Announcement of 30-day tourney Marianka Cup C 30.7.2013

1.Gd2! th. 2.Se5#
1...Gc3 2.Ga2#
1...Gc5 2.Ga6#
1...Sf4 2.Gxf4#
1...f6 2.Ge6#

Two main variations show incarceration of black rooks and as a consequence mates over immobilized units.

1.Rc4? th. 2.Qe4# A
1...Bd4! a

1.Bc4? th. 2.Qe6# B
1...Sd5! b

1.Gc4! th. 2.Rf8#
1...Bd4 a 2.Qe4# A
1...Sd5 b 2.Qe6# B
1...Sd7 2.Bxd7#
1...f3 2.Rxf3#

Clearcut example of typical grasshopper strategy in the change of move function. Orthodox linemovers guard e4 and e6 from c4, but they can be shut off on d4 and d5. Grasshopper on c4 does not guard any of two squares, but the same defences now provide hurdles for guarding e4 and e6. As a result we get pure Dombrovskis.

1.Qg3! th. 2.Qf4#
1...Sc6 2.Qf3#
1...Se2 2.Qe5#
1...Sb3 2.Sxc3#
1...Sf5 2.Qd3#
1...Sb5 2.Sxc5#
1...Sf3 2.Bd5#
1...Sc2 2.Bxh7#
1...Se6 2.Qe3#
1...Gh4 2.Qd3#
1...Gxg3 2.Re5#

Wheel of Sd4 is further unified by black errors: in all cases it is closing of the black line. While 1...Sb5 and 1...Sb3 close normal lines of black rooks, all other knight moves close black grasshopper lines with bK as a hurdle.

1...Gh2 2.Ge5#
1...Gxf3 2.Ge6#

1.Kc6? th. 2.Sd5#
1...Gxf3 2.Gc7#
1...Gaa8 2.Ge5#
1...Gea8!

1.Kc5! th. 2.Sd5#
1...Gxf3 2.Gc6#
1...Ga5 2.Ge5#

An instructive example of changed play in three phases: mate after 1...Gxf3 is changed three times (wK moves and as a result arrival square of battery mate is changed), while antibattery mate on e5 is three time transferred (depending on which bG guards d6 over wK). Z-32-44 composed of Z-31-13 and Z-31-31.

1...Gf6 a 2.e3# A
1...Gf7 b 2.e4# B

1.Gf7? th. 2.e4# B,e3# A
1...Gf6! a

1.Gf8? th. 2.e4# B,e3# A
1...Gf7! b

1.Gb2! th. 2.Qc1#
1...Ge1 2.e3#
1...Kf1 2.e4#

This modern mechanism includes not only move function changes, but also multiple threats. In the set play moves of bGs to fire white direct pawn battery, combined with indirect battery to f1 and indirect antibattery to f3. Two tries guard f3, threatening both pawn moves as mates, now grasshopper defences defend by line closing (resulting in 4 D-paradoxes). In the solution white creates another battery, with grasshopper as rear and queen as firing piece. Unfortunately, both black thematical defences do not defend and moreover allow set mates.

1...Rxf5 2.Sf3#

1.gxf4! th. 2.Rxg5#, Se3#
1...Rxf5 2.Rf3#
1...exf5 2.f3#
1...Bxf5 2.Bf3#
1...Sxf5 2.Sf3#
(1...Kxf5 2.Se3#
1...Bxf4 2.Rxf4#)

Four thematical defences to f5 (by R, P, B, S) lead to four thematical antibattery mates to f3 (by R, P, B, S respectively). As there is dual avoindance in each variation, it is in fact Stocchi quadruple avoidance with additional unification.

1.Ge4? th. 2.Gfd5# A
1...Kd6 a 2.Gdd5# B
1...Kxe4 b 2.Gbd5# C
1...Gf5!

1.Gd6! th. 2.Gdd5# B
1...Kxd6 a 2.Gbd5# C
1...Ke4 b 2.Gfd5# A

The try and the solution show a remarkable analogy resulting in the Shedey cycle. Both keys provide hurdle to threat mate and at the same time remove one distant guard by grasshopper (on c7/e3). This guard has to be renewed after non-capturing defences by bK, while after capturing defences the third grasshopper has to be used to keep the original guards.

1.Rc4! zz
1...Gf4 2.Sec3#
1...Gb4 2.Rcc3#
1...Gxd2 2.Rdc3#
1...Gxd6 2.Sdc3#
1...Gb6 2.G5c3#
1...Gf2 2.Gec3#
1...Ga1+ 2.Gac3#
1...Gh8 2.Be5#

Black Gd4 jumps to 8 different squares in the zugzwang position. To avoid return defences by bG, 6 of mates are given by just used hurdles to c3. One further mate to c3 is motivate by check (provoked by the key), and the last defence to h8 is met by direct check on the opened line.