Instructinator

Games can be broken down in many ways, you could divide the level design and the core design, when describing the application of challenge. You could further divide that core into UI, mechanics, and couple them with the level design and talk about gameplay. But before you have any of that, during the conceptual phase it is important to look at the game in lager sense.

The Hook:
The hook is the fun new thing in the game that makes it stand out from others in the genre. This is usually a primary feature of the game.

The Core:
The core mechanics, including but not limited to; perspective, genre, UI standards, and primary mechanics.

The Fantasy:
The fantasy aspect in a game refers to the intended level and focus for the suspension of disbelief. It’s the illusion that you are not sitting in a chair, that you are controlling an avatar doing something else somewhere else.

Its a quick way of describing a game and hitting the high points. A good tool for elevator pitches, marketing speak, and to identify the pillars of the game during the conceptual phase.

This method can be applied loosely to other forms of new media. Film will sometimes have a hook, a core and obviously the big one in film the fantasy aspect.