Sudoku is a number placement game. It is a game where the numbers 1-9 are used diagonally, horizontally and vertically to fill in a grid. You can only use the numbers one time in each column or row. The grid for the game is broken down into smaller blocks that are 3×3, and are three across and three down. This gives you a total of nine rows and nine columns and a total of 81 spaces.
Number games have been around since the 19th century and Sudoku was introduced in 1984. In 1986, there were only 32 ways the numbers would work and the puzzles become symmetrical.I was looking for more information and found it here. The most popular grid is the 9×9 with smaller 3×3 grids. Of course, with the way the puzzle has become popular in recent years people have been making different size grids, and playing around with different sizes. A smaller version of the game is now published in magazines and newspapers across the world. There are some other variations of the game and one is called cross sums Sudoku. This is a game where clues are given of cross sums. Since 2006, there have been world competitions taking place. This is a nice puzzle game with numbers for those who like to keep their mind sharp.