# M2 - M Layer Cases Explanation



## DennisStrehlau (Oct 13, 2012)

People keep asking how to solve the m-layer-pieces. I answered to that question and then i thought: There are other people out there who have the same problems, so i will post it here. Some people prefer written explanations and dont like videos. So for all of you who understand the idea of M2 but dont fully understand the m-layer-cases, this is for you:

If you know how to solve every piece besides the M-layer-pieces, you understand the basic idea of M2, like i already said. Now we want you to understand how the M-slice-pieces get solved.
There are 4 pieces in the M-layer. 

1. DF/FD - This is your buffer. You dont have to solve this because when you solved every edge, this piece will be solved, too, as you will know.

2. UB/BU - This edge will be solved with a normal algorithm. You dont have to keep track about odd or even numbers of M-slices. It simply doesnt matter. You solve it with the belonging algorithm and thats it. 
The algorithm for UB is: M2.
The algorithm for BU is: F'DR'FD' M2 D F' R D' F or you use this one: (U M')3 U M (U M')4 (Thanks to JasonK)

So there are only 2 pieces left now. So you only have to understand UF/FU and DB/BD to fully understand M2. There are 4 algorithms left now. I will write them down here and in the following text i will only mention the name of the algorithm, so i dont have to write it down every time:

UF: U2M'U2M'
FU: FERUR'E'RU'R'F'M2
DB: MU2MU2
BD: M2DR'UR'U'M'URU'MRD'

Now its really easy. There are 2 possibilities now. 

1. You solved 0,2,4,6,8,.. pieces alreay. So the next piece you have to solve is a "good piece". 
That would mean that you simply use the algorithm that belongs to your piece. For example, you solved BL, DR, RB, FL and now you have to solve one of these 4 cases i just wrote down (UF, FU, DB or BD). Then you would just use the belonging algorithm. For example if it would be UF, you would use U2M'U2M'. 

2. You solved 1,3,5,7,9,.. pieces already. So the next piece you have to solve is a "bad piece".
That would mean that you dont use the algorithm that belongs to the piece. You have to use the opposite case. To know what the opposite case is, take a look here:

UF - DB
FU - BD

DB - UF
BD - FU

As you can see, its the same: UF is the opposit of DB. 
And DB of course is also the opposite of UF.

Now there are different possibilities to know if you already have solved an odd or an even number of pieces and if you have to use the belonging algorithm or the opposite algorithm (good/bad)
You can count, you use 1 image for 2 pieces, you can memorize in locations where you alway put 4 images in one location point and so on.

Questions? Feel free to ask!

PS: Let me know what you think because this is my very first "tutorial", even if its just a really small and specific one.

Greetings, Dennis


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## Schmidt (Oct 13, 2012)

Vielen dank. I wanted to learn M2 (set-up, M2, set-down seems easy), so this was a very nice explanation of the not-so-easy stuff.


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## Cubenovice (Oct 13, 2012)

DennisStrehlau said:


> The algorithm for BU is: F'DR'FD' M2 D F' R D' F
> 
> UF: U2M'U2M'
> FU: FERUR'E'RU'R'F'M2
> ...



For the BU case you may want to explain what the alg actually does:
F' D R' F D' = set up to flip the buffer
M2 = M2 obviously 
D F' R D' F = undo the set up

You could also use algs that flip the BU UB piece to achieve the same goal:
for instance B' R B U R2 U' which has a nice symmetry to it.

Using the same type of alg to flip the buffer would be: 
F' R F D R2 D' M2 D R2 D' F' R' F

An alternative for FU is just using the opposite cycle of the BD case
FU: D M' R' U R' U' M U R U' R D' M2
BD: M2 D R' U R' U' M' U R U' M R D'

To help understanding: all the M slice targets except UB and BU are actually edge cycles proceeded or followed by an M2 move.


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## Schmidt (Oct 13, 2012)

How do I swap DF - UB if they are the only pieces left??


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## Cubenovice (Oct 13, 2012)

Impossibe 

Cubelaws dictate there must be something else off: either the M slice or some corners


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## Mikel (Oct 13, 2012)

DennisStrehlau said:


> 1. You solved 1,3,5,7,9,.. pieces alreay. So the next piece you have to solve is an "even piece".
> That would mean that you simply use the algorithm that belongs to your piece. For example, you solved BL, DR, RB and now you have to solve one of these 4 cases i just wrote down (UF, FU, DB or BD). Then you would just use the belonging algorithm. For example if it would be UF, you would use U2M'U2M'.
> 
> 2. You solved 2,4,5,6,8,.. pieces already. So the next piece you have to solve is an "odd piece".
> ...



You have "Case 1" and "Case 2" Backwards. If you have already solved 1,3,5,7,9 pieces, you need to shoot to the opposite piece. If you have solved 0,2,4,6,8 then you can just use the algorithm.


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## DennisStrehlau (Oct 13, 2012)

Schmidt said:


> How do I swap DF - UB if they are the only pieces left??



If you only have to solve the UB piece, then its like that:

M2, then the parity algorithm: U'F2U M2 U'F2U. Or just M2, then solving corners and then the pariy algorithm.

Greetings, Dennis


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## DennisStrehlau (Oct 13, 2012)

Mikel said:


> You have "Case 1" and "Case 2" Backwards. If you have already solved 1,3,5,7,9 pieces, you need to shoot to the opposite piece. If you have solved 0,2,4,6,8 then you can just use the algorithm.



Thanks!! Fixed that..

Greetings, Dennis


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## JasonK (Oct 14, 2012)

Cool guide :tu

An alternative alg for BU: (U M')3 U M (U M')4
You can replace all the Us with U's if you prefer (that's what I do).
That alg is also useful for flipping edges - replace the last M' with an M and it just flips DF and UB.


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## DennisStrehlau (Oct 14, 2012)

JasonK said:


> Cool guide :tu
> 
> An alternative alg for BU: (U M')3 U M (U M')4
> You can replace all the Us with U's if you prefer (that's what I do).
> That alg is also useful for flipping edges - replace the last M' with an M and it just flips DF and UB.



Thats a GREAT algorithm. I added it to the tutorial.

Thanks, Dennis


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## A Leman (Oct 14, 2012)

I would use [B’UR’BU’, M2] without the second M2 for the BU case. I really like the feel of that insertion. I don’t use M2, but maybe someone would like this for edge flipping.


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## Cubenovice (Oct 14, 2012)

A Leman said:


> I would use [B’UR’BU’, M2] without the second M2 for the BU case. I really like the feel of that insertion. I don’t use M2, but maybe someone would like this for edge flipping.



I used that initially but ditched it in favor of the symmetry in B' R B U R2 U'
I made too many errors with burbu-ubrub as I used to call it.


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## DennisStrehlau (Oct 14, 2012)

Cubenovice said:


> I used that initially but ditched it in favor of the symmetry in B' R B U R2 U'
> I made too many errors with burbu-ubrub as I used to call it.



I call it ubrub-burbu  
I really do it while solving 4x4 BLD or 5x5 BLD..

Dennis


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## JasonK (Oct 15, 2012)

Just noticed:


DennisStrehlau said:


> 1. You solved 2,4,5,6,8,.. pieces alreay.


5 isn't even


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## DennisStrehlau (Oct 15, 2012)

JasonK said:


> Just noticed:
> 
> 5 isn't even



Fixed that, too. Thanks 

Dennis


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## Cubenovice (Oct 15, 2012)

DennisStrehlau said:


> I call it ubrub-burbu
> I really do it while solving 4x4 BLD or 5x5 BLD..
> Dennis



I only started doing M2 on 3x3 after learning r2 for 4BLD 
At a given moment identified burbu-ubrub as one of my reasons for DNF. Even when "saying" burbu-M2-ubrub in my head I noticed my fingers sometimes executing the last two moves in reversed order.

Another thing I like in the symmetrical version is that it is very easy to mirror.
I am now working on including the left hand mirror when UB is followed by an L face target: this can get you up to 6 move cancellations


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## DennisStrehlau (Oct 15, 2012)

Cubenovice said:


> I am now working on including the left hand mirror when UB is followed by an L face target: this can get you up to 6 move cancellations



What do you mean?

Dennis


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## Cubenovice (Oct 15, 2012)

Typically for BU I use B' R B U R2 U' - M2 - U R2 U' B' R' B
But if the 2nd target is on the L face I might use the left hand mirror>

Example of the best case:

If I have target BU followed by LD:
BU: B L B' U' L2 U - M2 - U' L2 U *B L' B'* 
LD: *B L B' *- M2 - B L' B 

=

B L B' U' L2 U - M2 - U' L2 U *B L' B' B L B' *- M2 - B L' B (20 moves)

=

B L B' U' L2 U - M2 - U' L2 U - M2 - B L' B (14 moves)


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## DaveyCow (Feb 17, 2013)

This thread was made about only 4 months ago so I don't think it counts as a necro thread so Ima take my chances and make a reply 

Just to say thx Dennis much for this! it really cleared up some things for me as (like others) M-slice has been really hard for some reason. I might be able to 12/12 edges now! yay!


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## Mikel (Feb 17, 2013)

DaveyCow said:


> This thread was made about only 4 months ago so I don't think it counts as a necro thread so Ima take my chances and make a reply
> 
> Just to say thx Dennis much for this! it really cleared up some things for me as (like others) M-slice has been really hard for some reason. I might be able to 12/12 edges now! yay!



YAY! Dave is learning BLD


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## DaveyCow (Feb 17, 2013)

lol trying to anyway <hug>


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## Masterlaue (Aug 8, 2013)

Thank you so much!! This tutorial really helped me


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## Martial (Aug 9, 2013)

Just to tell that parity alg can be *D'L2D M2 D'L2D*, it seems more finger friendly than U'F2U M2 U'F2U


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## antoineccantin (Aug 9, 2013)

Martial said:


> Just to tell that parity alg can be *D'L2D M2 D'L2D*, it seems more finger friendly than U'F2U M2 U'F2U



I currently use this.


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## uberCuber (Aug 9, 2013)

Martial said:


> Just to tell that parity alg can be *D'L2D M2 D'L2D*, it seems more finger friendly than U'F2U M2 U'F2U



I actually prefer the latter and can do it pretty quickly. The D M2 in the first alg is awkward for me. Clockwise D is difficult for my right hand, so I do it with my left ring finger, but that's also the finger with which I begin the M2. :/


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## Forte (Aug 9, 2013)

Martial said:


> Just to tell that parity alg can be *D'L2D M2 D'L2D*, it seems more finger friendly than U'F2U M2 U'F2U



D' r2 U M2 U' r2 D ?


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## antoineccantin (Aug 9, 2013)

Forte said:


> D' r2 U M2 U' r2 D ?



I LOVE YOU


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