First, welcome!

Second, to begin, there are quite a few variables to discuss here since you don't really have much to work with, but this is pretty much the whole point of this!
- Premise: What exactly are we going to do in this game? Is this going to be an exploration sort of platformer or a more race to the goal kind? Along with other little details we'll probably discuss later on
- Characters: Who is going to be the main character we're playing as and who else we're going to meet, including friendly characters and enemies.
- Setting: Like where in the world are we going and what time this is going to set in, since... well, there is a time skip.
- Collectables: Basically what you want to collect when we are exploring each level
- Art Style: Either sprites, vectors or 3D
- Game Engine: Flash or something else entirely
Third, you have me intrigued.