General overview of the whole Game Design Document, this section contain overall information about the game design with link and reference to more detailed and more specific information in other pages
Game Mechanic includes the main game rules and core mechanic with the most important and highest influence in the games. To make it simple without this mechanic, the game you want will be a different game
Camera, Control and Player Action
Game Feature is a rules that supporting the game Mechanics so it can work properly. While mechanic shape the game, the feature support those mechanics so the user can have better experience while playing the game. Game feature has the second highest influence after game mechanics.
Game System is a collective of mechanic and feature. If mechanic is the main rules, and the feature is it support, the game system make sure all of those mechanic and feature is work together as a game/apps and accessible for the user and help the user or client to use the game or apps as a whole