This is my first contribution to puzzling!
A while ago I composed this problem based on Article 6.9 of the Fide Laws of Chess.
Your goal is to determine what the result of this game should be after White runs out of time: victory for Black or draw? (Naturally, it is White to move.)
FEN: 6kB/p3p1P1/2p3P1/p7/8/4P3/PKP5/8 w - -
I hope you enjoy it!
If there exists a continuation from the given position that ends in a black win then the game counts as a black win. There is no need for this continuation to be plausible, it just has to be a sequence of legal moves.
If such a continuation does not exist then the game counts as a draw.
I claim that by this standard the result is
a black win.
Proof:
As black has only a few pawn pushes left before becoming completely immobilised it falls to white to somehow release black from deadlock.
Clearly, there is only one way of achieving this: Promote a white pawn (after clearing the file by capturing opposing black pawn(s) with the king) and allow black to capture it creating a passed pawn for black.
But is there enough time before black runs out of moves?
Black has 5 moves in the a file and 3 in both the c and e files. Hence a total of no more than 8 moves once white has captured the pawn it must capture.
White needs at least 1 move to move aside its king, 5 moves to promote the pawn (to a bishop which is the most mobile option that doesn't accidentally checkmate the black king) and another 2 to sacrifice it.
This leaves 0 slack for white, for example after capturing and stepping aside the king has no time to be checked by an advancing black pawn.
From the given position:
1. Kb1 ...
funnily enough white starts with a waiting move
1. ... c5
as this pawn will be captured anyway its moves do not count towards the 8-move total. We can therefore afford to push it all the way down the board.
2. Kc1 c4 3. Kd2 c3+ 4. Kxc3 ...
the clock has started in earnest
4. ... a6 5. Kd2 ...
the only square that will not be in check later
5. ... a4 6. c4 a3 7. c5 a5 8. c6 a4 9. c7 e6 10. c8=B e5 11. Bg4 e4 12. Bf3 exf3
and from here it is obvious that black can win the game.
To paste into your favourite chess program:
[Variant "From Position"]
[FEN "6kB/p3p1P1/2p3P1/p7/8/4P3/PKP5/8 w - -"]
1. Kb1 c5 2. Kc1 c4 3. Kd2 c3+ 4. Kxc3 e6 5. Kd2 e5 6. c4 e4 7. c5 a4 8. c6 a3 9. c7 a6 10. c8=B a5 11. Bg4 a4 12. Bf3 exf3
or use the replayer on our sister site Chess Stack Exchange (some scrolling might be necessary due to the replayers expanding in other answers).
