Beyond Diabolical... Sudoku Madness!

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▶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

[@xcountryguy0]

"This Sudoku is monstrous so I will employ all techniques" is one of the nerdiest things I've ever heard.

[@phs125]

You're a sudoku fan? Name every technique.

[@KittyXCross]

Botheration!

[@jestfullgremblim8002]

​@@phs125i actually know the names of most of them! Including the ones from Sudoku's variations

[@DevilishlyDutch]

video: 39 minutes me: that's alright, I'll let you handle this one

[@alielkhatib7023]

LOL

[@calvinvondracek1418]

Love your name lol

[@DevilishlyDutch]

@@calvinvondracek1418 heh, thanks, especially appropriate here with all those diabolical puzzles huh? 😂

[@djlungo]

I really like the long ones!

[@erezsolomon3838]

Lol I did it in less than 29 minutes

[@Salami250401]

Simon: Uses the ‘crank handle’ trick using five squares to get a digit in an extremely obscure way Also Simon: has a square pencilled in as either 7 or 8 despite the fact there’s a 7 in its row, column AND box

[@Dukewatermelon]

The penciled "3" in the top left box also got to me... but I've worked on puzzles where the brain just goes and I have nothing but sympathy for the act of solving this fabulous monstrosity.

[@MGmirkin]

How, at 25:00, has he still not penciled in 9's in the top right and middle right squares of the top left box?? Should have been in the first "basic" pass. That ain't rocket science. Those two are ruled in as the only candidates by the other two columns in that column of boxes.

[@frostbound]

@@MGmirkin I stared at those nines the entire solve and it was literally the last digit he got....

[@peterboneg]

Not very obscure. It's called a w-wing. He just didn't know the official name.

[@Goryus]

The madman actually did it!

[@jamest745]

Derek Neal this puzzle is crazy. Well done.

[@RandomBurfness]

I didn't check for any slot machines whilst doing my solve, did you hide any in there?

[@dougmelven2597]

@@RandomBurfness I checked for slot machines as soon as I saw it was one of Derek's puzzles and didn't find any.

[@achad1607]

@@dougmelven2597 There is one for nines in box 2.

[@chuffer595]

We need to see a blooper real of the times you've had to give up on puzzles! We all experience it and I would love to see the times it happens to two such fantastic solvers like you both

[@hepenypacker]

I was just thinking about this very thing. Where he's filming and he's about 45 minutes in and gives up. This must have happened. Some of these puzzles are extremely difficult

[@djddm8760]

To be honest, they are all fairly simple. At least the classic ones. But I think commentating while solving is where these two guys really shine. But unfortunately having to commentate rules out anything harder then this difficulty.

[@vctrsigma]

Not even a schadenfreude, I would like to see this at least once as a surprise. Shame we just had april fools.

[@dougmelven2597]

I love blooper reels. One from this channel would be great.

[@vctrsigma]

I also watch mechanical puzzle solvers, one posted two different times he had to give up at solving "Excalibur". It just made it more epic months later when he did finally get it. Nothing wrong in having to take a break and start over.

[@beatrizribeiro2417]

" I'm running out of colours" *Has used 2 out of the 9 available* This is called Diabolical Confusion, my friends, caused by the puzzle

[@stevenlomon]

This contains basically every Sudoku technique you need to solve hard Sudokus! 5:58 Swordfish 14:50 Hidden triple 17:11 Empty rectangle 22:18 X-Wing 24:50 Y-Wing/Bent triple 28:35 Another hidden triple 30:38 Another Y-Wing 32:26 "The crank handle" 34:40 One last empty rectangle

[@pedromigueltavaressilva23]

Didn't even know strategies like this existed, its just crazy, now i want to learn all of them

[@stevenlomon]

@@pedromigueltavaressilva23 I've learned a crazy amount watching this channel over the last three months or so hahaha

[@redarndiculous]

Literally watched the video thinking "now I just have to re-watch it 100 times until I have all those techniques he showed down"

[@laurv8370]

No Octopus ? Disappointing ! :D :D

[@peterbutterjam97]

Why does the swordfish not work for the columns as well? I’m bad at logicking those

[@jncdi1535]

Reminds me of my days as a student pilot following along on the controls whilst the instructor is demonstrating a difficult manuever. I can follow along, but am in no way capable of doing this on my own.

[@loldebiteloldebite1607]

This is remarkably relatable!

[@jonfbanks]

Something which happens to me in every Simon video: Me: Is glued to the screen. Completely into what is happening. Simon: "I realize this must be very frustrating to watch."

[@albertkirk5916]

He said that exactly as I was reading this comment

[@grimsqueaker5333]

Yeah, this mere mortal is trying to follow Simon's logic so hard.

[@pierrejoseph4797]

I need a 30 minute video on you giving up on puzzles

[@ericveneto1593]

Simon: PLEASE upload your blooper reel!

[@JeremyButlerquarterthru]

19:20 BOTHERATION! That's a new one. lol

[@davidevigiani1401]

I have to say: this puzzle was fantastic. My capabilities are far from yours but i had such fun learning new stuff and contemplating such marvellus sudoku.

[@Pyromonkey83]

TWO BLOODY HOURS. That's how long this took to solve. Derek Neal, please know that your name inspires fear in my mind. I had to bifurcate (or I guess, follow a long chain, technically). I found the swordfish. I found the X Wing. I found the Skyscraper. I found the finned X Wings. I found the triples and the pairs. I found the Y Wings. I STILL had to bifurcate. Good god this was hard.

[@Goryus]

If it makes you feel any better, the subject of my email to Simon when I sent him this puzzle was, "I apologize." :) I hope spending 2 hours on this helped take your mind off of current events for a while.

[@simpleman4251]

Did the long 'chain' you found involve a whole ton of implications on 5's and 6's? I think we followed a similar solve path if so haha

[@andrewbieny4564]

The puzzled wrapped up for me with the xwing 7 as that cleared up most the 5, 6, 7, 8's. Simon missed 2x 7's after the 7 xwing. Don't get me wrong. It took me an hour to get to that point but then i facepalmed. Great puzzle for these long days!

[@AractusPuphlicus]

It took me an hour, on my 4th attempt. I got through it with a single bifurcation. I bifurcated the 7's as they interacted heavily with the 3's and 9's.

[@balthazarbeutelwolf9097]

Took me about 40 minutes. Swordfish? No, didn't even know what that was till this video. Even missed the Xwing. So, what did I do? Bifurcate, and click undo like a monkey; bifurcate again. Repeat. About 5 bifurcations did do the trick. This works ok on-line, cannot do it this way with a pencil+paper sudoku. Not sure I would even want to deploy a swordfish after seeing this, but the bent triples were cool.

[@toddschaefer5488]

Thought with this many givens, this would not be that tough. It did not give up its secrets easily. Great solve.

[@lulzmoney99]

Is it strange that I keep repeating "now we're cooking with gas" while I solve sudokus?

[@tanujbhojwani]

No

[@zephr8786]

it's definitely not as weird as me doing a Scottish accent and dictating the pencil marks and digits that i place... i have no idea why i do it, but i do

[@phs125]

Unless you're cooking with wood and you didn't even find a way to make fire at that point...

[@moonglum101]

32:26 "There is a trick". How on earth do you see something like that?! Amazing! I still have much to learn.

[@RocketsharK7]

After struggling and only completing half of most of the puzzles on this channel in about an hour, just to watch you complete them in 10-15 min, its oddly satisfying watching you struggle through this one :)

[@jeanotzubler2477]

i feel you

[@hariman7727]

I found this one via googling cracking the cryptic classic sudoku... and I gave up after a certain point. I am GLAD that I gave up, because it took an expert as long as it takes me to solve a regular not all that hard sudoku.

[@Nevir202]

I really enjoyed watching this solve, Simon felt like I feel solving any decently difficult Sudoku. 😅

[@alltradejack]

So all we needed to do was spot a swordfish, an X-wing, two bent triples and a... crank?? Yeah, this is beyond diabolical and so is Simon. Now if I could watch Mark bifurcate the heck out of this, that would complete my belittling.

[@wilfriedlechner6299]

Swordfish!! How to spot then an zwingen am then a bent triple! Coulda anybody of u do this diabolical one!!!!! Without the help of Simon Anthony!!! Let me know / I love toughies!!

[@blobblub9424]

What is bifurcate?

[@alltradejack]

@@blobblub9424 Mark sometimes does this thing where he plugs a number in somewhere and follows the ramifications of that placement to see if it causes problems elsewhere so that he may eliminate that possibility. It is incredibly hard to follow and even harder to do yourself. What it allows Mark to do, however, is get to a solution faster without having to figure out the logical path to the solution which may be fairly narrow and hard to figure out. My comment was an allusion to the fact that I can neither figure out the logic like Simon nor bifurcate like Mark. Especially not on a beastly puzzle like this.

[@blobblub9424]

@@alltradejack ah thank you very much! You explained it nicely, but yeah, I love to watch and be amazed, but I could never do this myself!

[@austinhernandez2716]

I never noticed the w wing("crank") even though I looked really hard for it. What I did spot though were two finned jellyfish and that solved it

[@joshandrews8913]

21:50 - 36:50 It only took 15 minutes for him to realize he pencil-marked a 3 in a box already containing a 3. I would've been stuck on everything else, though. Great video.

[@Alcadain]

he still wouldnt have been able to place a digit in until right before he noticed it when he ruled out the 4. That solve gave me anxiety lol

[@chris5619]

And right after, "now why did I have a 7 here when that can't be a 7?"

[@wilfriedlechner6299]

Yes that 3 was there for a long time but there was a 3 in the box itself already

[@wilfriedlechner6299]

Are u heavy solders??!!

[@wilfriedlechner6299]

I meant: heavy solvers??? Diabolical ones???

[@DaIe]

Watching you unravelling that at the end was so satisfying, and I was holding my breath with you there. Keep it up!

[@RandomBurfness]

A time of 53:05 for me! I had to pencil mark the whole grid but I did find the X-Wing on 7's, the jellyfish on 3's, the subsequent hidden 29-pair in column 6, the yet again subsequent hidden 167-triple in box 5, which lead me to discovering a 1456-quadruple in column 3, and then I found the Y-Wing in R2C34+R3C4 which FINALLY unraveled the X-Wing on 7's and then from that point and on, it was smooth sailing. Derek Neil's puzzles in the Classic Sudoku app really did prepare me for this one!

[@fleaship6134]

I've no idea what you are talking about. The swordfish, X-wing etc are far too complex to wrap my head around hence why I steer clear of the extreme sudokus. Something that infuriating loses it's fun.

[@16m49x3]

It's not frustrating to watch m8. It's comforting to see you also struggling. :P

[@stridedeck]

I learned a lot from these very hard ones!

[@tezcharold]

I love these long video's and absolutely don't mind any pauses while you stare at it or a moment. This one was especially fun to watch you pull one magic trick after another out of the sudoku hat and the puzzle kept resisting anyway.

[@samtravis4822]

That’s the most outrageously difficult classic sudoku I’ve ever seen. Every digit took about 3 different advanced techniques to get, I’m stunned

[@ThomasHDBass]

Then try the following ;-) ..68..925 .2....1.. 1....6... 6....5... ....3.... ..14...57 .3....2.. 2....4.1. 4....7..6 Created this a while ago, but did not publish it, because it's just too extreme. There are lots of extreme sudoku possibilities out there, but they wouldn't be fun as you would just have to plough through endless logical chains (or simply resort to trial and error). Derek's puzzle is much better, as it is solvable with techniques relying on recognising typical pattern, and not just endless variants until you can rule out single digits.

[@m0s12]

@@ThomasHDBass @ Solved it in almost 2 hours its an extreme puzzle with hidden triples and all sorts of wings ! The 5th row is 5 7 2 6 3 8 4 9 1

[@ThomasHDBass]

@@m0s12 Thanks for the feedback - but I'm curious - was it worth the time? And did you enjoy solving such a fiendishly difficult puzzle?

[@forkevbot]

Nice to see you struggle with a puzzle from time to time :) makes us peons feel a little better.

[@balazsadorjani1263]

OMG. This one is so difficult, so far beyond my capabilities that in fact by putting random numbers in random locations I would solve it sooner than by thinking.

[@Rikoshima]

tried doing this on my own and came to the video for tips when i was truly stuck. i learned a lot! that "bent triple" technique is very useful, but i just don't spot them

[@Blindpig14]

“Whoa....I am not unhappy with that”...What an awesome line to close it out! You made my day with that!

[@brachypelmasmith]

I thought we were up something with that triple, but we just aren't are we? Exactly my sentiment during this entire puzzle. Great one. I couldn't spot that 3-4-5 relation and 1-3-4

[@FryuniGamer]

That's it, it's decided, after this video I'll finally start the project that I though a few weeks ago. I'm gonna code a general sudoku solver where you can describe those unorthodox sudokus and see a solution! Or at least I'll try

[@Taaneria]

How is it going?

[@jamba_d2225]

This was a great puzzle for repeated explanations of your techniques. Very helpful for struggling novices like me. Thank you.

[@jenningssun953]

Is it just me or does anyone else also enjoy watching Simon struggle? Ngl I'm kinda attached to these "long" videos and starting to belittle those "easier" puzzles, even though it still takes me hours to solve them.

[@hamzahussain7794]

Anyone noticed and annoyed by the obvious 9 in r1c3 getting ignored halfway through the solution? 😂

[@stevesebzda570]

@Hamza Hussain, only after the 7 was put in and seeing you mention it But yes after a bit though lol

[@samtravis4822]

Patreon $5 option for access to the blooper reel?!??

[@dougmelven2597]

I would pay $10-15 for a blooper reel from this channel.

[@3laserbeam3]

That was absolutely brutal! Love it! Needed hints o_o... Otherwise, some feedback: Do you feel leaving the colors for xwings/swordfishes in helps you after you've already used them? I feel like once you've resolved those patterns (and made other annotations) they clutter the grid a bit.

[@bobuardodavinci93]

“Very occasionally, we do sudokus that are monstrously hard” It’s obvious this is an older video 😆

[@DavidNayer]

I found this late in the stream as well. Like you, I've gotten used to most of these techniques. Not that I spot them easily. At least I know how they work.

[@grampsca]

Took me just over an hr, and I ended up erasing all my pencil marks half way through so I could try a different logic. I did it totally differently than you, but in all fairness I dont have a clue what I'm doing most the time. Just brute force it. Dont look for or even understand what Y wings X wings or any of that other shit is lol. Thanks for the content man. Would love to see some of your "blooper reel" stuff sometime.

[@UltraLuigi2401]

The 78 that had a 7 in its row, column, and box for at least 5 minutes though.

[@KingMagenta]

He put a 346 triple in box 1 that had a 3. Spent almost 15 minutes with that. Felt bad that his mental focus was deteriorating the longer he stared at the puzzle

[@roland9189]

I screamed at the screen after the xwing got solved because of that.... Although it would not have changed anything.

[@tomekduresov706]

This is crazy good, how could someone dislike this?

[@LeonEllisZ]

16:52 "This must be very frustrating to watch" Lol, oh no my good sir. Quite the contrary. It's comforting to know that even an incredible mind like yours can get stuck on difficult puzzles. Make ME feel not so bad when I get stuck too.

[@adrianhead6272]

"That can't be a 7. Why did I think that could be a 7?" Don't know... but probably the same reason you penciled 346 into a cell when the grid already had a 3 in it, immediately prior to spotting the error!!!

[@leefisher6366]

34:23 - I can see it, Simon! I can't believe it, but I can see it. Top right hand square. In four squares, you know it's (1,4), (1,3,4), (5,6) and (3,5,6) sort of going clockwise, but NONE of those squares can hold a Budgerigar. So there's a Budgerigar in the square above the nine, and yes, I'm being silly. (It's clearly a crocodile).

[@nicoleleboeuf-little1048]

"But NONE of those squares can hold a Budgerigar." Which would explain the lack of bird sounds in this video...

[@leefisher6366]

@@nicoleleboeuf-little1048 Which explains why you didn't tweet this comment. (YES! I've been waiting to do this!)

[@nicoleleboeuf-little1048]

@@leefisher6366 WELL PLAYED, FRIEND. WELL PLAYED.

[@alimoh]

Can someone help me understand how Simon implemented the swordfish pattern? How did the pattern eliminate 3's in cells of C5,R8 and C6,R7?

[@EmilJohanssonEOC]

I see what you did with the thumbnail and the abbreviation of the video title. You little rascal! ;)

[@dvdspndl]

33:00 is called W wing.

[@whocareswho]

This one isn't too difficult... IF you are young, stubborn and have a long life ahead of you to solve it.

[@viodragon974]

can I slap you for forgetting your own 7,8,9 only spots that became the final fills of this puzzle? It is a good showing on how over thinking can make you forget discuss earlier points. nicely done.

[@DWOBoyleMusic]

This puzzle was a crash course in so many advanced techniques. Wow

[@robl4836]

Too hard for me... So I wrote a brute force program to solve it. The solve took 20 secs, but writing the code took more than 40 mins, so Simon still beat me!

[@albertreitsma988]

But you can use the same code again 🤭

[@terracottapie]

That "BDSM" acronym in the title had to be on purpose, right?

[@darrensexton1020]

17 minutes in and I'm yelling at the screen "Get rid of the 7 in the middle square"

[@TheDillon8825]

Damnnn I did it in 48:11 minutes. I used guessing and trying out different numbers to see if they broke the puzzle (which I don't know if people consider it as valid) but feel pretty good with this time, specially comparing it to the god Simon himself.

[@nabin6976]

No people don't consider it valid, especially Simon.

[@barrydavies2977]

If you found it difficult, imagine how the rest of us felt. My brain is worn out just watching.

[@elwoodhopkins]

I like how the first 3 or 4 digits are blatantly obvious, and then it suddenly becomes a total nightmare

[@bristolrovers27]

Stared a while, filled in a few numbers stared some more, tried to remember the slot machine, gave up watched a manful struggle, well done a dogged solve

[@fluxoteen]

21:07 You witness the soul leaving the body

[@ryfors]

I just watched this for the first time and being used to Simon solves I feel like he's really improved during the year that's passed

[@woodchuk1]

This one took an X-wing, multiple Finned X-wings, a Swordfish, an XY-wing, two type 3 unique rectangles, and a Sashimi X-wing to break. This was pretty brutal...took about 45 minutes and that was with an eventual hint given. Short of using alternate forcing chains or exotic strategies like Sue De Coq, aligned pair exclusion, or ALS-XZ, this is about as complex as you can get. Bravo Derek!

[@jackieenois]

Thank you for this video, you are an excellent teacher those techniques were very well explained. Also I think your mind was quite sharp in this video, I've been watching you everyday and you seemed extra focused on this one. Very entertaining also.

[@ngchorhong3174]

2 hours 13 minutes 30 seconds Call me crazy but I used BRUTE FORCE because I was so desperate At least I finished :-)

[@tbpotn]

Guess ill do the starbattles xD looking forward to your solve though

[@lakarto19]

41:30 solve time! To be honest I'm really glad to see a challenging classic sudoku on the channel for the first time in quite a while. For this puzzle, after seeing the length of the video, I went into full-candidate notation mode pretty early on... saw the x-wing on 7's but missed the swordfish on 3's, which was costly. After some complicated chaining eventually managed to get to the end. Hope to see more great classic sudokus!

[@the_dingles_is_my_sht2859]

You will get a near identical puzzle if you replace the upper right box 8 into a 4. I messed up and got everything right expect that one box messing me up! So that wrong 8 was effecting two boxes. And nothing else. Fascinating

[@patrikbak8161]

Seems difficult. And yet without the 8 in the first column it still has a unique solution.

[@renerpho]

Yes, but removing that 8 destroys the symmetry. And it would be obvious that the missing digit was an 8, because anything else would look ugly. ;-)

[@Hoezi02]

Usually i can at least follow the explanations, but with this one.....man!

[@DasOfTheBroken]

Nobody else sees the acronym...? Just me then? Welp

[@Tickles_The_Oaf]

3 years later, but yes, I see it! 😁

[@cypher686]

7 minutes in and he’s already making mistakes... he seemed to have forgotten there is no 3 in column 6 at this moment in time so his swordfish thing was a bit of fluke.

[@valeckseimu3132]

The 5TH number that is the VERY FIRST not given by the startin number came after 22 minuts, this is a real puzzle! 3:26 "Slowing down now" UNTIL 26:06

[@vezokpiraka]

One of the most satisfying videos from this channel. It's really cool to see you tackle puzzles that are very hard.

[@kapochung9990]

I spent 80mins to solve this puzzle by my own. so many fun. Love to see more video with difficult at this level

[@Keyboardje]

I gave up after 4 times trying, just sat down and enjoyed watching Simon! Wonderful!

[@ivydior6518]

Those 8s were sticking out like a sore thumbs after he placed that one 7 and it was driving me crazy that he didnt notice it.

[@EnderStine]

anyone gonna talk about the name *B*eyond *D*iabolical *S*udoku *M*adness

[@mikeE997]

2:13:52 - And I thought I was good at this, broke it like 4-5 times. Oh my....

[@zimmicks3170]

How can you possibly deduce that the 3 will ONLY appear in the purple squares you highlighted without first completely ruling out all the OTHER squares that the 3 could appear in? For instance in the upper-right corner Box, you only have 1 square highlighted as a 3. What about the other empty squares in that Box that could also be 3s? Why not pencil those in as possible? Or the other 2 possibilities in the upper-middle Box? You should have a LOT more purple squares highlighted for 3s.

[@Luna_Aberra]

On my beginner try on this one, for no reason at all had a feeling that in c3r9 will be 4... dunno why I thought that, felt kinda right and funny enough, it turned to be correct. YAY me... still failed obviously to do big progress. I am kinda hopin to learn how to solve sudoku better, it's brilliant and elegant logic game.

[@diy_rabbithole]

From 18:40 he says that 2s can be either locked vertically or horizontally, but can't they be locked in the third possible combination like the block below it? Why did he ignore that possibility? And he uses this trick again from 35:10... I'm going crazy not seeing which is obvious to him.

[@NelielSugiura]

That one (naked single?) sitting at r6c9 for a good ten minutes was the only thing that really bothered me on this one... well, okay, that seven in the centre cell was amusing, at least. Ahhahahaha... -=cry=- I make that same damn mistake you did with the 36 in r2c1 all the time... I do not get why, but glad to see you do it. Glad I watched through to the end to see that sigh of relief from you.

[@fuxpremier]

At the same time he could have placed the 1 in r6c9, he could also have placed the 8 and 9 in column 3 (they were all earned thanks to the trick with the triple than gave him the 7 in column 3. Actually, from then, the path was really straightforward but it was really funny to watch him struggle to find a new trick each time to unravel numbers one by one! :-p

[@ayannababii]

Is this how people feel watching sports??? THE ONES!!! THE ONES!!! BOX SIX!! THE ONESSSSS!!

[@jonnystruve]

I thought for sure this would be a variant when I saw 40 minutes... but dang. Classic? Looking forward to it

[@francoisduez601]

Well I'm glad I didn't try this one 😂

[@marcos.traverso]

You did perfectly perfect Simon! The time doesn't matter!

[@realGBx64]

Watching this after Simon solved an infinite variety of sudoku derivatives, let’s see how this goes!

[@adamc91]

That 3 (below the 1 in the top rhc) was sat there for 15 long agonising minutes 😂 Had to remind my self that you can’t hear me nor can you see me pointing it out 😂 Icl I’m surprised I even noticed straight away 😂 Love watching your videos.. but still can’t get my head around the swordfish (Because it looked like to me that in the middle bottom box - the number (believe it was a 2 or 3) could have gone in the box to the right of the 2 purple highlighted boxes, am not sure why them two boxes were highlighted when there was another box it could have gone, but maybe when I watched it I was missing something to explain the reason why. Will just have to keep watching your videos and hope a swordfish appears again soon and that time you explain it again and hopefully I’m able to understand it’s significance (Including how to spot it, why it works the way it does and when it won’t work, it’s purpose and the technique to help solve missing numbers and how and where it can be used in other sudokus etc)

[@colinbrash]

“Computer? We will be employing all techniques. Engage technique X.” “Are you sure, Sir? Technique X is an experimental technique. It requires more testing.” “Never mind, Computer. This is an emergency!” “Very well, Sir. Technique X deploying in 3, 2, 1...” 💥

[@austinhernandez2716]

I did it! It only took me 1:46:11! 😂 What solved it for me was truly insane, never happened before. After an hour and a half, I noticed a FINNED JELLYFISH! And then a naked quad, which led to ANOTHER finned jellyfish! And that FINALLY solved it. I started having a headache immediately afterwards. Craziest puzzle I've done in a while And yeah I put in a little too many notes, but it still worked.

[@Majromax]

At 34:15, there's some slot-machine-esque logic possible. R5C7 is a [34]. If it were a 3, then R5C1 would be a 4, R3C1 a 5, R4C1 a 6, R4C3 a 5, leading to a contradiction on R4C9. Ergo, R5C7 must be a 4.

[@austinhernandez2716]

BTW that "crank handle"(nice name, I like it) is also known as the w-wing. I guess it's just called that because we already have the x-wing, xy-wing, and xyz-wing, so someone just went back in the alphabet and called it the w-wing. Essentially, it's nothing more than anotrher typical AIC(alternating inference chain), just one with a common shape you can notice more easily and use as a technique. Also that's funny because I looked everywhere for it because with the common pairs everywhere I highly suspected it, but I never spotted it.

[@theblackswan84]

i wish i had your amazing working memory capabilities

[@joubess]

52:37 for me. Not bad at all given how extremely hard this puzzle is! Today is 11/21/2021 I don't think they give up forever on many puzzle. I would guess they save them and keep trying until they manage a solve. If there are some puzzles that have been tried by both Mark and Simon multiple times with no success, I would consider those the ones to give up on. I still don't think they ever give up completely. They are so many times better than I am at this, and over the last couple of years I can solve puzzles I wouldn't have tried when I started. I'm sure they have gained significantly more skill, and something they couldn't solve last year, they could probably solve now. I wouldn't bet against either of them after Tatooine Sun at any rate.

[@JaggerG]

27:45 I found something real gross there. I had eliminated the 3 from box 1 because it has one already of course. I also noticed the 6’s in box 5 pointed at box 4, so r5c1 could only be 3 or 4. So I noticed that r3 has only 2 positions for a 3. Either far right, or far left. The interesting thing is that placing a 3 in the far left places a 4 under it, and 5 6 are placed above, lining up alongside box 2’s 5 6. That made a 5 6 pair in box 3, eliminating that top 3. The originally placed 3 also placed a 3 in box 6 in column 7, eliminating the 3 in that column in box 3. That only left one place for a 3 in the box: r2c9. So either the 3 is in r4c9, or it’s in r4c1, forcing another in r2c9. In either result, r9c9 could never be a 3. And because it could never be there, the box 9 3 must be in column 8, eliminating the 3 at the top, so in fact it’s still a 5 6 pair after all. Ultimately that’s the kind of bifurcation that makes me think mayyyyybe sometimes everything is a bifurcation until it’s given a name. It’s so similar to a bent triple, but inverted, and like 5 steps removed.

[@seldikster]

As always, I did the puzzle before watching the viceo. Paper, pencil and eraser. I enjoyed this hard, challenging... but nice sudoku.

[@selenasilverstep7981]

I got as far as the X-wing of 7 and the Swordfish of 3 then go watched the video :( EDIT: from 3:20 to 26:05 is over twenty minutes of pencil-marking without a single digit. Simon must be very patient... EDIT 2: 36:55 "why is there a 3 here" Simon asking the real questions

[@lonewaer]

I gotta say, you are a master at seeing obscure patterns, and FAST, too, I have never seen this. Similarly when you finally start bringing down the puzzle, you are extremely fast. Maybe I feel that way because I'm trying to follow you instead of going at my pace, and maybe I would go as fast, but I don't think so. I have especially noticed that on some other videos of yours. "Hey look, look at those three cells. They work that way. Now look at this one, at the other side of the puzzle. Look at how the first three solve it." Me : "Wait what ?" I'm honestly still confused by the swordfish pattern. I get how it solves the 3's in the pink cells, but I don't get how that eliminates every single other possibility of having 3's in the white parts of the squares.

[@flipfloppoet4377]

I could not follow starting at around 8:30. Maybe because it's the first time I heard of the swordfish pattern, but why was column 8 chosen to correlate with C2 and C5? Seems arbitrary to me. What's to say the 3 can't go in C6 or C9 of Row 1? Couldn't follow the logic.

[@legobil_]

One question, @19:01 you deduce what numbers can go in box 3 top middle cell, and eliminate 2 since (I guess) the pencil marked 2s in box 2 top cells. There is however a third pencil marked 2 in the bottom of that box that you deduce away based on the this previous assumption. I guess what I am questioning is if restricting the 2 in box 3 to only the bottom 2 cells really can be done logically without the risk of a mistake...?

[@Freeedy]

That was a challenging puzzle... my head hurts. The naked 9 could have been placed in row 1, col 3 somewhat earlier after placing the 7 in row 2 but not surprising to miss on such a diabolical puzzle. Thank you for showing us a crank handle and the bent Y. Those are delightful techniques.