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Sliding-block chess puzzles have gone a little cold, so here be a hearty warm-up! ;D

In the below position that I created, it Black to move, but there is a twist: the stipulation is that it is a series-mover-helpmate.

enter image description here

UPDATE: I finally got the postion fixed. The f8 pawn doesn’t attack anything, but it is protected.

You may not know what that is, so here's a brief summary.

A series-mover is a type of chess problem in which one side, in this case it's Black, makes moves by themselves, and the other side will never make a move, except on the very last move in some problems such as this one. However, you must know that the moving side may never be in check or put the other side in check, except on the very last. They can be in check in the initial position, however

A helpmate is problem is a problems where both sides work together to checkmate a side. In this scenario, Black shall conduct a series of moves that will lead to a position where White is capable of mating Black in one move.

What must Black do to help White checkmate Black, and how many moves will that take?

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    $\begingroup$ Has a correct answer been given? If so, please don't forget to $\color{green}{\checkmark \small\text{Accept}}$ it :) $\endgroup$ – Rubio Aug 26 at 0:32
  • $\begingroup$ The position is really ugly. You can easily show the same kind of problem without using a pawn on the 8th rank (!) nor promoted units. Moreover, there are many tools to check the validity of your problem before posting it, including Popeye : sourceforge.net/projects/popeye-chess . Finally, a normal stipulation like ser-h#15 (if the fastest serial helpmate takes 15 moves) would be more welcome imho than asking the solver to guess the number of plies. $\endgroup$ – Evargalo Sep 27 at 8:28
  • $\begingroup$ @Evargalo I have tried to use Popeye before, but all I’ve ever seen are a sea of useless files. I have no goddamn idea how to use it, Thanks though. $\endgroup$ – Rewan Demontay Sep 27 at 11:07
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I assume the Pf8 is just a unit that cannot move.

There are many, many solutions, one of which takes

42 moves.

It goes:

10...KxBa4, 15...KxRe8, 19...KxBa8, 27...KxRh1, 32...KxPh6, 34...Kg4, 39...h1N, 42...NxPg7 when White mates with 43.Rxg7#

I suspect that what you are trying to achieve is

a finish with 39...h1R, 42...Kg1, 44...Rg2 and 45.0-0-0#

But anyway there are many flaws and duals along the way.

edit:

Black must promote to knight, not queen nor rook, to avoid checking the white king.

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I think the goal is to

Sneak into the little crevice on f7, so black can do g3-g4-g5-f6-f7, and then white’s crushing blow is Rf1# (If I understand what the puzzle is, which I didn’t the first time)....

Retry:

Black can do g3-g4-g5-f6-e6-d6-c7 (7 moves), and then I think the checkmate is Nd5#.

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  • $\begingroup$ But then the Black king can escape via e6. Nice try though! $\endgroup$ – Rewan Demontay Aug 21 at 2:33
  • $\begingroup$ Updated! Interesting puzzle haha! $\endgroup$ – El-Guest Aug 21 at 2:58
  • $\begingroup$ Goddangit. I did not see that at all.... $\endgroup$ – Rewan Demontay Aug 21 at 3:02
  • $\begingroup$ There be a mistake in the puzzle now... $\endgroup$ – Rewan Demontay Aug 21 at 3:12
  • $\begingroup$ Oops! Sorry about that $\endgroup$ – El-Guest Aug 21 at 17:41
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I suspect the answer hinges on

the pawn at f8, which is illegally placed. I.e. when a pawn reaches the last row it must be promoted to something other than a pawn. Given that you include "helpmate" as part of this puzzle, I suspect white promotes this pawn to a knight.

Black then

moves his king as g3-g4-g5-f6-f7

White then

finishes the job by either a king side castle or just Rf1.

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    $\begingroup$ I actually wanted to answer the same, but rot13(guvf vzcyvrf gung gur cbfvgvba vf zvq-zbir (v.r. Juvgr whfg zbirq uvf cnja gb s8 ohg fgvyy qvqa'g cebzbgr vg), ohg gung'f vzcbffvoyr orpnhfr Oynpx vf va purpx ol gur ovfubc ba n8 (erzbivat gur ovfubc, ubjrire, fbyirf gur fvghngvba)). $\endgroup$ – trolley813 Sep 27 at 7:29
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    $\begingroup$ @trolley813 I agree with you which is why I edited my answer so that rot13(gur cebzbgvba bs gur cnja jnf abg n pbzcyrgvba bs juvgr'f cerivbhf zbir). $\endgroup$ – Jens Sep 27 at 7:35

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