Shadows in the Shade (chaos construction, yin yang)
(Published on 29. September 2026, 12:10 by Chilly)
- Yin Yang: shade some cells in the grid so that all shaded cells are orthogonally connected, all unshaded cells are orthogonally connected, and no 2×2 region is entirely shaded or entirely unshaded.
- Chaos construction: each row, column, and region contains the digits 1–9 exactly once each. A region is an orthogonally connected collection of cells, and regions are to be determined. *All shaded cells in a region must be orthogonally connected to each other, and all unshaded cells in a region must be orthogonally connected to each other*. Note - some regions may contain no shaded (or unshaded) cells, or may contain a single shaded (or unshaded) cell.
- Dots: digits in cells separated by a yellow dot must sum to the total in the dot, if given. These cells must have the *same* shading. Digits in cells separated by a white dot must be consecutive. These cells must have *different* shading. All dots mark the position of a region boundary.
Shadows in the Shade
by Chilly
The Rules:
Solution code: Column 5 with '-' for each region border (not including grid edges).
Comments
on 30. September 2026, 08:26 by marcmees
Very nice. YY well used for CC. Thanks
Thanks - glad you enjoyed.
on 30. September 2026, 07:25 by by81996672
How do I mark the position of the area boundary?
Does it mean that the location of the white dot is the boundary of the area?
What about the yellow dot? How should it be marked?
**
If by area boundary you mean region boundary, then both white and yellow dots mark the position of region boundaries.
on 29. September 2026, 19:13 by Franjo
Thank you very much for creating and sharing this extraordinary gem. After an hour or so I got the CC and YY. But then I was lost in desperation not able to put in the first digit! So 3* for dissections, and 5* for solving the Chaos Sudoku. That was tricky! And satisfying in the end, for sure.
Thanks. Glad you enjoyed. Several testers commented on the Sudoku being hard. But I also had one tester say the Sudoku was not too tricky, but the region building was very tough - seems like different parts are tricky to different solvers.
on 29. September 2026, 18:13 by Snookerfan
Wonderful puzzle! Relentless from start to finish, but so rewarding. I can't imagine how hard it must have been to set this. Thanks
Thanks so much for the kind comments - yes, it took quite a bit of setting!
on 29. September 2026, 14:19 by lmdemasi
This was so cool. The way all the pieces came together was quite the sight to see.
Thank you!
My pleasure - glad you found it cool :)
