Twinning by exchange of two statical units 2

a) 1.Qb2 Be2+ 2.Kc3 Bxd2#

b) 1.Qc3 Bf4 2.Kd5 Bxb3#

Very good example of thematical twinning. White piece at b1 pins in mating picture bQ that interferes with own rook, while other piece from e6 guards some squares. This kind of twinng “only” needs finding adequate roles for both pieces. If these roles are unusual, surprising, it is better.

a) 1.Be4 Rb6 2.Kd5 Rd6#

b) 1.Gb5 Kd2 2.Gd5 Rb4#

No big content, only two model mates with grasshopper(s). The role of exchanged pawns is worth noting in the context of out 10th TT. In a) both pawns contribute to the mate - wp supports Rd6, bp blocks. However, in b) only black pawn blocks, white pawn is used as a hurdle for black grasshopper. It means their use is imbalanced, but it can be a source of inspiration.

a) 1.Gc4 Gd8 2.Gd2 Sed4#

b) 1.Gd2 Ga7 2.Gf2 Sbd4#

Here we see one of the most common mechanisms used in problems with twinning by exchange of two stationary units: black king and the unit blocking his flight exchange places. This implies also precise roles that both units have - bK is usually mated (or at least checked in selfmate) and the other unit at least blocks. We’ll see more examples of this kind in the upcoming orthodox helpmate files.

The problem in general is standard example of echo diagonal-orthogonal with grasshoppers, satisfying work.

a) 1.a1B Rh8 2.Bxh8 Gh7#

b) 1.a1R Ba8 2.Rxa8 Gb7#

Another echo diagonal-orthogonal, this time we have by chance a book example also for older 7th TT CCM that required mates by hopping pieces (here wG in both positions) over enemy immobilized unit (here bG thematically exchanged with bS in the twinning). Black kinght from twinning takes part in mates as a pinned unit. Moreover there are promotions, long anticritical moves, annihilation of white force... all in all, well motivated helpmate.