Advanced F2L

In the previous post, we have learned the basics of F2L, of how to solve the corners of the first layer and the edges of the second layer in just one step. We have learned the three basic cases and how to insert connected pairs. But without further adjustments to the method, this requires a lot of turns.

Normally, you first have to bring corner and edge to the top layer, then eventually split them up, then pair them, then insert them. The first three parts can be combined into one step.

In all examples, we see the bare solution for the general case on the left, and a complete solve on the right.

We also assume that the bottom cross is white. Exchange "white" with whatever colour is at the bottom.

The overall solve usually takes two steps: First, the pair gets connected or set up in a way that the corner can "catch" the edge. Then the pair gets inserted, respectively the edge gets caught. For simplicity, we always do both steps in the same slot. But that is not enforced. You can pair them up in one slot and insert them in another. That will then require additional U turns.

We also always insert the pair into the same slot, more precisely the slot at the front right side. One way to improve your F2L performance is to learn to insert the pair in any of the four slots without regripping or doing a cube rotation.

We always start by trying to find a bottom layer corner or a second layer edge in the top layer. If they are both in the top layer, we are lucky. We have either found one of the basic cases or one that can be solved with the methods described below.

Split in Top Layer in One Step

We first look at the cases where the corner and the edge are connected but not aligned correctly. In order to be able to insert them, we have to split them up first.

Top Stickers Match

Tilt the layer with both pieces, so that the corner is over the edge. Another way to say this is to "hide" the edge so that the corner is over the edge. Then move the corner out of the way and tilt the edge back:

This case is a little bit awkward because in the variation shown here, it requires a cube rotation, unless you are okay to use F or B turns which most people try to avoid because they are awkward to turn. R, L, and U turns are sometimes called "natural" moves because of this, whereas F, B, and D turns are called "unnatural" moves.

You can actually see that you need a cube rotation before you even start. The colour of the F face is red'. But the colour of the sticker facing upwards is green. This is called a "bad edge" because it is impossible to insert that that edge into its slot with R, L, or U turns only. You either need a cube rotation or you have to also use F or B turns.

Side Stickers Match

Turn the pair away, so that you can no longer see the matching stickers. Bring the target slot up and hide the corner in it. Now move the edge over the corner. Take the corner out, move it over the edge and take the pair out. The corner and the edge are now connected.

No Stickers Match

White Facing Up

Tilt the layer with both pieces, so that the corner is over the edge. Move the corner out of the way with U2. Tilt the edge back. The corner and the edge are not set up.

This is similar to the case above where the top stickers match, only that you turn the corner away with U2.

White Facing Long Side

Turn the pair so that you can no longer see the bottom colour sticker and hide the corner. Move the edge even farther away, and take the corner back out. The edge is now set up.

Twisted Pair (white facing short side)

Move the pair out of the way so that you can still see the bottom colour sticker. Tilt the target slot to the top layer and hide the corner in it. Move the edge over the corner and tilt that side bringing the corner up. Turn the corner to the other side, tilt the edge back up. The edge and the corner are now set up for catching the edge.

This is similar to the case above where the side stickers match, only that the corner is not moved over the edge but in the other direction.

Corner in Top Layer, Edge in Second Layer

Now, let's look at the cases where the corner is already in the top layer but the edge is in the middle layer and has to be brought to the top layer. Of course, we want to bring up the edge in such a way that it is either correctly connected with the corner or set up to be "caught" and inserted.

Note that we assume that the corner sits on top of the edge. That will usually require one or two U turns. If the first turn of the solution is the reverse U turn of that initialisation, you can optimise by omitting them both. But, of course, detecting that case is harder.

White on Top

Corner and Edge Match

Just take out the pair and insert it.

Corner and Edge Do Not Match

There are three popular options.

You can make the Sexy move twice for pairing up, and a third time for inserting the pair into the slot.

If you understand the anatomy of the Sexy Move, you know that you can do exchange it with the reverse Sexy Move and achieve the same result.

Alternatively, move the corner out of the way and align with the sledgehammer. This will save three turns but involves awkward F moves.

White on Side

Corner and Edge Match

Move the corner out of the way, so that you can still see white. Hide the corner, and move the edge over it. Bring the corner back up, and the pair is connected.

Alternatively, move the corner in the other direction. Hide the corner, move the edge over it, but further with a U2 move. Bring the corner back up, and it is set up to catch the edge.

Corner and Edge Do Not Match

There are two ways to solve this.

Move the corner away so that you still see the bottom sticker. Take out the edge in the same direction.

Or turn the corner away with U2. Take the edge out so that the stickers on the U side do not match. Move the edge over the target slot, and connect the corner and the edge with a side turn.

Corner in Bottom Layer, Edge in Top Layer

Now, let's look at the cases, where the corner is already in the bottom layer and the edge is in the top layer.

You first have to find out whether the corner is correctly oriented or not. This is obvious, when the corner is in the target slot. If it is not, just try to see the bottom colour (white). If it is not visible, then the corner is "correctly" oriented. If it is visible, it is not correctly oriented.

Corner Correctly Oriented

You use the generalised method for the second layer from the beginner's method. You make the edge match with the side sticker, move it away from the corner and do the Sexy Move.

It is the generalised version because you now use whatever slot the corner is in for the first Sexy Move. That connects the corner and the edge. You then insert the pair into its correct slot with the second Sexy Move, omitting the final turn of the U layer because it is useless.

You can avoid the cube rotation by using the sledgehammer:

Corner not Oriented

Front Colour and Top Colour Match

The front colour is the visible colour of the corner that is not the bottom colour (white).

The "X" marks the front and top colour match. Turn the top layer so that the edge and the corner are both in the layer showing the front colour sticker of the corner. Hide the edge, move the corner over it, and tilt back. The pair is now connected.

Front Colour and Top Colour Do Not Match

Again, bring the edge into a common layer with the corner but this time into the layer showing the bottom colour of the corner. Hide the edge and move the corner away from the edge. Then bring back the edge. The pair is now set up for catching the corner.

Corner in Bottom Layer and Edge in Second Layer

These cases are mostly awkward except for one case. Unless you have hit the one lucky case, you will try to avoid them. Avoiding works by using the slot with the misconnected pair for pairing up another corner with its corresponding edge.

Theoretically, you could also artificially produce these cases by D turns, but again, unless you are good enough to spot the "lucky" case, you should rather do another pair first.

Long story short: When you follow common sense, these cases are only relevant for the last F2L slot.

Corner and Edge Paired Up

Let's start with the lucky case which is a no-brainer and does not really deserve an explanation. You simply take out the pair and insert it into its correct slot.

Corner and Edge Not Paired Up

There are three more cases where the corner and the edge are not paired up correctly and all of them are nasty. It does not make a lot of sense to learn specialised algorithms for them. Instead, you can just bring the pair into the top layer and split it up with three turns, and these three turns are always the same. After that, you end up in one of the three base cases of the beginner's F2L method and simply follow that.

Given the fact that the cases are easy to avoid and that the intuitive solutions are just marginally worse than the specialised algorithms - sometimes even identical to them - you rather invest the time for memorizing these long algorithms in other optimisations.

Let's look at one such bad case:

The first three turns - in this case shown on the left side - bring up the edge and split it up, no matter how the corner and the edge were oriented. This leads you to one of the three base cases of the beginner's F2L method. In this case, it is the case where the bottom colour faces up. As you have learned before, you hide the edge, move the corner over it and bring the pair back up connected. You then just insert it.