Region Geometry
(Published on 13. May 2022, 18:29 by 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.
Solution code: Row 7 followed by column 5.
Comments
on 31. March 2024, 06:46 by Mr.CHEN
A Chinese solve video(SPOILER ALERT):https://b23.tv/J45UOmQ
on 13. March 2024, 00:33 by Fool on Hill
I made a couple of mistakes in solving this - including miscounting a numbered room clue and retaining legacy pencil-marks. Once I nailed those it solved - smoothly but far from easily.
I did think I would have to wait till after Easter to get it done - glad to have made it before.
Just a brutal, brilliant conception and execution. Fully 7/5 for difficulty and will only ease slightly by familiarity with aspects of the logic.
on 5. March 2024, 23:34 by Tim Dunkley
Brilliant. Brutal but loved it. Four hours 13 minutes for me.
on 5. March 2024, 19:34 by OGRussHood
I thought that X-Sums and Sandwiches was mad. This puzzle was... yeah, I have no words for how mad this construction was. I was solving along with Simon's bonus video, and I beat him by about 45 minutes.
on 24. February 2024, 16:23 by wand
phew, the deductions during the break-in were very exciting and led to a relatively smooth first half. stuck for a while in the middle, but the breakthroughs there were just as satisfying, and never as difficult as I feared. great puzzle
on 22. February 2024, 22:47 by zzw
Completely insane that this works at all, and to be so smooth and fun too... Incredible puzzle!
on 22. February 2024, 22:45 by Myxo
Wow! An absolute masterpiece!!
on 10. February 2024, 20:10 by Chilly
Well, that was amazing! Required two solves since I broke it really close to the end, and didn't have the energy to rewind until I'd taken a long break. What's most amazing is that it has a unique solution at all :)
on 15. September 2023, 12:14 by nervyplant
Finally got it! Forgot a rule and spent a good day bashing my head against a wall but a beautiful puzzle.
on 7. July 2023, 12:36 by Yann
Oh my god, what a puzzle ! Probably the hardest and most rewarding one I ever solved. Each step felt miraculous but intended, and they were all so clever and beautiful that in the end, the difficulty didn't latter. Those rows 6-9 were incredible, and the regions are so restricted. To come up with that logic is an (almost) impossible task, but to set it with only question marks is one step further. Thanks for this puzzle, kolot.
Ps: I found it much harder and much more beautiful than the x version, but that puzzle's smoothness is something else.
on 12. February 2023, 01:34 by joecat
What an amazing puzzle. Thank you.
on 20. November 2022, 01:02 by lerroyy
Incredible puzzle!
on 4. November 2022, 18:34 by halakani
Probably the best puzzle I have ever solved.
on 25. October 2022, 17:03 by peacherwu2
Have to be this difficult?!
on 8. October 2022, 00:10 by ONeill
You really weren’t kidding when you said region geometry. This is an incredible construction, I’m scared of the second…
on 6. June 2022, 22:33 by numslinger
I've only been solving sudoku puzzles for a few months, and I don't know what got into me thinking I could attempt this monster... But I solved it, after almost six hours! After that miracle, I couldn't resist making an account just to see my name listed in the handful of people who've cracked it. I'm quite proud of myself!
Thanks kolot for the joy of the puzzle, and for alleviating what would otherwise have been a rather dreary day!
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Thank you so much for solving the puzzle and for your very kind comment! It is amazing for me that this puzzle made you create an account for just submitting your solution. I am not sure if it was really intended but it seems like you reduced the rating of the puzzle from 100% to 99%. In any case thank you for your rating, 99% is a very good rating.
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Well, seeing as this was my first puzzle submitted, I thought I shouldn't give it a "very nice" rating as I have nothing to compare it to. But you're right, it is a shame to bring down the overall perfect rating solely for this reason. I have changed my rating :)
Besides, now this can become my point of comparison!
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I respect your reasoning. It makes perfect sense. It would be fine with me if you didn’t change your rating. Thank you anyway!
on 3. June 2022, 19:17 by Garford
Bam! Took 2,5h to solve. What a great puzzle! Thanks for setting it.
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Thank you so much for your time!
on 3. June 2022, 00:19 by Prutsbeest
Wow, what a puzzle! I can't even imagine how you set a monster like this :-) thanks, kolot!
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Thank you for the solve and this kind comment!
on 31. May 2022, 22:33 by Vebby
Great puzzle! Quite a challenge to solve. The logic was fresh, interesting and rewarding. Thanks Emre! It's been a pleasure going through your catalogue. :)
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Thank you very much Vebby, for solving all of my puzzles. I really appreciate it.
on 30. May 2022, 12:00 by Lizzy01
I just published a puzzle inspired by this, you might like to have a look at it:
https://logic-masters.de/Raetselportal/Raetsel/zeigen.php?id=000A1U
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It looks very interesting. I will have a look.
on 26. May 2022, 00:49 by 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!
on 24. May 2022, 21:48 by 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.
on 24. May 2022, 21:23 by 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!
on 20. May 2022, 18:34 by 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.
on 20. May 2022, 16:32 by kolot
Minor change in the wording of the rules.
on 19. May 2022, 11:07 by 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!
on 16. May 2022, 15:11 by 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!
on 16. May 2022, 13:30 by 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.
on 16. May 2022, 04:13 by 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!
on 15. May 2022, 12:40 by Jesper
Marvelous, thanks!
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Thank you! :-)
on 15. May 2022, 08:56 by 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.
on 15. May 2022, 06:29 by 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.
on 14. May 2022, 20:09 by KNT
this is unbelievable
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Thank you! :-)
on 14. May 2022, 18:48 by 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!
on 14. May 2022, 14:11 by 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!
