Notation and Mechanics

A standard 3x3x3 Rubik’s Cube has 26 visible cubies arranged around a fixed central spindle. There are 6 centers, one per face, which are fixed relative to each other and therefore define each face’s color. There are 12 edges, each a two-color piece sitting on one of the cube’s 12 edges, and 8 corners, each a three-color piece at one of the cube’s 8 vertices. Because centers do not move relative to each other, the color scheme of a solved cube is fixed; once you know where White and Green sit, the whole solved state is determined. The standard Western color scheme places White opposite Yellow, Green opposite Blue, and Red opposite Orange, with White, Green, and Red meeting at one shared corner arranged counter-clockwise.

Notation was formalized by the mathematician David Singmaster and is used universally. Each capital letter names a face to rotate 90 degrees clockwise as viewed when looking directly at that face. A prime mark (') indicates a counter-clockwise 90 degree turn, and a trailing 2 indicates a 180 degree turn whose direction does not matter.

Wide turns (Rw, written lowercase as r in some sources) rotate the named face together with the adjacent inner slice and appear often in F2L and in algorithms that would otherwise require a cube rotation. Slice turns M, E, and S affect only the middle layer between two outer faces: M follows the direction of L, E follows D, and S follows F. Rotations x, y, and z rotate the whole cube without permuting any pieces and are used to re-orient between algorithms without counting as solution moves.

Two move-counting metrics matter in practice. The half-turn metric (HTM) counts a double turn as 1 move and is the standard for God’s Number. The quarter-turn metric (QTM) counts a double turn as 2 moves. A third metric, execution turn metric (ETM), counts cube rotations and slice moves as 1 each and is used to compare honest execution costs between algorithms.