Two-look PLL
Move the last-layer pieces to where they belong in two steps: corners first, then edges. Six algorithms, or seven if you want the comfortable one.
By the end you will be able to
- Spot headlights and tell an adjacent corner case from a diagonal one
- Permute the last-layer corners with two mirrored algorithms
- Finish the edges with one of four algorithms, chosen at a glance
- Say why the edge step can only ever be one of four cases
The top face is one colour and nothing is in the right place. PLL — permutation of the last layer — finishes the cube. Twenty-one cases in one look; in two looks it comes down to six algorithms, and every one of them is part of the full set.
Corners: look for headlights
Ignore the edges entirely for now. Look at the two top-layer corners on each side of the cube. When they show the same colour, with something different between them, they are called headlights — and headlights mean those two corners are correct relative to each other.
- All four faces show headlights — the corners are already done. One case in six.
- Exactly one face shows headlights — two corners need swapping with each other, next to each other. Four cases in six, so this is what you will usually get.
- No headlights anywhere — the two corners that need swapping are diagonally opposite. One case in six.
For the common case, hold the headlights at the back. One of the two corners now facing you is already exactly right — all three of its colours match the faces it touches. Which one it is tells you which algorithm to use.
B2 turns are the awkward part, and they buy you a version that needs no cube rotation, which most published ones do.Edges: one of four
With the corners right, the edges can only be in four arrangements. That is not a simplification for teaching, it is a fact about the puzzle: corners in place means the edges must be an even rearrangement, and there are only twelve of those — one solved, eight three-cycles, and three double swaps.
U turn reversed, which is the whole of what you have to remember.| Edge case | How often | What you see |
|---|---|---|
| Already done | 1 in 12 | Everything matches; the solve is finished |
| U permutation | 8 in 12 | One edge correct, three cycling round it |
| Z permutation | 2 in 12 | Two pairs of neighbours swapped, no edge correct |
| H permutation | 1 in 12 | Every edge opposite where it belongs |
What this costs you
Two-look PLL runs about twelve turns longer than the one-look version and adds a second recognition pause. The six algorithms here are all part of the twenty-one, so none of the work is wasted when you go on to the full set. The four edge algorithms are precisely the cases a one-look solver meets when the corners happen to need nothing doing to them.
The two-look PLL algorithms Corner cases and edge cases, with the diagrams drawn from the moves themselves. Drill the ones you keep fumbling The trainer shows a case, times your answer, and comes back to the slow ones more often.