Introduction to the Game Design Document

From what I learned from the PDF a game design document can be an essential design and creational tool but a financial one as well. A design document can be a great reference tool for what your main goals are for a game.This written or typed document Can also help you stay on track and accomplish what needs to be done with without focusing to hard on something non- essential. What I meant by financial is that it can easily become a tool to maintain your funding  and keep them informed about the progress of the project. The if you're self funded and do not have a specific dead line it may not be as useful still good practice. All and all this  is one of the many practices for a professional game designer.