the solve. A "PLL skip" is the most common, occurring (when "unforced") approximately once in 72 solves, followed by an OLL skip with a 1 in 216 chance to occur. A combination of the two, a full "Last Layer Skip", occurs approximately once in 15,552 solves. The Cross and F2L stages of a competition-legal scramble are almost certainly not skippable, though a scramble may present the solver with "free" cross pieces or F2L pairs that are already solved or matched. As speedsolving time is closely related to the number of moves required, any opportunity to make fewer moves presents a significant advantage to the solver. Many speedsolvers have the ability, falling under the general skillset of "lookahead", to identify the likely permutation they will see for the next stage based on the progress of the current stage, and they can vary their solution to avoid permutations that require more moves or an algorithm they are slower to perform. This same ability can allow the solver, in specific known scenarios, to "force" a stage skip with a particular sequence of moves to solve the remainder of the current stage; for instance, by recognizing a particular OLL permutation and performing a specific OLL algorithm, the solver can simultaneously solve PLL, effectively obtaining a PLL skip. There also exist many advanced extension algorithm sets to be used alongside CFOP, such as COLL, Winter Variation, VLS, ZBLL, and more. However, it is not necessary to learn them in order to solve the cube or to use the CFOP method. Competition use CFOP is heavily used and relied upon by many speedcubers, including Max Park, Feliks Zemdegs, and Tymon Kolasinski, for its heavy reliance on algorithms, pattern recognition, and muscle memory, as opposed to more intuitive methods such as the Roux, Petrus, and ZZ methods. The vast majority of top speed cubers on the WCA ranking list are CFOP solvers, including the current 3x3x3 single world record holder (Yusheng Du (杜宇生)), with a time of 3.47 seconds. References External links Jessica Fridrich's official site CubeRoot has latest CFOP algorithms CFOP method on Speedsolving.com Wiki All OLL and PLL algorithms can be found on http://algdb.net/ How to solve Rubik's Cube Rubik's Cube