In a web site with topic the numbers could not miss certainly the game of Sukodu!
Sudoku whose full name is Suji wa dokushin ni kagiru (translation: Only solitaire numbers are allowed) is a logic game of Japanese origin in which the aim is to fill a square grid with numbers according to certain rules.
Logic games are very effective to keep the human brain active and young by the way, if you want to test the age of your brain you can do it with this nice brain age test.
The rules of sudoku are these:
There are sudoku of various sizes but the most classic is 9x9 and is also the one proposed on this site, so the numbers that will come into play are those between 1 and 9.
You can choose the level of difficulty using the selector at the bottom of the page, you can also get a suggestion or you can view the solution. There are plenty of sudoku puzzles to choose from!