Non-consecutive Yin-Yang
(Published on 6. August 2025, 18:31 by Schmupiter)
Non-consecutive Yin-Yang: Shade some of the cells such that the shaded cells and the unshaded cells each form an orthogonally connected set of cells and no 2x2 square is entirely shaded nor unshaded. Two adjacent cells that are either both shaded or both unshaded must not be consecutive.
Squares (with Yin-Yang): Cells with a grey square are shaded and contain an even digit.
Kropki dots: Cells joined by a white dot contain consecutive digits. Cells joined by a black dot contain digits in a 2:1 ratio.
Solution code: First (highest) row from left to right
Comments
on 28. August 2025, 14:45 by Schmupiter
@apothycus that is exactly the trick. I also saw the same entry on puzzling stack exchange and wanted to create a puzzle where this trick would be useful.
@henrypijames I would also love to see Simon explain this on CTC, I think he never used this trick. I wonder if Simon and Mark are aware of it...
on 22. August 2025, 00:38 by NRB
For me, I manage to,solve the sudoku with the help of ying Yang constraints, but every time the ying Yang doesn’t work. If the is 3/4 star I think it’s a broken puzzle. After 5 attempts.
on 14. August 2025, 05:45 by henrypijames
It's a really fascinating trick - that I didn't know, and certainly didn't use to solve this puzzle. I would love to see Simon explain it on CtC.
@apothycus: You forgot a third case: There are no color-separating edge vertices because there is no change of color along the grid edge.
on 7. August 2025, 12:39 by Martina
So what's the trick?
on 7. August 2025, 05:40 by henrypijames
I've been able to finish the sudoku with most of the grid still undetermined in terms of YY.
on 6. August 2025, 20:54 by RBGamer
I did use a few yin-yang tricks, but oh I needed digits to progress the pattern. The beginning was magic, and the final break very hard.
This is my first comment on this page, and I want to thank you Schmupiter for a fun and beautiful puzzle
on 6. August 2025, 08:44 by Schmupiter
--- Spoiler Warning! ---
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Hint: The puzzle is intended to be solved using a (general) trick about Yang-Yang puzzles, that I think, is not very well known. Using this trick, it is in fact possible to solve almost the entire Yin-Yang part without placing a single digit or (digit) pencil mark. It is possible to solve the puzzle without that trick, but it is much much harder that way. (I would say 5/5 without the trick, but something like 3/5 with the trick, that's why I didn't want to set the difficulty to 5/5)
