At first glance, Sudoku, crosswords, and other puzzles might seem like simple pastimes—things people do to pass the time on a lazy afternoon. But for many, puzzles are more than just entertainment.

While most people play sudoku by themselves ... to use them has to arise organically — but he liked to reset his puzzles as a way to test his knowledge. “I’ve always been a stubborn man ...

Mr. Chollet’s colorful puzzles test the ability to quickly identify visual patterns based on just a few examples. To play the game, you look closely at the examples and try to find the pattern.