# Rubik's cube, a dream from your childhood

Each Rubik's cube has 26 cubies. (why not 27?). Each cubie has 6 sides just like every other cube in the world. But the cubies in the Rubik's cube are a little different. There are 6 center cubies which only show one side with color; all the other sides are hidden. There are 12 edge cubies which only show two sides with color; 8 corner cubies which will show three sides with color. So it doesen't matter what do you do, the centers will always be centers, the edges will always be edges and the corners will always be corners.

### Rubik's cube movement notations

Each cube has six sides. They are:
L: left side;
R: right side;
D: down side;
U: up side;
F: front side;
B: back side;

There are two directions: clockwise and counter clockwise. For example, R denotes clockwise, R' denotes counter clockwise.

There are also three hidden layers:
M – Middle layer – between left and right.
E – Equatorial layer – between down and up.
S – Standing layer – between front and back.

When we use M,E,S to denote movement, the direction of M is the same as L; the direction of E is the same as D; the direction of S is the same as F.

Other than these sides/layers, there are also axes. If you have learned geometry at school, you know that we live in a 3 dimensional world. Every point in space could be denoted using 3 coordinates. For example, using longitude, latitude, and elevation, we could pin point the exact location of an object. However, we are not going to go there. We will use, x, y, z.

x: axis with direction from left to right.
y: axis with direction from down to up.
z: axis with direction from front to back.

When we talk about cubies, to pin point the exact piece, we will say: left-up-front corner or right-up-standing edge (that's the same as right-up-center edge) or right-front-equatorial edge (that's the same as right-front-center edge) ect;

Sometimes we will move two layers together, which will be deonted by a lowercase letter.

All of the standard movement notations are shown in the animation below. Usually we only need a few of them. Sometimes, we will also see number 2 following a letter. For example R2 or R2' or R'2, which is equal to RR, or R'R'. The result of the movements are the same. That is: turn right side 180 degrees (clockwise or counter clockwise).

There are so many notations, do I need to remember all of these? Don't worry. Actually you only need to know U U' R R' F F' D to understand all of our basic formulas!

### Clockwise and Counter Clockwise

Some people are very good with directions. Some people are not.

I have always had trouble with clockwise and counter-clockwise. Fortunately we have a convinent way to do it. Make a "thumbs-up" with your right hand, put it on any side of the cube, thumb away from that side, the direction of the other four fingers is counter-clockwise.

Similarly, clockwise could be representd by the direction of a left hand "thumbs-up", thumb away from the side.

The left image shows the direction of U'; the right image shows direction of R'.

The animations in the website are adpated from Jason Graves. They perform well on Chrome and Safari, but not on Explorer.