***"sudoku 1200 Challenging Puzzles with Answers*volume 1-6"***

Sudoku is a number puzzle game played on a grid in order to fill the empty spaces, so that each row contain of the same numbers. For example, in a 9x9 grid, it is the aim to put the number 1 to 9 in each of vertical and horizontal lines. This place 9x9 divided into nine squares of 3x3 in nine rows and nine columns, for a total of 81 small squares. The unsolved Sudoku puzzle provides some random numbers in the squares. To solve the puzzle, the remaining places will be filled with the numbers 1 through 9 appearing just once each square on row, column and on 3x3 square. It varies in sizes starting from 2x2 until 100x100.