Secret letters are inherently familiar to young people who love team activities, groups, skill camps, scouting... and are an indispensable part of big games.

The secret letter compiled by author Tran Thoi will introduce to readers 9 types of secret letters, from the simplest forms such as reading backwards, reading the words, removing the head and removing the tail, to the morse notation, the alternate form, the reading form. by key, pictogram or coordinates… After each introduction, you will quickly be challenged with small secret messages.

In particular, the author also introduces "invisible ink" to create mysterious "white secret" copies with surprisingly simple solutions.

Let's open the book and brainstorm