Since it'd be messing with perspective, it's automatically similar to Echochrome The idea with this one is that you can grab stuff which prevents it from changing with perspective.

So, you can walk really far away from something, lock it, then walk close again and now it's small.

Mechanics

I've done some thinking on this.

I think there'd be a few different locks. Shape lock would be essentially like picking an item up. It maintains its perspective by moving with you when you move, appearing constant to you but moving relative to the other objects.

Position lock would be the interesting one. In this case you move around, and it appears the same. This is not because it's changing position, though, but rather becaue it's changing shape and size to appear the same despite the change in perspective.

One obvious use of this is to look at an item and and walking away from it or towards it, like above, which would make it smaller or large relative to the other objects.

Another one, though, is finding some really weird long pointy shape, but finding that when it's viewed from on point it looks kinda a like a cube. Now when you lock it there and move down the shape it becomes a neat little box.

With position lock you can obviously do some motions which would make it impossible for the object to shape itself to still look the same. This is true also if you're just carrying an item around, though, and walk into a wall.

So, at some point if you've got an object position locked an moving in some way would cause the object to be impossiblly positioned or shaped, then you just hit a wall, same as if you were carrying something through a wall.

Gameplay

I don't know what kind of game I want to make. It could be an FPS game where you have the ability to do this.

It could be a First Person Puzzle Game where the goal is to get shape A into position B.

It could also be an Abstract Puzzle Game where you're just a disembodied force in a zone of floating shapes. The goals here would be the same as the above, where you have to get the shapes from some initial configuration into some target configuration.