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It was a bright sunny day of the sort that we occasionally get in this part of the world (it was the fifth Friday in March). In the park was a van advertising its wares under the banner "Hyper Ices", and that's where I met my friend Megan, who was wearing a beautiful light summer dress.

"What lovely hot weather we've been having", I said.

"Yes -- my husband and I have got the table out on the patio. The other day we had a game of chess out there."

"Didn't know you played chess."

"Well, not very well -- he beat me, as usual. He took a photo shortly before checkmating me. I've got a copy of it here."

Megan retrieved her mobile from one of the many pockets of her shoulder-bag, and showed me. Now, however good her husband was at chess, he wasn't all that good at photography -- how washed out the colours were in that bright sunlight! There was Megan, wearing a dress in white and gold (or at least I think those were its colours -- it was hard to tell), and there was the board. 8/1K1R4/B7/8/1P6/2PK4/8/8

I could tell which way round it was because it was one of those with file-letters and rank-numbers round the edge, but... I couldn't tell which of the chessmen were white and which were black.

"Yes, it does look like you're in a tricky position" I said, as I pondered the position.

"Honestly, how could I have let him get into that position?" she replied -- then it struck me -- I could work the colours out and also a bit of the previous play.

"Anyway by that stage I knew I was losing," she went on, "and he mated me two moves later." I didn't know that before, but, yes, I could see that there was a way a checkmate could happen that soon.

So, specifically:

  • What colour was each unit?
  • What were the last three single-moves?
  • How could the winning side mate two (full) moves later?
    The first two parts of this puzzle are a problem by Nikolaj Burljaev.
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    $\begingroup$ "wearing a dress in white and gold (or at least I think those were its colours -- it was hard to tell)" - boom. Nice one. $\endgroup$ – Rand al'Thor Apr 2 '17 at 10:36
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Since the rook and the bishop are in a threatening position for both kings, they must belong to the same color. I can see but one explanation for this:

enter image description here

and the last step was

an en passant capture from d4 to c3. This is what gives away the color of every piece except the pawn on b4. Of course, this also implies what the last three single moves were.

As to how a mate in two was possible from here, let's assume the colors were like this:

enter image description here

Then Megan could have been mated with:

1. Kc2 b3
2. Kb1 Rd1

(From the story we can assume that Megan probably didn't play with an optimal strategy)

EDIT:

As Tyler Seacrest noted, the white king was checked by the bishop before the en passant. Black must have discovered that check, and he could do so only if the b4 pawn was black. Actually, this is what the 3rd half-move before the photo was. (Yeah, I'm not very good at counting. Sorry.)

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  • $\begingroup$ Maybe you meant to imply this, but doesn't the last three single moves include how the white king was checked by the black bishop before the en passant capture? Wouldn't that have to be a discovered check forcing th pawn on b4 to be black as well? $\endgroup$ – Tyler Seacrest Apr 2 '17 at 19:57
  • $\begingroup$ I didn't trace it back that far, but I think you're right. That bishop didn't teleport there. $\endgroup$ – BaSzAt Apr 3 '17 at 5:58
  • $\begingroup$ Ah, I missed that Megan could plan non-optimally after this point. The question just asks a possible way to have a checkmate that soon. You can actually say one more thing about the fourth single-backstep, since there is no other white pieces that could have moved, it must have been the white king moving into D3, although it could be either from D2, E2, or E4. $\endgroup$ – justhalf Apr 10 '17 at 8:39

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