The top shows a yellow cross. But the edges are usually in the wrong order. Look at the SIDE of each cross edge. Each one has to match the middle sticker right below it.

Turn only the top and count how many edges match. You will always find four, and then you are done, or exactly two. Three cannot happen. If you think you see three, count again.

The two matching edges are either side by side, or opposite each other. Look down at the top and decide which.

Sune is R U R′ U R U2 R′. It moves three edges round and leaves the FRONT edge alone. It shuffles the corners as well. Ignore them. They are the next two steps.

Side by side? Turn the whole cube so the two matching edges sit at the back and at the right. Run Sune once. Then turn the top until everything lines up.

Opposite each other? Run Sune once, holding the cube any way you like. Now they are side by side. Count again and finish as above.

Done-check: the ring of colours round the middle now runs straight up into the top. All four sides match.

Watch it happen

See the states

The cross is yellow but the edges are out of order, so the side colours do not line up. Ignore the corners.

Sune moves three edges round, and the front edge never moves

Try it yourself

Move the top edges round until each one matches the middle below it. One set of moves, called Sune, does the work.

You get a cube with everything before this step already done — only this step is left.

The algorithm

Sune

RUR'URU2R'

Two matching edges side by side? Hold them at the back and the right. Run Sune once. Then turn the top to line it all up. Two matching edges opposite? Run Sune once from any angle. Now they are side by side, so finish as above.