Sunday, September 23, 2018

board games - Help Black slide the blocks to solve this chess problem


Here's a chess problem which plays very like a sliding-block puzzle, hence the rather unusual tag combo.



Ljubomir Ugren 2nd Prize, Mat, 1976; John Nunn, Solving in Style, no. 183


White Kd1 Rb4, Black Kb1 Qb2 Ra1c2 Ba2 Pa3a4c3c4d2


sh#19


To explain that stipulation "sh#19": This problem is a serieshelpmate in 19. In a serieshelpmate, Black starts, and plays a series of moves, with no White moves in between. Then, at the end, White plays one move, which checkmates Black. Black is not allowed to move so that his king is in check. Black is not allowed to give check on any move except the last move of the series. In this problem, Black plays a series of 19 moves before White plays the final checkmating move.


You, the solver, stipulate all the moves -- that's the help bit. It's not like an orthodox problem where you must specify what White does against any defence from Black.



Answer



After looking at the other answers, I think I found something they missed:



1. ... Bb3 2. ... Ra2 3. ... Qa1 4. ... Rb2 5. ... Ba2! 6. ... Rb3 7. ... Qb2 8. ... Ka1 9. ... Bb1 10. ... a2 11. ... Qa3 12. ... Kb2 13. ... a1=N 14. ... Qa2 15. ... Ka3 16. ... Rbb2 17. ... Nb3 18. ... Qa1 19. ... Ka2 20. Rxa4#

By blocking on b1 with the bishop, a tempo is saved, compared to the lines where both pawns are promoted.




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