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Training puzzle 19577 - broken!

Sorry for another puzzle post. I think this one is definitely broken though...

http://en.lichess.org/training/19577

The first move is forced (Kc1), but then after that, no move continues as Best move. A few come up as good move, but you can do better.

Many thanks!
I have confirmed this bug. I tried all possible moves but no "best move" appears. This puzzle is unsolvable.
It's broken. I've also tried to solve it, but with no success...
No it's not broken, I've solved it...

So the idea is as follows: 1.Kc1 f5 2.exf6 Qxh5 3.fxg7 Qh7 4.g8=Q+ Qxg8 5.Nxg8 (White wins!)

and here's why: white is threatening Rh8# so f5 is forced to make space for the king, and after exf6 (en passant) attacking the black queen, the queen has to take the rook because white is actually up material despite losing their queen, and if the queen moves out of the way then white will simply exchange rooks and still be up material (don't overestimate the queen's strength), then fxg7 and again white is threatening to promote to a queen and it will be mate (g8=Q#) and black's only way to stop that is by covering the promotion square with their queen, hence: Qh7 or Qf7 or Qg4 is forced but then white just promotes anyway to queen to force the trade of queens and be (again) up material and eventually win the endgame (you usually want to trade pieces when you are up material and that's the main idea behind this puzzle).

*Notice that this idea is possible because 1.it's forced 2.white's king is completely safe and the black's queen and rook don't have time coordinate to deliver mate.

**I saw another possible line : after 3.fxg7 Rg5 4.fxg5 Qxg5+ 5.Nf4 Qxg7 (sacrificing the rook for two pawns), but then black is left with a pawn down and only a queen vs two knights and a rook which is also losing for black.
I agree I was wrong. I forgot en passant capturing.

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