# Better understanding of the M2 edge method for 3x3 BLD



## ArniKing2001 (Feb 15, 2015)

I started learning BLD around 5 days ago, from cubing worlds videos (NoahCubes). The problem is I can't seem to understand why a specific target has to go into UB position and not just any, and don't know how to solve the cube part by part after " set-up move, M2, undo set-up move". These are the most confusing parts of M2, I feel. Could someone either make a simplified video or just an understandable description in form of a reply. Thanks.


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## Berd (Feb 15, 2015)

The move M2 is equivalent to the Y perm in OP corners.


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## Leo123 (Feb 15, 2015)

If you are finding it too hard to understand M2 do what I did: Learn OP edges. I watched a different tutorial on OP edges and it was confusing so I recommend Zane C's tutorial.


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## moralsh (Feb 15, 2015)

ArniKing2001 said:


> I started learning BLD around 5 days ago, from cubing worlds videos (NoahCubes). The problem is I can't seem to understand why a specific target has to go into UB position and not just any, and don't know how to solve the cube part by part after " set-up move, M2, undo set-up move". These are the most confusing parts of M2, I feel. Could someone either make a simplified video or just an understandable description in form of a reply. Thanks.



what part of M2 did you understand? 

The basics of most blindfolded method are to memorize a cycle of pieces and then swap one or more pieces, depending on the method.

On M2 you have a buffer (DF) that you want to interchange with the target (UB) and you need an algorythm to swap both pieces (in this case an easy one, Just do M2). Suppose that your cycle is A-B-C-D-E when you start you have sticker A in the buffer and you know that it goes to place A, in place A you hace sticker B which goes to Place C, in place C you have sticker D and so on.

if you (set up) move sticker B to UB you can swap sticker B with sticker A, when you undo that set up move you're moving sticker A to place A, that sounds nice, doesn't it? 

After this, you have sticker B in DF, you now have to set up sticker C to UB and do M2 again (which again swaps sticker C with sticker B) placing sticker C in the Buffer (DF) and sticker B in the target (UB) when undoing the set up move sticker B ends in place B. I think you can take over from here.

just a basic additional rule, set up moves can not mess with the M layer, when finished (the set up move) the rest of the M layer has to be the same as before, or when doing the M2 alg you'll be altering more than the pieces you want to alter.

Hope this helps.


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## Stefan (Feb 15, 2015)

ArniKing2001 said:


> I can't seem to understand why a specific target has to go into UB position and not just any


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## Berd (Feb 15, 2015)

Stefan said:


> http://i59.tinypic.com/1zfq7hh.png


That's a really good way of explaining it.


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## penguinz7 (Feb 15, 2015)

That was beautiful.


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## Stefan (Feb 15, 2015)

A bit more explanation for beginners who don't already know how it works...
The comic is intentionally general, the explanations below are for the M2 method.


The "colorless" guy/place on the right is usually called the "buffer" and in the M2 method it's the DF place. His sole job is to temporarily hold one piece that the owner then comes pick up (in exchange for someone else's piece). He's not trying to get his own piece, instead he's trying to make *everyone else* get their own piece. As kind of a side effect, he thereby ends up with his own at the end.
The spot where the guys walk to to swap their cube corresponds to the UB place.
Walking there to receive your own cube (bringing the not-your-own cube there) corresponds to the setup moves.
Swapping two cubes corresponds to the M2 move (which swaps the pieces in DF and UB (and has some side effects in the M layer that are going to get undone with the next swap)).
Walking back to your spot with your own cube corresponds to undoing the setup moves.
In reality it's a bit more complicated, but that's the basic idea.

Comic btw inspired by heartbleed xkcd.


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