is named after the Swiss crystallographer Louis Albert Necker, who in the mid-1800's saw cubic shapes spontaneously reverse in perspective. The human mind perceives the 2-dimensional shadow of a cube as a 3-dimensional object, but the 2-D image doesn't distinguish the front and back faces. You can perceive either face as being in front.
You might see this as a wireframe cube rotating in 3d space, complete with perspective effects. However, you can, either by an effort of will, or chance, make the 'back' face (the smaller square) appear to become the 'front' face, and vice versa. If you succeed in this, or you started out seeing it that way, then the object appears to distort strangely as it rotates!
This picture is ambiguous in three ways:
Rubik's Cube was invented in 1974 by Erno Rubik, a lecturer at the Department of Interior Design at the Academy of Applied Arts and Crafts in Budapest, Hungary. He was intersted in geometry, especially 3D forms and their construstion. One day while watching the Danube flow over some smooth pebbles, Rubik got the idea for a cylindrical internal mechanism to allow easy manipulation of his 54-surfaced block.
VirtualCube is an electronic version of the Rubik's Cube. It features: Scramble to play a 2x2x2 or 3x3x3 or 4x4x4 VirtualCube with a button click; Click on a directional arrow to turn one of cube slices; Rotate the VirtualCube or View the VirtualCube in any direction; Seek help in SolveAll or Solve1Step button with adjustable animation speed; Perform any of the patterns you see listed with a button click; Setup VirtualCube with any valid scrambled colors and watch it solved; and more.