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Moves for doing the last layer of Rubik's Cube |
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What follows is an explanation of why I wrote this page when there are so many solutions on the net already. If you only want the solution, then skip on to here. IntroductionI could always solve the first two layers of the cube just by moving things around, utilising the fact that changes made to what hasn't been done yet don't matter. As the cube progresses though it gets harder to do this, since it is difficult to move a piece without affecting something that has already been done. For the last face I always had to resort to set moves, which I originally obtained from reading the now famous booklet by David Singmaster. To save me hunting through the booklet for the moves I needed, I drew up a crib sheet on Isometric graph paper.
My trawl on the Internet had turned up the excellent Cube Explorer program by H. Kociemba and using this I was able to revive my memory. Having done this I decided to document it so that I wouldn't forget it again. NomenclatureIf you already know the conventions you can skip on to the moves themselves.The conventions are as in David Singmaster's authoritative guide. A cube has centre pieces,
edge pieces and corners. The centre pieces are fixed relative to each other and cannot move
their positions, just rotate. The edge pieces and corner pieces can migrate around the cube.
The edge pieces can flip and the corner pieces can twist. A cube can be coloured in different
ways and may not be the same as shown here.
To refer to the pieces they are named by the position they occupy, i.e. which faces they
are part of.
The moves are described by the face that is twisted. A clockwise turn is represented by the single letter of the face name. An anti-clockwise move is represented by the face name with ' added. FF is shortened to F2. F3 is the same as F' and so is not used. F4 does nothing in effect since the cube is back where it started before the move. If a series of moves is repeated it is placed in round brackets and a super-script indicates the number of repeats. The effects of moves are shown as a list in round brackets of the pieces affected and the positions they move to. If two pieces swap they would be shown as (FU,UR). This means that the piece in the FU position moves to the RU position, but is flipped, i.e. the F of FU moves to the U of UR and the U of FU moves to the R of UR, viz the order matters. This move could also have been written as (UF,RU). Note that the second piece moves to the position of the first under the same rules. Often, pieces do not swap but move in a cycle of three. An example of this is (FU,UB,UR), the cycle is always read from left to right. The same convention is used for showing how corners move e.g. (FUR,UFL)(BUR,UBL), here the FUR and UFL pieces swap places and the BUR and UBL pieces swap places. The movesOrient the cube so that the two completed layers are underneath, and the layer to be done forms the U face. In the diagrams below the bottom (orange) layer, or D face, remains unchanged throughout (except procedure E) and so is not shown. The B and L faces which would be hidden in the perspective view have been 'hinged' out to show them, (technique cribbed from H. Kociemba). In showing the effects of these procedures it is possible to depict it with two diagrams; 'before' and 'after' images. Whether you prefer to visualise the move as restoring a scrambled cube to the completed position or how the move would affect a clean cube is a question of how it is easier for you to visualise it. I have shown both in the diagrams below. Either use the first two cubes for the first method, or the last two cubes for the second.
A : FURU'R'F' = (FU,UB,UR) (ignoring corners)
B : (U²R²)³B'UB(U²R²)³B'U'B = (FU,RU,BU)
C : F(URU'R')³F' = (FUR,UFL)(BUR,UBL)
D : URU'L'UR'U'L = (FUL,RBU,UBL)
E : R'DRFDF' = (FUR)+ {lower layers scrambled} EndpieceThere are many different ways to solve the cube and the method that is best for you depends on how your mental processes work, and how you visualise the cube, and what is happening to it, during the process. It is usually a trade off between a lot of different procedures for different circumstances for a quick solution, or a few simple procedures that are applied over and over again until the solution eventually drops out. The method I have presented here is definitely one of the latter ones. There are people who don't use crib procedures at all but just twist away and can do it 90 seconds or so.I will resist the temptation to make a page of Cube links since much of the stuff out there is on personal pages which are apt to move without leaving a re-direction link, or even just disappearing. However the official site will hopefully be around for a bit. Happy cubing. |
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Copyright © 2004 - JG Weston, all rights reserved.
This document is http://www.sturnidae.com/rubik.php.