A game that’s 100% platforming in 2D, 2.5D and 3D. It may sound a little different than usual, but I believe it can work really well.
The player is Dotty, a small point in the entire universe. She is the only thing that lives there, she can’t see anyone else, and for what she knows, she’s alone. The catch? She lives on a sheet of paper.
For some reason she can’t understand, she decide to see the end of her world. She walks, and the player assumes the control – a single dot in a white paper, moving only in one plane. Until she find the end of it, and gain the power to “go beyond”.
She understand, then, the world. And she want to leave this so called “room”.
The problem: how can she leave the paper, and go through the window? By removing her limitations. When she’s just a Dot, her movements create lines, and she is able to move normally on a single plane and “teleport” on it: if she’s in the floor, she may be anywhere in the floor, and may go anywhere.
When she decides to become a Line, she’s able to change her way: she can still move around in a 2D world, but is able to comprehend the world in three dimensions. Not only she’s able to see the world, but can also change planes: If she was aligned to the floor, and want to become aligned to the wall, it’s possible. It’s a whole new world of possibilities that are unavailable in her “Dot” form.
The last way she can use to interact with the world is going 3D, in an Object. She can move anywhere, but there’s a limitation: the basic shape is based on how she developed herself: if she walked a little and stopped, she becomes a little cube, or if she goes around she may becomes a sphere, and is not able to maintain the Object form for long times. This form can walk normally, but is also able to interact with the world: creating bridges or smashing barriers, all of that is possible when it’s an object.
The main challenges would be to have the player assuming control of different stances: Dot would be better to move around, because it’s faster and can teleport, rewarding the player who explores. But the Line can see the world in 3D, and change the way Dot walk around. And, in the end, Object is slower, but can move things on her own and is able to move in all three dimensions at same time, if necessary.