Diagonal Sudoku: 200 Puzzles With An X (Paperback) by Dj Ape

9781440475160. New condition. Trade paperback. Language: English. Pages: 120. Trade paperback (US). Glued binding. 120 p. Diagonal Sudoku (Sudoku X) puzzles add another twist to your favorite game: both diagonals must contain all digits from 1 to 9 precisely once.This additional rule forces you to use new solving methods which are explained in the introduction.The books contains 200 puzzles split into 5 levels of difficulty. None of the puzzles are too easy and they cannot be solved without using the "X" rule.