A game design document or GDD is basically the design brief before the development of a game this will include the following: 1. A summary of what the game is about. 2. A description of the layout of the game. 3. Who is the games target audience e.g. kids, teenagers, adults. 4. Where the game is set e.g. in space, another planet etc. 5. The controls and mechanics of the game. 6. What platform it will be used on PC, XBOX, Playstation. How do you create one Any format is acceptable but depending on the person and how they would like to present it they can use a variety of options such as Microsoft Word , Powerpoint, OpenOffice, Google Docs and any other type of text document. The brief should be very clear as it is not only useful when presenting it but also useful to look back over especially to the designer if they go off track when designing their specific game. Example Template of a Game Design Document Source: Reddit Also found this Reddit page helpful towards games desig...