Corners First methods, abbreviated as CF, are speedcubing methods that solve all of the corners (relative to each other) before anything else. There are not very many serious CF solvers for 3x3x3 these days, because it can be hard to get under 20 seconds with a pure CF method, but CF methods are relatively easy to invent and were very popular in the 1980s. At least in theory, CF methods exist for all puzzles with corners, although for many puzzles (such as big cubes) they are impractical for speedsolving. For the 2x2x2, on the other hand, there are only corners, so any method is in effect a CF method, and ideas from 2x2 solving can be applied to CF methods on any larger cube puzzle. The most popular methods for solving the corners are Guimond, Ortega, and CLL; there are many ways to do the edges, perhaps the most efficient of which is the Waterman method.
The first ever solve of a Rubik's Cube was by Ernő Rubik himself in 1974, and he used a corners first solution he developed himself over several weeks. One of the first published guides specifically intended for speedcubing was Jeffrey Varasano's 1981 book Conquer the Cube in 45 Seconds which used a corners first solution. The first official speedcubing World record (in 1982) was done using corners first (22.95 secs by Minh Thai). Around that time Marc Waterman and Daan Krammer developed the Waterman Method, a highly evolved corners-first method with more than 100 algorithms, allowing Marc Waterman to achieve sub-17-second averages and some of the fastest times of the 1980s.
In the 21st century very little attention has been paid to corners-first methods for 3x3x3 cubes although there are similarities with the highly-efficient Roux Method. In 2017 a Roux-Waterman hybrid known as WaterRoux has been proposed.
Beginner CF Methods
There are no specifically named methods in this group, but a typical beginner CF method may look like this:
- Solve the corners of the first layer using intuition.
- Orient the LL corners using R U R' U' R' F R F' or a similar algorithm.
- Permute the LL corners using a 3 cycle of corners (A Permutation)
- Move centres into position using slice turns (trivial).
- Place the edges of the E layer using moves like (AUF) + M' R U' M U R'.
- Place the edges of first layer using M' U M or M' U2 M.
- Orient the last layer edges using EOLL.
- Permute the last layer edges with EPLL (for the most basic methods this can be done with only the U-perm).
- Josef Jelínek's Rubikscube.info, has corners first solutions ranging from beginner methods to the Waterman method