(18.09.2013) A nice fairy original by Nikola Predrag from Croatia with complete explanation of the thematic complex by the author.

   1.VAf6? (zz)

1...BHg4 x(a) 2.Kg5# X(B)+Y(B)

1...RHe5 y(e) 2.Kg5# X(B)+Y(B)+Z(D)

1...BHe4!

   1.PAd4! (zz)

1...RHf6 y(a) 2.Kg5# X(B)+Z(D)

1...RHg5 x(b) 2.Ke4# Y(C)+Z(D)

1...BHe4 y(c) 2.Kg4# X(D)+Z(B)

1...BHg4 x(d) 2.Kf6# Y(A)+Z(B)

Cyclic transfer of 2 reciprocally exchanged functions (x/X,y/Y) by Black/White on 4 squares (a/A,b/B,c/C,d/D): x/X=block of bK's flight; y/Y=line-interference as a hurdle

(flight-blocks are complemented by flight-guards=Z)

...->hurdle f6(Black)+block g5(White)->

   ->block g5(Black)+hurdle e4(White)->

   ->hurdle e4(Black)+block g4(White)->

   ->block g4(Black)+hurdle f6(White)->...

Initially, wK attacks g5+g4, due to the 'observer' wSg3.

Respectively, after black selfblocks on g5/g4, wK abandons the guard of g4/g5 but plays to observe (as a hurdle) PAd4/VAe7 which will attack g4+h4/g5+h4.

Respectively, after black hurdles on f6/e4, the mates must be changed-> VAe7/PAd4 do not attack but only observe g5/g4, so wK must block these squares but now (due to a new 'observer') wK can attack h4 and continue to attack g4/g5.

The specific features of Patrol chess are presented by Black/White cyclic exchanges of hurdle/block functions and the reciprocal exchanges of attacking/observing functions of white pieces. (Author)

Patrol Chess: A piece can capture or give check only if it is observed by a piece of its own side.

PAO: Moves as Rook, but captures only by hopping over a hurdle to any square beyond.

VAO: Moves as Bishop, but captures only by hopping over a hurdle to any square beyond.

Rookhopper: Moves along Rook-lines over another unit of either color to the square immediately beyond that unit. A capture may be made on arrival, but the hurdle is not affected.

Bishophopper: Moves along Bishop-lines over another unit of either color to the square immediately beyond that unit. A capture may be made on arrival, but the hurdle is not affected.