Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 sub-grids that compose the grid contain all of the digits from 1 to 9.You do not have to be great at mathematics, but you will surely increase your memory and concentration powers. Through playing Sudoku you can greatly reduce the chances of developing Alzheimer's by keeping your brain active. In this edition you will find: A selection of 100 all-new puzzles. Level: Very Hard (Evil).