Something absolutely crazy happened....

Hello everybody! (As not many of you know) I compose chess problems. And @Assios, the organizer of Advent of Chess has decided to include one of my problems this year (2025, day 21). It is a collaboration with Joachim Hambros (@JoWovrin), an Austrian composer specialized in Proof Games (Proof games are a type of puzzle where you have to reach a position in a certain amount of moves). So, we started off by me sending a cool theme idea and Joachim just casually making it even cooler, and that's how we got to the puzzle a year ago. We waited publishing it until this next edition of Advent of Chess, and so it just lay there for a full year without anybody looking at it. Before I show you what exactly happened, let me show you the original puzzle:

PG 10.5 (composers talk like that yes, it stands for Proof Game in 10.5 moves)

You can try to solve it here: https://adventofchess.com/year/2025/day/21

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So, this is not a very easy puzzle. In fact, only 572 participants solved it in the time limit of 24 hours. But what happened next is absolutely wild:

Same position, but colors reversed. What is absolutely wild though, the solutions to both are unique! e.g. there is only 1 single solution. Before this, there had only been found 5 other cases of this, all of them very short, the longest being only 6.5 moves (e.g. white makes 7 moves and black 6). So this is by far the longest, and also the most complex case of this ever happening!
Craziest of all, it was by pure accident. Neither Joachim, nor I noticed it, until this random guy checked it. Who knows if it would have been found if we had published it somewhere else...

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For anybody curious or too lazy to solve the puzzles themselves: I'll put the solutions a few lines down.

Solution to the original: 1. d3 e5 2. Qd2 Ke7 3. Qg5+ Kd6 4. Bf4 Kc6 5. Nd2 e4 6. O-O-O e3 7. Re1 exd2+ 8. Kd1 dxe1=N 9. Bc1 Nf3 10. exf3 Kb6 11. Ke1
Solution to the Duplex: 1. e4 d6 2. e5 Bh3 3. Qg4 Nd7 4. Ke2 Ndf6 5. exf6 Rc8 6. Qxc8 exf6 7. Qg4 Qd7 8. Kd3 Qa4 9. Qd1 Bc8 10. Kc3 Qg4 11. Kb3

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Also gotta say, huge shout-outs to Joachim Hambros who made this possible!