Unit 3: Pre-Production
Once you have a general idea of the genre of game you want to make you have to think about what to put in it. Brainstorm about how the player will progress, how they'll move around and how'll they react to certain parts of your game. You brainstorm about the player will move, what mechanics will be used, how the story will progress. This is the time where you will plan what will be in your game, this is the time where you write down and know what you want. In this stage you should get a GDD, a Game Design Document, this is a detailed document on what is planned on being in your game from the characters to the main gimmicks of a level. When planning out every detail you want in your game you will have to give players the illusion of choice.
Choice and Convexity
Known as the illusion of choice, convexity is the process of giving the player choices while ultimately arriving at the same goal. Convexity can be as complicated as having different dialogue options affect the ending you get or as simple as giving players alternate ways of completing one level. No matter how you implement Convexity you have to make players feel like their choices matter, and that is a difficult thing to do because you cannot predict how the player will react to certain parts of your game. Convexity can be traced down to how the player deals with enemies, do they kill it? do they run from it? do they jump over it? The game designer gives the players options through mechanics and the player chooses how to dealt with obstacles, and they still get to the end all the same.
Artifacts - Create a UI Prototype
^ Here is a basic concept for UI of an standard RPG game.