The Official Utterly Addictive Number-Placing Puzzle Spring has sprung! You'll have more than just hours of entertainment with these all-new Difficult level Su Doku brain-teasing puzzles that are sure to please. Su Doku engages your mind, improves your concentration, and helps you stay mentally fit. With 150 brand-new puzzles to complete, you'll become a Su Doku master in no time!