Series helpmates with twin by moving black king 1

a) 1.h1R 2.Kh2 3.Rg1 4.Kh1 Rh4#

b) 1.g1S 2.Sf3 3.Sh4 4.Sg2 Rf1#

Black king is confined to a small space in the SE corner, further limited by pawns. As a result of minimalistic twinning we get changed promotions and echo mates.

a) 1.Kd2 2.Rc1 3.e1R 4.Qe2 5.Kd1 Rd4#

b) 1.c1B 2.Be3 3.Bg1 4.Qf2 5.Kf1 Bh3#

In seriesmoves it is sometimes difficult to match lengths of two different phases and various means are used to artificially lenghten shorter of phases. With king-moving twin it is not so difficult. Some preliminary moves might be forced by placing him strategically.

The result might be worth the price, e.g. as in this case: pin mates by wR/wB with reciprocal change of their functions.

a) 1.Ra2 2.Rxa3 3.Rxa4 4.Rxa5 5.Rxa6 6.Ra7 Sb6#

b) 1.Kxa6 2.Kxa5 3.Kxa4 4.Kxa3 6.Kb1 Sxc3#

Naturally, the classic Hungarian duo cannot be missing from this overview. GB & LZ have produced a lot of funny problems with interesting geometric themes.

Here we see captures of the whole column of white pawn in opposite directions. Minimalistic twinning.

a) 1.Sd3 2.Sc5 3.Sxa6 4.Sc7 5.Sb5 6.Ka4 7.Rb3 Ra8#

b) 1.Kg4 2.Rf3 3.Rf6 4.Rxg6 5.Rh6 6.Kh5 7.Sg4 Be8#

Again an artificial lengthening of the solution in b), but otherwise good analogy: annihilation of white pawn on the mating line, self-pin of moving black piece, self-block pin mate. This time there is clear exchange of functions of two pairs of pieces: wR-wB and bS-bR.

a) 1.h1B 2.Bf3 3.Bd1 4.c1R 5.Rc7 6.Ba4 7.Bc6 8.Bb7 e8Q#

b) 1.c1B 2.Be3 3.Bg1 4.h1R 5.Rh7 6.Be3 7.Bh6 8.Bf8 exf8Q#

Promoted bishops immediately shield wK from rook checks, then rooks block and the bishops move to block/provide capture possibility to wK. Model mates and less-than-100% analogy is even adding a spice to the problem in my view (i.e. I see it in a positive light).

a) 1.d6 2.dxe5 ... 6.e1S 7.Sd3 8.Sb4 9.Ka5 Rh5#

b) 1.Ke7 2.d5 ... 5.dxc2 6.c1R 7.Rc8 8.Re8 9.Kd8 Bg5#

For a good measure the third artificial lengthening out of six problems. Otherwise standard Ilievski's work with excelsiors, with good use of material. Again pin mates and this time two white exchanges of functions: wB-wR and wB-wS.