Agreed. That part's rather simple, though it will change the gameplay a lot. We'll need to test it.

I think what's more difficult to decide is how we'll manage the whole "gravity-changing" ability.

-The initial idea was that the player can switch gravity up and down, or even left or right.
-I think Georges idea was that the player can't do so by hitting a key, but only by hitting a switch in game.
-And if I understand txesmi (what does your name mean? I can never remember it :P) right then his idea was that gravity does not (only) switch by player action but by moving through special zones that have previously been defined.

Now the question is, how can we combine these three ideas? I really do want to keep the first idea as the basic ability in the game, because if we only use switches then the game is too linear: if we let the player decide where and when to switch gravity, then there might be multiple ways of solving a level.
Of course, switches can still be used to manipulate gravity. For example, switches could be used to add an additional gravitational pull: boxes are sitting ontop of the place where you wanna go to, so you push a switch which makes them fall towards the ceiling and then you can walk to the place where you wanna go, without the additional field affecting you.

As for the regions: Same thing goes. If we ONLY switch gravity using regions, the player actions will be predefined by us. So I'd vote for a mixture. The way you showed the regions they're basically objects that always attrakt the player to be facing them and fall towards them. Superku showed something like that in his prototype.

And Enemies: Can we find a way to make moving enemies NOT kill the player? I always found that annoying, 3 lives, then you die, collecting extra lives... I dunno. That's retro, and we just had a retro contest. Instead, we could make the enemies block the way (large golem-guards?). Or maybe levels where the guards mustn't see you, so you need to switch gravity to make them fall into some dark corridor or something, and then run past.

Story-Wise, I have an idea. Do you remember Angelas World? I'd take a character like in that game as our main character: a small girl. She has to go and find her little brother, who's gone missing. She just happens to have that gravity-switching ability. I don't really think we need an explanation for that. When she finds her little brother (in level 8 or so) you can then play both the characters. You switch by pressing "1" or "2" and when you play her, you can switch gravity, when you play him, you can switch times/ages.
Goal is to get back home, past all the dream-world creatures that the two of them imagine (or that are really there, but only children can see. whatever. I'm thinking of a world that goes along with the background in george's prototype).

The advantages of this two-character game idea:
-it is more difficult (just changing time AND gravity at all times is too easy), because the player must look after two characters at the same time.
-The explanation of the game could be done using dialog between the two, in game.
-We could add a funny twist: the smaller brother sees monsters that the older sister can't see. She'll always say that he's only imagining them and pull him along.
-The two siblings can help each other: he'll stand on a switch to change gravity, while she'll walk and get the rope that they'll need to finish the level.

Sorry, long post...