About this 3D model

In response to a challenge on the Thingiverse Blog http://blog.thingiverse.com/2012/02/21/oo-someone-make-one-of-these/ I offer this first attempt to print the visual illusion of balls rolling uphill. When viewed from the correct angle, this piece should give the illusion that all 4 ramps slope up to the middle platform. Viewing from any other angle gives the game away!