\begin{definition}[Definition:Rubik's Cube]
'''Rubik's cube''' is a toy consisting of a plastic cube divided into $27$ smaller cubes, interlocking at the center cube and allowing each face to rotate independently of the others.
Each of the $6$ faces of the main cube is colored with one of six contrasting colors. Rotating the faces of the cube causes these $6$ faces to become mixed up.
The object of the exercise is to restore the $6$ faces to their original single colors.
\end{definition}