamond, and the whole figure will have a three-dimensional effect in an instant, which looks like a cube piled in the corner. The three kinds of diamonds are the faces that can be seen from the left, right and top of the whole three-dimensional figure, and their numbers should obviously be equal.

Strictly speaking, this is not a mathematical proof. But it combines a pure combinatorial mathematics problem with three-dimensional space graphics, which is really amazing. Therefore, this problem and its ingenious "proof" spread widely and are deeply loved by mathematicians. This classic figure is impressively printed on the cover of the book "Mathematical Puzzle: The Collection of Appreciators". In mathematics, there are countless similar rogue proofs, but this one is probably the most classic.