I found today’s featured Wikipedia article quite interesting. Sudoku (Su Doku) is a number puzzle of sorts, popularized in Japan in 1986 and more recently in other countries in 2005. In a nutshell:
The puzzle is most frequently a 9×9 grid made up of 3×3 subgrids (called “regions”). Some cells already contain numbers — the “givens.” The goal is to fill in the empty cells, one number in each, so that each column, row, and region contains the numbers 1 through 9 only once. Each number in the solution occurs once only in each of three “directions,” hence “multiple isolations.”
There’s obviously more to it, and as expected with anything Wikipedia the article goes into a ton of detail. Enjoy!