4-book series with kakuro puzzles that start hard and get even harder. Kakuro is a logic puzzle that involves adding, and these are the toughest ever written.
Conceptis Puzzles is the leading number-logic and picture-logic puzzle supplier to magazine, newspaper, book, mobile, game console, and board game providers all over the world. Every day, over 10 million pages with Conceptis puzzles are printed in 40 countries worldwide.
