The Hardest Sudoku... And How To Solve It

You can try the puzzle you voted for, Hidden Clone by Sam Cappleman-Lynes from the UK Sudoku Grand Prix, here:
cracking-the-c...
The test is available here:
gp.worldpuzzle...
▶TRY OUR CLASSIC SUDOKU APP◀
AppStore: apps.apple.com...
Steam: store.steampow...
Android: play.google.co...
▶TRY OUR SANDWICH SUDOKU APP◀
AppStore: apps.apple.com...
Steam: store.steampow...
Android: play.google.co...
▶SUPPORT US + ACCESS EXCLUSIVE "CRACKING THE CRYPTIC" PUZZLES/VIDEOS◀
Patreon: / crackingthecryptic
▶SEND US PUZZLES TO SOLVE/CONTACT US◀
[e-mail]
▶FOLLOW US◀
Twitter: #crypticcracking
@crypticcracking
Instagram (for how to solve daily clues from The Times): www.instagram....
▶SOFTWARE◀
Play the puzzle in the video by clicking the link under the video (above). We are building a website which will allow you to enter your own sudoku puzzles into the software and this is coming soon!
▶ABOUT US◀
Hi! We're Simon Anthony and Mark Goodliffe, two of the UK's most enthusiastic puzzle solvers. We have both represented the UK at the World Sudoku Championships and the World Puzzle Championships. We're also "cryptic crossword" aficionados. Mark is the twelve-time winner of The Times championship and Simon is the former record holder for most consecutive correct solutions to The Listener crossword. We hope we can help your puzzle solving while also introducing you to some of the world's best puzzles.
Thank you for watching!
Simon and Mark

[@pozxyyy]

I really wonder how I can just sit here and watch this guy solve a sudoku for half an hour, and be intrigued the whole time. Great stuff

[@Sam_on_YouTube]

Best KZbinrs make boring stuff interesting. I'm not into death, but I like Ask a Mortician. Same with language and NativLang, art and Echo, and music and Todd in the Shadows. I like the creators. They make their subjects fun to watch, even if the topic is inherently boring, or just not my general interest. I do like puzzles though. But I don't think I would like watching someone else do them if I didn't like the way they present.

[@Poyni]

today i spent 6 hours on one puzzle

[@Sam_on_YouTube]

Actually, I only watch Simon, not the other guy.

[@azharshaikh8944]

pozxyyy woooord

[@theeldergamer700]

I do this while only understanding a 50% of the things he says because I'm from Spain and my english is clearly not the best XD

[@wonderbop2656]

I want him to do one of these puzzles with the eye trackers on the screen

[@simonbrignoli8726]

Man that's a good idea!

[@jxs9229]

Was thinking the same aye

[@GunganWorks]

I second that!

[@joelanttila7927]

BRUH. that would be sick

[@sarzan71]

Yes please

[@mitch-lawless]

“I am lost in admiration”, what a beautiful and endearing sentence.

[@riyo.38]

The structure of this Sudoku is so insanely perfect. You're sat there, wondering during the whole solving of the Sudoku, if your approach was correct or not. It's like watching a movie, where the main character follows calculated assumptions and you as the viewer, are always second guessing him. He gets hints all the way, which seem to lead him nowhere, right until the end, when his first guess, with the final piece of evidence, comes true and the whole case resolves, like a perfectly put together Swiss watch, with all the gears fitting perfectly. It's just brilliant. Mind blowing, how this is solvable and even more mind blowing, if you think about the fact, that someone has put this together.

[@Garymaster4321]

very well said

[@NiNash1]

Damn well said!

[@r4myyy999]

Oreohunter 38 damn u talk too much

[@riyo.38]

@@r4myyy999 yeah, has gotten out of hand kinda. But I'm a copywriter as well, so writing is my job basically 😂

[@leporid257]

I've been wondering! He has no clue if he had to go up or down with the clone, did he?

[@crhulsey56]

this is far beyond me i like Sudoku but i have never searched google or youtube and some how this is on my Recommended page. lol great job

[@shnooel3952]

I opened the soduku app on my phone for the first time in a year yesterday and this was in my recommended 2 hours later lol

[@hm09235nd]

its just generally trending and you guys happen to have a connection

[@obsoleteprofessor2034]

The vaccine chip has a YT link

[@jestfullgremblim8002]

@@obsoleteprofessor2034 lmao

[@OddSauce]

I think it's safe to say this quarantine is getting to me

[@insertcringehere5833]

same

[@korvo9936]

big same

[@famoussession7426]

OddSauce Not me

[@lilaclyliac]

Samee

[@curtisgroce973]

OddSauce same

[@KurtHugoSchneider]

incredible puzzle, managed it in 23:13 and I felt like I moved pretty quick.. absolutely crazy that the top people are solving this in 10 minutes.. too good

[@harrisons62]

Kurt Hugo Schneider still pretty good I doubt I could ever solve this.

[@finlayhutchinson7370]

humble brag lol

[@realitant]

Still waiting for the next nerd alert video :)

[@loominatyproductions9444]

Master chess player, Sudoku wiz & incredible musician, you got it all Kurt!

[@kolosmenus]

I think the only possible answer is that they were familiar with the "clone" idea and were instantly able to pin point the possible locations. Because I really can't imagine them analyzing this and then filling up the grid.

[@Animefan1803]

it´s 1.16 am. On a tuesday I´ve never tried a sudoku in my entire life. Yet here i am. Quarantined and drunk. Watching this guy solve sudokus on 1.75x .

[@Animefan1803]

@@account5223 that´s to fast. Wanted to understand what he was saying

[@Delephene]

It’s 4:10 on a Thursday morning watching on 1.5x. I’ll have to upgrade my game to 1.75x now

[@issaile]

ah i see youre a man of culture as well

[@H1nted]

I dunno but as a soduko lover i watch this at normal speed to see if i can see things faster than him

[@Animefan1803]

@@H1nted Point is: I never even googled sudoko. Yet somehow i´m here. The Algorythm works in mysterious ways.

[@Fristytoes]

Just discovered this channel, and I must say I am hooked. This was my first attempt at a non-standard sudoku. Did it in 4:02:42, which is kind of an embarrassment, but I was still proud of completing it anyway lol. I thought if I did the "hardest" one, then the rest would be relatively easier. (But I doubt that!)

[@1mSeal]

nothing embarrassing about it, if anything you showed perseverance and resolve, this is admirable that you didn't give up and watched the video to get the solution that you knew you have had available. also, this is a first attempt for you at a non-standard as you pointed out, and this is a very hard one, so it makes sense that it would take you longer than to someone who is doing advanced sudokus like these regularly.

[@derkaffeenator9172]

Reater Jr. yeah that’s pretty much what’s going on here

[@jasmith4183]

Took me 4:08:00

[@oxey_]

thats good dude, I probably like most others gave up after messing around with for a bit without really seeing progress. Great job

[@anidleteen]

I was debating whether to try it, but I think I'll watch it and try another one instead 😹

[@jumpingjflash]

I'm fascinated by all the features you have in your software: 1) the ability to mark and write in multiple squares at once 2) you have 2 types of pencil marks, centre and corners 3) the ability to shade squares with different colours What app are you using, and is it available to download?

[@ianh1504]

This is a year late, but you ought to check the video description :)

[@boots4snootin571]

"Click on the link below the video see the software"

[@agentg5233]

Go to 13:17 man that was the most British thing I’ve ever heard

[@Jota1]

AgentG5 lmfao

[@michaelorange4879]

HOH HOH HOH

[@lancelotray]

French laugh: Hon hon hon British laugh: HOH HOH HOH

[@needfoolthings]

Eh-chawchawchaw.

[@JaharNarishma]

I think 23:25 is quite good as well. At least it's an expression I haven't heard before.

[@hilcovanbreeschoten720]

1:13:12 That took a very long time. Even getting an idea how to even start took me like 10-15 minutes. It involved a lot of new logic for me, and I'm very happy I solved it without resorting to the video.

[@nielsdewolf9991]

Same, did it in 1:22:52

[@FetnerVideos]

01:19:57 for me. Damn its satisfying to complete once you do.

[@hakai1488]

Same, did it in 1:11:38

[@ginrodino8542]

I'll be honest, I looked at it really confused for 30 minutes and gave up. I had a headache trying to figure out what could go in and mirror xD

[@ginrodino8542]

Not mirror, copy

[@ainsleemcnamara7514]

"I wanted to explain that slowly... for myself" what a mood

[@smeutr1]

The algorithm suckered me in with one video, and now I’m hooked

[@chaosenergy1990]

The algorithm is skynet.

[@ardemus]

I enjoy the logic for translating the shaded region: You can't translate more than 2 squares in any direction without leaving the grid. You must translate in both X and Y to avoid row and column duplication. The rest comes down to moving every shaded cell into a new region. Four of the shaded squares are in the corner of an outside/middle region. They can't move 3 spaces to cross the far boundaries, so they must all cross at least one near boundary. That forces either up/left or down/right. Finally, you must move 2 squares in both X and Y so the four central shaded squares escape the central region.

[@henrihell]

You can think about it even simpler than that. 1) Must move in two directions. 2) Can't move more than 2 in any direction. 3) Any knights move or moving 1+1 breaks the middle box, so you have to move 2 steps in 2 directions. 4) Row 3 Cell 4 can't move 2 up and two right and symmetrically r7c6 can't move 2 left and 2 down, so the shape will have to project onto itself.

[@Penguat]

@@henrihell I don't see why R3C4 can't move 2 up and 2 right - the rules don't specify that the clone has no numbers filled as yet?

[@henrihell]

@@Penguat R3C4 2 up and 2 right keeps it in the same 3x3 box. The fact that there's a digit in that square has nothing to do with it. :)

[@Penguat]

@@henrihell of course, thanks!

[@brodhax6148]

I have no idea what hes talking about. Im just sitting here listing to smartness in action

[@nielsliljedahlchristensen4924]

You're not very bright then. Sorry :(

[@brodhax6148]

@@nielsliljedahlchristensen4924 Nope, but im tall and good lookin, ill get by

[@johnjackson393]

Niels Liljedahl Christensen that’s kind of a dick thing to say

[@mvdb843]

@@brodhax6148 hahahaha love that

[@nielsliljedahlchristensen4924]

@@brodhax6148 And pretending to be stupid for likes. Why is stupidity attractive?

[@Kelarys]

It never crossed my mind before that there was competitive sudoku, and now that I know there is, I just thank god I have music or else I would feel like I missed my calling haha

[@jestfullgremblim8002]

Lmao

[@ep1873]

15:18 during the competition, in which I got 44th place. This puzzle really helped me who is extremely inept at classic sudoku.

[@Ruminations09]

I don't know how I stumbled upon this video - it's been many years since I last did a Sudoku - but I figured I'd give it a try. Took me 1 hour 16 minutes 17 seconds. About double the times some of these other comments put down, but considering how long it's been since I've done a Sudoku puzzle, I'm still pretty proud. This was certainly a challenging one.

[@ZuchinniOne]

Thank you so much!! Loved it! Also I took a different approach to the initial assessment of what positions the clone could be in by looking at the four middle squares and noting that they could not ever translate in such a way that any one of the 4 squares initially in the middle box remained in the middle box after the shift. Seemed a bit easier to visualize that way :)

[@pdnh8275]

"So _ goes in this square here because it can't go in that square" Me: spends 10 seconds trying to find out why it can't go in that square and gives up and decides it's better not to question anything

[@stephanberger3476]

I was like that, too. With the bottom-right 5.

[@evandroa4845]

@@stephanberger3476 Bottom right 5 had to go there because if it was put in one of the two squares bellow that one it would force the bottom left 5 to be next to the 2, which would conflict with the top left 5. Another way to look at it is to notice that was the only square in row 7 where you could put a 5.

[@dijoxx]

Maybe you need to find something else you can enjoy with your level of intelligence?

[@Xonarag]

@@dijoxx Way to be an elitist lol.

[@bnagybalint]

57:29 for me. I don't understand how you ended up being certain that the shift is two squares up-and-left. At around 12:00, you start by trying this shift and it works out fine, but it wouldn't have to. The down-and-right shift was equally likely at this point. Were you trying this approach in a hope that if you chose the wrong way, you would get a contradiction quickly? Or was it luck? Or am I missing something? Thanks!

[@patricepederson9211]

Same here! Reading the comments to figure out how he knew it was that one of the two. I got as far as that myself (pats self on back), but couldn't figure out how to differentiate.

[@timavery850]

he got lucky, but going down would have resulted in an 8-9 pair and a 5-9 pair as the 4 options which would rule it out

[@theknewwon9453]

This was the first non-traditional Sudoku that I was able to complete from this page without any help from the video! It took me 1:31:48 (which is insanely slow in comparison), but it's an achievement for me nonetheless. The logic behind figuring out how to clone the region was so amazing to figure out. Thanks for sharing these puzzles. I never would've thought about Sudoku with outside constraints if I hadn't found this channel!

[@TraytonOtto]

45:18, though I listened through 6:08 of the video for a hint for how to think about the hidden clone. Really a beautiful puzzle that I can't imagine doing under time constraints.

[@Autoskip]

39:23, and I notated both directions at the start, so I knew the whole way through that had the right hidden clone. Plus, I found it rather helpful to label a few extra cells with the cloned cell colours - it meant that I could, without knowing which numbers they were, “solve” a few cells earlier than I would have been able to otherwise.

[@baccarah7010]

Im sure this guy can guess a girls phone number by just beeing given 2 digits.

[@JaggerG]

Of course not! He doesn’t guess, he uses sheer logic to discover the rest of it! Also, give him a thermometer and he doesn’t need any givens. :^P

[@unperrier5998]

He'd start by saying to her: - you're definitely not a 8 or a 9, maybe a 7... And he'd get a big SLAP in his face... now finding the rest of the digit is pointless. Poor him.

[@patricepederson9211]

I feel like this comment was vastly underappreciated by the other commenters. So I just had to comment to say that this was hilarious.

[@Herculean.Aficionado]

@@unperrier5998 that one was good 😂😂 made me actual LOL

[@vesanius1]

I don't have the patience to do sudokus myself, but watching this videos is just so relaxing for some reason. It's very easy to follow up and even as an amateur I still understand the reasoning behind everything because it's all well explained. Wathing this for sure will improve you as a sudoku maker as well. Not in a million years I would've thought that I'd end up watching a guy solving sudokus and never skipping a second and hours at a time. Genius.

[@t1nytim]

22:44 certainly challenging, was a lot of fun though. Though I did take the time to confirm that in transformed in that upward direction, rather than the downward direction.

[@mickaelzehren8249]

How can you confirm that? I didn't understand the argument of the video.

[@dopaminecloud]

@@mickaelzehren8249 two pairs contained a 9, no matter how they resolve, you'd end up with two 9s in the box

[@erickthomas6133]

This puzzle looks impossible at first, props for getting through that and huge props to the puzzle maker.

[@DWestheim]

41:04, including 18 minutes of dutifully coloring every cell that could be a "corner" of the clone of the given shape without realizing that they were actually almost all impossible and that there were really only two possible locations for the clone. Sometimes I'm just dense.

[@dsch772]

Took me 41:02. Pretty close :)

[@J7Handle]

Took me an hour and I proved the clone in the top left in the first five minutes. I’m just bad.

[@mikspurins1455]

38:00, honestly just glad I could solve it at all :)

[@Asdayasman]

Yeah but you had fun drawing a pretty picture so it's ok.

[@Lorefall]

When your trying solving a puzzle and you cant even understand the rules, your in trouble.

[@doemaeries]

*you're

[@KB-ee8xf]

When you are typing in English and can't understand the syntax, you are in trouble.

[@KB-ee8xf]

@@account5223 yes, he spelled You're incorrectly. But, I argue that he used the wrong word to make the sentence, so therefore he use improper syntax.

[@KB-ee8xf]

@@account5223 as stated previously, he should have used "you're" instead of "your" Yes, you can argue this is a simple spelling error but since this spelling error changes that word completely and therefore makes the sentence unintelligible, it is also a syntax error.

[@KB-ee8xf]

@@account5223 this spelling error resulted in a entirely different word, that word made the sentence have (or contain) a syntax error. Google the definition of syntax and then think abstractly about what I am saying. You aren't wrong that the spelling needs to be changed, I am just saying that there is more than spelling involved in this error. There is also grammar and the syntax of the English language.

[@ninnygrantier9931]

"this is so clever, this is so clever. ha ha" the small laugh got me

[@gogigogi_flover]

39:27, it took me 1 minute to find the only two possible locations for the clone and 20 minutes to find out logically why the clone cannot be at the bottom right, then spent rest of time cleaning the remaining grids. This is a great one!

[@Tierdas]

stuck on your channel now after finding you through recommended videos. am not a sudoku solver but I really enjoy your vids! I solve along in my head and it's nice to keep the braincells working without having to do much. hard to explain but to put it short I really enjoy your content despite not being your target audience!

[@lalzeriiiiii]

you know you're on the final stage of finishing youtube when you watch a game of sudoku for half an hour

[@itsmegeorgeous]

Don't know how or why this came up in my suggestions but I quite enjoyed it. I am a total novice at puzzle solving and soduko but thought i'd give it a go as it had come up on my feed. It took me 01:02:58 which is clearly not good but I'm not displeased as I hadn;t even seen a soduko in years. It has inspired me to have a go at some more and look at some other types of puzzles.

[@RandomBurfness]

39:00 flat for me! It took me a while to get into the logic but when I did, it sure was beautiful.

[@bringforthyeshadow]

I've started doing Akari puzzles because of your last video, they are really quite interesting!

[@kimlightfoot]

That was terrific. Foundyour channel by accident, but as an expert solver myself. I followed your logic, this is the first time seeing variations, I am not normally a fan of sudoku variations, but this was awesome to follow, and see if I could beat you playing along. I had your 89 combo solved before you did, but only because I solved the top right and bottom left numbers earlier than you did. I could never have figured out the cloning as you did, having never before seen chess type rules, or clone rules before. But I loved it. Now to my expert books. cuzz I am in sudoku mode now. lol. You earned a subscriber today!!

[@vlarsen10]

Solution to your bifurcation problem in real-time: You showed that the green cells can't be 7 (this is actually true NO MATTER which way the pattern shifts; very important). That makes an 89 pair in central box. Thus, red is 5 and purple is 2. The 2 prevents the pattern from shifting downwards, because of column 7.

[@BrunoFiss]

Came here to say the same. It's a bit more elegant than guessing :)

[@matthiasney4871]

What a beautiful solution. In fact, even when you do not decide whether to shift up left or dowm right, still you can exclude almost all numbers from the crucial cells, leaving vou with two pairs of 8/9. Excluding the 8 and 9 from the other grey cells, you are left with a safe 2 and a safe 5. All this, as you said, without having to decide which direction to shift. What a piece of genius this Sudoku is!

[@BallerineMimi]

A great challenge, the colour shadingfunction on their website is sooo handy! Took about an hour and a half, very proud!

[@lakarto19]

Nice puzzle. My solve time was 59:36, about 40 of which I spent trying to figure out the initial logic with where the 'clone' could be placed. Got there in the end, but took a bit too long. As for the video solve, I would have personally preferred it if the contradiction (with what happens when the grey area shifts diagonally downwards) had been shown before the correct solve, since most of the video felt a bit like bifurcation otherwise. Once again, huge respect to people who compile and solve these puzzles in competition settings, and looking forward to more puzzles from the grand prix.

[@AxillaryPower2]

how in the world does one even make these kinds of puzzles?

[@lukemit6640]

I think I'd retire if I made that haha

[@TheSarahskaninchen]

I was so proud of myself for figuring out it had to move two squares diagonally, but then I was stuck for a while and I was so amazed that he immediately ruled out the seven - and so fast too!

[@S3c13nt]

took me 57 minutes. with a little bit of your help. but since i am new to sudoku with changed rules or added rules, i think that is quite impressive. im proud of myself. and i wanted to say i love your vids.

[@70acres]

Why are you referencing the Knights Move on this puzzle? I don't see it in the instructions. Does Knight's Move always apply to these puzzles? I love Sudoku but am still a novice.

[@bnagybalint]

Any "knight-move" mapping between the highlighted region and the clone would violate the uniqueness one of the center box's four highlighted squares. E.g. imagine a shift of two to the left and one up: his would break the center box's center-right square as it would have to be the same as the upper-left corner of the same box.

[@eliaskar5084]

I've been watching this channel over the past week. This is the first puzzle I managed to totally solve on my own before watching the video! I'm so excited :D

[@rowandeblok5472]

this is my very first time where I've finished a solve before Simon, though without his help I wouldn't have gotten there at all

[@JT-tm5vj]

I gave it a go! Did it.... took me 2hrs - I don't partake in much sudoku - I felt like a genius!

[@Odesawaan]

After watching the first five minutes I paused the video and did the puzzle myself. I'm a novice at doing sudokus though I have an interest, and this one looked really intriguing. It took me over an hour but it was fascinating to watch how this logically unfold in a counterclockwise spiral across the fields. It was like an interwoven web weaving its own shrinking possibilities. I spent about ten minutes just repeating it some parts to myself simply because I started to secondguess myself once I started picking up speed by following the threads. I'm in awe from it.

[@Embre07]

I didn't know there was a sudoku side of youtube and that it was so mesmerizing. I bought some sudoku just for that and god mine are simple compared to his but I'm so slooow ! I admire him for that mental capacity of seing all of this tricks so quickly ! Amazing.

[@muntoonxt]

Took me just under two hours! 1:55:47. You managed to figure out the diagonal pattern and its restrictions in 10 minutes whereas it took me the entire hour. :) (I'm not an advanced sudoku person.) One nice property of the puzzle that you may have missed was that many of the constraints were repeated for **both** possible locations of the pattern. The lower right pattern possibility could then be eliminated entirely using the "89" pair that you discovered.

[@MrSaydo17]

1:04:17 - Super happy i was able to get this without guessing if it went up or down the diagonal. It was the 7s in box 3 that did it. If C4R3 and C5R5 are 7, and it shifts up the diagonal, then 7 must be in C2R1 forcing 7 in C9R2, but the 7 in C9R4 rules that out. If it shifts down the diagonal, C8R7 must be a 7, foring C7R3 to be a 7, but C4R3 must also be a 7 therefor C4R3 and C5R5 can never be a 7. Then the 2 in C7 rules out the shift down the diagonal

[@ChilliDuck]

im always stunned at how fast youre solving until i realise that i watch at 1.5 speed, so i can go to sleep punctual. but youre still so incredibly fast! everytime you get amazed from a puzzle and say you slip into the mind of a greater person than i can only give that statement back at you for being able to solve those at that speed

[@yichen6313]

I finally got it at 2 hours! It's not too hard to figure out where the shadow is, but the 7 elimination he did at 16:09 took me forever to spot

[@alienrenders]

For some reason, I thought this one was rather easy. I just colored the board red where the bottom gray cell couldn't move to and it left only two cells along the diagonal. Then I colored the gray cells as you did and noticing the 7 couldn't be used meant the rest solved as a regular sudoku. I did use a specific color for 8 and 9. I didn't know which was which, but I did know which ones were the same. So instead of numbers, I could color it in. I started the shift of gray cells toward the bottom and saw there weren't enough digits. And the fact that all four colored cells were in the same box meant they had to be different digits. This is what led me to believe I was on the right track as to the clues you're supposed to figure out. Really cool puzzle. Thank you for showing it.

[@gregoryshipley4637]

Thank you so much for sharing these puzzles. I've been watching and it has reignited my latent puzzle love. Very proud of myself as this is the first of this kind of "hard" puzzle I've solved without assistance. Took me over 30 min to get a digit in but it was a very satisfying solve.

[@DmitryArciszewski1]

Wow! Not only I enjoyed watching the puzzle being solved, but also learned new English idiom, "start cooking with gas".

[@deanhickerson1000]

This was easier than I expected; I took about an hour to solve it. I found the solution at 55:06, but I'd trifurcated so for completeness I went back to explore the remaining option, which took another 5 minutes or so.

[@randomcubing7106]

I love how this was the Hardest Sudoku back in the days

[@super_7710]

Woop! It's been a few years since I've tried a Sudoku. I thought I'd try this one to see how hard it actually is. Managed to solve it in 1:14:16! The trick is to understand that the clone can only be in one of two places and that it must overlap. Then it's just normal sudoku - testing rows, columns and boxes until you find situations where a number has to go somewhere.

[@historymysteries4134]

This may come up but how did he conclude that the translation must go up/left and not down/right? ETA: 28:40

[@jessvarey2597]

This is brilliant! I love watching you solve these. I don’t even do the puzzles but maybe I should start with some easy ones. Thanks for the entertainment.

[@Atchfam77]

Woo! After understanding the thought process behind the translation, I was able to solve along with the video in just around 33 minutes. I would get stuck or go pretty far ahead and cross-reference the video to see you do the same steps as I did and it reassured me to keep going forward. I missed a few simple resolutions that I had pointed out to me in the video, but like always once you get momentum, the whole thing seems to solve itself. Very cool puzzle.

[@nickieshadowfaxbrooklyn5192]

I've noticed a few steps in the process you missed, I guestimate they could have sped up by 5-7 mins, but noway it's doable in 10 min limit for me. Great puzzle, btw. So elegant and mathematically beautiful. I enjoyed it along.

[@demerion]

I'd love to see the other puzzles sometimes!

[@miraculix666]

I recommend the tic-tac-toe!

[@phillish2258]

Du hier? O:

[@Wecoc1]

I voted for the tic-tac-toe indeed

[@demerion]

@@phillish2258 Loooool, was ein Zufall, hi!

[@pawn9261]

01:06:11 well i did a cheat a bit. Needed to look at your pattern. Loved the video thanks.

[@nopenopessson317]

This was in my recommend. I've never tried a soduko before but I saw this entire video and enjoyed it. KZbin knows me more than I know myself. Gonna learn soduko now

[@nicksm7980]

Start with the correct name of the puzzle.

[@richardhenrysutterrosendo3439]

58:51 Had to check which of the translations along the main diagonal was the right one, with backtracking. Really nice use of the color tool for this puzzle.

[@bogdangiusca5057]

It took me over 1 hour with restarting the clock and a few hints from him so how someone cand do this in under 10 min is beyond me

[@chrisvaughn4399]

I'm not quite understanding the reasoning for the 'dis-proofing' being justified by saying 'this can't be true because it would put too many 9's in the bottom right box's. The proof was found at 16:55. The 2 is blocked by shifting diagonally down by the 2 provided in the top right box. Therefore the clone must shift up and left. Great puzzle. Regardless of the direction of clone shift from the start point, top left and bottom right box each begin with 4 possible 9's.. and none are provided as a starting number?

[@kuroganeyuuji6464]

it means he would have only 3 numbers(589) to put into 4 boxes, which dosn't work, so it is possible to rule that out from the start

[@LostMagyk]

Took around 30 minutes, after thinking I wouldn't be able to solve it. Figured out that the clone could only be in 2 places and worked out the digits for each number leading to an 89 pair. Then saw that 5 was the only digit left for a number in the main region, giving 2 as the other number and pushing the clone to only be possible at the top. Logic after that was fun to follow. Really enjoyable.

[@cl5rys]

My teacher taught me the rules of suduko a few days ago it’s easily become my favorite puzzle, if use to be my most hated now I enjoy it and look for time to do it

[@juanander]

Quite proud of 28:40 after staring blankly the first 5 minutes. Mind boggling how the world best can do it in almost 1/3 of the time!

[@tbmike23]

I just spent 10 minutes shouting at the tv: the shape can overlap and repeat! They give you answer, the constraint is always the clue.

[@toantu3005]

He was trying to find the solution with 100% certainty

[@spinningdog2578]

Didn’t know sudoku can be this fun! Tried it and did it in about one and a half hours. The guy who solved this under 10 minutes must be a genius!

[@karl-erlendmikalsen5159]

What I think is truly fascinating is how differently we solved it. Well, of course I started with the clone-area, but I started with the bottom right rather than the top left, and I colour marked everything that couldn't be the bottom right in the cloned area. Then, I'm not really sure what we did differently, but I swear that before I was half way through I had solved all the 1, 2 and 3's.

[@nady2296]

49:29 took me some time to be sure where to place the "new" shadow region. And then it was quite long but not SO difficult

[@alandouglas2789]

Nady 22 nah, got proof?

[@GareginRA]

Tried this before watching. It took me more than 3 hours.

[@Sam_on_YouTube]

Took me a little less time, but I screwed up. Had to watch his video until 25 minutes in to see where I made my mistake. Fortunately, I didn't have to undo too much. Once I fixed it, I solved the rest pretty easily.

[@sfvgrol3533]

Same, it took me about 3 and a half hours. But we did solve it ourselves, so that is something right? :D

[@plusjeremy]

Well I have to say, I’m pretty proud of myself for solving this one. But I guess that makes sense: I’m pretty rotten at sudoku, but I have a math background. Once I applied some logic to the theme, I was able to make progress almost immediately. (The remainder of the puzzle was standard for me, which is to say, difficult, because it’s sudoku.) Looking forward to watching the video now!

[@corruptconverter2616]

I narrowed down the possibilities for the clone to 2 in about a minute or two by imagining it like a grid of possible offsets from the center. That narrows it down to a 5x5 since anything outside puts something off the grid. Naturally the center is narrowed out because of complete overlap. It then becomes 4 2x2 squares because of lateral and vertical problems (Sudoku rules). The inward corners of these 2x2s are narrowed out because (+-1, +-1) in any direction isn't possible due to sudoku (Middle grid), then (+-1, +-2) and (+-2, +-1) are narrowed out too, again due to sudoku in middle grid, leaving me with (+-2, +-2). ++ and -- are narrowed out because of sudoku in the outer middle grids, so it has to be (+2, -2) or (-2, +2) Hope that made any sense. I haven't finished watching the video yet

[@Sam_on_YouTube]

I was with you until 25:55. When I did it myself, I put a 3 in the wrong spot and screwed the rest up after that. Happy to get that far before making the mistake though. Took me a LOT longer than it took you. I went backn until I found the incorrect inference that lead to the mistake and redid it from that point. Solved the rest quickly from there before watching the rest of your video.

[@GhostZeroGZ]

It might have taken a while to explain that, but I came to the same conclusion just by looking at it and I didn't know why I felt it was true. You slowed me down and showed me the math to why I was right

[@ShadowMark474]

41:40 for me, time might not be accurate though, because I had the tab opened in the background while I watched the video a bit to see the rules. I honestly didn't think I'd be able to solve the puzzle so I didn't worry too much about my time lol. Really fun and interesting puzzle though, glad it was chosen, but I'm also curious about the tic-tac-toe one. Also kinda disappointed that you didn't rule out the down-right transition before continuing, but it was pretty easy to do, so I can forgive you lol.

[@chrisi1466]

This is the first one out of watching and trying myself before watching I actually got without using the video for clues. I’m so proud of myself despite my previous 50 failures lol

[@Sirakle]

I cracked it in 1 hour and 48 minutes and I'm quite pleased with that. I may not be ready for the Grand Prix yet though...

[@erickehr4475]

I completed that in 22:21 which I am very pleased with. I’ve not watched the video yet so haven’t checked if my logic was sound, but I believe I managed to restrict the position of the clone to one of two places; couldn’t see an obvious way to work out which was right and just guessed. Luckily I guessed right, else there’d have been a load of backtracking! E.t.a. Having watched the video, I’m amused , and quite frankly surprised, to see that Simon basically did exactly the same as me! Although he was dedicated enough to check why the other way wouldn’t work, so hats off to him for that.

[@aamocryp]

there was in the end a way to logic where the clone could go, as two of the cloned digits needed to be 8&9, and the other possible placement for the clone wouldn't have worked with that restriction! (it would've required two of the cloned digits to be 5&9 in addition to the 8&9)

[@glennmelven3414]

Waaaay beyond me. Loved watching Simon though.

[@bfish89ryuhayabusa]

I'm surprised you just went with the upward shift. I put both as possible, which works because you can rule out anything in the outer clone boxes that intersects both versions of the same cell, which happens enough to work. Combine that with the middle clones are the same as each other, either way, and you can narrow it down and then eliminate one of the two moves.

[@andrejsskrebecs1642]

Am I missing something, or how did he rule out the shift downward along the diagonal? For me it took looking at restrictions in the center square and locking in 2.

[@BlueCyann]

Someone said he did it by looking at box 9. (I can't watch just yet, so sorry if that's misinformation, but I did it that way so I know it works. Box 9 clone contents would reduce to an 89 pair and a 59 pair: impossible.)

[@petemagnuson7357]

He goes back and checks after the puzzle, skip to 28:38. Tl;Dr 4 cells are limited to 3 values and the puzzle breaks.

[@andrejsskrebecs1642]

@@petemagnuson7357Yep, should have watched it til the end... )))

[@vaporleon8887]

He recognized in the video that he did NOT rule it out. But after solving he went back at 28:34 to discover why he could not go down. Effectively he guess in the beginning.

[@BlueCyann]

@@vaporleon8887 After watching, I found that kind of funny. I'm still not sure whether he intentionally set out to make that guess, or whether he just got a little too caught up in the logic to stop and decided to just run with it.

[@Aerialdan1]

Simon. I'm just wondering, in test conditions, would the 10-minute guy have tried both options briefly to see which one was incorrect or would he just chance it one way or the other? You proved the 2nd way didn't work almost in a matter of seconds but I'm thinking that with a different grid it might take a lot longer to figure which is incorrect, and then it becomes a bit of luck which way you choose.

[@glennmelven3414]

He did in a few seconds of video time. He didn't show how he got those candidates. That was quite a bit of work off camera.

[@BlueCyann]

I'd almost bet money he did look at both options. Otherwise he's starting almost from scratch if he gets it wrong. It's very little benefit for someone like him, vs a potential loss of minutes.

[@EddieOtool]

Over an hour and a half... Did it on paper and got quickly lost into pencil marks. Also hadn't done a Sudoku in over one year (OK, maybe just one or two), so a bit rusty. ;) And I was tired, so I feel I got all the best excuses in the world to still think I can compare to the best in spite of my underwhelming performance. :P In all seriousness I am just glad I could crack it open... means the brain's still half-working at the very least. Still lacks quite a few gigs of RAM tho; I'm overdue for a rebuild.

[@stephanberger3476]

Other people watch sports, but not me. Much more excitement in watching Sudoku's being solved. Yelling at the screen and all!

[@klappvideos5350]

Just for completeness. The translation of the region can be disambiguated without tial and error. If you pencil-mark only the middle squares and discard every directly seen digit and every digit, that is seen by BOTH outer squares, you get the 89 pair as well and the 2 disambiguates.

[@kamikazegargoyle]

think i got a respectable 46:42... and i did it WITHOUT bifurcation ETA: my approach was a bit different cos it involved finding that 1346 couldn't be in the pattern either way (they all see too many of the target cells), then that 72 could only be in if the pattern moved up, and that at least one of them had to be because four numbers were already ruled out. only then did i rule out the bottom pattern and find that 7 couldn't be in because it'd repeat and clash with top right box. i'd already got 89 for r1c9 - you can get it at the starting position so it made sense to me that this was right cos i had 89 pair in the top row. tbh kind of disappointed that simon made a lucky guess and got away with it, he's usually more logically rigorous

[@dukdog]

How I solved without bifurcation: Make the alternating pattern across the entire diagonal. Recognize that any colored boxes in the top left or bottom right are optional, and you can only remove an item from that color if it is eliminated from the other boxes, or both the corner boxes together. 4 is a perfect example for this. It is not removed from any of the central boxes, but it eliminates from all of the 8 possible colored boxes in both corners, so it is not part of the repeating pattern. Eventually you get down to 2,5,7,8, & 9. It was the elimination of the 7 that then became the trickiest for me.

[@michaelclarkj]

Got it. Used your web app and close to three hours, but I got there. Super fun. :)

[@dracaaarys]

Sometimes the most enjoyable videos are the ones you hopelessly know (as an amateur solver) you'd never be able to solve on your own. Cheers Simon

[@dascandy]

Whoah. Got it in 28:05. First 12 minutes spent on the gray boxes and how to move them, and eliminating the options there. As soon as I had all the box values the rest just falls into place as a sudoku.

[@miraculix666]

@15:50 The "green" digit in box3 can't be 7 because of r4c9. Therefore there is 89pair in the right column of this box and r1c8=7 and r3c7=1. In fact, the rest of the sudoku is surprisingly simple (given the upwards shifted clone)