## A Brief Introduction to Rubik's Cubes

### Some History

The Rubik's Cube is a puzzle that was invented in the late 70's by a Hungarian named Erno Rubik.
The goal of the puzzle is, after 'scrambling' (mixing up the cube), to twist the cube in such a way that the cube is a solid color on each side.

Before reading, please watch the first 3:12min of this video.
It should help give you a very quick overview of the puzzle.

### Cubie Names

The Rubik's Cube is composed of a number of smaller 'cubies':

• A 'core' that has 6 axis and sits in the middle of the puzzle
• The 'center' pieces that sit at the end of each of the core's axis.
These never move relative to each other, and there are 6 of these.
• The 'edge' pieces, having 2 stickers each. There are 12 of these.
• The 'corner' pieces, having 3 stickers each. There are 8 of these.

### A Universal Notation

Imagine you're holding a standard, solved Rubik's Cube, with the white stickers on top and the green stickers towards your chest.

As a cubing society, we have come up with a way to notate a number of things related to the cube with a standardized notation.
For example, the side with all of the white stickers is referred to as "Up" or "the Up side," commonly referred to as just "U."

This notation is used for:

• Referring to a particular side (such as "look at the U side")
• Notating what turn to make on a cube
• "U" meaning "Turn the U face clockwise"
• "U'" meaning "Turn the U' face counter-clockwise"
• "U2" meaning "Turn the U2 face twice (180 degrees)"
• Pointing to a specific cubie. For example, if you want to refer to the white-green edge in this case, that would be the edge between the UP and the FRONT faces, so you could call this the UF edge!
Given this notation, we should note that there are 6 sides on a Rubik's Cube, and thus 6 such basic faces.
Specifically:
• U(p)
• D(own)
• L(eft)
• B(ack)
• F(ront)
• R(ight)

### Algorithms

While in many scenarios, the word 'algorithm' may be used generically to mean "a series of steps to produce a final product," in the cubing world, we specifically mean a series of MOVES on a cube.
Such an algorithm could look like this: R U R' U R U2 R'
This is a rather simple algorithm, in which we:

1. Turn the Right side clockwise
2. Turn the Up side clockwise
3. Turn the Right side counter-clockwise
4. Turn the Up side clockwise
5. Turn the Right side clockwise
6. Turn the Up side twice
7. Turn the Right side counter-clockwise