12a) Notation for NxNxN Cubes:
12a1) Face Moves (outer slice):
12a1a) Clockwise, 90 degrees: F (front face), B (back face), R (right face), L (left face), U (upper face), D (bottom face).
12a1b) Counter-clockwise, 90 degrees: F', B', R', L', U', D'.
12a1c) 180 degrees: F2, B2, R2, L2, U2, D2.
12a2) Outer Block Moves (outer slice with adjacent inner slices). For each of the moves defined below, n is the total number of slices to move, which must be in the range 1 < n < N (where N is the number of layers in the puzzle). n may also be omitted, for an implicit value of n = 2 slices. Outer Block Moves are:
12a2a) Clockwise, 90 degrees: nFw, nBw, nRw, nLw, nUw, nDw.
12a2b) Counter-clockwise, 90 degrees: nFw', nBw', nRw', nLw', nUw', nDw'.
12a2c) 180 degrees: nFw2, nBw2, nRw2, nLw2, nUw2, nDw2.
12a4) Rotations (entire puzzle):
12a4a) Clockwise, 90 degrees: x (same direction as R or L'), y (same direction as U or D'), z (same direction as F or B').
12a4b) Counter-clockwise, 90 degrees: x' (same direction as R' or L), y' (same direction as U' or D), z' (same direction as F' or B).
12a4c) 180 degrees: x2, y2, z2.
12a5) Outer Block Turn Metric (OBTM) is defined as:
12a5a) Each move of the categories Face Moves and Outer Block Moves is counted as 1 move.
12a5b) Each move of the Rotations category is counted as 0 moves.
12a6) Execution Turn Metric (ETM) is defined as: Each move of the categories Face Moves, Outer Block Moves, and Rotations is counted as 1 move.
and from the guidelines:
E2c4+) CLARIFICATION Examples of symbols or combinations of symbols that are not permitted in solutions for 3x3x3 Fewest Moves: M, e, r, Y (uppercase), T, U1, Ui, U3, U-, R++, R2', R'2, L'w, 1R, 2U, 2f, 2-3r, 1Rw, 3Rw, 2-3Rw, rw, Rr, *, →, ⮐, /, ., ?, [r], [r u], [F], <f>, [f]', [f]2, [x], (x), (L), 2(Rw), (U)2, (U)', (R U)', (R U R'), [R, U], [R: U].