As a side note, it occurs to me that many, if not most, of Zelazny's novels center around characters that create new worlds - Lord Demon, the Amber Chronicles, Eye of Cat, Donnerjack, et al.
Anyway, I like the idea of being able to have several different worlds, each with its own rules, and be able to logically (more or less) fit these widely varying worlds into a single over-arching storyline.
The second source for this idea was the novel 0X, by Piers Anthony, wherein the protagonists must travel between worlds in a particular order in order to find their way home.
The third was the concept of recursion, which I studied while learning to program.
The game story would go something like this: You are a genie/sprite critter who lives in a bottle. One day while outside your bottle you are attacked by a group of Bad Guys, and in the process of fleeing, while entering your bottle, something goes wrong and you pull the bottle inside of itself. The bottle fragments and you find yourself in a hall-of-mirrors analog, with bottles scattered all over your world. Each one is a variation on the one you live in, and each contains each of the others. You must travel through them in the right order, braving the new worlds in each one, in order to find your way back out.
Oh: And the bad guy was caught in the same accident. Now there are variations of the enemies throughout the worlds, and each was transformed along with the interior of the bottles.
Good luck to you.
There are so many wonderful ways a game like this could be presented, in gameplay style, graphically, thematically...every facet could be changed to suit the needs of the overall game.
This system would also allow for expanding the game, post-launch. The way the bottle fragments could be modified, the number of bottles could be changed, and new worlds could be added at whim.
A world like this would also lend itself admirably to a MMO game. Each player starts off in a small, plain bottle, and based on where the bottle is, and what is in the bottle, many adventures could be had.
But I need to keep myself reigned in so I don't start building something so far beyond by current capabilities that I spend all of my development time learning to program instead of programming. I will burn that bridge as I am crossing it.