ZZ-CT

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ZZ-CT method
Information about the method
Proposer(s): Chris Tran
Proposed: 2015
Alt Names:
Variants:
No. Steps: 4 (EOLine, F2L-1, TSLE, TTLL)
No. Algs: 200
Avg Moves: 40-50
Purpose(s):


ZZ-CT is a 3x3 method proposed by Chris Tran. It is a variant of the ZZ Method with a unique 2 look LSLL, divided into TSLE and TTLL.

TSLE inserts the last edge whilst orienting all corners. This step is completely 2-gen and all states can be solved by a linear combination of at most three R U R', R U' R' or R U2 R' triggers, which permits simple memorization and executions. Many of the TSLE insertions are the same as the traditional F2L algorithm, and has a much lower move count than other last slot methods since it ignores permutation of the corners and edges except UF. Using RUD, LUR, and non-2gen algorithms improves upon ergonomics and move count and allows for even shorter inserts.

TTLL solves everything all at once and forces an LL Skip with 72 cases (42 when mirrored, 30 non-trivial), and is named after Chris Tran (who created the method) and Blake Thompson (who generated a significant portion of the algorithms).

Steps

  1. EOLine
  2. F2L-1
  3. TSLE: Insert last edge and orient corners. (Tran Style Last Edge - 108 cases) 100% 2-gen
  4. TTLL: Force an LL skip. (Tran-Thompson Last Layer - 72 cases) 33% 2-gen

History:

The original goals of ZZ-CT were to fix every shortcoming of ZZ-A (ZZF2L + ZBLL), and to create the first feasible LL-Skip method under 200 algorithms. Several months of brainstorming and evolution led to ZZ-CT.

The core fundamental concept is the orientation of corners before reaching last layer.

By abusing rotational symmetry statistics of oriented pieces, it was observed that algorithm count could be reduced by at least an order of magnitude or more. This pre-orientation also allowed for simple and obvious recognition of permutation.

The first incarnation of this method was one which oriented all corners during the completion of the third slot, and then forced LL skip (~800-1000 algorithms).

ZZ-HW was the next big improvement, which oriented all corners and inserted the corner in the fourth slot, followed by forced LL skip(~200 algorithms). However, this method was limited by algorithm ergonomics, since diagonal corner swap and edge insertion algorithms are too long and are not sufficiently ergonomic for competitive speedsolving purposes.

However, by maintaining the same concept and algorithms, but inserting an edge instead of a corner, this hindrance could be ignored, and novel beneficial attributes were serendipitously discovered, as reported herein.

Advantages:

When compared with ZBLL, ZZ-CT solves the issues of large algorithm count, recognition, statistical hindrances, practise requirement, and steep learning curve by having a significantly lower algorithm count, obvious colour blocks (PLL recognition), and better statistics for the same amount of looks.

TSLE is also easily recognised, and only involves looking at orientation of corners and finding the last edge. This requires a similar mental load as OLL, and does not require knowing where the last LS corner is.

Similar to intuitive edge control in CFOP intuitive corner control can be executed to simplify TSLE.

For example, in CFOP, intuitive edge control is seeing that there are no oriented edges and doing R F R F'(sledgehammer) instead of U R U' R'. This ensures no dot cases, reducing OLL by 7 cases.

In ZZ-CT, intuitive corner control is as simple as observing there are no oriented corners, and doing R' U2 R instead of U R' U R during third slot to avoid all misoriented corners, which reduces TSLE by 16 cases. Intuitive corner control can even force superior TSLE cases with better execution, recognition, and move count, in the same way that intuitive edge control forces a better OLL.

Lookahead into TTLL is also similar to lookahead into PLL during OLL, which is an advantage over ZBLL lookahead. Since oriented blocks of colour are being put together, it is easier to predict the last algorithm. This is opposed to ZBLL, in which formation of LS brings together misoriented colour blocks, which are harder to discern for lookahead purposes.

Statistically, ZZ-CT leads to good single times due to the following attributes:

  1. PLL occurs 20% of the time. Leading to a well known algorithm that most cubers already know.
  2. True LL skip occurs approximately 0.27% of the time(1 out of 360 solves), as compared with 0.0064% in CFOP(1 out of 15552 solves), and 0.051% in ZZ(1 out of 1944 solves). Which means that the probability is increased by orders of magnitude.
  3. 2-Gen TTLL occurs 26% of the time, as compared to 15% chance for a 2-gen ZBLL and 1.8% chance for a 2-gen LL in CFOP.
  4. Individual TTLL probabilities are similar to OLL. In comparison, the statistics for ZBLL cases are profoundly lower. This means that some cases will only pop up every few days during solves, meaning that it requires much less practice to execute TTLL than ZBLL.
  5. TSLE is skipped approximately one out of every 400 solves (accurate statistic pending), which adds another level of reduced single times.

Disadvantages:

You have to use ZZ.

Example Solves:

Scramble: R2 F2 R' U2 R2 B2 U2 R' B2 D2 U' L2 F L' R2 F' U2 R2 U F'

EOLine: X' D' L' F L U R2 D'

F2L-1: R U' R' U R' U2 L U2 L U L R' U R D R U' R' D' U

TSLE: R U2 R' U' R U2 R'

TTLL: y' U R' U R U' R' U2 R U R' U' R