The Rubik's Revenge (aka the Master Cube) has 4x4x4 blocks, making it harder to solve than the original Rubik's Cube. This puzzle was released in 1981 and was actually invented not by professor Rubik himself but by Péter Sebestény.
The most common algorithm for solving the Rubik's Revenge is called the "reduction" method. As implied by its name, this algorithm focuses on solving the 2x2 center pieces and 2x1 edge pieces first - thus "reducing" the problem to a 3x3x3 puzzle, which can be solved exactly like a regular 3x3x3 cube (Except for two parity cases that require further algorithms).
This puzzle has more parts than the Rubik's Cube, thus many more possible permutations. The number of possible permutations of the Rubik's Revenge is over 7.4x1045. The Current world record for solving it is 19.36 seconds, and it was set by Feliks Zemdegs from Australia at the LatAm Tour - Arequipa 2017.
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