200 quickfire Su Doku challenges, increasing in difficulty as you progress, designed to get the brain cells working. These mini puzzles are the ultimate short, sharp number-crunching workout. A compact puzzle gift book for everyone who enjoys a Su Doku challenge but doesn't have too much time to spare. Smaller grid sizes: 4x4 and 6x6. 3 levels of Su Doku are included with the solutions at the back of the book.