Tic-Tac-Toe Code

The Tic-Tac-Toe Code is a cipher developed by the Penguin Secret Agency to allow their agents as well as those of the Elite Penguin Force to communicate to each other without their messages being intercepted and understood by civilians or enemies.

Syntax
The cipher is built around three grids of three spaces by three spaces. Each space contains a letter of the English alphabet. Each grid contains a maximum of nine letters, positioned on each row in order from left to right, three at a time. The first grid is made up of blank spaces and represents the letters A through I. The second grid's spaces contain an "X" symbol and represent the letters J through R. The third grid's spaces contain an "O" symbol and represent the letters S through Z.

The Director's signature
The final space in the third grid represents no letter. The Director of the PSA and EPF uses this symbol as her signature.

Trivia

 * The Tic-Tac-Toe Code is based on the Pigpen cipher.
 * The Director's signature may represent the letter that would come after Z. Some codes would make this letter AA, in this case referencing Aunt Arctic.