✓ Great gift for family, friends, or work colleaguesThis Calcudoku book is packed with the following features: ① 365 Easy to Hard puzzles for every day of the year② Each puzzle is guaranteed to have only one solution.③ Answers to every puzzle are provided.④ Four puzzles per page (8.5 x 11 inches).Playing Calcudoku on a daily basis helps to keep an active mind and players often see improvements in their overall concentration.Includes free bonus puzzles you can download. ★★★★★ 2021 Calcudoku Adult Puzzle Book offers hours of entertainment for adults of all ages, from young adults to seniors ★★★★★♥ We hope this will be an entertaining and uplifting mental workout, enjoy Calcudoku ♥