The Official Utterly Addictive Number-Placing PuzzleSpring 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!