Take your sudoku to the NEXT LEVEL with these challenging puzzle variations: Sudoku X Hyper Sudoku Sudoku Twins Triathlon A Triathlon B Marathon Samurai 12x12 16x16 David Karn Sudoku comes in many other editions as well. VARIETY OF LEVELS: David Karn sudoku books are available in one or a mix of several levels of difficulty. There are six levels (Beginner, Easy, Medium, Hard, Very Hard, and Extreme) and they come in various combinations of those. Please check the title and book cover for details. EASY TO READ AND FILL OUT: Available in various font sizes so that even those with poor eyesight can easily read the numbers. There is a choice of extra large (42pt), large (36pt), regular (24pt), and medium (18pt) font sizes. SOLUTIONS: If you get stuck, there are solutions in the back of the book. BOOK SIZES: You can get our books in the standard large 8.5" x 11" size or a much smaller 5" x 8" travel size that's easy to carry in your purse or backpack. You can take them to work, school, on a roadtrip, or to the beach. And even the small travel edition is available in large print! A GREAT GIFT ❤️❤️❤️ Puzzles are perfect gifts for parents, grandparents, elderly, or anyone stuck in a hospital. They make wonderful birthday gifts, stocking stuffers, and are a great value as presents for any occasion.