The Fog Sudoku Theorem

[@ChrisNeffshade]

ChinStrap here. Thank you so much for the brilliant solve. It was a joy working with sujoyku! I really appreciate how much of the puzzle you demonstrated. I especially am glad you went back to find the real logic to resolve the green line without requiring diagonal vision gimmicks. While we did mention that the lines are thick and can be seen like that, we did that solely so that people wouldn't necessarily worry about it one way or the other. If we could do it easily we would rather they just not be there, but since they are inevitable if we have to reveal those cells, we might as well make them thick. But 100% of the solve path made sure to not need to utilize that. Thanks again and thanks to sujoyku for such a fun collaboration!

[@nilsleder2957]

What a treat! Thank you for this wonderful feature, Simon. I was so happy seeing you rewind once you figured out that the "eyesight test" was not needed for solving the puzzle. ChinStrap and I were torn about it (also in respect of rule wording): People who saw it might want to use it and that is fine. But we never liked to rely on this being an inevitable step for finding the solution. You followed our intended solve path and you trying to "disprove the truth" for the red line was giving me a broad smile. Thank you again so much for the solve! I also like to thank ChinStrap for this nice cooperation. He is not only a great setter, but also a very kind person to work with. Kind regards, Nils/sujoyku

[@martinbull-gundersen8878]

Thanks for a very nice puzzle! I was also very happy when he rewinded. My "screams" of index just took a little while to get through 😛

[@martysears]

This was fantastic work from two of the best (and nicest!) setters in the community - my collabs with them both have been joyous. The core conceit of this puzzle, the circles having to contain triangular numbers, was beautiful and simple, and thoroughly warranted this puzzle being made, despite the slightly clunky rules. Loved the aesthetic styling too, and some brilliant choices of fog reveals. And a perfect ending with the 5s, 6s and 7s. That sort of thing always tickles me for reasons I have yet to fathom. Excellent solve from Simon too, and I'm really happy he went back and found the more satisfying route at the end. I knew Chinstrap and Sujoyku would not have released a puzzle that relied on using the tiny diagonal sliver of green playing peekaboo. The dynamic fog thing is very interesting, because every time you get a reveal it feels so satisfying, and then any time you don't it feels a tad worrying, like 'have I made a mistake?' But from a setting point of view, you couldn't / wouldn't have every correct digit reveal something (which is what I tried to do the first time I set a dynamic fog puzzle with Rat Run 19), because then the whole flow ends up feeling very bitty and you lose that sense of the fog focussing your attention. I learnt that from Chinstrap. So it is much better to clump the reveals to happen less frequently, and as a solver, if you don't reveal fog after inputting what you feel is an important correct digit, the next thought should be 'there's probably a bit more sudoku I can do here...' (The setter can tell the puzzle to only reveal a fog cell when a certain set of cells are entered correctly, and if it's just a few bits of sudoku then its sometimes impossible for the setter to predict what order those cells will be filled) Great video! :)

[@nayanasilvers7501]

I am in tears I’m so happy to receive a birthday wish on the channel! I have been hoping since I found your channel that someone would send one in. (Definitely gonna give some kisses to my friends for remembering hehe)

[@jannemec2483]

I see a long video, that scared me away from solving myself. Whatever Simon cannot solve in about 45 minutes, I most probably can't solve at all. I will just had my fun watching instead! 🍿🍿🍿

[@AFT3RDAY5]

Actually those are the ones that intrigue me the most to try myself 😅

[@steveunderwood3683]

This one takes some time to work through, but it doesn't require any clever insight, like some of the puzzles he has solved on this channel. It didn't take me an exceptionally long time.

[@Ell355ar]

Whenever I see one of those intimidating puzzles, I follow along with Simons explanations until I feel like I understood enough to try on my own. Then when I get stuck again, I resume the video to see if Im on the right path. Took me til around 55:30 today (with a few breaks where I tried on my own), but after that I finished on my own. One day I wont need to take a peak at the vid anymore.

[@paula-zzz]

Cathi‘s poem is so beautiful, thank you Cathi (and Simon) for sharing it with us!

[@ronjohnson6916]

Love the rewind near the end. A much more satisfying end.

[@asliceofjackie91]

It's always fun watching Simon solve things with grid furniture. Even with the rules specifying "lines are thick to show diagonal movement", which I interpret as yes it is not only okay but even intended to use grid furniture clues, he adamantly refuses and finds different ways! Admittedly, I would be more insecure about it too if I was colour blind, I can't imagine what that's like!

[@craigfjay]

As much as I enjoy ChinStrap’s index lines, this puzzle proved impossible for me because the rules were not clear at all. I was trying to correctly place a diamond on the line next to a circle, but including the other circle as the last cell on the index line. Fair enough, I misunderstood the rules. But doing it this way still fits the wording of the rules, so they need to be made more clear by stating “the index line does not include the circle cells”

[@HunterJE]

Interesting having a line clue type with such a high minimum length-a pea-index line cannot have the line portion with a length of shorter than 5 in an otherwise standard 1-9 sudoku (would be considerably less constrained in a 0-8 variant though)...

[@HunterJE]

(Noticed this while interrogating whether the break-in deductions in blue are still valid under the later clarification by the reds that same-color clues can have multiple segments-the minimum length makes it impossible to fit a compound line and its circles there even without the 1-to-n restrictions)

[@HunterJE]

(And then unpaused and Simon noticed that same thing in a different context moments later hah)

[@Ardalambdion]

If Simon is so fond of fog puzzles, he should make an attempt to find some submarines with Marty Sears. That puzzle was released about 2 weeks ago.

[@martysears]

also by Chinstrap, another Chinstrap collab :)

[@ChrisNeffshade]

@@Ardalambdion I concur :)

[@A_CC_K]

Yes another fog of war puzzle. My evening is now sorted.

[@brickboy2096]

Does anybody know how to write in? It is my birthday coming up and I do not want to miss it.

[@FleckerMan]

Their email is towards the end of the description of the video, expand and scroooooll :)

[@eefaaf]

That bit of green in the corner was VERY hard to spot. Hadn't noticed it until Simon pointed it out, and even then I wasn't sure. Maybe they should have gone for a darker colour there.

[@penningmeestercgkdelft9159]

It is quite striking that the Hobbit sudoku hunt puzzle #5 (Riddles in the Dark) is the only puzzle in the series of 19 puzzles that consistently is solved by more people than the previous puzzle... This is true day after day that Simon shows the number of solves, I see. In all other cases, the trend along the number of solves of puzzle #1-#19 is almost linear (descending) on a logarithmic scale :-)

[@DoongXiouHua]

I solved the puzzle without using the green line in box 9. Actually I can't see it until I revealed the fog at R8C7, before that I was wondering why putting 5 in R8C8 didn't reveal any fog. The line is just too blur to be seen with fog covering around.

[@willpomeroy1743]

I struggle with pastel shades too. But as the last line of the rules hinted at the thick lines I could see no other reason for the 4 in box 9 showing that bit of line than to link with the green line.

[@PassionPopsicle]

Ooh, interesting. And by "interesting" I mean "I'm not touching that with a ten foot pole". Good luck, Simon! (Which you obviously don't need, seeing as you've clearly managed to solve the puzzle, but retroactively)

[@spatulamahn]

Index lines are Simon's kryptonite! Such a complex way of figuring out that the 8 can't be at R5C2 when he had that info 5 minutes earlier when he removed 4 from the 8th index!

[@spatulamahn]

And a minute later finally gets it! :)

[@MrBobopoe]

Wow, you must be pleased with yourself for spotting that.

[@penningmeestercgkdelft9159]

31:47 And boom! The 8 in r9c2 appears to be the golden digit clearing most of the sky at once 🙂

[@LednacekZ]

41:16 for me. Made a mistake on the green line, but got lucky and it was a very easy fix.

[@compiling]

Solved in 54:22, but I made a mistake during the solve because I couldn't see the bit of green line in box 9 and tried to make some deductions from its "absence".

[@НабокаДарина]

I always wondered does the melody in the beginning of each video has a name and/or a story behind it?

[@michaels4340]

1:18:02 for me, just narrowly skirting under the video length. Very nice puzzle :)

[@cotroneigiuseppe888]

Let's get cracking as always!!😂

[@PassionPopsicle]

He really should start saying "let _me_ get cracking" - I for sure would not crack anything but my sanity 😂

[@grahamania]

00:56:01 for me. Fantastic puzzle! Need to keep a keen eye out for the diagonals though :) Kind comment.

[@denisdodelin-m1e]

Yes, a very queen eye, I missed the last one and struggle for another 1/2h. Wonderfull puzzle anyway ^⁠_⁠^

[@Afterthoughtbtw]

Absolutely not as scary as I thought it was going to be. 33 odd minutes for me.

[@kayqm_711]

Why u changed the title😂

[@Paolo_De_Leva]

Lots of recommendations by the CTC community = guaranteed to be world (or even cosmic) class‼ 😏👍

[@Paolo_De_Leva]

*1-5-4* set of red peas = cosmic class‼ 😍👍👍👍

[@HunterJE]

Trying so hard not to use the kind of information that the last line of the rules pretty much explicitly says you're expected to use makes for a frustrating solve to watch...

[@PassionPopsicle]

He uses it a lot for the red line. Progress

[@spatulamahn]

Same thought I had!

[@nilsleder2957]

Even though it is of course fair to use this spot as a deduction, Simon did it in our intended way when he got back to that point.