Folded Forty
(Published on 22. November 2025, 04:18 by mellowrobinson)
I folded under zero pressure to make another fold-in Chaos.
- Divide the grid into four orthogonally connected regions, and fill every cell with a digit from 0-9 so there are no repeats in a row, column, or region. One region border is given.
- Mad Fold-in:
- If the grid is "folded" so the red dashed lines meet and columns 3-6 disappear, the region borders in the resulting 4x5 grid must also form two orthogonally connected regions, each containing the digits 0-9.
- Note that a region border on a fold line will always have a matching border in the same position on the other fold line, because they are on the same gridline after folding.
Solution code: row 4, with a plus (+) for region borders
Comments
on 22. November 2025, 15:17 by mellowrobinson
fixed solution code
on 22. November 2025, 11:33 by marcmees
Fun. Thanks. (With or without period, the solution code remains the same -> better use -, + or / to seperate regions)
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Thanks for catching that! updated -mellow
on 22. November 2025, 08:44 by Eespi
Super fun! Almost thought there were two solutions at the end, and then the folding rule resolved it. Beautiful.
on 22. November 2025, 08:10 by Artham
Nice puzzle, the break in looks obvious but one still has to prove it and I got a bit stuck there, Once I got past that it's an easy solve.
One remark, the word 'fold' is misleading, it would mean that the paper is folded ALONG the red line. The rules don't allow for that interpretation so I had to struggle to make sense of it all. I would use the word slide instead. Or, I would actually do the fold, and the folded grid would be the columns 2187 in that order, each end mirrored into the smaller grid.
That would bring many possibilities for an origami-inspired grid with various folds intricated into each other.
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Yeah, I get what you're saying about fold vs slide. However I think we're stuck with the "fold" wording, since the genre comes from MAD magazine folding centerfolds. In origami terms I think the red lines would be a mountain fold and there is a valley fold somewhere in c3-7, allowing the two to meet in the middle unchanged. The fold rule that you described would be very interesting though.
Might I recommend Nell Gwyn's fold in Hexuro, its not quite as crazy as an origami grid but there are two folds and it's absolutely brilliant. https://logic-masters.de/Raetselportal/Raetsel/zeigen.php?id=000PWQ
- mellow
on 22. November 2025, 04:19 by mellowrobinson
psst. here's the folded grid version. try to solve it without first :)
https://sudokupad.app/aq2el20ges?setting-nogrid=1
