The other thing I've learnt is that by writing it down I can start to see what's missing. The image in my mind of how the game will play needs to translate to text. I actually have a mental picture of people sitting at a table, writing on paper, flipping over cards, rolling dice. It's wonderful guidance. I'll be able to explore that mental image (footage?) to find the game tools that are missing from the text.
This game is part of The Stockade project.