Hard sudoku puzzles

"Printable hard sudoku puzzles"
By SoftCns Editor: Printable hard sudoku puzzles.The game of sudoku originated in the eighteenth century. It means 'only one number'. It is basically a number in-line game of filling in numbers, it does not involve any calculation knowledge but needs reasoning and logical thinking to come up with the answers.it is a good way to give the mind some exercises.