Three Great Sudoku Techniques

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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.
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[@dibenp]

Was able to solve the puzzle up until the swordfish at 10:00 ... and then I got stuck at the Y wing at 11:00. At least I found the bent triple. 😅 Thanks for the explanation, Mark!

[@lamosos]

I think bent triple and Y-wing are the same thing.

[@TheSunshinebob]

@Nathan-DTS I'm the opposite. I've seen the swordfish explained a few times but don't understand it. I still managed to finish the puzzles without it.

[@lsmart]

@@TheSunshinebob I'm not a big expert, but a swordfish is really simple. It is when three rows (columns) do not have a given number outside of the same three columns (rows). However, the condition is only that the number does not exist in any MORE than those three columns, but they may be in LESS than those three columns in one or more of the rows. Here, for example, it was not such an obvious swordfish (see picture at 10:15), because while the three common columns were 3, 6 and 7 - in row 1 the twos were only in columns 3 and 6, in row 2 the twos were only in columns 3 and 7, and in row 9 the twos were only in columns 6 and 7. But in each of them, the twos appeared at MOST in columns 3, 6 and 7. I hope this helps you or anyone else having a problem understanding the swordfish.

[@ChaoticNeutralMatt]

@@lsmart ye this part caught me.

[@cj719521]

I got stuck at each of the techniques. :facepalm: still learning

[@emplore]

Got stuck quite a bit at the end. Took me 45mins. An excellent classic. Probably my favourite sudoku ever. On a side note keep up the classics please. I only watch the classic videos to be honest. The others are too wild for me

[@ChaoticNeutralMatt]

Honestly prefer the more restrictive puzzles. Sad to hear about app completion, though I can understand. Got stuck a little before he finished the 4th, 5th, and 6th boxes.

[@dsquirrel]

You don't need the swordfish or the y-wing. At 10:05 in the video, we have two pencil-marked 9s in box 8, requiring the 9 to be in either r7c4 or r8c4. But r7c4 cannot be a 9 - if it were, we would have to place 2s in r8c4 and r7c9, and we would have no way to put a 2 in box 7. This contradiction means we have to put a 9 into r8c4 and everything else unwinds quickly from that.

[@emplore]

Interesting find. Is there a name for such a technique?

[@georgesthibaudeau1533]

@@emplore Doug saw the same thing as I did. I call the technique In Plain Sight ! That is because I have absolutely no technical ability. But this puzzle ended up being quite easy.

[@lawrencekallal6640]

Nice forcing test find by Doug. ​ @Esse San ... I call this force testing (FT) or a forcing test. Basically one picks one of the candidates in a square, column or row, and tests what the forcings are with either of the 2 candidate numbers or positions. It's my goto method I use to solve all sudoku puzzles. FT means you rarely have to find swordfishes, finned x-wings etc. It's kind of like a universal solving method. Unusually just have to follow a couple or few numbers around the grid to force a number, as in many cases a short forcing chain can resolve a number. In his case at 11:42, I FT'd the 9 in the top right 3x3 block. In either position, RC75 ends up a 4 -- and that was enough to crack the puzzle open. Doug's FT was a shorter more direct find than the one I used.

[@jobo2612]

@@emplore I think it's "inference chain"

[@jalsing]

the reverse technique of this, using the 2/3 in box 7 and the 2/9 pairs in box 8 and 9 eliminates the 9s from R7C4 and R8C7 is called a W-Wing I believe...

[@jalinth52]

I've been watching the channel for a few weeks and this was the first Sudoku I have ever tried. I got stuck, missing the swordfish and the Y-Wing, but my logic seemed to match up until there. Once those were pointed out in the video I paused and was able to get to the end. I'm looking forward to trying more puzzles in the future.

[@xaostek]

This video only goes to show how much more I have to learn in classic sudoku! I got very stuck and and to watch the video. I admit I've let myself get quite spoiled by the Miracle Sudoku app as I got too used to using other kinds of logic before needing anything on this level.

[@JM_-ix7yh]

good example of a puzzle that has a definite end point for beginners. like a lot of chat i got to around the 8 min to 10 min mark and then had no way of continuing.

[@aere481]

For the record, I don't want to complete an app. I want them to continue indefinitely!

[@WhoStoleMyAlias]

10:57 At this point I found that r7c4 mirrors whatever you enter in r3c9 and so you get a 2-9 pair in box 8 and a 4 in r3c4. This completely unwinds the puzzle.

[@matthewjamestaylor]

52 minutes on my second try. That was the most difficult classic I have ever seen. I still don't recognize triples very well, and swordfishes are beyond my casting. Cheers.

[@stephenbeck7222]

Rather disheartening when Mark just blinks and sees hidden swordfishes and blinks twice and sees a Y wing, isn’t it.

[@gposchman]

Thank you, Mark, I still have problems with swordfish and y-wing but each time I watch you and Simon I continue to learn more. Gene

[@nepiris]

Even after he explained the swordfish i had to watch it 3 times again to figure out what he meant, lol.

[@emilywilliams3237]

I feel sure I watched this one before, but I was not sorry to give it another view because it was very enjoyable and very interesting. By this time in my solving career I think I could spot a swordfish, I think I understand how a bent triple works (and I could probably find it), and I could eventually solve this sort of puzzle. Not fast, but I could get there. Everything I just listed I learned about from watching this channel, and especially from watching you, Mark, in this sort of solve. Thanks so much for all of this!

[@StephanSpelde]

I've solved it without the swordfish , but I did use the same cell. Before you used the Swordfish there was a 129 in c7r8, looking at a 29 in its box in c9r7 and a 29 in its row in box 8 in c4r8. So if the 129 cell was a 9, the other two cells would both be a 2 and that would mean there couldn't be a 2 in box 7, since the 2 could only be placed there in either r7 or r8. Removing the 9 from the 129 cell, put a 9 in the 29 cell in that box and the rest was pretty straightforward. Really liked this puzzle!

[@Jodawo]

I like the solve. I consider myself an above-average Sudoku solver but I did see a technique that I will incorporate in my future solves. I do wish if you have short videos you might put in some bonus material so we can get them up to 30 minutes at least. I believe yesterday's puzzle was one of your best solves because of the difficulty we got to share your logic while you were solving it. I think that's why we are here not only to see the entertainment but to learn something. You should thank Simon for choosing that one for you to do. I think you even impressed him by how you were able to logically get through the puzzle. I was also definitely impressed.

[@RichSmith77]

These short videos ARE the bonus material. They only started doing two videos a day because of the COVID-19 lockdown. Not sure how long they will continue. They probably never anticipated doing it for this long. I'm just grateful for whatever they release.

[@stephenbeck7222]

I would actually say the 30+ minute videos are the bonus. Look at the typical solve times before lockdown. Simon had that one hidden skyscraper that took like 45 minutes. Otherwise everything was basically under 20 minutes unless it was the monthly cryptic or a novel variant (but nothing of the level we have seen in the last few months).

[@Jodawo]

@@stephenbeck7222 It's the struggle that I like because we've all been there. We get stuck and when they go outside their comfort zones we get to see how they deal with it and get unstuck. I was always told you learn from mistakes but if you do something that you don't have a chance to make mistakes what have you learned. I think we learn more by watching their struggles. So I don't think a 15-minute video it's too much of a struggle. I know he can go faster than that but I'm glad he doesn't because it would be like putting the puzzle into a computer and just show you the answer. I personally, want to see the work and how they got there.

[@Jodawo]

@@RichSmith77 I believe the extra content increased the number of people watching and help their Channel grow to what it is now. Sudoku is been around for quite a while, now we get to see new variances. It used to be that the only differences in Sudoku puzzles were the categories Easy through Diabolical. Now with the new variances, it has become entertaining and worth watching. There's a reason there is no paint drying Channel on cable because it's not interesting. If they did not to commentary when they are solving it would be less entertaining. If they are going so quickly that you can't follow what they're doing that also takes away from the entertainment.

[@lonelyaura]

how do you know it's a naked single six at 3:39? It would be very helpful if you would explain the logic. I believe it's because the other squares have notations 1 and 4, while the square where 6 goes has neither, but explaining every logical step is ideal. Thanks.

[@jamesahibbard]

Have a look at the box. There's 3 numbers to place, 6, 4, 1. There's a 4 and a 1 in row 4, so the only possibility is a 6. A naked single is not a "technique" worthy of explanation.

[@JK7H]

@@jamesahibbard in a video meant for beginners, yes it is.

[@keithpatrick4173]

@@jamesahibbard he stated the 41s as a result of claiming the naked single 6 hence it is worthy of explanation. But that wasn't actually the logic he used.

[@brendanw5178]

Thanks Mark, great video! I just downloaded the classic app so these techniques will help greatly.

[@k.m.8825]

I solved it in 90 min. It was the first sudoku i did since my childhood and it was a real brainscratcher. My only contact with sudokus where with this channel i sometimes watch to relax (mostly the chess and miracle ones). So i didnt really know any tricks and just tried to solve it with logic and thinking. It worked out at the end but it took me a long time, i didnt know how hard it would be (i choose a random puzzle from you website)

[@Danishbuddha]

that swordfish had me struggling also, so bad at seeing those. But nice to see a classic with some difficulty in it without being a brain burner.

[@sorrowinthewind4258]

31:14 for me. I think I'm good at finding swordfish but I take long to start looking for them because I make sure there's no other way to continue XD

[@beloelobelo2387]

I got to a point in the puzzle where regardless of the order of the 2-3 pair in column 1, you get a 2 in the same spot in box 3 as a result which solves row 3 completely, and I proceeded from there... was not as clean but I liked that I didn't have to do too many steps after a bifurcation to be happy with the reasoning (about as many steps as a Y-wing would be...)

[@praematura]

17:44, though I honestly made a lucky guess near the end. Missed the y-wing near the end of the puzzle, oh well. :) Fun puzzle.

[@jnjsorr]

I've been working my way through the classic app. I'm currently up to 6 star and have found myself improving really fast. I've gone back to some 3 stars which originally took me over 40 minutes and have resolved in less than 20 minutes. I came to this video super confident and got all the way up to the swordfish within 15 minutes and was stuck. I eventually gave up but am comforted to know that this is about as hard as it gets (at least within the app)- so I'm not too ashamed.

[@beamer908]

Which app are you referring to? They reference a handful in the notes. I'm looking for one that works like their webapp but I don't think have a native app for that yet, right/?

[@georgesthibaudeau1533]

While you were working so hard in the bottom part of the puzzle, it was plainly visible that the 2 was restricted to the upper right hand square in the upper middle box. That solved the puzzle very quickly without difficulty in the bottom.

[@neokart2660]

10:00 At this point in my solve I noticed a W-wing: pivots (r8c4;r7c9) and switches (r7c1;r8c1). So, 9 can be removed from r8c7, so: r2c7=9 and r3c9=2. Then r2c7=9 sees cell r2c2 and solves a lot, and r3c9=2 sees cell r3c4 (which shouldn't have candidate 9 at this point, because of the double 9 in box8) and solves everything else.

[@graemegeldenhuys9102]

I got to the 10 minute mark without problem, but then I got stuck. I don't really understand your W-wing idea, but indeed, as soon as I removed 9 from r8c7 and made r2c7 = 9, then I could solve the whole puzzle without issue. I'll try and find YT videos on W-wing, to hopefully understand that logic a bit better. Thank you for posting your comment though.

[@neokart2660]

@@graemegeldenhuys9102 One way to explain it is: if r8c4 and r7c9 are both 2, then 2 cannot be placed on c1. So at least one of them must not be 2 and therefore is 9, and both cells see r8c7. So, 9 can be removed from r8c7. In any case, it's great that you watch videos about it, many explain it very well (I learned it in Spanish so maybe the terms "pivot" and "switch" may not be very correct in English.) Thanks for answering, it's always nice comment and learn from other comments too.

[@jojk952]

I'm kind of an beginner and I got stuck around 07:30 which already it took me really, really long. I missed the triplets, but even if I would have got further, I would have certainly missed the swordfish and the y wing (of which both I never have heard before). But even though I'm a little disappointed that I didn't get it, I think it was quite alright.

[@granndkane]

Ye can place the 6 in box 7 instantly as there's a 689 hidden triple in column 2 in boxes 1 and 7 (689 triple in box 4 c13), and the only place in box 7 sees 8 and 9 hence only 6 remains

[@ssesf]

I got to 10:00 - 11:30 before having to check the video. Glad it was there to get me to the end! Aha, something called a swordfish and Y-wing!

[@sampathkumar-ej7xl]

Mark used the 29 in box 8 to resolve the 1s and 2s. Alternatively the pair 34 in row 7 column 5 will always be a 4. To see that we start in box 2 and look at where 3 can go. It can be on row 1 (col 4 or 5) or in column 5 (row 1 or row2). In both cases if we follow through we see that row 7 column 5 is always 4.

[@CompletelyCr]

56:56. Bloody Y-wings.

[@brianmcadam443]

50 minutes for me, but mostly because I had to take a phone call in the middle of it. Still hoping for a pause button, at some point. I got stuck for a bit at the same board state that Mark did at around 10:00. I was looking for some kind of remote pairs situation on all the 2/9 scattered around, and cracked it open at R8C4. Placing a 2 there would immediately place a 2 in R7C1 and a 9 in R7C4, leaving R7C9 unfillable.

[@Just2Dimes]

Just write down the time when you take a break and when you continue. The time in a mobile browser doesn't continue by the way (on Firefox on Android at least), so also an option.

[@MartsGarage]

Thanks very much. Please continue to post classic solves. I would never have found that y wing at the end.

[@jimmckinley8110]

At 7:21 he enters 2 into row 6 col 8. I don't see how he knew that before he completed row 6 col 4, which he does after.

[@trevorsimmons313]

Thank you very much, Mark, for a great video, and for explaining so well the techniques you used. Hopefully it will help me go to the next level in classic sudoku.

[@samquilter8300]

This is the first puzzle I tried since watching this channel for the first time and it took me a combined 4hrs with one reset I want to die.

[@MisterNohbdy]

I guess this is the path the testers meant when they said the logic was interesting. My route just used an XY-chain between R7C5 and R3C4 (which would be visible at 9:52 if not for the extraneous 9 possibility marked in R3C4; the 9s in box 8 prevent that). Said chain cracks the puzzle wide open pretty easily. ( *EDIT* : mistyped a number )

[@davidh.4944]

I have no idea how long it was in total, but this one took me hours. I had a general idea of what to look for, but I just couldn't spot the patterns I needed. I even put it aside, got a good night's sleep, and started over to be sure that I hadn't screwed up somewhere. I ended up hunting down a sneaky little w-wing, then an xy-wing, , and then after finally noticing the triple at the top, another xy-wing to break it open. Each step with at least an hour of searching in between. Seeing Mark solve it in 12 minutes in such a straightforward manner is quite embarrassing.

[@justinsinger6953]

I didn't see the swordfish or Y-wing, but managed to use an empty rectangle on 3s in box 8 (with a longish chain) from the same place in the solve to fix the 2/3 pair in box 7 which was enough to finish the puzzle. I enjoyed this one.

[@brianbirish]

Learned something with that 3,6,8 trick at 6:40

[@isaura5915]

13:29 really good

[@sunriselg]

Solved it in 24 minutes. I hate it when a puzzle drops you straight into endgame. But I'm happy that I found the Y-wing, I rarely do.

[@alarictaqiarentza9451]

Wow that was brilliant solved and very amazing puzzle! I didn't spot that Y-wing so need to bifurcated. Y-wing is always my weakness in classic XD.

[@grenvillephillips6998]

It wasn't long ago that Mark never mentioned fish in his solves. He's definitely refined his technique during the lockdown. It would be interesting to know what method he used to get over that hurdle.

[@pardox28]

Spotting triples is getting easier after the weeks of practice I'm getting thanks to this channel. But spotting swordfishes & y-wings alludes me. Might I suggest a video down the line where you crack 3 classics that all need to be solved by spotting swordfishes or y-wings? I could use the practice.

[@MisterNohbdy]

"Elude", not "allude", is the word you want. ^_^

[@thomaswilke6312]

Yay!!! Classic sudoku time

[@AndreAy1975]

Nice techniques shown in the video!

[@joekerr3638]

Got a like from me for doing the check on screen. A lot was going on in the puzzle for a classic sudoku.

[@RylanStorm]

I tried this last night. It was my first ever puzzle. I think I did alright for a first Sudoku attempt and I got really close. SOmeone along the way I made a false leap in logic and I couldnt complete. I need another puzzle to try now.

[@brucerose4383]

This was very hard .. needed much remediation to get through it .. it is crucial to recognize the bent triple hinge near the end of the solve is the "29" in r8c4 .. thus the bent triple wings have "1" in common - and they can both see the hinge .. I keep missing this .. instead I saw a bent triple with "9"s on the wings which does not exist since any hinge for this triple cannot "see" both wings .. this is very tricky .. and really struggle to ID them ..

[@SuperOrcy]

I still suck at classic sudoku, even though I can manage quite difficult sandwich and thermo sudoku's.

[@winoodlesnoodles1984]

To be fair, this sudoku had a fair bit of advanced logic at the end : bent triple into a swordfish into a Y-Wing. If you don't have experience spotting those, this sudoku has a nasty bite at the end. I caught the bent triple, but missed the swordfish and Y-Wing. This required doing a bit of extra logic to figure the puzzle out, so I was my standard 50% slower than Mark. Sandwich and thermo sudokus seldom have this advanced logic in them which is likely why you do better at them. I'm still learning to spot some of the advanced logic myself, so don't feel bad.

[@thepimentninja7340]

At least you are not alone

[@Asphalt_Ship]

I still suck too... but less! Watching this channel had me notice a clear improvement and I'm really happy about that

[@sfumato8884]

Classic sudokus can be much more difficult than variants. Less restrictions generally means higher ceiling of difficulty.

[@chocolatecake50000]

@@sfumato8884 knight sudoku is my favorite

[@MrLinks14]

Does anybody know how he got the 6 at 3:33? I’m lost as to how he know that should be placed there

[@IanKrigsman]

1,4 & 6 were remaining digits in box 5. 1 & 4 already in row 4, leaving 'naked 6'

[@user-or7kr3tx9m]

it's brilliant it took me an hour to solve, but I've used the other way decision came up through the 6th block though

[@aeoline2851]

I wonder, what is this about the distribution of the given digits often being point-symmetric? It is like that in the daily sudoku of our local newspaper like every day. Does it implicate some kind of solvability or something?

[@GlennBroadway]

Watching you solve these shows me that you spot the swordfishes and Y Wings, but I want to know HOW you spot them. What are you doing in your mind that leads you there? Is there a process or is it just pure familiarity?

[@christopherkillinger2457]

Instead of the y wing I did the thing where the 4 corner 2x2s equal the ring around the center box.

[@julieenslow5915]

Loved watching you - this one is a little (ok a BIG) stretch for me at this time!

[@simonockwell3485]

Without picking up logical paths from this channel I would have been there all day too :)

[@inikous58]

i happened to check your site, and try my best for this sudoku...I didn't know it was that hard...Believe it or not, it was my first ever difficult sudoku, to solve... Somehow i found that 9 in the bottom right corner cell way before the Y thing you did...Now i am not sure if it was by mere luck...Lol

[@glum_hippo]

Was this submitted by Trent Bipple, master of the bent triple?

[@ArunIyerS]

Nice solve Mark! One can avoid the Swordfish and Y-Wing at the end by noticing that the box 9 column 7 will either have 12 or 19 pairing (since 1 is fixed that column). If it was a 19 pair then it immediately puts 2 2's in box 8, giving a contradiction quite quickly, thus eliminating the 19 possibility. Rest is pretty straightforward from that point.

[@Afterthoughtbtw]

17 minutes. Great time for me especially considering I blundered through without spotting the swordfish. Spotted the Y-Wing though, which is unusual for me.

[@mattikorhonen7188]

Solved it different ways. I do not get an idea how at 3:33 you can see naked single 6. What rule is used here not to consider a change, at this point of game, column 9 to be number 6?

[@nashydn]

Just after seeing this comment. I have the same question. What rules out R4C9 for that 6 at that time?

[@nashydn]

And again at 4:49 how does he determine R3C1 is a 6? What eliminates that 6 from 2nd column of B1?

[@mattikorhonen7188]

Now I got it, middle box is missing 146, it can not be 14, since those are on same line, must be 6. New day, new eyes

[@mattikorhonen7188]

@@nashydn Need to be 236 in that column, line restrict it to be only 26. 2 is already ruled to be in column 3 in that box.

[@nashydn]

@@mattikorhonen7188 Thanks!

[@nathandwire2103]

My time was about 27 min. I totally missed all three of the techniques and got stuck for a while at the end. Ended up using the Pfistomofel ring to crack it open in the end😂

[@asakazhao2349]

why r8c4 can not be 3 at about 9:30 what excludes it

[@Coyotek4]

16:12 I'm content with my time, but once again I couldn't find the purely logical path: I bifurcated via r2c2 (narrowed it down to two choices, and my first guess led to a break). EDIT: I missed the track at 6:45 of the video ... by now, I would have thought I'd be used to that trick. EDIT EDIT: I also missed the swordfish ... but I *didn't* miss the resulting bent triple. So ... 1 out of 3?

[@winoodlesnoodles1984]

I caught the bent triple but missed the swordfish and the Y-Wing. I did figure out the swordfish logic but that is why it took me a 17 minutes.

[@stevenlomon]

Really nice showcase of more advanced Sudoku techniques for us mortals hahaha

[@Kinada]

Im an idiot and missed the tripple in box 2, after that it got to a point where I noticed that the 4 in r7c4 could be eliminated by the 29 pair in column 9 since no matter the arrangement they forced a 4 somewhere else. That chained completions through the rest of the grid.

[@user-gq4lo2cz9p]

At the end I used some different logic. There are quite a bit of 29 possibilities. Colouring the 2 polarities gives you 2 polarities looking at C6R9. Therefore it couldn't be a 2 and it had to be a 1.

[@PrometheusZandski]

Thanks for the not so intuitive tips. I need to upgrade my spotting of Y-wing.

[@zynzane9680]

I still don't really understand how to see the Y wing. I wish someone could explain it really simply. Maybe it's this: Four cells, each having two numbers, have the same three numbers distributed between them. Like this puzzle, (29), (19) (12) and (12). The cells all see each other in some order. Then you can guess one way (as in, the 29 cell is a 2) and see how that affects the other three cells. Then try the other way (the 29 cell equals 9) and see how that affects the other three cells. In this case, both times the (12) cell in column 7 is "not 1", making it a 2.

[@Gilroid]

I saw how the 2/3 pair in C1 matched with the 2/9 pairs in boxs 8/9. Either place for the 2 would yield a 9 in box 8 or 9 any other cell that saw those 9's could be eliminated.

[@jalsing]

yes that's what I saw as well. I believe this technique is called "W-Wing"

[@chrisranielesparagoza2074]

Nice!!! It helps me a lot.

[@robertjandegraaf5557]

No need for complex swordfishes or y-wings. Just straight forward finding a box where a digit has only 2 places. I learned to only go for complex tricks when all other things fail, it becomes quickly too complex otherwise.

[@nashydn]

Just beginning to do these puzzles. At 3:30 he puts a 6 (naked single) in R4C6. How does he know that 6 can't go in R4C9 at that point? What rules out R4C9 for that 6?

[@zynzane9680]

Because that cell must be a 6, it sees every other number except 6.

[@MencrakP]

76minutes, i got stucked and try it 3 times :p not a good time but I was happy cause this difficult

[@964cuplove]

2:16 solving starts

[@jeremyfinn7684]

at 4:50, why cant the 6 go in one of the 2 spots where the 8 pair is in that box?

[@nathandwire2103]

its not that it can't go into either of those, its that 6 is the only number that can go in that location

[@lauramcastro4897]

The last stretch was a bit different from me! I eliminated the 2 in C6R3 using an empty rectangle... and that made a nifty x-wing in R3 and R7. Took me forever tho!!

[@avtem]

It would be great if your app had a functionality: generate new game.

[@csvidyasagar]

Respcted Sir, I am an admirer of your videos on Sudoku. But I have not understood at video time of 3:31 you placed digit or big number 6 in cell Row 4 Column 6 (R4-C6). At this point of time there are three empty cells and the numbers which can go there are 1,4,6. But you placed digit 6. Can you kindly explain why did you place 6 in that cell.

[@csvidyasagar]

Sir I understood why placed 6 there. Because in row 4 you have 1,4.Hence the last digit is 6. Thank you. Sorry for bothering you.

[@bapu.nt99]

34:20 for me. That was fun, but I was slow lol

[@alastermyst]

11:42 for me. Nice puzzle. I'm getting better at spotting tripples.

[@Myskully14]

I got quite far in quickly... but then there's no way forward. I've spent over an hour checking every single box, row, column, number, and even cross referencing my pencil marks (for when a number can only be in one of two places in a box) and I cannot find any place where I can say "this number for sure goes here." I've got 6 in box 1, the 6 and seven in box 3, 1 5 and seven in box 4, 6 and 8 in box 5, 7 and 6 in box 6, 4 6 and 8 in box 7, 7 in box 8, and nothing in box 9.

[@Myskully14]

Wow... I started to watch the video and its rather eerie but he solved exactly the same way I did... pencile marks and everything... until we had the exact same progress at 6:06. His next step... getting the 5... I did not see that. I had looked for two number versions of that before but not three number versions.

[@rabidsamfan]

Nice. 19:16 and now to see how Mark did it.

[@Avatar2124]

15:55, closest classic puzzle I've gotten to their time

[@BlazingsNL]

Got stuck at around 8:00 but took me 45 minutes haha

[@GK-pc4qb]

I got lost at the naked single six (3:31) how do you know it must be a six?!

[@zynzane9680]

That cell sees every other number except 6. Look at the its row, column and block, all the other numbers are there.

[@ChrisBreemer]

Somehow I breezed through this one using only the most rudimentary techniques (I haven't even familiarized with the Y-wing and swordfish yet). So I guess something obvious must have been overlooked here.

[@MariaVlasiou]

I solved independently and got stuck at the same spot. Are you sure you didn't make any hasty conclusions at any step?

[@ChrisBreemer]

@@MariaVlasiou I don't think so, or I would not have stated I breezed through it. Because this is quite an exception for me - I often get stuck and need to resort to bifurcating 😁

[@ChrisBreemer]

@@MariaVlasiou Thinking more about it, I guess it could be. Typically a wrong deduction ruins the puzzle, but you could also get lucky 😃

[@dashxdr]

12:18 the 35 pair in row 8 means it's a 2 in r8c1

[@tomtheultimatepro]

Actually finished in 6:16 but I used none of the techniques Mark used...interesting

[@mathemitmanger3913]

How about an auto-check function once the grid is completed? ;-)

[@stephenbeck7222]

I rather like the minimal evasiveness of the website personally.

[@mathemitmanger3913]

Stephen Beck So do I. It was just a little mocking of Mark’s check function phobia ;-)

[@jsands27]

ooooooof, had to restart, misclicked somewhere before, then got hopelessly lost at the swordfish, was staring at my screen like an idiot for 50 minutes!

[@yafu2599]

for sure took me two jiffies.

[@jefftaylor9938]

Hi Gentlemen... Isn't a Y-wing just a short bifercation or short chain logic?

[@andymoss]

Anyone care to explain the naked single six at 3:33? I just can't see that.

[@zynzane9680]

That cell sees all the other numbers except 6 so has to be a 6.

[@lucatrotta9727]

How did he get that "naked single 6" at 3:32?

[@MrTheirlandais]

1,4, & 6 left in the box and 1 and 4 already in the row

[@chief_01]

The box is missing 1-4-6, and the row is ruling out 1 and 4.

[@lucatrotta9727]

Oh gosh, thanks!

[@d4r4butler74]

The Box needed 146 and Row 4 already has 1 & 4, so that left a 6 in the empty cell and a 14 pair in the Box.

[@RichSmith77]

Alternatively: 2, 3, 6 left in the row and 2 and 3 are already in the box. Same thing, just a different perspective depending on whether your scanning the row or box first.

[@Kuryoku]

I'm wondering if I did something wrong since I solved this in a very different order.

[@Heistergand]

I did not see the 368 triple in Box 2. For me it was unsolvable without that info.

[@graemegeldenhuys9102]

Row 3 already contained the 368 and the Column 6 also contained the 368. That eliminates 6 blocks in Box 2, which meant the 3 remaining blocks had to be a 368's.

[@sper1585]

I got stuck at the ywing.

[@miraculix666]

If r7c4=9 then both r8c4 and r7c9=2, which contradicts col1.

[@shivamrohilla1496]

How he put naked single 6 in middle box?

[@zynzane9680]

If you look at the box where he put the six, it sees every other number except 6. So by default it had to be a 6.

[@user-A168]

Good