## Region Geometry

(Eingestellt am 13. Mai 2022, 18:29 Uhr von kolot)

After my X-sums and Sandwiches puzzle, I was thinking whether I can construct a Chaos Construction sudoku with an empty grid and only question mark clues outside the grid. I was not sure about which constraints to use. After the puzzles Thonk? by purpl and Ilsensine by KNT, I decided to try Skyscraper and Numbered Room variants, and together with the region constraints they worked even better than I thought. Finally, I got this puzzle. I hope you enjoy it. Your comments and ratings are highly appreciated as usual!

RULES: Each row, column, and region must contain the digits from 1 to 9 exactly once. Each region is a set of orthogonally connected cells and must be determined by the solver. Clues outside the grid represent any integers from 1 to 9 inclusive, and they act as both skyscraper and numbered room clues with additional region constraints.

Skyscrapers: Considering each digit in the grid as a skyscraper of that height, clues outside the grid indicate the number of skyscrapers seen from that direction where taller skyscrapers hide the shorter ones. For each clue, all visible skyscrapers must be in different regions.

Numbered rooms: Clues outside the grid indicate the digit in the Nth cell from that direction where N is the digit in the first cell from that direction. For black clues, the first and Nth cells must be in the same region. Red clues may or may not obey this region constraint.

NOTE: If you feel stuck and need help at any point during your solve, please feel free to contact me at CTC Discord server or leave a hidden comment here. I will be very happy to give you a hint for the next step.

CHALLENGE: I would like to note that this puzzle is not exactly in the form I was thinking of when I started constructing it. I leave it as a challenge for everyone to construct a 9x9 Chaos Construction sudoku with an empty grid and only question mark clues outside the grid where exactly the same rule applies to all question mark clues in their respective row/column.

Lösungscode: Row 7 followed by column 5.

Zuletzt geändert am 20. Mai 2022, 16:33 Uhr

Gelöst von Niverio, purpl, KNT, polar, marcmees, Jesper, LittleBallOfPurr, Lizzy01, DVFrank, ns08, ma3n, MagnusJosefsson, tinounou, henrypijames, Mr.Menace, Piatato, Agent
Komplette Liste

### Kommentare

Zuletzt geändert am 26. Mai 2022, 04:50 Uhr

am 26. Mai 2022, 00:49 Uhr von Agent
This is a masterpiece. It's still amazing to me that this puzzle solves uniquely with so little clues. Thanks for creating this!
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Thank you for solving the puzzle and for your kind words!

Zuletzt geändert am 24. Mai 2022, 21:59 Uhr

am 24. Mai 2022, 21:48 Uhr von Piatato
Just a magnificent achievement! Such a fantastic construction, with wonderful logic throughout! Felt reasonably smooth too — took me about two hours. Made a penpa link with answer check if anybody wants one: https://tinyurl.com/yuk8jj8k
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Thank you so much for solving the puzzle, for your kind comment, and for providing a Penpa link! I am happy to see that you found the puzzle reasonably smooth.

Zuletzt geändert am 24. Mai 2022, 21:27 Uhr

am 24. Mai 2022, 21:23 Uhr von Mr.Menace
What a journey. Had to let it rest for more than a week, but got back into it and solved it. Very satisfying and a great feat to construct something like this. Hats off to you!
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Thank you so much for getting back to the puzzle and cracking it, and for your very kind words!

Zuletzt geändert am 20. Mai 2022, 18:45 Uhr

am 20. Mai 2022, 18:34 Uhr von henrypijames
Incredibly hard puzzle with a brutal break-in - as bewildering as it looks on the onset (unlike X-Sums & Sandwiches). Feels really good belonging to the selected few who have cracked this one.
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Thank you so much for giving it a try and cracking it.

am 20. Mai 2022, 16:32 Uhr von kolot
Minor change in the wording of the rules.

Zuletzt geändert am 19. Mai 2022, 11:25 Uhr

am 19. Mai 2022, 11:07 Uhr von MagnusJosefsson
An amazing puzzle! Incredible interesting and challenging logic all the way from the initial steps through to the end. Quite an achievement to set this with so little information in the clues!
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Thank you so much for these very kind words and for solving the puzzle!

Zuletzt geändert am 16. Mai 2022, 15:18 Uhr

am 16. Mai 2022, 15:11 Uhr von DVFrank
Wow, what an incredible construction! It took me absolute ages (about 4 hours over the last few days) and I broke it twice. That must have been one of the hardest but also most rewarding puzzles I ever solved! Thank you for setting this beast :^)
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Thank you so much for this great comment and for your patience while solving the puzzle!

Zuletzt geändert am 16. Mai 2022, 13:37 Uhr

am 16. Mai 2022, 13:30 Uhr von Lizzy01
Very nice, and very hard! It took me 198 minutes and a hint, but I got through it! Awesome puzzle, HAS to get on ctc!

I have set a chaos construction with lots of ?? recently too, but it's not as empty, and most definately not as hard! You might like to look at it here:
https://logic-masters.de/Raetselportal/Raetsel/zeigen.php?id=0009JY
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Thank you so much for solving the puzzle and for your very kind comment. I have solved the puzzle you suggested. It was a very nice puzzle with some very nice logic. I also recommend that puzzle to everyone.

Zuletzt geändert am 16. Mai 2022, 04:19 Uhr

am 16. Mai 2022, 04:13 Uhr von LittleBallOfPurr
What a brutal yet beautiful puzzle. My poor brain hamster are exhausted from running in overdrive on their wheels the past few days. This seems right up Simon's alley, can't wait to watch him make deductions in 4 seconds that took me 4 hours, CTC <3

Thanks so much Kolot, for the wonderful puzzle and for helping me understand a few mistakes along the way!
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Thank you so much for you patience and keeping up with the puzzle! Also, thank you for your very kind comment!

Zuletzt geändert am 15. Mai 2022, 12:49 Uhr

am 15. Mai 2022, 12:40 Uhr von Jesper
Marvelous, thanks!
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Thank you! :-)

Zuletzt geändert am 15. Mai 2022, 09:20 Uhr

am 15. Mai 2022, 08:56 Uhr von marcmees
After showing me my (silly) mistake in C9, the puzzle changed completely into a wonderful journey via excellent deductions. thanks.
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Thank you so much for completing the puzzle. I am very happy to see that it was a wonderful journey for you.

Zuletzt geändert am 15. Mai 2022, 08:10 Uhr

am 15. Mai 2022, 06:29 Uhr von polar
Totally enjoyable and absorbing puzzle from start to finish. Thank you very much!
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Thank you so much for solving it! I am really happy to see that it was enjoyable.

Zuletzt geändert am 14. Mai 2022, 20:11 Uhr

am 14. Mai 2022, 20:09 Uhr von KNT
this is unbelievable
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Thank you! :-)

Zuletzt geändert am 14. Mai 2022, 18:53 Uhr

am 14. Mai 2022, 18:48 Uhr von purpl
I spent over an hour with a broken grid before I got some assistance from the constructor himself, but every deduction was such a blessing. I cannot express how much I loved this puzzle, I am so happy to have inspired this with Thonk?

I cannot think of another puzzle I have enjoyed so much despite accidentally breaking it 3-4 times. To solvers: Do yourself a favor and solve this puzzle!
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Thank you so much for inspiring me with the puzzle Thonk?, for solving this puzzle, and for your very kind comment!

Zuletzt geändert am 14. Mai 2022, 14:23 Uhr

am 14. Mai 2022, 14:11 Uhr von Niverio
Masterful. Every single deduction is so hard, yet is so rewarding. 5 difficulty is an understatement, but the way the puzzle resolves at the end is just glorious.
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Thank you so much for being the first solver of the puzzle and your great comment!

 Schwierigkeit: Bewertung: 100 % Gelöst: 17 mal Beobachtet: 3 mal ID: 0009WX

Lösungscode: