Chaos Construction: Surround Sums
(Published on 17. March 2025, 22:45 by PixelPlucker)
Rules:
Divide the grid into nine regions, each consisting of nine orthogonally connected cells. Enter a digit into each cell such that each row, column and region contains the digits 1 to 9 once each.
Some cells contain number clues. For each such cell, consider the (up to) 3x3 area centred on that cell and including the cell itself. In the finished puzzle, this area will be partitioned by the region borders into one or more blocks of cells, such that each block is contiguous within the area and all cells in each block belong to the same region. The numbers are the sums of the digits in these blocks, in no particular order.
(A "?" may stand for any digit, but two-digit numbers may not begin with 0.)
The puzzle:
Links for online solving:
Solution code: The digits of row 4, read from left to right, with the letter I inserted between any two digits separated by region borders. (I as in Igloo.)
Comments
on 27. March 2025, 12:01 by PixelPlucker
Thank you all for your nice comments!
I have chosen to reveal an additional clue to make part of the solution path easier, as I have come to believe that this would improve the puzzle overall. The "??" in R2C1 is now a "1?"; the image and links have been updated. All valid deductions that can be made in the previous version remain available. Thanks for understanding!
on 27. March 2025, 01:24 by peacherwu2
Wonderful wonderful wonderful!
on 20. March 2025, 13:23 by MagnusJosefsson
Fantastic puzzle, very challenging and rewarding!
on 20. March 2025, 09:44 by marcmees
One of the hardest CC's made lately. Great concept. Very satisfying solve. Thanks
on 19. March 2025, 20:58 by Jesper
Great CC, enjoyed it a lot!
on 19. March 2025, 10:11 by PixelPlucker
Clarified the solution code
on 19. March 2025, 06:02 by henrypijames
Yeah, is that a uppercase-i, a lowercase-L, or a pipe symbol? In any case, it requires constant switching of keyboards on a mobile to enter. Much better to use a simple hyphen "-" which is unambiguous and part of virtual numpad.
Really tough puzzle, full 5 difficulty. I had to constantly remind myself that a region might contribute to more than one block around a clue - that made the endgame even harder.
on 18. March 2025, 20:52 by Da Letter El
took me a second to realize that solution code wants an "I" as in Igloo to separate the digits. really fun puzzle
on 18. March 2025, 10:20 by Piatato
Awesome puzzle, with a lot of that good old PixelPlucker arithmetic magic! :-D
