Wednesday, January 16, 2008

Get to Know the Edges (ignore the corners for now)

[May 7, 2008: I no longer use the following method of getting the edges, but am leaving it here in case I ever want to refer to it in the future.] This is Part 2 in a series of posts to help you get to know the Rubik's Cube. If you really want to read all this, do yourself a favor and get a 3x3x3 Rubik's Cube first. Last time I checked they have them at Walmart, Target, and Kmart for less than $10. At Walmart in Oroville just before Christmas I saw them on sale for $5. Start with Part 1, which is the Vocabulary section. Study the actual cube as you read through it. Then do this section, which is the Edges section. Then when you are able to consistently get the edges go on to the section on Corners.

Edge/Center Pairs Pair up an edge with its matching center. Do it for various edges getting a feel for what is involved in various scenarios. When you get good at it, pair up four edges with a common color to their common center. Do so in such a way that you end up with a single-color cross on one side made up of the center and four edges. Do this for each of the colors, focusing on only one color at a time. If it hasn’t occurred to you yet, the next step is to solve the cross in such a way that each piece is in its Home Position. In fact from now on when I refer to a cross it means with each piece in its Home Position.

Middle Edges Make a cross on one layer. With the cross facing down, move any three of the Middle Layer Edges to their Home Positions, leaving one Last Layer Edge Piece in the Middle Layer. You will have to temporarily move one piece of the cross at a time out of position, but it will go back into position as you put the Middle Edge pieces into place. If the Middle Edge piece is in the U layer it takes only 3 or 4 moves to put it Home. If the Middle Edge piece is in the Middle Layer but in the wrong place or in the right place but flipped, then it could take 6 moves—3 to move it up to the Upper Layer and 3 to move it Home. If all four Middle Layer Edges are in place, move one of them to the LL, and replace it with a LL Edge Piece. After you figure out how to take a Middle Edge Piece Home from any of the possible places it may be, scramble the cube, get a Cross, and take 3 Middle Edge Pieces Home, leaving one Last Layer Edge Piece in the Middle Layer.

3 Last Layer Edges Make sure one of the Last Layer Edge Pieces is in the fourth Middle Edge spot. Hold the cube so the unsolved Middle Edge is in front with the Last Layer color facing front. The edge piece is on two layers: the Front Layer and either the Left Layer or the Right Layer. Spin the Upper Layer—I could have said “Spin the top” but the short version is “U” for Upper—so that the last middle edge piece lines up on the same side—either L or R—as the unsolved middle edge spot. Spin the layer that contains these two edges away from you. If it is on the right, do R; if it is on the left, do –L. Spin U so that an edge piece that does not have the Last Layer color face up replaces the edge piece you just moved up. Spin the R or L side back down so that the First Layer Cross is restored. Continue this process until there are 3 Last Layer edges with the Upper Layer color face up. My suggestion is to scramble the cube again and get back to this point several times before going on.

Finish Edges You now have 3 edges in the Upper Layer that belong in the Upper Layer. But how many can be positioned correctly at once by spinning the Upper Layer?

If only 1 at a time can be placed correctly by spinning the Upper Layer, use the Edge Piece Series on three of the LL Edge Pieces so that there are still three face up, but now two of them are in, or can be spun to, their Home Positions. Proceed to the next paragraph.

If 2 LL Edge Pieces are Home, or you can spin U to take two Home then hold the cube so the LL Edge Piece that is still in the Middle Layer is at the front of the cube with the Upper face color facing front. Spin the top so the LL Edge Piece that is not correct in relation to the other two lines up on the same side—either L or R—as the piece in the Middle Layer that needs to replace it. Either use R or –L, depending on whether it is on the Right or Left, to spin the Edge Piece up to the top. Spin U so that the last of the Middle Layer Edge Pieces spins down into place when you spin the side back down toward you. Spin U if necessary so all the LL Edges are in their Home Positions. All of the edges are now in place! Go to Step 3.

If 3 LL Edge Pieces can be placed in their Home Positions then hold the cube so the LL edge piece that is still in the Middle Layer is at the front of the cube with the Upper face color facing front. Spin U so the last Middle Layer edge piece is at the front. If the LL Piece that is still in the Middle Layer is on the Right, do: R U –R U R U –R then spin U so the LL Edges are Home. If the LL Piece that is still in the Middle Layer is on the Left, do: –L –U L –U –L –U L then spin U so the LL Edges are Home. Once you do this a few times and understand what is happening, you won’t think in terms of R’s, L’s, and U’s at all. You won’t think about clockwise and counterclockwise. It is a simple sequence, but was easier to explain as face turns, than in words.

You know the drill—scramble the cube and get all the Edges Home. Do it over and over again until you can do it consistently without looking at any notes. Now you know the Edges, and are ready to get better acquainted with the Corners.