Create a synopsis (game concept/idea) of few of your game ideas (3 or more). Synopsis is a brief summary of your game concept. Approximately one to two pages is enough for synopsis. You will choose one from your synopsis for writing the game design document.
Use these questions to help you write the synopsis. **This is not an interview!** Don't just answer every single question there is. Pick ones you can use to flesh out your idea and write it in your own format!
