F (Front): the side currently facing the solver
B (Back): the side opposite the front
U (Up): the side above or on top of the front side
D (Down): the side opposite the top, underneath the Cube
L (Left): the side directly to the left of the front
R (Right): the side directly to the right of the front
ƒ (Front two layers): the side facing the solver and the corresponding middle layer
b (Back two layers): the side opposite the front and the corresponding middle layer
u (Up two layers) : the top side and the corresponding middle layer
d (Down two layers) : the bottom layer and the corresponding middle layer
l (Left two layers) : the side to the left of the front and the corresponding middle layer
r (Right two layers) : the side to the right of the front and the corresponding middle layer
x (rotate): rotate the entire Cube on R
y (rotate): rotate the entire Cube on U
z (rotate): rotate the entire Cube on F

4×4 Notation