This CANNOT Exist... (And Yet It Does)

** TODAY'S PUZZLE **
[Simon writes] I'm pretty sure now that this was a prank by Mark and that he didn't think I'd actually try this puzzle once I saw what it was... it's called Self-determination and it's the (unbelievable) work of Stephane Bura. It is the most daunting ruleset/grid combo I think we've ever seen. Good luck!!
Please do leave a comment if you enjoy this video - in our opinion, Stephane deserves all the plaudits in the world for somehow creating this one.
You can try it at the link below:
app.crackingth...
Rules:
Place the digits 1 to 8 in each row and each column. Each horizontal domino that has both its digits in the first 7 columns forms the coordinates of a digit in the grid: The leftmost member of the pair is its row. The rightmost member of the pair is its column. Its value is the row in which the pair is. For instance, if R4C1 contains 7 and R4C2 contains 5 then R7C5 contains 4.
More examples of how the rules work can be found here:
logic-masters....
** A New Series Of Videos On Patreon **
Simon & Mark have made a video in which they collaborate to solve the puzzle Jabberwocky by DadJokes as a special Patreon bonus video. The feedback so far has been wonderful - thanks to all those who've taken time to comment. Jabberwocky can be played here:
tinyurl.com/5n...
Join us on Patreon to watch the video for as little as $2/month here:
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We've released a FREE app full of handmade puzzles - simply download the Cracking The Cryptic app on Android, Steam or App Store and then select the 500k pack. We're streaming a playthrough of this app and you can watch the first two episodes here:
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The coupon code is “500SUBS” and it can be redeemed at checkout here:
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** Our New App Is OUT **
Our new app is OUT on App Store AND Android AND ON PC (via Steam)!!
We've completely revamped the interface. Now you download the basic app free and you can choose to download additional content. So there's a FREE pack of puzzles by Prasanna Seshadri and a paid pack: DOMINO SUDOKU!!! Prasanna's free pack includes one puzzle for each variant of our existing apps (so there's a killer sudoku, a miracle sudoku, a thermo sudoku, etc). Domino Sudoku is a pack of 100 handmade puzzles (40 on launch, 5 added each month for a year) by some of the best constructors in the World: Phistomefel, clover, jovi_al, Christoph Seeliger, Qodec, Sam Cappleman-Lynes and Richard Stolk have all contributed sudokus!!
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(Please note to use our real names rather than 'Cracking The Cryptic'.)
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[@wunderlicha1]

Watching Simon go through the 5 stages of sudoku grief is quite entertaining: -surprise -confusion -anger -birthday messages -curiosity

[@birthdaygirl1126]

This gave me quite a laugh! 🤣

[@xhoodyx]

This comment is so brilliant :)

[@belqazi]

pictures from people 😊 hey 👋🏻 😊 hey 👋🏻 hi mi 😊 😊 hey my

[@57daysproductions]

ngl this got me xD

[@deonas]

🤣🤣🤣😂😂😂😂

[@StephaneBura]

Thank you for the feature and the wonderful solve, Simon. This puzzle took me weeks to set - it's the puzzle that took me the most time. I indeed wanted to make a puzzle with minimal information given to the solver, hence the self-referential structure I had played with a bit in the past ("Coordinate Sudokus" on LMG). The core insight for me, after understanding the role of the diagonal and the 8s, was to realize what RxCx represented. If you follow the logic, its value must be the position of x in column 8. From there, you can build a puzzle that follows those rules, instead of blindly searching for a grid that works. I'm sorry I scared you but you made my work worth it.

[@davidrattner9]

As Simon would say..Absolutely bonkers from you..just mesmerized how you came up with this!! Phenomenal!!

[@kathyjohnson2043]

Your efforts are truly appreciated!

[@pouletbelette]

Sorry your comment hasn't been pinned (yet), Stephane. Thank you very much for leaving it, though. Excellent puzzle, mind blowing new logic. It will definitely inspire other setters.

[@StephaneBura]

@@pouletbelette Thank you :)

[@Xerion404]

this looks like some of my more fun creations in excel ;)

[@allhailklisz]

This must be the sort of reaction Mark hopes for when he asks Simon to open the puzzle on-camera.

[@brianj959]

I couldn’t stop giggling!

[@humanbirdsong]

Same! This properly tickled me.

[@andrewsparkes6275]

"hopes for"? He knows Simon pretty well. He KNOWS that'll be the reaction Simon will have, and that' exactly why he asks him to do it!

[@letMeSayThatInIrish]

Mark is at it again with his nice little challenges 😄 Personally I have looked at this on and off for hours and still haven't filled in a single digit.

[@emmahird2795]

Apparently mark expected Simon to just switch off the video

[@sallad814]

Simon’s out here solving impossible puzzles in an hour all the while I’m out here trying to figure out which one is a column and which one is a row.

[@nstents7781]

Exactly. It took me 10 minutes to figure out he was counting from the top left, and not the bottom.

[@humanjuices]

very good joke

[@xChikyx]

lol me too xD

[@Emulleator]

column= think of Greek Colums, the one they used on their temples and rows well they aren't columns

[@EmberLeo]

... I think as long as your answer is *consistent* it should solve? Though not for the checker...

[@juliadefranco1130]

I love how Simon manages to be simultaneously very smart and very good at not making people watching the videos feel dumb. It's an impressive combination to pull off and he makes it look easy.

[@dudeilligence6441]

Yeah until he said "I haven't had an intelligent thought in the past 20min" and you worked on your own up to the same point he did 😂 basically meaning my 20min of work was basic level dumb 😂

[@indigoziona]

​@@dudeilligence6441and it took me longer than 20 mins, hahaha... and I felt smart!

[@ruthphelps1440]

The way Simon said, "I'll do the birthdays" killed me. 😂

[@B1GB1RDB4G3L]

Hehe he’s so cute :3

[@chironchangnoi]

I'm super glad I didn't try to get a birthday shoutout today! Hahahahahaha

[@karynmorton4843]

Lol Yes.

[@Bruno-xs3xl]

4:42 😂

[@AngelWedge]

I wasn't paying much attention at that point, trying to see how many digits I could get in the grid before he started (usually I don't get any, so this puzzle was a lovely ego boost)

[@jamesandrewes9640]

Simon: “This is something you take on holiday with you, and you have it by the side of the pool, and you look at it occasionally and just shake your head and go back to drinking your mojito, and, you know, maybe at the end of two weeks you have some sort of thought that allows you to make some sort of progress so that in six months time you might be able to solve this puzzle.” Me: … notes video is an hour long…

[@iabervon]

When he said that, I immediately thought "How many mojitos is he going to drink in the next hour!?"

[@KusaneHexaku]

@@iabervon tell you what, that'd make good Patreon content

[@956675]

@@KusaneHexaku yep, I'd increase my patron if Simon did that. Or maybe as a live stream so I could effectively buy him a drink.

[@Rdlprmpf12]

22 min 13 seconds between first pencil mark and puzzle solved. The rest is complaining that it's impossibly difficult. For the Americans: I'm just kidding, of course...

[@skasperl]

Some holidays go by so quickly...

[@shalaz1981]

Mark understands what makes for good content. Simon is likable, why not torture him. 😈

[@TheRoblington]

Immediately one of my favourite ever comments.

[@UTU49]

Isn't that a trope called "breaking the cutie"?

[@KeithOlson0326]

This comment currently has 666 likes. 😈

[@chitraagarwal8259]

The moaning was thoroughly justified... And the solve that followed was just exhilarating! While the puzzles like the 16x16 filomino and the various yin-yang logics come naturally to Simon coz of his vast experience in solving those puzzles, today was a reminder of what makes him truly great. There are many great solvers who would probably crack this in less than an hr but only Simon can do this in an in camera video without taking a break or a walk around to let the logic seep in. Perhaps thats the reason why he is such a precious resource for the whole community. The way you can be intuitive about a solution to a puzzle with a never seen before logic while continuing to think aloud for an hour is absolutely rare and unparalleled.

[@LyuboRyuk]

❤️

[@Aerialdan1]

The funniest bit was when Simon sighed and said, "I'll do the birthdays." LMAO

[@Antinomiste]

Simon: "I've spent 7 minutes complaining, haven't I ? I'm so sorry..." Me: that is the best video on the channel so far

[@gregind01]

Definitely the most hilarious video intro ever!

[@BeheadedKamikaze]

@@gregind01 My day is made, and my enjoyment immeasurable!

[@tarotfool07]

"It's impossible...it must be broken...it can't be solved...OK, I'll have a go...Oh look, I've solved it...". Simon said exactly the same thing about the original Miracle puzzle.

[@TheGerkuman]

Eventually he'll learn to believe in himself!

[@FireSiku]

It reminds me of the original Wrogn puzzle as well. "Its impossible! We have no information! Everything is negative! It cant be solved... Oh, but I suppose its either a 1 or a 9 in this cell. But its impossible! Oh, and the next cell to it has to be a 1, so I guess that's a 9... But this IS UNREAL! There is no way it can be solved beyond these two digits. It was a fluke! Oooh, 5 goes in this row. THIS IS UNSOLVABLE"

[@dragonspight]

The five stages of Cryptic

[@newp0rt]

@@FireSiku reminds me of playing a video game. "this game sucks! i hate it!" while playing it for the next 12 hours. it is what it is. smack talking a frustrating task while continuing to complete it is just the way of life. "this task is too hard its impossible!" an hour later and its done.

[@TheSSBOABand]

At 56:20, Simon says something about making the purple area a torus somewhat jokingly. Fascinatingly, that actually works, and if you treat column 7 and 1 as a domino with 7 as the row indicator, they all map correctly

[@BookofAeons]

In fact, they must work that way. Discovering that was my final step to cracking the puzzle

[@TempuraFriedJoystick]

Funnily enough, that was one of the first things I thought after reading the rules - heavy study into graph theory and that kind of stuff, mapping digits onto toroids, came to me as an intuitive jump from the self-referencing aspect. Super cool to see, and it tells me that Stephane probably comes from a math background!

[@LavenderGooms]

Similarly column 8 references back to the negative diagonal if you treat it as a double coordinate. R7C8 is a 5, and R5C5 is a 7.

[@nevrwork]

This is amazing.

[@MrRenneck]

Fist thing that came to mind after seeing the rules was the prisoners delimma problem. That and Markov chains... no idea still if there's a relationship there, but this fact about making the puzzle into a torus makes me happy lol

[@EnemyStand]

Simon: Proceeds to solve an insane puzzle Also Simon : "I don't know how I did this"

[@YourGlenn]

I can't believe they actually managed to solve this without even using a lot of the dominoes that got filled throughout. The amount of times they reasoned what a certain cell had to be using other indicators, only to find out the domino pointing to it was already filled, actually made it more impressive!

[@Coldheart322]

Seeing this and all the other "am I actually going to be able to solve this" videos, I really want to see a compilation of videos Simon doesn't finish. What twisted, fiendish puzzles are truly so difficult they never see the light of day.

[@emanuelebabici]

I think it's those that don't follow a linear logic, but rather a a logic that develops in parallel ways and forces you to bounce between them constantly. I believe that if there is any linear logic, Simon is able to crack it step by step after having the initial intuition, but I've seen him absolutely confused in a puzzle where he had to continually bounce between tho thinking processes. The other type of puzzles that never saw the light, are probably those where he couldn't get the initial intuition that allowed him to crack it digit by digit

[@MartinFindon]

You know it’s going to be good when Simon says he’s going to turn the camera off! 🍿

[@TheFrogfather1]

and yet there is a video so you know he didn't :P

[@BeheadedKamikaze]

@@TheFrogfather1 it is interesting to ponder how many videos got started, that we didn't see!

[@kamilkaczmarz3080]

@@BeheadedKamikaze Simon said in an interview I saw on LinkedIn that on average this happens on about 1 in 5 videos

[@BeheadedKamikaze]

@@kamilkaczmarz3080 wow that seems like a lot! Bit of a shame. Thanks for the info!

[@Rose-ou2xj]

I am creasing myself at how resigned he sounded at ‘I’ll do the birthdays’

[@thoughtbyte]

This one took me 2.5 hours. I never would have imagined solving something like this until recently. Mark and Simon, you are like mentors to me in what has become a cherished hobby. Thank you so much! And bravo Stephane, this one was mind blowing, and one of the solves im most proud of.

[@StephaneBura]

Thank you :)

[@BaldorfBreakdowns]

Ey, it took me 2.5 hours too!

[@maximilianmaier3950]

I'm 9 years old and I solved it in 2 minutes

[@emilyscloset2648]

@@StephaneBura +1

[@bowzert]

@@maximilianmaier3950 900+ IQ

[@Veeno00]

That's probably the most dejected "let's get cracking" ever uttered by Simon. 🤣

[@noambbyp]

I'm proud of myself for realizing the negative diagonal never can be indexed before Simon did. Still wouldn't have had a chance of solving this myself. Well done!

[@markthompson2874]

Same thing for me. I was thinking they'd all be 8s at first.

[@jasond4084]

Me too! I am a little disappointed Simon didn’t “click tick…Yay!”

[@bennettgardiner8936]

I'm still confused which OTHER cells can't be indexed, didn't we say there are only 48/64 cells that are being indexed, where are the other 8?

[@markthompson2874]

@@bennettgardiner8936 they're being indexed using columns 7 and 1 with column 7 being the row and column 1 being the column. It just didn't need to be stated in the rules for an unambiguous solution.

[@adrianp5465]

@@bennettgardiner8936 both diagonals don’t seem to be indexable

[@TheArmyKnifeNut]

I just discovered your channel with this video and possibly the highest praise I can give you is that you are the Lockpicking Lawyer of Sudoku.

[@MeriaDuck]

Welcome to the channel, there are lots of very lovely videos to watch. The one that got me here is the very great Miracle Sudoku. Certainly recommend that.

[@HonkeyKongLive]

That rule set is both batshit crazy and absolutely genius.

[@jimmyh2137]

You know what they say, "there is a fine line between..."

[@Nevir202]

@@jimmyh2137 I'd say it's more of a blurry line lol

[@fiona4450]

I loved this. Also, Simon: "This is *impossible!*" who then proceeds to spend an hour proving that it is indeed possible. Very enjoyable to watch you solve this, Simon.

[@brockjansen1617]

I don't always watch second-by-second, but I always turn and watch when Simon says, "Ah..."

[@NeroSaja]

First he says he knows it and it's impossible to solve. Then he tries to reason logically why it is unsolvable and starts to bite himself. After that he tries to explain to himself that it is unsolvable and hangs on the hook. Then a logical thought comes to him and in 20 minutes it is solved. 😂 No matter how you do it, it's great to watch you do it again and again. Awesome job! 😁👍

[@Cheeseyx13]

There's a couple of very elegant hidden 'features' to this ruleset that Simon didn't see. First, that you can take a 'domino' with the first digit from the 7th column and the second from the 1st column, and that must be an accurate indexing by the pidgeonhole principle. That means you have a full 48 cells indexed, missing only the major diagonal (which is pseudo-indexed by column 8). Second is how the solution creates diagonal bands of the digits 1-7 in increasing order, which wrap at the edges of the box containing the first 7 rows and columns. In fact this ruleset with a blank board has only seven valid solutions. In that sense, giving the 1 as a given digit was a bit generous, rather than something like an arrow or line that would only provide a useful clue once you fully understand the symmetries required by this ruleset.

[@Arkhs]

Goddamn. I was impressed with his ability to figure things out. The fact you got so many other hidden rules and figured out all the valid possibilities in an empty grid is just amazing to me.

[@ankitlamsal1098]

He actually does figure the first one out at 56:21 and just ignores it😂

[@j.tizzyy]

If you try the possible starting positions for the 1, only the one given in this puzzle leads to a valid solution. So a complete blank board only has 1 unique solution

[@r4vendusk]

@@ankitlamsal1098 One could be a coincidence though, not that strange to ignore it.

[@ankitlamsal1098]

@@j.tizzyy that is actually what I meant!!(without using the word coincidence)🤦… why else would he ignore it!?

[@michalinamaniecka6614]

I love when Simon in any crazy sudoku says 'Ah' because I know that after this he will do something epic

[@humanbirdsong]

I think I’ve watched the introductory “contains a 4… what… why?!” moment about 15 times now. Your baffled, almost indignant incredulity is inadvertent comedy gold and my favourite intro in CTC history. Great solve!

[@coconuts2513]

Laughed so hard 🥳

[@isaacpianos5208]

The vocabulary of the people that watch this channel oftenly is so satisfying to see

[@tomr6955]

@@isaacpianos5208 I like oftenly lol

[@XpOzgamingx]

Can't stop laughing at the introduction.

[@alexandragoff6609]

Ikr! Reads the instruction, reads an example following the instructions, baffled “What? why?”: perfect reaction, lol. Also the blatant assumption he’s going to turn the video off. Absolutely hilarious!

[@amysteele2488]

A simple like is not enough for this incredible puzzle, and equally incredible solve. It would probably have taken me well over 6 months to puzzle this one out. Well done Simon and Stephane. Amazing! Still shaking my head in disbelief and will probably need to watch this again later to fully grasp the beauty of it

[@emilywilliams3237]

Well said!

[@MartinFindon]

04:30 *sighs* … I’ll do the birthdays” ha ha!

[@davidsingleton5432]

Just noticed this after the puzzle was solved. But the purple cells wrap around and still reference cells with column 7 and column 1. For example, R1C7 is a 7 and R1C1 is a 3, so R7C3 is a 1. This works for all the Column 7/1 pairs.

[@six_5000]

Simon noticed this too but he didn’t explore it

[@ildar.ishalin.chelovek]

56:13 he notices it, marks as weird and never goes back to😄

[@AngelWedge]

It has to. The two "unreferenced" copies of each digit must be in the two rows and the two columns that don't contain a referenced one. So the row numbers of the unreferenced digits are in columns 7 and 8, and the column numbers are in columns 1 and 8. So either column 8 references the position of a digit on the main diagonal and columns 7 and 1 are a wrap around domino, or there's a domino in columns 7 and 8 and another wraparound one in columns 8 and 1. The second option is ruled out because it makes the number of dominoes greater than the number of non-diagonal cells in the grid. Maybe my brain's weird, but that was my starting point :)

[@nonyobisniss7928]

​@@AngelWedge That would have been a good way of figuring out that all non-diagonal squares are pointed to by a domino in the pinks (including the wrap arounds mentioned above), but I'm not sure it would have helped much, except giving you more options for how to deduce the numbers at the end maybe.

[@Qsalis]

the last column gives info on the double-coordinates diagonal if you treat it as double digits

[@MarushiaDark316]

This is a puzzle that truly reveals Simon's genius, since I probably still wouldn't have gotten it after six months and he managed to do it in an hour.

[@Zardox2]

When Simon starts a video with such severe doubt... I gotta laugh, heartily, at the "Try it yourself" suggestion. Yeah, no. But will enjoy watching this head scratcher. You are a very brave man, Simon. I would have picked a different puzzle, restarted the recording, then called Mark for a belly laugh over his puzzle choice.

[@AlonAltman]

Some interesting facts about this structure: * As Simon guessed indeed the C7C1 pairs are also indexing resulting in a torous. * C8 ends up just indexing the diagonal I wonder how many solutions exist without the given 1 and how they vary. I'm also wondering if this pattern works with other sizes.

[@StephaneBura]

There are two 8x8 valid grids. The other one has the 1 in r8c3, but this one is more fun to solve. There is one valid 4x4 grid, two 5x5, and two 9x9.

[@HonkeyKongLive]

This one really makes me wonder if there can be a puzzle that is a truly blank grid (no cages, no dots, etc) with a rule set that only yields one solution without being overly complicated.

[@StephaneBura]

@@HonkeyKongLive I was shooting for it. The search continues :)

[@VeritasUnae]

@@StephaneBura I look forward to the results of your search!

[@tomsommerville]

Not only does the C7C1 domino work, but start with each 1 in the grid, and draw a line down to it's right. At row 7, wrap around to row 1, and at column 7 wrap around to column 1, but each time you wrap, add one row or column. You end up with 6 strings of the digits 1-7 in order :)

[@adabartta]

I love how you can actually reference every cell in this puzzle. Every legitimate domino references a cell(there are six dominos per row), every seventh and first cell of each row form a seventh domino (for example [1,7] = 7, [1,1] = 3 => [7,3] = 1), and every cell in the eighth column is an eighth same digit domino (for example [2,8] = 7 => [7,7] = 2). That means there are eight references per row and there are eight columns, so there are 64 references, which is equal to the number of numbers in the grid. Such wonderful design.

[@AmanuelNega]

This doesn't make sense, why? How did you derive that?

[@jesss.5864]

It does make sense, but the original commenter got their math a little wrong. They pointed out that the 7th and first cell in each row also form a domino (in a wrap-around sort of logic) that also indexes another cell. This was an awesome realization that I had missed and so had Simon. However, they claimed this makes 8 dominoes per row, but actually it creates 7 dominoes per row. 7 dominoes multiplied by 8 rows is 56 cells. “What are the last 8 cells then?” You may ask. Well, that would be the cells highlighted in yellow that cannot be indexed (1,1 2,2 3,3 etc.)

[@adabartta]

@@jesss.5864Yeah I guess I worded it a little wrong. I don’t think I got my math wrong though. The first seven cells in each row form seven dominoes, which means that’s 7x8=56 references. The last cell in each row is a domino by itself, making it both the x and y axis so to speak. So that’s another 8 references, making it 64 🤔 For example the number, let’s label it x, in the [1,8] cell ([1,8] = x) will be the coordinates for 1 on the diagonal ([x,x] = 1) The same goes for [2,8] = y … [y,y] = 2 and so on. If there are any gaps in my math, I’m sure I need to retake some classes 😄

[@limecows]

Absolutely crazy and I don't think that was intended by the creator, it's just logic that was produced as a side effect.

[@Dad_Jokes87]

This is one of the most incredibly set puzzles I have seen. Its fascinating that such a rule could populate a gird in the first place let alone have a solve path and a unique solution. In a word: Masterful! Kudos to Simon for working through it and featuring it. I wonder how Simon is going to get back at Mark for this one?

[@unique0987654321]

Who are all these mean genius followers he is always apologizing to?

[@sfcpudding]

Let's go! I finally beat Simon to a solve for the first time-my time was 42:10! This was an absolutely genius puzzle, major major kudos to the setter! It felt SO good to solve, too. I felt so smart every time I had any breakthroughs, and when it got rolling, it REALLY solved at breakneck pace. Such a fun puzzle!

[@iSolate77]

56:29 No, Simon! It’s not weird. It’s BRILLIANT!! It wraps on its self. If you take a domino starting with c7 and the second part is c1 it still does work!!!

[@TerrisLeonis]

And if you take values in column 8 as a double pair - e.g. a 6 in column 8 means row 6 column 6 - then THAT works too, as every cell in column 8 correctly references the corresponding diagonal cell, including row 8 column 8 which is self-referential.

[@Mardines007]

To the setter of this puzzle, you are super genius. To Simon, you never stop amaze us with your ability of solving puzzles of this caliber. Well done and to all the setters. You people are giving us all a good brain workout. Well done and keep it up.

[@aloevira6611]

This one took me 5 hours but I solved it! I'm still pretty proud of myself. This is the second one I've solved from the channel after the arithmetic quiz a few days ago. I'm not a sudoko person at all and only started watching cracking the cryptic a few weeks ago. This is probably a testament to how good Simon is at explaining logic that I learnt so quickly, and also how much excitement he exudes that made me want to do this myself despite swearing I'm only here to watch and not solve. I do think I'm terrible at regular sodoku logic, though. I just mis-see things and make so many mistakes, but I really enjoy cracking puzzles where the goal is to figure out some new underlying logic that makes everything make sense. I still need to work on accuracy though, because most of my time was spent redoing things and correcting my mistakes despite having figured out the 8 pattern like an hour in. Anyway, sorry for the long comment, but thank you Simon for getting me into Sudokus, I really enjoyed this one! I'm not making any promises to how many I will attempt in the future though haha

[@cyberrb25]

It makes sense it's called Self Determination, but would just as well be called Treasure Map, by the fact it's full of coordinates and triangulating the numbers in there.

[@christophstahl8169]

In the second half of the solve, it really feels like a treasure hunt too, you jump all over the map for digits. I love Treasure Map as a title!

[@BeheadedKamikaze]

Did you spot the self-determining digits that made a second (offset) diagonal? I was quite happy to have spotted that (look in R1C5, R2C6, R3C7, R4C1, R5C2, R6C3, R7C4), despite having no chance at solving it

[@milla_5028]

"You should understand this." 😄 And the way Simon's hair gets more and more messy while he solves the puzzle. 😂

[@emilywilliams3237]

I watched the live stream before watching either of today's videos, so had a hint from the chat as that opened that there was something special in Simon's video. Yes, yes there was indeed. I enjoy the "Mark told me to open this live on camera" openers, generally, but this one seemed to result in more disbelief than usual! Simon, your experimenting as you grasped the implications of the rules was very interesting. I felt that there must be a reason that there was a given digit, and that it was that digit in particular. I also thought that an interesting pathway of thinking would be about which digits were not indexed by dominoes and why they weren't (that resulted in the negative diagonal, yellow digits). At one point you said, "There may be another way to do this, but I don't know what it is, so this is how I'm doing it. " I applaud this for at least two reasons. First, because the way you were doing it made sense to me (and, from my skimming through about 100 comments) to others who watched this video. Second, because if a way makes sense to you, then you should do it pretty much unapologetically. We did not come here to watch a perfect, pre-worked-out solve of a puzzle, we came here to watch you solve a puzzle the way you see to do it. I have seen some of the pre-worked-out videos on other channels and they are not nearly as interesting or fun as you and Mark doing the live solves. In addition to the wonderful word 'baffling' that does not get nearly enough love from word fans, there was the thesaurus-emptying "multitude, myriad, plethora' phrase, which was very apt for the moment, and of course made me laugh soon thereafter because the large number of possibilities turned out to be a very manageable few once you pencil marked them. So very fun - thank you for battling, persevering, and emerging victorious!

[@Anne_Mahoney]

"We did not come here to watch a perfect, pre-worked-out solve of a puzzle, we came here to watch you solve a puzzle the way you see to do it." -- Yes. Exactly. Well said, Emily.

[@1wpc154]

Maybe the craziest thing to me (which Simon perhaps briefly noticed but then let go of while solving?) is that the "wraparound" dominoes formed by the 7th column and 1st column ALSO all point to the correct digits. For example, in the 1st row, we get a 7-3 domino, and indeed row 7, column 3 is a 1. Lovely puzzle!

[@hybridhavoc]

Bit like a snake eating its own tail.

[@egspoony]

Came here to find this comment... It blew my mind as he had solved it and I was looking at the wraparound pairs... C7,C1 pairs...

[@kristhebrownie]

Even the left to right diagonals of the first 7 rows and columns wrap around. The whole thing is crazy

[@arcticcat74]

The thing I find interesting is the dominoes do wrap from column 7 to column 1 and obey the rules.

[@DirkieB]

Same! Simon briefje noticed it in one row, but it works for all of them and it's .... weird.

[@nightish_one6007]

2:38 to 2:42 is a prime spot to make a GIF out of 👌

[@jamesdreyer602]

What????? Why????? If! love it

[@coconuts2513]

So good 🤣🤣🤣

[@srabbelier]

kzbin.infoUgkxVHAxZkhSYqDQSe-FV8YTezGpy_15JIF2 What? Why??

[@jgvandenkooy3966]

Endorse

[@GioPanStudios]

59:41 and I don't think I've ever been more proud of a solve in my life. Figuring out each step of the break-in felt like some sort of Zen enlightenment. Take a bow, Stephane.

[@tom4szc]

And actually the idea of purple area being a cylinder works, I think - if we treat column 7 as left side and column 1 as right side of a domino, they point to the right places :)

[@situzone]

Yo that blew my mind

[@Solatrus]

Glad I'm not the only one who noticed that 😄

[@AngelWedge]

Yep… I noticed that while he was giving the extended metaphor about taking months to solve this. Once you've got imaginary dominoes in col7;1 and col8;8, every cell is referenced and it's pretty quick to solve.

[@jamiewalton7268]

@@AngelWedge You can't do that unless you give a value reason for it. Is there a simple reason as to why this should work which I'm missing?

[@dylanfitzpatrick7740]

​@@jamiewalton7268 looks like you haven't gotten an answer so i'll take a crack, since this is how I solved as well. Take row 1, for example. The leftmost six cells are row indices of six out of the eight 1s. That means R1C7 and R1C8 must be the row indices for the remaining two 1s. Similarly, cells R1C2 through R1C7 are column indices of six of the 1s, so R1C8 and R1C1 must be the column indices for the two remaining 1s. This means that the indices of all eight 1s are specified in row 1, and by extension all cells are indexed somewhere in the puzzle! Now consider any diagonal cell, say R1C1. The only way for that index to be represented within a single row is for both the row and column indices to be the same cell, which is only possible in R1C8. Therefore one of the two remaining 1 has index (R1C8, R1C8), and the other remaining 1 has index (R1C7, R1C1). Same logic applies along the whole diagonal, so we can think of col7-col1 and col8-col8 as additional dominos.

[@tonymason6637]

This was an incredible solve of an incredible puzzle. Well done! Also, there's something to be said about this being quality "edutainment" to me. First off, I never would've been able to solve this - I figured out the self referencing thing but got stuck in the dead-end loops, and decided to just watch a master at his craft noodle through it. Watching Simon's logic unfold is tantamount to magic.

[@coconuts2513]

THAT'S 3 IN THE CORNER! 🥳🥳🥳

[@Entlty007]

Something very interesting about this puzzle that he glazed over with “that’s weird” is that if you ignore the white column and let the dominoes wrap around, the referencing still works. For example, in the second column, the digits 7 and 3, if treated as the pair 7,3 actually refer to a two in the 7th row, 3rd column. And that applies to all dominoes of this nature. In column one, 6,3 refers to the position of a one, in column four, 5,4 refers to the position of a four, and so on

[@ubk42]

Once the 8's were known I think it can be demonstrated that it had to be that way.

[@christophstahl8169]

Man that was a hard start... Fantastic puzzle yet again. Once i got the eights i still felt i had no idea how to solve it but then you get a couple more digits right away and it just unravels jumping back and forth with referencing and even a little sudoku at times... just lovely. Starting it really way the hard part because it looks so daunting. And i really got a nice "I did that today" feeling out of it. Also a brilliant reaction to the puzzle reveal from Simon - but of course he managed to solve it, as if it was ever in doubt :)

[@jasperlanda5276]

I've been watching you brilliant men for about 3 years now, and this must be the one video that made me smile the hardest. Firstly, because I'm a mathematician and this puzzle is just liquid gold logic. Second, to see Simon finding out how the logic works and see him go from "to bobbins and beyond" to "I'm going to solve this". Amazing solve!

[@livesolhaug]

I assure you NOBODY's yelling at their screens telling you that you should get it

[@sanctionbuster]

I want to go drinking mojitos with Simon.

[@Zardox2]

Yep! That was also my biggest take away from this puzzle. Mojitos with Simon, and other CTC patrons/subscribers!

[@wmchristie]

Well done, Simon! It seems not too unlikely that Stephane is a C programmer.

[@markcbaker]

**p=p;

[@fredericpirot3004]

It would be easy for him to understand ** if not

[@Anne_Mahoney]

Naah, assembly language. Or really old school, putting in the machine language directly from the front-panel switches! (yes, I've done that, back in the day) C is too high-level for this stuff!

[@stevenvangemert7196]

Ahhh yes, pointers in a linked list... Nice analogy.

[@kamallewis-gopie6956]

So I got thru the first 6 puzzles in the 500 subscriber special (no hints/no error highlights etc) and was feeling pretty good about myself. Some took a couple hrs, some longer over the course of a few days, but I got them done. Then I opened puzzle 7. 6 is currently the limit of my abilities.

[@yadiracamacho499]

Is that the classic sudoku? I hat to use the hints with that one

[@kamallewis-gopie6956]

@@yadiracamacho499 nah although I found that really hard. That was 5 and was for me worse than 6. 7 is the sandwich sudoku

[@Mystery_Biscuits]

56:21 “If you treat the first 7 columns as a torus, then it works” Looks at the finished grid, that’s actually true! I assume that’s a consequence of the logic and not a sly party piece Stephane has put in but I wouldn’t be surprised if it was tbh

[@George4943]

an hour for simon; time for me to just watch

[@hubertnnn]

Well, he spend half an hour saying that there is no way he can do it.

[@th.nd.r]

Again, what a sheer run of puzzles we’re on. This is a blessing of a video. What a miraculous, genius discovery by Stephane, and what an incredible, genius solve by Simon. I especially love the thrill of how the video feels hopeless until Simon raises his eyebrows and says “ah,” at which point the wonders just start to flow. Dang it I love this channel. PS, sorry to give you a hard time about this, but the 3 in the corner didn’t get its song!

[@PauxloE]

One hint (for Simon as well as other people trying this): In the options, you can enable row/column numbers. This way you don't have to count to know which row/column is which. (It's less needed in a normal Sudoku with boxes, but here we have just identical looking rows/columns everywhere.)

[@wariolandgoldpiramid]

good advice

[@DuelScreen]

That's good to know. I would actually prefer spreadsheet references since they are easier to express to me. Columns are letters and rows are numbers so C1, D3, etc. Maybe Sven can add that as an update in the future.

[@Waggles1123]

Interestingly, the Row 7-Row 1 wrap-around domino is *also* a coordinate. That's where the "missing" 8 coordinates are. There are 48 (6 dominos in 8 row), plus the un-indexable 8 cells negative diagonal, and then 8 hidden dominos to make 64 total cells.

[@miradrgn]

this was one i was never even gonna try attempting on my own, but i was able to keep up with simon's thought processes and walk along to the next step pretty well through the whole thing so i feel fairly good about that. and i did grok a few key details before he did, the very first thing i picked up on was that row 1 (probably) needed an [8,4] pair, and then i was waiting eagerly for him to realize the NW-SE diagonal comprised 8 of the un-referenced cells. i also had a hunch/hypothesis/hunchpothesis that the other 8 'missing' cells might just be sneakily referenced by the 'fake' dominoes on the far right, which wasn't quite true, but as simon briefly sort of noticed with his torus comment, the far right edge of the purple zone wraps back around to the left to create the last 8 missing dominoes, so there essentially are 56 indexes in the puzzle and all the cells outside that diagonal are accounted for! definitely a fun one to watch along

[@n8r8rutube]

I know I didn't rigorously prove the the logic for the break-in to myself, but about 5 minutes in I had a hunch about the diagonal 8's and I decided just to go for it and see what happened. Finished in 40m40s. Out of a couple hundred puzzles I've attempted, this was only the 2nd or 3rd time I've finished faster than Simon, though I don't really consider this one a victory as my solve wasn't entirely logical.

[@benshapiro8506]

U still need 2 have a word with Mark. who says what doesn't kill me makes me stronger. send him a puzzle he can't refuse.

[@Orenotter]

He thought that his brain might just burst. The puzzle seemed simply the worst. For according to lore, No one solved it before. Congrats, Simon! You are the first!

[@Anne_Mahoney]

Eventually it did get solved on Logic Masters. And I see there that there's a second variant of the puzzle -- scary thought!

[@stardancer119]

I've decided that I'm okay with following along with Simon and letting his genius mind help me learn ☺️ I kept forgetting how he proved different digits/patterns, but I had a breakthrough when I realized every digit had to be self-referencing when it's in its own row...at which point the title smacked me in the face, lol. 😂 I did finish the solve without watching, and then went back to double check my answers against his, and see how he logicked it out. Wasn't until the rewatch that I noticed the mirroring squares of yellow/purple, 8/x digit, down the diagonal...

[@PaulMurrayCanberra]

Note that the mapping of each row automatically obeys sudoku, because the row itself does. Row 3, for instance, will put 3s all over the board. But it will only put one 3 in each column and each row.

[@furbyfubar]

I'm happy I didn't watch the intro before solving this or I wouldn't have even attempted it. Took me 95 minutes with most of that was spent trying stuff out until I figured out the break in with the diagonal.

[@steveunderwood3683]

I was feeling pretty good, solving it myself. Then I compared my result with Simon's, and I'd got something swapped over. I think it was just sloppiness, but I still got it wrong. It sure looks daunting at first sight, but once you start focussing on where things can't got, rather than where they can, it starts to make sense.

[@amelielune1553]

A friend recommended your channel to me after I mentioned my love of sudoku. I've only ever done classic sudoku and refused to try any variants, but I watched a few of your videos and they sparked my interest. Then this video was recommended to me and I decided to give the puzzle a go and see how far I got before I'd switch to watching you solve it. 82 minutes later I was staring at my screen in disbelief because I'd actually solved it 😂 I've rarely felt such a strong sense of accomplishment mixed with joy and excitement. This was absolutely wonderful. And now I may be about to fall down a rabbit hole...

[@StephaneBura]

Congrats! Enjoy the rabbit hole 🙂

[@MrMisterMaster]

This took me 510 minutes to solve over a couple of days... Now I can finally watch this video and see how Simon finds the solution within an hour! I have no prior experience in solving logical puzzles like this (besides regular Sudokus in magazines), but after watching this channel for a while I wanted to give it an honest try. I'm happy I actually managed to find the logical path and solution. :D

[@nagualdesign]

I'm new to this channel and have watched 3 or 4 videos in the past few days without even considering trying to solve the puzzles myself. I think the next one that pops up in my recommendations I'm going to have a go at before watching him find the solution.

[@MrMisterMaster]

@@nagualdesign Go for it! Some of these puzzles really challange your logical thinking and force you to think outside the box. It is very rewarding to solve them by yourself.

[@inspiringsand123]

Rules: 01:30 Let's Get Cracking: 07:53 What about this video's Top Tier Simarkisms?! Schrödinger Cell: 1x (13:18) And how about this video's Simarkisms?! Hang On: 10x (02:42, 11:09, 20:26, 27:22, 27:30, 34:00, 39:26, 39:26, 39:26, 42:26) Ah: 8x (00:52, 00:53, 27:14, 27:22, 34:23, 41:05, 43:47, 52:42) Sorry: 6x (02:47, 07:41, 30:48, 42:37, 49:34, 1:01:29) Clever: 6x (03:39, 34:23, 34:26, 1:01:17, 1:01:17, 1:01:21) Bother: 5x (50:59, 50:59, 50:59, 50:59, 50:59) By Sudoku: 5x (44:57, 45:00, 45:02, 57:00, 58:02) Pencil Mark/mark: 5x (33:23, 41:59, 49:35, 49:37, 54:34) Beautiful: 4x (05:48, 32:25, 32:29, 1:00:24) What on Earth: 3x (14:19, 14:21, 22:32) Brilliant: 3x (05:21, 05:27, 05:34) In Fact: 3x (13:14, 54:03, 1:00:41) Baffling: 3x (07:17, 34:26, 46:14) Unique: 3x (13:29, 13:39, 1:00:12) Good Grief: 2x (34:03, 54:17) Progress: 2x (04:17, 17:16) Wow: 2x (34:11, 49:57) What Does This Mean?: 2x (02:15, 36:52) I Have no Clue: 1x (06:34) Lovely: 1x (41:26) Insane: 1x (54:54) First Digit: 1x (44:00) Deadly Pattern: 1x (58:09) Our old Friend Sudoku: 1x (53:31) Shouting: 1x (30:44) Of All Things: 1x (58:02) Magnificent: 1x (06:17) Surely: 1x (29:06) Corollary: 1x (27:01) Alexa: 1x (08:03) Phone is Buzzing: 1x (22:59) Plonk: 1x (54:31) Wake Up: 1x (1:00:00) That's Huge: 1x (53:05) Cake!: 1x (05:16) Most popular number(>9), digit and colour this video: Sixteen (8 mentions) Eight (91 mentions) Purple (32 mentions) Antithesis Battles: Even (7) - Odd (0) White (2) - Black (0) Row (124) - Column (84) FAQ: Q1: You missed something! A1: That could very well be the case! Human speech can be hard to understand for computers like me! Point out the ones that I missed and maybe I'll learn! Q2: Can you do this for another channel? A2: I've been thinking about that and wrote some code to make that possible. Let me know which channel you think would be a good fit!

[@macosacifaburro]

Quintuple bother in a second, gg simon

[@gary.h.turner]

That's one small hour for Simon, one giant year for the rest of mankind! 👨‍🚀😲

[@thelostpiranha]

The rule set alone almost broke my brain. But I thoroughly enjoyed this. What a brilliant puzzle. Thank you as always, Simon!

[@ronjohnson6916]

I've never laughed out loud before on any puzzle before this. The reaction was so great. Thank you for having a go. (Never mind figuring out how to solve it)

[@coralfeatherstone7019]

How come Mark never gets surprise puzzles? 🤔

[@CrackingTheCryptic]

[Simon writes:] Because I am a nice and kind person :) :) :)

[@bibliopolist]

@@CrackingTheCryptic This one, the mother of all indexing puzzles, would have been great for that, though...

[@NaHBrO733]

This is an AMAZING puzzle 132:38 (It took me so long!) My thought process 1) the diagonal The first thing that came to mind (it wasn't obvious) is the diagonals must not be determined (by a domino). Or else we need a domino with both the same digits. Playing around came the first rule: (1a) If X in (Y,Y), then Y in (X,8) If not, then (Z,Y) or (Y,Z) is a domino in the X row, which means (Y,Z) or (Z,Y) contains X, contradiction (1b) 8 in (8,8) 8 in (A,A) => A in (8,8) => 8 in (A,8) (use (1a) twice). So A=8 (1c) digits cannot repeat on a diagonal Corollary of (1a), else (X,8) has two digits 2) All is determined From (1a) and (1c). I know that the last column determined where the digits 1-7 are in the diagonal By the rule, 6 out of 8 numbers of a digit are determined by the dominos There is one number left not determined by current rules, WLOG let it be A in (X,Y). X != Y, which means A is not on the diagonal (2a) if (A,7) contains X, (A,1) contains Y, then (X,Y) contains A Look at row A, col 1-6 and col 8, determines 6 rows of 6 A's and one A in the diagonal, the row of last A must be the number in (A,7) Similarly the column of last A is in (A,1) (2b) The grid determines the position of every single cell From (2a), we can now see (A,7),(A,1) as a domino that determine the position of A. Combined with (1a) and original rule, this is proved. 3)duality I got to nowhere with (2b), so I started specifying on single dominos (3a) a pair of dominos determine each other (including the col7,col1 domino) Let A in (X,Y), B in (X,Y+1) (*we say 7+1=1), then X in (A,B) Let Z in (A,B+1), then A in (X,Z), therefor Z=Y So we know that [A in (X,Y), B in (X,Y+1)] if and only if [X in (A,B), Y in (A,B+1)] (3b) A=X iff B=Y Corollary from (3a), Really important because from (2b) digit A in row A will be determined by a domino in row A, which is a case of A=X 4) Where are the 8's This took me too long to realize... from (2b) the grid determines the position of every single cell, including col 8 (1a) X in (Y,Y), then Y in (X,8) => (X,8) is a domino in row Y => 8 in (Y,Y+1) (*7+1=1) 5) piece it up 5.1) all 8's (9/64) 5.2) 8th row, and by (3a), another 7 dominos (8,1)~(8,7) (22/64) 5.3) A in row A, by (3b). Remember the other A in the dominos (43/64) 5.4) Try out the diagonal, only two possibilities, finish What a wonderful puzzle

[@hodor6159]

So proud of myself for solving this after you found the diagonal of 8s for me 😅

[@JRHainsworth]

I was waiting for him to notice that, other than 8’s diagonal, every diagonal in the top 49 squares is 1234567 repeating.

[@karsaanita]

This took me AGES! I almost quit and watched the whole video after a few hours. But then I learned that I’m not dumb; it’s just a super difficult puzzle and I persevered!

[@SamTills]

This took me over a week of obsessing over it to solve but the positions of the 8s in row 1-7 finally clicked for me today and then it only took three hours

[@StephaneBura]

Congratulations!

[@lincolnsorensen6833]

This channel is the BEST! Thank you Simon, and thank you Mark!

[@lukeverso]

What amuses me the most - and I haven't finished watching this video - is the fact that Simon really takes his time to makes the puzzle easier to be understandable. He literally goes through every possible idea before finding the one that allows him to solve it logically. That's so, so, so amazing...

[@chuckmanion1128]

One thing that helped me a little was to realize that in c1=c6 each digit appears 6 times. Same with c2-c7. That means that in each row and column 6 digits are pointed to and 2 are not. since you can already know same digit coordinates (1-1, 2-2, 3-3, etc) are not pointed to, any other digit you can determine isn't pointed to can also be highlighted in yellow. that means you can highlight each other digit in that row and column green (or at least I used green) and determine that digit IS pointed to. So for example, you can quickly determine that the 6 in r8,c2 is not pointed to. That means the 3 in r7c2 is pointed to and therefore a 7-2 domino DOES appears in r3. Like wise you can later determine by numbers in columns 1,7,8 that the number of that row won't be pointed to in that appropriate row or column and thus can be eliminated as a possibility from green digits. This only ended up providing minor help but the highlight was useful to me.

[@nemanjamarsenic1626]

Spent 15 minutes trying to get a first digit. Gave up. Spent another 15 minutes writing this in C#. Took 0.097s to execute and give correct solution. Now, let's watch Simon do it while I fall asleep :) var grid = new int[9, 9]; var usedInRow = new bool[9, 9]; var usedInCol = new bool[9, 9]; var stack = new Stack(); TrySet(8, 4, 1); while (TryGetEmptyField(out int r, out int c)) { for (int val = 1; val

[@Piatato]

It's a fantastic puzzle, I can recommend everyone to give it a good try before watching the video! 😁

[@JohnSmith-zq9mo]

Instead of "our old friend Sudoku", it really should be "our old friend Latin square" in this one.

[@gregind01]

Firstly: Congratulations Simon on successfully contorting your mind to be able to complete this sudoku!👏👍 Secondly: Thankyou Simon for your introduction to this video which was the best laugh that I have had in ages, hearing all of your complaints about how ridiculous this puzzle is yet knowing that you will successfully solve it! 🤣🤣🤣

[@TormodSteinsholt]

Look up the word "relentless" in the dictionary and the picture of this guy appears. "Daunting, impossible, mental....... let's get cracking". How's that for life lesson?

[@Lifeheart]

10 months later and I found this. I watched the solve with some initial ideas of how to get started but nothing concrete enough. Seeing Simon, eventually, take my rough ideas and form them into workable logic was magical and really boosted my confidence to take on tough puzzles I normally avoid. As said by others, the start was very funny to watch Simon's reaction. Even if it was a prank, good on ya for powering through and working it out. Good solve!

[@yannickhein9788]

I haven't solved it yet - sort of. So I didn't solve it myself, but I programmed a small powershell script to brute force it. I wanted to know if there are more than one possibilities, and actually there is only one with the given 1 on the eigth rank. Not sure yet if I will be able to solve it without trial&error at some point. For all who are interested, THERE IS ONE AND ONLY ONE DIFFERENT SOLUTION (with the same game rules but not restricting R8C4 to a "1") : start with 6 on the lower left position (R8C1). I will post some hints to make that easier to solve if folks are interested.

[@mcunibrow6399]

I love videos where Simon goes “this is unsolvable in the beginning, because you know your in for a real treat!”

[@thezanycat]

53:19, super proud of myself. Once you realise there's a problem with (X,X) coordinates it all starts to fall into place, then you realise the interplay with 8s and it all just collapses. BRILLIANT BRILLIANT BRILLIANT puzzle

[@johnglass6725]

"It's not suitable for a video, Mark." Come back in an hour or so and see...

[@DwajZ]

Did anybody else see him age about 40 years in 35 minutes and then slowly become younger again for the las 25 minutes? 😂

[@Robert_H.]

*Short summary of the first **36:57* - in each row and column each number must occur once (Sudoku) - if the number Y is in the X-th diagonal cell (coordinates X,X), the number X must be in the Y-th row, because the diagonal cells still form valid dominoes with the number to the right of them (at least the first 6) - if this number X is in a pink cell, it forms a valid domino with an adjacent cell, so the adjacent box must also contain the number X to reference the diagonal cell (row X, column X), but this breaks the rules of Sudoku - so the number X in the Y-th row must be in a cell that cannot form a valid domino => a white cell in column 8 - so to the right of the number Y in the X-th diagonal cell is the number 8 - since this is true for the first 6 diagonal cells, since they have a pink cell to the right of them, all these pink cells to the right of a diagonal cell contain the number 8

[@Meeghwho]

I just did it. "only" 560min using the browser so I dunno the exact time. normally I don't even comment but this puzzle got me hooked. the problem is I don't know how or why it worked it just felt right. somehow it's still not satisfying because I did it but I don't really know if it was lucky or not. gonna watch the video now and maybe I'm smarter afterwards. thx anyways for this experience

[@mjosifovic227]

In the past few years, I have become able to solve such puzzles I couldn’t have dreamt of solving before I discovered CTC (a few months before the first Covid lockdown, so sometime in 2019). Simon and Mark, I know I’m speaking for many when I say that you have awakened a love for puzzles in us that we can all enjoy and share in this community. I had a small breakdown during the lockdown and CTC helped me to stay sane by engaging me to think. I never knew so many sudoku variants existed before I discovered this channel, but learning how to understand them and solve them has been one of the most wonderful experiences in my life so far. Thank you for being consistent and loyal. Let’s get cracking!