I have to be honest - when concidering game design as defined, I've not given it hardly enough thought as I could of done.

I either have a story I'd like to tell (as a fiction book is a story) or I have 'game-mechanics' in mind that I'd like to play with (IE minecraft style, Elite space style)

Actually thinking about the specifics is something I've not yet done, how will the players life work? is it a fixed amount that decreases? is it the 'recovery' style used in call of duty?

If it's a FPS, will there be goals? switches to pull? monsters to shoot?

It seems a lot trickier than it appears at first glance!