Intuitive Last Layer
Getting the Basic Idea with OLLE
To get the basic idea, let's try understanding the OLLE step.
Think about how to flip an edge in the top layer while leaving the rest of that layer unchanged. Messing up the first two layers is fine.
In other words, how do you get:
Here is one such move sequence: F E F2 E2 F
Observe how it works. If you memorize this as an algorithm, that defeats the idea of intuitive LL.
Let me emphasize that. Did you understand how the move sequence above worked? If not, do not continue on with this page. Go back and try the move sequence several times until you can understand it.
Now, consider the reverse sequence; F' E2 F2 E' F'
It flips the same edge. After all, the inverse (or "going backwards") of flipping an edge is flipping the same edge! If you do the original sequence (F E F2 E2 F) followed immediately by its inverse, you get back to where you started.
Now, how do we use this so flip the last layer edges?
We have to flip two edges at a time. Consider the following situation:
Let's flip the UF edge with our sequence:
Okay, one edge down! Now for the UB edge. Try this: turn the U face so that the UB edge is now the UF edge. (Do U2.)
Now, do the inverse sequence!
Not only are the two edges flipped, the first two layers are restored! In fact, except for the two pieces you flipped, all the pieces remain the same!
Summary of the method.
You can break the example above into three substeps.
- Flip the first edge using the sequence.
- Position the second edge correctly, with NO cube rotations. You may turn the top face.
- Flip the second edge using the REVERSE of the sequence used in step 1
(There's actually a 4th substep, which is undoing substep 2.)
You can invent any sequence to flip the first edge, and as long as you use the inverse of that sequence to flip the second edge, it will work! Do you see why? Think about what your sequence does to the first two layers. The inverse undoes all of it!
If you can understand this part, you have truly gotten the concept of intuitive LL. Don't worry if you do not though; it is a bit mathematical in nature (group theory anyone?), and as long as you can remember the three steps, you will be fine.