(also known as " ") is a placement puzzle. In this sudokus main diagonals also contain the digits 1 through 9. This book introduces you to the amazing world of Sudoku X puzzles. It will help you understand the rules of this puzzle. This book is perfect for players of all skill levels and ages. You will find exciting puzzles, both for beginners and for professionals. It is a grid, partially divided by black cells into compartments. The puzzle is most frequently a grid made up of subgrids (called "regions"). Some cells already contain numbers, known as "givens". The goal is to fill in the empty cells, one number in each, so that each column, row, and region contains the numbers 1 through 9 exactly once. Main diagonals also contain the digits 1 through 9. Each number in the solution therefore occurs only once in each of three "directions".