Unlike classic Sudoku, Sudoku 12x12 is based on a 12x12 grid, and the object is to place the numbers 1 to 12 in the empty squares so that each row, each column, and each 4x3 box contains the same number only once. There are 100 hard puzzles in this book. Due to the large grid and the difficulty level, this book is a real challenge even for Sudoku experts.