Everything We Love About Sudoku

** Today's Sudoku **
This is an absolute stunner today courtesy of twototenth. It's called Serial BoX and it is ridiculously clever/beautiful. Play the puzzle at the link below:
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Rules:
Normal sudoku rules apply. Purple lines must contain a set of consecutive, non-repeating digits. Cells separated by an X must contain digits summing to 10; not all possible Xs are given. The clue outside the grid gives the sum of the digits along the indicated diagonal; these digits may repeat if allowed by other rules.
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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.
Thank you for watching!
Simon and Mark

[@troymcg]

If you call the light grey 'silver' and the medium grey 'charcoal' then the colours become that much more exciting.

[@viri6839]

And call black obsidian :D

[@eclectichoosier5474]

Vermillion, Ochre, Canary, Kelly, Cerulean, Puce, Silver, Charcoal, Onyx?

[@macmccolgan5952]

And it's not black, it's very, very, very, very dark gray

[@OkRake]

@@eclectichoosier5474 Your color vocabulary is sexually arousing.

[@Hertog_von_Berkshire]

@@OkRake, worrying ....... especially as I agree 😁

[@tremkl]

I think Simon would have had a much easier time with this puzzle if he had just committed to 2 colors, since it turned into a high/low puzzle. He had realized that himself when he colored an entire renban at the bottom blue, but he was too attached to his 28s. Great solve of a great puzzle, though!

[@RescueMichigan]

Yeah that color scheme confused him multiple times and made the grid look like vomit.

[@laurv8370]

tremkl: yep, agree, quite too complicate

[@maggieelliott5896]

Way too complicated! I took the other approach, and beat his time by over 20 minutes! I kept the individual colors for each pair, flashed the mates as I figured them out, and let the little killer solve it.

[@adipy8912]

What I really liked in this video is that you didn't apologized or talked like you were bad for not spotting things. It's a beautiful sudoku.

[@HunterJE]

Feel like Simon didn't really need to worry about "polluting" the 28 coloring, because if you know a cell is 2 or 8 high-low coloring is going to be identical to "which 2 and 8 is it" coloring - if you know an orange 28 is purple, you know any purple 28 is going to be orange, so "orange" just becomes a synonym for "purple 28" and orange shading adds nothing that isn't already conveyed by a 28 pencil mark plus purple shading.

[@krazykowsr]

Yeah, he intuitively had the right idea, and then complicated it by overthinking when he tried to explain his thought process. On the other hand it made me explain to myself „purple is not yellow, therefore it’s orange“ for the top right cell, which I think is a beautiful sentence just by itself.

[@martinepstein9826]

Wouldn't be a Simon solve if he didn't use 6 colors to represent 2 possibilities :p

[@oscarhoz5854]

, ,

[@lexihopes]

I think there was a short period where it was still helpful to easily see where the 28s were, but in general yes. Either way I'm glad he took a moment to explain he was doing parity, because I was confused about from when he labelled the bottom renban cells blue until he started on the first row, right before he explained.

[@kslingsby]

Instead of using colours, I used central pencil marks and corner pencil marks for the two scenarios.

[@antalbojtos4413]

I mustn't be the the only one who wants to know what Simon had for dinner after mentioning it so many times, c'mon.

[@andrewe7381]

Overcooked, whatever it was!

[@DeborahJLeslie]

@@andrewe7381 Or cold, more like

[@zacharyscherr4151]

One interesting observation about the rule set is that the renban and X constraints alone can't lead to a unique solution. This is because you can always send a digit d to 10 - d and get a valid solution. I haven't checked, but it seems that without the 48 diagonal there would be two solutions and the 48 disambiguates between them.

[@derekfordyce9]

Would a diagonal sum of 52 give us the other solution? 9 cells *10 - 48

[@conorpappas3871]

There are more than 2 solutions I believe. Solving without the 48 clue leads to a grid with a BUG on 3/4 or 6/7 with two unknown cells on that diagonal. 40, 42, 48, and 50 force the unknown cells to the same value of 3/4/6/7 and resolve the bug. 41 and 49 for the diagonal clue resolve your high/low parity, but still leave the BUG and therefore don't resolve the grid. So I see 4 solutions that would be unique with the diagonal clue, and 4 more which cannot be distinguished with the diagonal alone.

[@minamagdy4126]

The number you're looking for is 42, not 52. You're calculation was slightly off your words. I personally like to call that antisymmetry, as it is a sort of reflection on the digits 1-9. Fun fact: if a sum clue of length n was exactly 5*n, then the antisymmetry wouldn't be disambiguatable, as the antisymmetrical map would preserve the sum.

[@derekfordyce9]

@@minamagdy4126 yes, I meant 42, thank you

[@gordonbos5447]

It does. I somehow jumped to the conclusion that r1c9 had to be an 8 and I came to what was effectively a deadly pattern where the 48 diagonal should fix that and I was unable to complete the sum. It turned out that all I had to do was reverse the numbers (i.e. 2 8, 3 7, etc) to make it work. Finished the puzzle in 42:22

[@julieannmyers8714]

I'm having a helluva a time following the logic on this one. I am totally lost for the first time ever. Rather than being the key, the colors are cryptic.

[@itsmeagain1745]

Usually the colouring is helpful - I sometimes see cell colouring that Simon misses completely. This time though, my brain just had a melt-down.

[@stephenbeck7222]

Yeah Simon needed to just stick with 2 colors and declared it a high-low parity puzzle. I think that would have made it easier to follow.

[@johnh2052]

I think using just two colours would have made the discussion (at about 50:00) regarding the little renban in box 2 easier to see. The simple issue is: if there's no 5 in it, then the renban is two cells of the same parity, either purple or yellow, made up of the 37 and 46. But you already have a yellow 37 and a purple 3467 in the row, so that's not possible.

[@Leyrann]

Amazing puzzle. Incredible amounts of intricate logic, yet never extremely hard. I absolutely love how the entire puzzle is high/low coloring with 19, 28, 37 and 46 pairs and only a single clue to disambiguate it all. And not just that, that single clue ALSO takes care of a deadly pattern in purple at the bottom of the grid. One of the best sudokus ever, in my opinion.

[@jonhansen9622]

@3:32 "My dinner is in the oven." **Looks at length of the video** WELL, someone's going to have a burned dinner tonight!

[@RKelleyCook]

I've never attempted a Simon hour+ puzzle before since those seemed unsolvable by mere mortals. But I misread the video time and started at this beast and kept at it, getting a deduction for a color or two every now and then. After nearly 4 hours, I'm quite proud that I completed it by myself and my answer matched Simon's!

[@rontyson6118]

Congratulations.👏🎉 I attempt 'em but always mess up something. But after 2 and a half hours I finally conquered this one. :)

[@RollcageTV]

Actually, mathematically you can say more about a 4-cell renban than, "It's total is even." You can say, "It's total is even, BUT *NOT* DIVISIBLE BY 4." Don't know how useful this is, but there it is nonetheless. 😉

[@pfeffer1729]

You can say that the sum of two four-cell renbans is a multiple of four. Which would lead to his conclusion that the remaining digit is 1, 5, or 9.

[@fuuryuuSKK]

@@pfeffer1729 that isn't the full picture though, because while the sum of two four-cell renban is indeed divisible by four, it is also important to note that the sum of a single four-cell renban is 2 mod 4

[@inspiringsand123]

Rules: 01:50 Let's Get Cracking: 03:13 Puzzle Solved: 1:10:28 Simon's time: 1h7m15s What about this video's Top Tier Simarkisms?! Bobbins: 1x (18:26) ​Scooby-Doo: 1x (28:00) You Rotten Thing: 1x (56:18) And how about this video's Simarkisms?! Sorry: 10x (05:58, 10:30, 19:26, 31:17, 42:54, 44:07, 47:20, 47:20, 48:11, 1:01:10) Beautiful: 9x (03:52, 10:16, 11:01, 19:13, 19:53, 20:24, 21:48, 21:52, 31:42) Hang On: 7x (18:42, 22:48, 25:29, 56:09, 1:04:16, 1:06:19, 1:06:23) By Sudoku: 6x (16:09, 17:43, 21:00, 45:19, 59:37, 1:02:16) Clever: 4x (09:35, 19:13, 23:30, 1:10:54) Stuck: 3x (01:08, 42:54, 55:51) Magnificent: 3x (1:10:24, 1:10:41, 1:10:54) In Fact: 3x (40:09, 50:36, 54:26) Wow: 3x (1:05:54, 1:10:29, 1:10:32) Secret: 2x (07:07, 07:09) I Have no Clue: 2x (27:58, 39:43) Brilliant: 2x (00:41, 01:04) Elegant: 2x (08:38, 31:51) Gorgeous: 2x (10:57, 37:01) Obviously: 2x (02:59, 04:20) Good Grief: 1x (24:41) What on Earth: 1x (39:25) Useless: 1x (10:22) Bother: 1x (1:01:05) Horrible Feeling: 1x (47:05) Lovely: 1x (08:31) Fascinating: 1x (49:06) Ridiculous: 1x (36:50) Inarticulate: 1x (19:26) Going Mad: 1x (51:02) Deadly Pattern: 1x (1:10:00) Take a Bow: 1x (1:10:57) Famous Last Words: 1x (13:05) Of All Things: 1x (56:27) Surely: 1x (1:00:32) Disappointing: 1x (1:10:13) Full stop: 1x (51:59) Progress: 1x (06:42) Unstuck: 1x (55:55) Most popular number(>9), digit and colour this video: Ten (14 mentions) Five (118 mentions) Yellow (97 mentions) Antithesis Battles: Low (19) - High (7) Odd (15) - Even (12) FAQ: Q1: You missed something! A1: That could very well be the case! Human speech can be hard to understand for computers like me! Point out the ones that I missed and maybe I'll learn!

[@przemekmajewski1]

Hilarious!

[@xarzneimittel8220]

Your dedication is brilliant! Here's your star 🌟 Jk aside, I loved this so much hahahaha

[@timparenti]

I know it's not technologically feasible, but oh my goodness, if it were, Simon's singsongy "ah-ha-HA-ah" at 1:05:59 would totally make the list.

[@MikeMarlinTube]

The much easier way to solve this is just to guess which Renban is high, and which low. Then solve the puzzle, and finally check the diagonal, because this is the only thing that disambiguates highs from lows. It makes the puzzle far easier to solve. Having said that it still took me as long as Simon - but at least I could understand what I was doing - whereas I got completely lost after about 20 minutes when I then watched Simon's solve!

[@Skullman1985]

I was so looking forward to the colored-in grid getting disambiguated in the end by the 48, and now Simon made me cry by looking at the 48 before he finished coloring. 😭

[@badradish2116]

thats what i expected too. man that wouldve been flashy.

[@vega1349]

Wow, it always astounds me how you break into these puzzles.

[@RoderickEtheria]

This is one of those puzzles where it's better to pick a side, and flip to check.

[@caseyglick5957]

A useful trick for 4-cell renban lines is that they are always divisible by 2, but not by 4. x, x+1, x+2, x+3 = 4x+6, without loss of generality, and which is divisible by 2 (2x + 3) which is itself not divisible by 2. That gives another way of getting R1C1; 2 four cell lines *is* divisible by 4, giving 3 options: 36, 40, 44. Which leaves 9, 5, 1 as the remaining square.

[@th.nd.r]

What a BEAUTIFUL puzzle and solve. INCREDIBLE. Every. Single. Deduction. One right after the other. Awesome. And it truly takes a solver like Simon for us to witness the puzzle’s beauty. twototenth and Simon, take a bow each. EDIT: Another thing I noticed that I liked - Simon, when you left and came back, I know that threw you off your game a little bit, but it also allowed you to clean up a couple notation errors. Perhaps you should look at breaks a little less like a mental eraser and a little more like a mental restarter!

[@miran248]

"My brain is telling me this doesn't work. Why doesn't it work, Simon? Use your brain." Love it when it happens. Also, I hate it when it happens.

[@conorpappas3871]

I decided to save myself a coloring headache and did the whole puzzle just assuming one of the high/low parity. I was ready to swap all the cells at the end, but won the 50/50 on my initial choice.

[@sveneberhardt5581]

Same here, but I did have to swap - I had to pretend the diagonal sum was 42 for a while since it is also required to disambiguate the cell in the bottom left.

[@leickrobinson5186]

Same here! (I also got lucky. :-D )

[@Harry-qq2ww]

Same here! It felt a bit like cheating, but made life so much easier. It's fun to see quite a few others in the comments who did the same thing.

[@TheRumata23]

Congrats to twototenth, this was one of the best solving journey I ever had with any sudoku!

[@Coyotek4]

Took me almost 90 minutes (1:26:09), but I made it ... one of my most prideful solves. Incredible puzzle!

[@Gonzalo_Garcia_]

49:36 for me. What a puzzle!! That was so tough at some points, but so enjoyable. Btw, I solved it using colors but I think I’ll change the strategy the next time I solve a puzzle such as this one. I could have probably saved quite a few minutes if I had chosen one of the high/low possibilities and change it to the exact opposite at the very end if it broke the puzzle.

[@przemekmajewski1]

This was an absolutely beautiful setting. Took us over 2 hrs... but bringing it to an end without disambiguation... only to have the diagonal sum doing the trick was great... additionally, there are 4 different sudoku hidden there, depending on the diagonal's sum (if you'd set it differently) :D Fantastic.

[@tehjoch]

me watching simon: ah yes, I probably could have found that logic me trying it myself: hmm so these 8 squares are an octuple

[@leojs5673]

A big CTC video is the best way to spend a nice rainy day inside 🤓

[@SolverTom]

Took me quite a while to figure out this was a high/low puzzle, nothing too difficult but so many great deductions to be made. Well done twototenth, an hour solving this was well spent!

[@thehermitkingdom]

Me: "I just came up with the most difficult sudoku puzzle". Simon: "Hold my beer"

[@BergenVestHK]

What an incredible puzzle, and a splendid solve. Such a joy to watch. Thanks a lot for the entertainment. :-)

[@nairit4600]

something about watching a British man talking passionately, and speaking English like it was meant to be spoken has kept me hooked for 2 years now.

[@jongvopnfjord]

I’m 50 minutes into the video and I can’t focus on it because I’m way too concerned about the food in the oven

[@DeborahJLeslie]

Did anyone else become increasingly agitated as Simon kept postponing going down to dinner? (A dinner prepared by someone else, possibly?) It would be hard for anyone not to be at least a little in love with Simon, but I'd guess "a little" is what his nearest and dearest are feeling about now. (-;

[@davidhyams2769]

That's why buzzing a phone is so ineffective. His other half coming storming into the room to tell him his dinner is in the dog would have been a wonderful sight. His insistence on continuing the puzzle made me so annoyed that I gave up watching at about 40 minutes. I know Simon solved it because he never posts an unfinished puzzle.

[@paulmdt1]

Simon's wife: There are three of us in this marriage. You're going to have to choose - either me or sudoku. Simon: OK, bye.

[@paulmdt1]

Deborah J. Leslie - I liked your [apparently deleted] reply!

[@MaikaSHTsukiko]

I gotta say, I laughed so hard at "I'm fed and watered" I will use this in my everyday life from now on!

[@SpeedyBozar]

The most brutal sudoku from this channel I have solved so far. For almost all of my solving time I was giving it like 2% that I am actually on the right track. It felt ridiculous that this is the way to solve it. I am almost shocked it turned out correct. I had only a few 5s and all cells covered in colors before knowing any number. Then I was staring at it for like 20 mins being sure I did something wrong because there was no way for a unique solution. And then I remembered that 48 diagonal and suddenly I started to believe. Amazing! :D

[@HunterJE]

53:42 Worth noting here, at this point you can place and even color 19 in box 3 using banding logic once the purple 234/678 are placed in the same column in boxes 369 - you already know the 19 in box 3 are not in column 9, and in box 9 they have to both be in column 8, so in box 3 they have to be r23c7, where they see the pink 19 in box 1 and so can be colored.

[@HunterJE]

Although when he later identified the 19 in that domino by other logic he didn't mark it anyways and later had to find it again by ANOTHER method, a classic Simon trick XD

[@ApesAmongUs]

49:00 I think he would have seen the 5 if he didn't have so many unneeded colors and was just thinking in terms of high/low. 34 or 67 must be either yellow or purple. Which ever one it is kills either r2c3 or r2c9, so one of them must be a 5.

[@dk81990]

Wow. Incredible puzzle! My coloring got super-confusing so part-way through I decided to clear out all the flashes and just went with a 2-color high-low which was much easier. So much great logic with the renbans ...

[@TiagoMorbusSa]

Ooh boy, we're in for a long one!

[@babyroseofvongola]

Woo!

[@pixllo]

Managed to finish it under 40 minutes. Very nice puzzle, i felt like the next step was never easy but never impossible and the puzzle gave hints on where to look. Brilliant setting. I went for modular maths then high/low parity (within reason numbers could be swapped to the one with which they add up to 10) then basic sudoku with disambiguation in the end with the diagonal. Now i'll check the video to see how Simon solved it, he might have used some crazy but interesting way to solve this.

[@pixllo]

Addendum: After watching some of the solve, as expected Simon's solve is more elegant by far. That said, me finding out that I could arbitrarily chose some high/low parity and change it if it didn't work because: swapping x for 10-x would affect neither renbans or Xs was what made me gain so much time. And it was, I feel, a pretty cool deduction on my part as it is not bifurcation.

[@Danee0113]

At 27:25, after Simon deconfuses us, confuses purple and yellow 🙂

[@colinbrash]

This puzzle was so good!! Really really elegant, absolutely loved solving it!

[@alexmilioris7641]

Simon, i've been a long time viewer (not so but a year or so).If you have problems seeing the light grey flash it must be your monitor at fault(or the brightness setting) .Because i really have problems with colors due to my colorblindness .Give it a research ,for a more color accurate monitor with an IPS (In Plane Switching) panel .Sorry for not commenting on this sooner but i recently been watching or might i say binge watching a lot of your videos an heard you complain about it a lot.

[@mute1085]

At first I tried colouring and writing down both low and high alternatives... but then I realised that aside from the diagonal 48, the rest of the puzzle doesn't care which is which, so I just went with one alternative, solved nearly everything ignoring the 48, and then checked that it didn't break (if it did, all I would need to do is to swap each digit to its 10-complement, i.e. 4 to 6). It made me breeze through the whole puzzle in 33 minutes (I think it's a first for me beating Simon by that much). And to be fair, while Simon didn't employ that technique here, it is something I learned to do from him some time ago.

[@LEEBLISSY]

hope you're feeling well simon!

[@pelahnar4]

48:15 It's interesting that you say you don't like taking breaks in the middle of solving a puzzle because you lose your train of thought. That does make sense, but personally, I find that if I work on a puzzle in one sitting I can end up getting stuck and frustrated (and therefore less likely to get unstuck) until I take a break and look at it again the next day. I'm always impressed that you can sit down for an hour and just steadily work away at a puzzle.

[@G4M1L]

As others have stated, I seemed much easier to follow the logic of the puzzle by picking one possibility for the long renban lines (high/low). It certainly was for me. I treated my pencilmarks as representing not only n, but also 10-n, keeping them as pencilmarks in a cell, even after the possiblities for that cell had been reduced to a single one, only filling in the 5s, as 5=10-5. Only when the diagonal was filled in far enough to disambiguate things, did I replace the pencilmarks with solution digits - turned out I had picked the wrong variant, but it was very smooth to just double click the unique pencilmarks and replace all the marked 1s with final 9s and so on. Actually i completed the puzzle the wrong way first, to be able to do that.

[@LednacekZ]

48:55 for me. Early on I gave up on thinking if it is high or low and chose one. solved it for that. Of course i chose wrong, but i had all the squares coloured in so ti was easy to just switch the highs and lows and make the 48 clue correct.

[@MikeMarlinTube]

Me too. Great puzzle.

[@bristolrovers27]

Over an hour ! Great stuff

[@Swisswavey]

It feels very much like cheating to solve the puzzle and then switch the high/low digits when you realise the diagonal doesn't add up. But that's what I did. I'd better look to see Simon's solution... It took me 61 minutes, by the way

[@Saryna]

Imo if you know that just switching them around will be the solution (so you can prove that without the diagonal there would be 2), then using 1234 and 6789 (instead of 19 28 37 46) is the same as using ABCD and EFGH and make them fit with the final equation. It's just that the program doesn't support variables, but I'm certain if it did it they would get heavy usage especially with puzzles like these.

[@sugarfrosted2005]

I mean its not really bifurcation because you're using 6 to mean "purple 4/6" and 4 to mean "yellow 4/6" in the parlance of the video just with slightly clearer notation.

[@RichSmith77]

That's the way I tackled it too. I rarely solve faster than Simon, but this approach simplified the solve enough for me to knock 15 minutes off Simon's time. Unheard of. 😂

[@nochsta]

You could just use a single centre pencil-mark, rather than inputting the digit. Exact same effect, but feels slightly less like cheating.

[@stephenbeck7222]

I think Simon even did that on a puzzle a couple years ago when the coloring options weren’t what they are now in the web app.

[@britlion]

It's late, so I am a bear of very little brain. But the colouring just bamboozled me, watching this. I think this is the first Simon solve I've really not been able to follow.

[@saphirelynn2000]

That was definitely one of the hardest puzzles to get started on that I have tried. Once I got through the logic of setting it up I got it but I had to follow Simon's logic for quite a while first.

[@joelstevens5670]

That was a fabulous sudoku, though I’m pretty sure Simon made some of it more complicated than it needed to be (e.g. by not fully noting the different X compositions, as is key in so many XV puzzles). That being said the modular arithmetic at the start was a lovely way to get going (I instead went with the ‘checking the effect of the Xs in row 1 vs column 9’ route, which had the same result but was a bit harder to keep track of). My favourite part of the solve was the renban line in box 2 (the logic that proved it had to contain a 5) but the way row 1 kept forcing column 9 and vice versa was also rather beautiful. All in all, a very neat idea and a cracking bit of sudoku setting. Thanks two-to-tenth and thank you to Simon for the solve video. :)

[@fleetingfootnotes9133]

I love how Simon digs in with the extra rules, at 37:20 he mentions the loss of yellowness on the 258-cell in r9c3. He could have also said that the 28-pair rules the 2 and 8 out of the 258-options. And sometimes scanning goes awry. At 55:30, for box 8, of course the 19 can go into two places. You need one 19 for the one and another 19 for the nine. Four cells already have other candidates, the two other cells on row seven are eliminated by sudoku (pair in box seven) and the column five is ruled out by the 19 pair in boxes two and five. Leaving r8c6 and r9c4. Since column four already has a purple 19, the one in r9c4 must be yellow and the r8c6 must be purple. Hmm. At 56:00 in, stuck? Place the five in box 3 by sudoku? At 59:30... we don't know what kind of yellow could be in r5c4 if it were yellow? The column already contains 28, 37 and 46 yellows so I presume it should be 19. Glorious solve by SImon, great puzzle too.

[@emilywilliams3237]

Enjoyed this very much. I always feel that I learn something, or begin to learn something anyway ... Thanks!

[@AndreAy1975]

Solved it with tons of help from the video.

[@victoriam6569]

I enjoyed solving this puzzle very much :)

[@fanyaugusts9760]

One of the most labour intensive puzzles I've ever done.

[@paulmyrin5028]

12:15 Per knowing one color cell is in a domino but not which one, I would be interested in having the ability to half color a square, e.g. green and white. Or maybe being able to "fill in" a square as white for this exact purpose.

[@AcanthaRayneOakMoon]

With the colouring you used, Sion; I have nicknamed this puzzle 'Rhubarb & Custard'.

[@dsaoub]

I sometimes use the flash myself. In my mind, I don't think of them as flashes but instead of "light" and "dark" of that color. So red with light grey flash becomes "light red" and with a dark or black flash "dark red". Especially in puzzles with Xs and high-low-parity like this one I find it more convenient than to think of them as "colour with a grey/black flash".

[@Athrolaxle]

The way I thought about the renban domino in box 2 around 50:00 was that if there is no 5, the renban is now a 34 or 67, and is either yellow or purple. If it's yellow, there is no fill for the yellow 37 in box 1, since either yellow has 34 or 67. If it's purple, there is no fill for the purple 3467 in box 3, since purple has either 34 or 67. Also, around 1:00:00, I was surprised you did not make use of the ribboning in columns 7, 8, and 9. That said, I didn't even make it that far before I mucked up my coloring along the left!

[@dwdei8815]

Colouring hint - I use a white flash (the zero digit) if it's a havering between two possible cells. Means I've the grey available if it starts to go all picnic-blanket.

[@mliggett81]

I absolutely love the 45 joke

[@ingiford175]

At 45:50 you already proved a 5 had to be on that line, as one of the 37 was yellow and the 46 was purple, which means you either had a 36 or a 47 in the line, and the bap between those two has a 5, QED

[@KayDubs77]

I was just thinking, it would be nice in the solver if we had the ability to apply white to a cell, that way when using Mark's "I'm not sure which of these is green" coloring, we can use white to make it look semi-colored (instead of gray).

[@icomvo6670]

That one grey 9 at the end

[@w0rmblood323]

Anyone know if Simon is going to attempt that new Phistomefel puzzle on stream?

[@RichSmith77]

I found the solution - I just happened to have encoded every cell with its anti-symmetrical value 10-x. But the solution is known. 🙂

[@timparenti]

Re 51:35, how do we prove that more elegantly? Suppose, for sake of exposition, r2c3 is a 3. By yellow/purple "parity", that leaves 6 and 7 as the only options in r2c9. If it's a 6, your options on the Renban line are reduced to just a 4-5 pair. If it's a 7, you've got a bit more latitude with the choice of 4-5 or 5-6… but in any case it must have a 5. (And the logic works symmetrically with the opposite parity.)

[@mwebazegilbert2008]

The secret is funny 😄

[@asherhiggins7853]

This is one sudoku that gave me very little joy.

[@johnsouza4391]

This was a simple rule set that produced a great puzzle.

[@ScottCabernet]

As we start to run out of colours, I wonder if allowing us to use A-Z (and be able to corner mark or center mark them like we do with numbers) would be helpful? That way we can track our variables and also have an easier way of tracking possibilities

[@rontyson6118]

You can use letters. Go to settings. :)

[@ScottCabernet]

@@rontyson6118 the setting was added after I made the suggestion

[@rontyson6118]

@@ScottCabernet Okay, sorry.

[@wixxed]

Oh my gosh I totally misunderstood the purple lines. I thought they had to be placed in consecutive order. I worked on it for over an hour after finding the top-left 5, then I had to watch the video.

[@piarittersporn]

A really great puzzle.

until now i've watched the half of the video and i'm sure you will solve it. but i'm also totally confused by the coloring this time... may be i have to watch the video again and again and again... ;)

[@Raven-Creations]

Nice puzzle. I've no idea why you kept the blue/orange, which was completely useless, made it harder to see what was going on, and gave you an extra thing to worry about maintaining.

[@nicholasiverson9784]

Out of context quote - for the YT algorithm. "I was wondering if we could do Sudoku, but we can't." - Simon

[@noitallmanaz]

might i recommend creating a color of clear so that you can make only half a square a color without another color as a flash?

[@GabyGrecu]

im waiting for the comments by people triggered by the gray 9 and the 2 in the corner

[@nadinegrace6898]

That one 9 that still has a flash of light grey…

[@pedroamaral3742]

Yes!!! I can finally say i beat Simon. 41:21 for me.

[@_-_-Sipita-_-_]

39:15 for me. everyone likes coloring.

[@nishanthn4927]

49:49 me EVERY PUZZLE EVER!!

[@kalengray4073]

The x in box 4 has gotten me stuck for a few hours… to the point where i gave up and watched till he got it

[@dinidini4000]

round 8:30 he gets the top right numbers but no matter what is the true digit dont the X have to be 1 9 every time? if 2 the 1 cant be on the lines if 8 the 9 cant be on the lines if 5 its only 1 9 that allow for 10 and leave 2 sets of 3 digits

[@terracottapie]

You can see the "gray flash" better if you don't use green. It's the color where the flash shows up the least.

[@darylogrady5826]

I haven't been this overwhelmed by colors since I opened my first box of 64 Crayola crayons.

[@rontyson6118]

LMAO 😂

[@deelkar]

Got a 5, got stuck, watched a bit of the video, slapped forehead, continued to solve.

[@GrahamRSteele]

A marathon of fun.

[@phuybrechts6875]

tip : keep coloring till the and ! grtz

[@SerikonIsHere]

i watched your last probably 300 Videos and never had a problem following your logic. i was completely lost on this one, your coloring threw me off completely

[@willemm9356]

20:00 That seems needlessly complicated. r6c1 is already coloured green and is therefore on the green X. By XV logic the green and blue X-es are different anyway.

[@specialkalberta]

Amazing but I had a hard time understanding a lot of Simon's deductions which usually make perfect sense to me. Not sure why this video seemed a bit different in that respect. Presumably Simon's deductions were all good since he solved the puzzle even if some of them were unclear to me.

[@davidblake6889]

My brain has now exploded, and the result is similar to the grid...

[@francoistrempe]

Orange and yellow, blue and purple should have matched up.

[@koyha5266]

I personally think this was a bit too hard of a puzzle. But then again, I am stupid. I'd really love to see some more pencil puzzles for us simpletons. With all that said, I still watched the entire video and followed almost all of the logic. I got confused in couple parts. I could not crack this puzzle, I don't even want to try.

[@ericpraline1302]

Infuriating. Got to about the 50 minute mark in Simon's solve and found I'd broken it. Backtracked a little and thought I'd sorted it out but then broke it again. Turned out my problems started when I missplaced the 5 in box 4 fairly early on. Wish I had Mark's ability to pinpoint where it all goes wrong.

[@quynhanh87]

Can you fix the link where if you refreshed it still cache your progress? I got so far and accidentally tap back and it wipe everything.