Before you start making your game you really should make a game design document – often referred to as GDD. Your GDD will help you keep you and your team organized, during the process of making the game, and on track. I generally make mine around the time I come up with a pitch or idea. It’s a way to flush out the ideas to see if it works on paper (before trying to prototype/white box it).
So what goes into a GDD? This is in no way an exhaustive list, but for most game ideas, these are applicable. You will notice in the GDD I provide as an example below that I tried to answer all of these ideas, but for many of them my answer will feel incomplete, because even on an open ended game some topics just aren’t needed.
You want to flush out the basics of your story and the background of your characters. Decide on a level design and way the environment/setting is going to feel. How is the game going to be played? If it is a shooter, is it third person or first person? Why? What is the objective of the game and what makes it flow from point A to point B? Is there difficulty? How will it progress? How do you want the game to end? Open or closed? What does the art look like? Is there music? What are the mechanics of the game that may or may not make it different from other games? What does the player see (Interface)? What platform are you aiming to release on? Who is your target audience and a personal recommendation, list similar titles? Is it hard to do this? Probably a good thing, then.
All of these are things to consider before starting the game, they will help you keep it on track, but remember, they aren’t set in stone. Your game will evolve as you develop, but not in a way contrary to what I said in my previous article, in the sense that you will realize things just don’t work or don’t look right and you will adapt as needed. Keep your GDD updated; it is your long form elevator pitch.
Here is an example of a pretty lengthy Game Design Document I made late last year. The game never went to development because it didn’t quite meet the guidelines for the contest it was to be made for. Your GDD doesn’t need to be this long, it just needs to accomplish what it sets out to do, which is to give you something to go back to in case you get lost when trying to make the game.