A RIDICULOUS Miracle Sudoku

*** TODAY'S PUZZLE ***
A pretty astonishing sudoku this evening from Shady Moon. Not only because it seems to contain barely any information in the grid but because this is the first puzzle Shady Moon has ever created! It's called Humidex and it's weird, wonderful and certainly miraculous!

Play the puzzle at the link below:

Rules:
Normal sudoku rules apply. Each digit in column 1 indicates the position of the 1 in its row. (eg if R5C1 is a 6, then R5C6 is a 1 as the 1 must appear in the 6th position). Column 5 operates the same way for the digit 5; and column 9 for the digit 9. Each digit in row 1 indicates the position of the 1 in its column. (eg if R1C5 is a 6, then R6C5 is a 1). Row 5 operates the same way for the digit 5; and row 9 for the digit 9. On thermometers, digits must increase from the bulb end. Along the marked diagonal, digits must not repeat.

*** FEBRUARY SUDOKU HUNT COMPETITION CLOSING SOON ***
Our February sudoku hunt from the Paint By Numbers Institute closes tomorrow!. It's called Where's My Mamma and features 11 new puzzles (and Clocksmith's lovely artwork!).

Check it out for as little as $2/month here:

*** LIVE CROSSWORD MASTERCLASS ***
On March 21, Simon and Mark will appear at the Word=Puzzles conference at Magdelen College, Oxford and do a live episode of their crossword masterclass! More information here:

*** NURIKABE WORLD STREAM TUESDAY'S STREAM ***
You can watch the last stream here:

The game is available here:

*** NEW FOG APP IS OUT ON APPLE (!), STEAM & ANDROID ***
Brand new incredible Fog Sudoku puzzles by the likes of Phistomefel, Marty Sears, James Sinclair, Qodec, Dorlir, ThePedallingPianist, Sandra&Nala, Peter Veenis, Mr Menace, Florian Wortmann, Math Pesto & HalfBakedLunatic.

*** CRACKING THE CRYPTIC APP ***
Our main app (which is itself completely free) contains packs featuring Fog, Domino, Lines, and GAS puzzles, with a few special free sets as well! All the puzzles are hand-crafted by us and some of the best constructors in the world, with hints by Simon and Mark.
AppStore:
Android:

▶ SUDOKU PAD - Use Our Software For Your Puzzles ◀

You can input classic sudoku puzzles into our software and help support Sven, the programmer responsible for the wonderful user interface we all use to play these puzzles everyday. The app also comes with 12 handmade puzzles from us:

iOS:
Android:

ALSO on Amazon: Search for “SudokuPad”

▶ Contents Of This Video ◀

0:00 Intro music and puzzle introduction
2:11 Patreon competition closing tomorrow
3:32 Myxo's masterpiece
4:07 A viewer's email
9:19 Happy Birthday
10:31 Rules
13:21 Start of Solve: Let's Get Cracking

▶ Contact Us ◀

Twitter: @Cracking The Cryptic

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Simon Anthony & Mark Goodliffe
Box 102
56 Gloucester Road
London
SW7 4UB

(Please note to use our real names rather than 'Cracking The Cryptic'.)

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#sudoku #puzzle #miracle

[LearningRS]

Hello! shady moon here. This put a huge smile on my face, thanks for the feature! I've been watching CtC for 5 years and have always been a fan of 159 puzzles, but hadn't seen a double 159 before. This intrigue finally gave me the motivation to set something. As usual, Simon's brilliance brought out the best in the puzzle and also made me realize things I had missed even when setting. I think there are many more beautiful interactions to be had with double 159. Cheers!

edit: thanks for all of the kind words in the comments too, and y'all are pointing out many different interactions I am just learning now. Much appreciated!

[ChrisPalmer]

The interesting pattern that Simon is looking for at the end, is that 180 degree rotationally opposite digits sum to 10.

[bobblebardsley]

Aside from everything else, "We're going to continue uploading two videos a day for as long as we're able" was one of the most reassuring statements throughout the pandemic. I agree with everything in that email and if the person who wrote it happens to read this, I hope I may have contributed to the kindness you felt at some point during the past five years.

[daboffey]

Humidex is a number that measures how hot and uncomfortable the weather feels, based on the combination of temperature and humidity. It's also known as the humidity index or heat index.

[Daymickey]

I agree with this email wholeheartedly. I found this channel shortly after my husband left me and our 1 month old. It has been such a joyful escape in a time of extreme transition, pain, grief and anxiety. Every puzzle and video feels like going on an exciting adventure of the mind with friends, full of twists and turns, with Simon and Mark as our guides. And unlike in my life circumstance, there’s always a neat and happy ending along with a feeling of accomplishment. I went from just watching, to then trying them out along with the video, to know being pretty good at doing them on my own (sometimes!). Thank you for creating this super cool community and for being a safe haven for so many of us. ❤

[aragaer]

An easy break-in is to consider where 1 goes in box 1 -- it can't go on thermo and the only red cell it can go is in the corner. But if it goes on the diagonal and not in the corner it must be indexed by two equal low digits. So it does go into corner. Same goes with 9 in box 9. In box 3 corner digit can't be low or it puts 1 (another low) in same column and it can't be high or it puts 9 (another high) in same row -- and it can be neither 1 nor 9 from previous step. So it's middly but 4 and 6 put 1 or 9 onto wrong ends of thermo, so both top-right and lower-left corners are 5. This puts more 1s and 9s into intersections. Now 9 in box 1 can only go onto tip of thermo and 1 in box 9 can only go onto end of thermo -- indexed by 2 and 3 in column 9 and row 9. We have to put 46 and 78 onto red cells in box 1 which means 235 go into white cells and 2 can't go into r3c2 since that requires 1 in tip of that thermo. This places 2 and also we disambiguate 35 pair by seeing that 5 in column 3 would require 3 in column 5. Similar thing happens in box 9. After that the puzzle solves itself -- we only have to notice that we can't put 1 or 9 onto main diagonal so we can't place 4 in column or row 4 and 6 in column or row 6 in any of the red cells.

[nitka]

I don't usually comment on YouTube, but there is something so remarkable in this puzzle that I can't keep it to myself. Simon mentions at 1:03:33 that there has to be a pattern hidden somewhere, and indeed there is. It is the fact that cells "opposite" throughout the centre of the grid contain digits that add up to 10.

To illustrate what I mean, let's consider an example. In the finished grid, R7C2 is the digit 6. The opposite cell would be R3C8, which contains a 4. It is obvious that 6+4=10, and this works for any pair of opposite cells!

Now let's discuss how it works. One can notice that the board is quite symmetrical. To be precise, the thermometers, diagonal, and the 159 rule are symmetric under 180-degree rotation through the centre R5 C5 of the grid. However, after rotating, the thermometers are reversed (the bulb is in the wrong place). We can fix this by interchanging 1 with 9, 2 with 8, and so on. This way, if the sequence along the thermometer increased, it is now decreasing (as required for our reversed thermometers). I will now get quite technical to explain the process in detail. Consider an arbitrary cell in RxCy, i.e., with coordinates (x, y). By the 180-degree rotation, I mean another cell at (10-x, 10-y). Indeed, the opposite of (7, 2) becomes (3, 8), just as in the example. Let's say (x, y) contains a digit D. The operation I tried to describe is "if cell (x, y) contains D, then put 10-D in the cell (10-x, 10-y).". Indeed, we can check that every rule is satisfied after this transformation! This means that the complete sudoku will have the digits in cells (x, y) and (10-x, 10-y) that add up to 10.

[GrandRand]

I concur with that email. CtC helped a lot during Covid and has been a welcome constant throughout these years. I also feel smarter and more thorough with the mindset that Simon and Mark exemplify. Funny how a simple puzzle game can elicit so much joy and discovery.

[paulunderwood]

The best ever foldable X puzzle ever ever. I've sent it to a friend and he printed it. He couldn't get it but he is now a CTC fan. He did it when you started him off. He is still watching old puzzles now so thanx and keep it going all of you. Even everybody else in the background we don't see. RESPECT. Over 5yrs and I'm still hooked. THANKS ❤

[garythegray]

That email was something I relate to even now. I have been scraping by with the same crippling anxiety and it's been a rough 6 years. CtC has been a comfort to me and I cannot begin to be able to express my gratitude to Simon and Mark for the calm I get whenever I watch.

[Mortan]

I have found that you get what you build. You and Mark have built a community of kindness with your kindness. This channel is a beautiful place of calm and genius where we can enjoy, play along, and struggle through life with great encouragement here.

[David_K_Booth]

This is a very elegant puzzle, both in its logic and the visual appeal of the grid. Well done Shady Moon for making a debut in such style.

[JPRobinso]

lovely email - hit me right in the feels. I'm only just not crying...
I tried this puzzle, it took me 148 minutes. Nice and easy if you plod at it. trying various options for 159 in boxes 159 and along the diagonal, opens things up, then noticing where 159 can/can't go. Fantastic.

[shawnmichajluk]

I was able to do it in under 30 minutes (had to restart once, also needed Simon's help at the beginning). That was a MIRACLE in more ways than one! Thanks for the puzzle and the solve!

[longwaytotipperary]

So much agree with the emailer! My heart goes out to them. The times we live in (in the USA) is very stressful. Some days I just can’t stand to watch or listen to the news. I am so thankful for this channel - I can tune out the world and listen to Simon’s soothing voice, his gentle humor, watch Mark take on Connections and Wordle and both of them explain cryptic crosswords. I also look forward to reading comments of kind, supportive folks. I enjoy and really need this community to stay somewhat calm and sane. Thank you - all of you!

[dustin_case]

I love that the implication of the rules being symmetric for low/high corresponding digits, plus the fact that the board is rotationally symmetric around 180° with flipping high/low corresponding digits, means that simply by analysing the board/rules, you could theoretically immediately place 5 in the center of the grid (since any other digit would break the high/low rotarional symmetry).

I also love how human brains are so good at finding patterns that even without understanding this underlying pattern, Simon, myself, and I'm sure many of you just KNEW deep down that the 5 had to be in the center, even if we couldn't quite express why

[JNaturman]

A 25:27 for me -- what an elegant puzzle! It felt like once I cracked how the indexing bounced around the puzzle I could ride the momentum all the way through. Great work, Shady Moon!

[reubenmckay]

In case it's not been pointed out already: The pattern is that when you rotate the grid by 180 degrees, the overlapping digits sum to ten (1 always ends up in a space occupied by a 9, 2 on a 8, 3 to 7, etc.). It's a lovely bit of symmetry in the puzzle.

[RomanPer]

One of these puzzles that just clicked right away for me. Just over 23 minutes.

[josephnation]

A few patterns in the grid in the vein Simon referred to:

Sets of 3 in index rows not only have the entropy constraint, but also have constant modularity

Sets of 3 in index columns, meanwhile, all have differing modularities such that they always add to 15.

Also it's a quick scan, but it looks like disjoint subset also holds.