Notation for (*) algorithms for using this object usually uses the letters F, B, U, D, L, and R, with prime symbols and 2's indicating reverse and double moves, respectively.
Early rigorous analysis of this object was performed by Morwen Thistlethwaite, while, recently, Davidson et al. used 35 CPU-years of Google server processing time to prove that its "God's number" is 20. Notation for (*) algorithms for using this object usually uses the letters F, B, U, D, L, and R, with prime symbols and 2's indicating reverse and double moves, respectively. Larger versions of this object include the Revenge and Professor varieties, which have more than three pieces along each edge. For 10 points, name this puzzle invented by a Hungarian architectural engineer in 1974, the object of which is to fill each face with nine pieces of the same color.
Early rigorous analysis of this object was performed by Morwen Thistlethwaite, while, recently, Davidson et al.
 Rubik's Cube