got too many pages stuck together
(Published on 8. November 2025, 08:11 by aqjhs)
So Flinty and gdc have teamed up to ask for more Mad Fold-In style puzzles, and I went to ThePedallingPianist to brainstorm what a folded Doppelgänger puzzle could be and we came up with this ruleset. It is partially inspired by a diagonal fold-in concept by oskode.
At first it seemed to be an impossible construction, but a miracle happened. Doppelgänger can fold-in. Hope you like it!
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Mad Fold-In:
- Dotted lines are clones: they have the same digits in the same relative position.
- By removing the space between the dotted lines a 6x6 grid with four 3x3 boxes is made.
- Folded Doppelgänger Sudoku:
- Fill each cell of the main 9x9 grid such that every row, column and 3x3 box contains a 0 and eight different digits from 1-9.
- Digits may not repeat on rows and columns of the folded 6x6 grid.
- On the 9x9 grid no two rows, no two columns and no two boxes may be missing the same digit.
- The number 0 must appear in every box of the folded grid, and digits do not repeat in boxes of the folded grid.
- On both the 9x9 and the folded 6x6, for each 0 in the grid the digits missing in its row, column and box must be all different digits.
- Cells joined by a V or X have digits that sum to 5 or 10 respectively.
- Cells joined by a black dot have digits in a 1:2 ratio.
Online in Sudokupad and an auxiliary grid (or both together).
See also:
Solution code: Digits on the row missing a 5 in the 9x9 grid.
Comments
on 14. November 2025, 02:23 by aqjhs
clarification: digits do not repeat on rows and columns of the 6x6 folded grid.
on 12. November 2025, 13:51 by bittersteel
Can digits repeat on the 6x6 rows/columns?
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no they don't, looks like i forgot to mention that. thanks!
on 10. November 2025, 21:35 by brimmy
yes!
on 10. November 2025, 19:31 by brimmy
yes!
on 9. November 2025, 06:06 by MathGuy_12
Some really weird interactions here that I am not sure I fully took advantage of, but I loved every bit of it!
on 9. November 2025, 02:42 by mezeji
can 0 be in a cell joined by black dot eg 1 to 2 ratio
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i'm one of those that believe there's a place for 0 in a black dot, but it would have to be with another 0...
on 8. November 2025, 20:36 by War
Very fair, probably the fairest doppelganger I have done in recent time. Enjoyable and logical. Using the Meta puzzle is helpful (both 9x9 and 6x6). I'm rating this a 3* difficulty only because Doppelganger tends to be way harder(maybe a 4* compared to all other variant sudokus).
Beautiful puzzle, thanks!
on 8. November 2025, 19:28 by TripleABattery
Wow! Brutal, though not unreasonably so, and absolutely incredible! Truly a miracle that this even works.
