"Oh I know! A deconstruction with overlapping regions!"
Many thanks to Vebby and Niverio for testing.
Place the digits 1-9 in the grid such that digits do not repeat in any row, column, or region. Regions are 9 cells large, and contain the digits 1-9 once each, but their shapes and locations must be determined. Not every cell in the grid must contain a digit, but every clued cell must.
Within the grid there are two snakes, Snake A and Snake B (one cell wide orthogonally connected paths that do not branch or touch themselves, even diagonally). A digit in a circle indicates the number of surrounding cells in the 3x3 area centered at that cell that are part of Snake A, likewise with squares and Snake B. The snakes may touch each other freely, and may intersect. If two snakes intersect (i.e. they both have a cell in common), they must "cross". More formally, no two adjacent cells in the grid may belong to both Snake A and Snake B. Snakes may intersect at corners, or even at their heads or tails. All is fair play.
Every region is either entirely part of Snake A, or entirely part of Snake B. Cells that exist at intersections of Snake A and Snake B belong to two regions simultaneously.
A consequence of these rules is that every cell with a circle, square, or given digit must belong to at least one of the two snakes. A second consequence is that because digits may not repeat in rows or columns, at least two cells in every column must not belong to either snake. These are two important insights necessary to make progress in the puzzle.
Below is an example image as to how the snake rules may work. Yellow here is Snake A, blue is snake B, and green are intersections between A and B. Below shows several different ways the snakes could intersect with each other: at their heads or tails (marked by h and t, but may be interchangeable as orientation of the snakes do not matter), at corners, or pass through each other like an X. This example image does not show anything related to regions, though.
And below is an image of the puzzle. The screenshot of the puzzle below is a Penpa+ screenshot, in which diamonds represent a square and a circle in the same cell. In the CTC link, these diamonds are not there.
Lösungscode: Row 9 followed by Column 8, ignoring empty cells.
am 28. Juli 2022, 18:52 Uhr von wenchang
am 28. Juli 2022, 05:44 Uhr von harrison
What a beautiful dark twisted fantasy that was!
am 25. Juli 2022, 22:23 Uhr von marcmees
an other masterpiece. thanks.
am 25. Juli 2022, 18:26 Uhr von Jesper
Thanks KNT, that was both really weird and cool. Always nice to wrap your head around something quite different!
am 25. Juli 2022, 18:00 Uhr von henrypijames
Don't be scared, people! This in only 4/5 difficulty - AKA a paper tiger. :D
am 25. Juli 2022, 17:21 Uhr von polar
Another brilliant construction! Thanks KNT :)
am 25. Juli 2022, 16:12 Uhr von JayForty
Amazing puzzle! Particularly enjoyed the multitude of different types of logic that had to/could be applied to solve it. Thanks!
am 25. Juli 2022, 14:06 Uhr von SirWoezel
Very tricky and at least as beautiful.
am 25. Juli 2022, 07:32 Uhr von Niverio
Very enjoyable and surprisingly smooth!
am 25. Juli 2022, 04:48 Uhr von RJBlarmo
Ruleset sounds pretty insane at first but the solve went quite smoothly for me. Lots of fun, thanks for setting!
Wow, that was a fast solve. Thanks for solving and I'm glad you enjoyed it! It certainly was a very difficult set for me, I've come back to this idea on and off for close to a month now, and I'm very glad I was finally able to make it work in a smooth way.
am 25. Juli 2022, 03:39 Uhr von Vebby
Mind-boggling, a real test! Very satisfying to solve. Amazing feat to construct this, oh evil setter, though I fear you suffered the worst DOS out of this entire escapade.
True, I definitely did DOS myself while setting this, haha