2GR (2 generator reduction) is an advanced speedsolving method that reduces the cube to the <R,U> subgroup, allowing for a very ergonomic F2L step and an 84-algorithm 1-look LL.
1. EOPair: create a 2x1x1 corner-edge pair at DBL-DL while orienting all the edges.
2. CPLine: complete a 3x1x1 line on LD while reducing the remaining 6 corners to <R,U>.
3. Block: expand the line into a 3x2x2 block.
4. F2L: complete the F2L.
5. 2GLL: complete the last layer in 1 look.
- Relatively low move count (comparable to Roux).
- F2L and 2GLL steps are quite ergonomic, since they are completely 2-gen.
- Very high skip chances (1/324 LL skip, 1/27 COLL skip, 1/20.25 LL completely solvable with a single Sune/Antisune/Backsune/Backantisune).
- Very steep learning curve: planning EOPair + CPLine is very difficult.
- Lookahead can be difficult during Block if edge pieces aren't tracked during CPLine.
- Movecount largely depends on efficiency during the intuitive stages, so it may be difficult to achieve high tps while maintaining efficiency during those steps.
The following techniques can be used to create more favorable LL cases, or turn bad LS situations into good ones.
- Anti-phasing: A lightweight technique to create much more favorable LL cases. Before F2L is completed, edges are forced to be unphased, avoiding pure twist 2GLL cases (the longest 2GLLs), Z perms (the longest EPLLs), and increasing chances of solving the last layer with a single Sune variant from 1/20.25 to 1/13.5 (this is twice as likely as an OLL skip in ZZ).
- Corner control: The last pair is solved while forcing a Sune, Antisune, Skip, or H OCLL case (these 2GLL subsets are the shortest), reducing LL movecount.
- CO at LS: If LS corner is already solved, an algorithm can be used to orient LL corners while inserting the last edge; if LS edge is already solved, an algorithm can be used to orient LL corners while inserting the last corner. Both situations leave an EPLL to complete the solve.