WoooHoooo! Thanks to @DaFluffyPotato for suggesting such an awesome theme!
I'm done brainstorming with this cool idea. Its very special and inspired by one of my favourite PC games! Also done with a one-page game design document. Its 12:30 AM here. I'll probably work for one more hour (just the concept and stuff) and then sleep till 7:30 AM. If you want help with your game design document, take this template! Short and to the point. (I'm using google docs by the way for the document)
Mantra: 1 line sentence refering to the UX to always remember throught development (ex: Epic robot battles with multiple story paths)
Summary; A short brief
Features: List of mechanics and unique characteristics
Target Platform: Where do I intend to publish my game
Target Audience; Profiles of who's going to play my game
Game: Layout of every detail of the game (this usually branch on more points specific to that game, like story, power ups, multiplayer, etc)
Interface: This includes player controls and how's the input (mouse, keyboard, controller)
Artstyle: Mostly reference to the art people of your vision
Music/Sound: What kind of music/sound you want and how is going to play
Development Plan: A very crude layout of the needed task to develop the game with a time estimate
Extracted from http://gdu.io/topic/game-design-documents. All credits to josehzz!