Book excerpt: Code-cracking skills can be put to the test in this entertaining book which teaches children how to write and decode secret messages. Includes Semaphore and Morse code, the Grid code used in the American Civil War, Egyptian hieroglyphics, number replacement and alphabet switching codes and more. Each page features a different type of code, with an explanation of how it works and a practice code to crack. All answers are available at the back of the book.