Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9x9 grid with digits so that each column, each row, and each of the nine 3x3 sub-grids that compose the gird contains all of the digits from 1 to 9. The puzzle setter provides a partially completed grid, which typically has a unique solution. “Su” means number in Japanese, and "Doku" refers to the single place on the puzzle board that each number can fit into. Don’t get confused with Sodoku which is a bacterial disease from rat bites and scratches.

 During the 18th century, a Swiss mathematician Leonhard Euler developed the concept of "Latin Squares" where numbers in a grid appear only once, across and up and down.  In the late 1970's, Howard Garnes developed what we now call Sudoku puzzles using Euler's concept with a 9 by 9 square grid. They called it Number Place.  The famous Sudoku puzzle came about in the mid-1980s by the president of the Japanese puzzle giant Nikoli, Inc., Mr. Maki Kaji. Nikoli gave the game its current name, and helped refine it by restricting the number of revealed to 30 and having them appear symmetrically

 Sudoku X  Killer Sudoku

 Hyper Sudoku  Greater-Than Sudoku

 Easy: 36  Medium:

 Hard: 28  Evil:

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2,7,82,3,5 3,6,83,6,8, 9 16,7,86,7,8, 9 4,6,8, , ,6,85421,7,81, , ,6,85421,7,81,

2,7,82,3,5 3,6,83,6,8, 9 16,7,86,7,8, 9 4,6,8, , ,6,85421,7,81, ,6,85421,7,81,

2,7,82,3,5 3,6,83,6,8, 9 16,7,86,7,8, 9 4,6,8, , ,6,85421,7,81, ,6,85421,7,81,

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