In life, an optical illusion is best because the viewer’s brain is doing most of the work. The object on the pad looks at first glance like a drawn cube, letting the watcher assume a convex shape.

Prepare to Be Amazed: Is That a Rubik’s Cube or a Drawing? From the correct angle, you’d swear that these are three-dimensional objects. Rose Eveleth - Contributor. November 28, 2012.