How to Recreate Silverback’s Parallax Effect
http://www.thinkvitamin.com/features/design/how-to-recreate-silverbacks-parallax

Annett, Paul
Vitamin
2008

Abstract:

When I was a lad, I remember being wowed by an effect in Sonic the Hedgehog known as parallax scrolling. Moving my little spiky friend to the right caused the foreground to move past the camera to the left faster than the background, creating a faux-3D view of Green Hill Zone.