Before we get started, we must work out a method for describing the various moves that will be made.
There are six faces, with the following notations:
- Upper, or top face = U
- Down, or bottom face = D
- Left face = L
- Right face = R
- Front face = F
- Back face = B
We can turn each face either clockwise or counter-clockwise, with respect to the center (i.e. a move that may be clockwise to you, when looking at the cube, may not be clockwise for that face, in relation to the middle of the cube). The names for the different kind of moves (I'll use the U face as an example) are:
- A 90-degree turn clockwise on a face is denoted by U.
- A 90-degree turn counter-clockwise on a face is denoted by U' ("U prime") (Also note this is the same as U, done three times).
- A 180-degree turn either clockwise or counter-clockwise on a face, is denoted by U2 ("U squared") and is the same as two clockwise turns, or two counter-clockwise turns.
We can refer to individual pieces by a two-letter (for edges) or three-letter (for corners) combination. For example, the piece in the upper right front corner is called URF, and the edge piece to the down and left of the cube is called DL. Also, these notations refer to the piece that is in that place at that time, not the piece that should go there.
Clockwise and counter-clockwise are also used to describe orientations of corner pieces. For the URF piece, for example, rotating it clockwise would result in the U side of the piece on the R face, the R side on the F face, and the F side on the U face. Similarly, for a counter-clockwise rotation, the U side of the piece would end up on the F face, the F side on the R face and the R side on the U face.
Also, note that during any sequence of moves the position of the center pieces with respect to one another is unchanged.