For those who don't have access to youtube: Perspective is a 2D platformer puzzle game in a 3D environment. Basically, you can pause the game and move around the camera. You then freeze the camera in place it plays like a 2D platformer exactly the way it looks. For example, you can change the angle at which you view lava so the pools appear shorter from that angle. You can then jump over them, whereas if you viewed it directly from the side you wouldn't be able to jump far enough.
It's certainly a creative concept. While something similar probably exists, I've never heard of this type of gameplay before.
I had never heard of echochrome before. I actually think echochrome has a slight advantage in gameplay as it doesn't require repeatedly pausing it, which might become tedious or annoying after a while.