Unwritten Rules are Not Part of the Game

In all games, within game contexts, you may only do things expressly allowed by the rules. This is what it means to have rules; it is the covenant you have agreed to by agreeing to play. You can play tic-tac-toe in a van while yodeling, but putting a Z in a box is out of the question. It is not up to any rulebook to say that you can't use a memory aid; rather it is up to the rulebook to specifically allow it, or else you can't use one. It doesn't matter how much the game for you is not about...