The 39 Clues game is an online game that provides an extension of the 39 Clues books. The game follows the adventures of Amy and Dan who hunt for clues in the books and again in the online game.
The online game offers Mission 0-8 to find more clues, solve secret messages, and crack codes. In order to play, the player must create an account and use the card found in each of the books to gain a clue. The game provides a practice area called the Arena 39, where players enjoy mini games that improve skills and adds points in the game.