Step 3 - recognition tips

Step 3 is a matter of recognising the edge configuration and finding the corner.

There are actually only 3 different edge configurations:

C1	C2	C3

All correct	Adjacent pair correct	Opposite pair correct

What matters is the order of the edges, not where they are relative to the base. Here are the same three configurations again, but this time they are more difficult to recognise since they are not aligned with the base:

C1	C2	C3

So how can you quickly recognise which one is which?

The approach I describe is designed for colour-neutral cubists. The trick is to memorise the opposite colours of your cube. My cube's colour scheme is plus-yellow, which means that the opposites of the three base colours red-white-blue are generated by adding yellow to give orange-yellow-green.

Let's identify opposite colours for the moment and make some interesting observations:

C1	C2	C3

Notice that the edge order is either blue-white-blue-white (as in C1 and C3) or it is blue-blue-white-white (C2). We can distinguish C1 and C3 by examining any pair of edges: if it is in order it's C1, otherwise it's C3. In the case of C2, there are still two possibilities depending on whether the correct pair is on the left or right: check one side, and if that's not it, it must be the other.

Finally, you need to learn how to look at any adjacent edge pair and recognise whether it is in order or out of order. Surprisingly, we can do this efficiently without having to memorise any order information. The trick here is to use your knowledge of opposite colours in combination with the order information that is available by looking at the front two faces of the cube. Here are all the cases:

	Out of order	Two opposite colours together.
	Out of order	Opposite colours not aligned.
	Out of order	One aligned, one not.
	Out of order	Reversed.
	In order	Both aligned.
	In order	Both aligned with opposite colours.
	In order	Shift.

Putting this all together, let's do an example:

Two opposite colours are together at the front, so we are in C2. This is the configuration that has one adjacent pair correct. Let's try to find it. By rotating the cube, we see the pair to the left is not correct, so it must be the one on the right. We don't need to look - one cube rotation was enough. Given where the corner is, we know instantly which algorithm to apply (press play).