This title includes 300 puzzles from prolific & popular puzzle & sudoku author - Frank Longo.It takes a page from karate - another Japanese art - each title is graded by colour: White for easy, Green for medium, Brown for hard & Black Belt for the super-tough!All in a handy-sized format, so puzzle lovers can play this addictive game wherever the mood takes them!Watch out - these sudoku might crush even the most stalwart of solvers!With a separate sudoku book for every level, all puzzle lovers can play this wildly popular, incredibly addictive game!From prolific and popular puzzle and sudoku author - Frank Longo, it takes a page from karate - another Japanese art - as each title is graded by colour: White Belt for easy, Green Belt for medium level, Brown Belt for hard and Black Belt for the super-tough solvers.Plus because each book has an amazing 300 puzzles, the fun can go on for hours.