For this scene, I wanted to convey a sense of space that is usually associated with 3D environments, but I wanted to do it completely in 2D. The sense of space, is created by moving and resizing the elements at various speed. There is no mathematical formula―the entire thing was eyeballed. I just kept playing with it until it looked right. Here’s a video showing how I go about faking the smoke trails moving on a perpective plane.