I have become more and more interested in mapping space to something besides space.
As I've said before, the basic idea of space (how you perceive it and move through it) is treated too generically for my taste. In essence, every game is fundamentally about navigating space. Sometimes the space is very fine and open, like a fighting game or a first person shooter. Sometimes the space is clunky and restrictive, like skill trees and dialog. But space is always treated as "generic". The only difference between here and there is simply that here is closer to the gold that we've placed on an arbitrary point in space.
Why not make a space intrinsically linked to some part of the gameplay?
For example, imagine a game in which you can fly. As you fly higher, it gets colder and harder to breath. There is a strong relationship between space and some part of the gameplay. This is rendered meaningless if you can't fly, though: the idea is that you have to be able to change your position and, in doing so, change the game dynamics.
That's the most basic kind of linking, and many games already have a vague Z-axis play modifier: falling. But that's basically saying "The difference between being here and being there is that being there sends you here."
How about something much more complex, though? How about a game where one of the play spaces is radiation? Walk right, you can sense ultraviolet. Walk left, you can sense infrared. Keep walking, and your senses keep panning away from the human norm.
If this was the main play field in a platformer, it could reveal platforms that are only visible to certain kinds of radiation - then you might have to go jump on that platform, which is invisible to you when you reach it. Or maybe it lets you see through things which are opaque to other wavelengths! Alternately, it could be a secondary play space, like the "sphere grid" the new Final Fantasy games use.
You could link space to anything. You could link it on one, two, or even three axes. You could link it to length of weapon, age, speed of attack, time, space in another play space, the health of a follower, gravity, research speed, the height of ladders, charisma: anything.
Suddenly you've got this weird game where where you stand affects how you play. If it's the primary play space, you've suddenly got a platformer where jumping while on the right side of the level might have a very different result than jumping while on the left side. Or where you can fly, but only where the updrafts are hot enough. Or something.
If it's not the primary space but is instead something like a power-up grid, the result of marching around on it is not scripted - the painful limitations inherent in scripting no longer exist. Walk far enough to the "fire" side of the grid and you take damage if the weather is less than 90 degrees outside. But nothing is stopping you: specialize as foolishly as you want.
Of course, you don't have to map it to space. You could map it to time, but that's pretty common. You could map it to velocity: While moving left, there is no gravity. While moving right, there is a lot of gravity. You could do all three, and make the player's head explode.
I think that would be fun.