Geared 2x2x2

a.k.a. David Gear Cube
Designed by David Tzur.
Left: Custom 3D print by Oskar Van Deventer / Shapeways, 2012.
Right: "David Gear Cube" sold by Mefferts 2018.
(plastic, 2.3" square;
yellow opposite white, orange opposite red, green opposite blue)

In the theme of the 3x3x3 Gear Cub, fully functional Rubik 2x2x2 with gears. On the left below the top layer has been turned, in the middle the turning of the top has completed to make the puzzle square again, and on the right the front layer has been turned until the puzzle became square again: