Sudoku Test: Get 1 digit in 5 minutes: Not An April Fool!

[@Deathranger999]

0:48 “So if you start it and think that you can’t get anywhere, that’s not my fault, that’s yours.” Simon is a straight savage, I love it.

[@bluerizlagirl]

Those threes -- the 2,3 pair and the 3,8 pair, which could never have been a 3 because it was in the same column as one of the possible threes and a knight's move away from the other, so either would have ruled it out -- were staring me in the face for ages!

[@Deathranger999]

bluerizlagirl Did you reply to the wrong comment?

[@bluerizlagirl]

@@Deathranger999 Probably. Thought I couldn't find it.....

[@WillWatches]

Solved it in 3 minutes! It’s a secret technique I use where you skip to the end of the video and copy Simon’s Solution

[@ryand8338]

Will Mcmeekin A reliable, foolproof tactic!

[@TRUNKKS777]

Damn you need 3 minutes to skip to the end, GENIUS

[@aradhyamn6950]

Lovely 😅😅😅 but u too 3 mins to write down the answer?

[@juak91]

Brilliant!

[@lucasnumb3rs52]

Got my first digit at 1 hr, 1 min, 40 sec. Darn, so close

[@Jrce11]

Are you a regular sudoku player who knows the process? I'm asking because I'm completely new and don't know the process fully, and I want to try to get 1 digit alone if it's not some genius exclusive task

[@currentmood9568]

@@Jrce11 Definitely give it a try!:)

[@Ryan-si6qu]

9:00 *gets a 6/9* “ahh thats still really nice”

[@darielarias8505]

Nice

[@haydenarratoon4841]

this is gorgeous ohohoho

[@voidraldarken]

I knew that there was gonna be a comment on this as soon as I heard and saw that.

[@LucasDarella]

"Now can we use that to our advantage?"

[@imnotfuckingusingthisaccou2574]

Dariel Arias Stfu

[@TheTalkoftheStreetPodcast]

Everything he says make sense. Nothing he says is something my brain would think.

[@timmilatte]

Does your neck get tired from holding up your ginormous brain? That was insane

[@madwicky461]

I actually placed more than 10 digits in under an hour But for some reason they were small

[@ilianos]

Haha, good one! :-D

[@Sorarse]

I tried to solve it without knowing about the knight move rule. Needless to say, I wasn't very successful.

[@angelmendez-rivera351]

Sorarse It doesn't have a unique solution without the antiknight constraint, since a sudoku grid only has a unique solution if it has at least 17 cells already given, and this puzzle only has 11 given cells in the grid. I'm positive this has at least 3 distinct solutions.

[@Leyrann]

@@angelmendez-rivera351 And not only that, but also note that not ALL sudokus with 17 cells given have a unique solution. In fact, it's theoretically possible to give 77 out of 81 squares and not have a unique solution. 17 is simply the lower bound where a unique solution CAN exist.

[@angelmendez-rivera351]

Leyrann You are correct.

[@DouglasABailey]

You'll only make that mistake once. I now watch the video long enough to know if there are special rules.

[@SadisticSenpai61]

@@DouglasABailey Yeah, I usually work on the placing obvious stuff (usually pencil marks) based on normal sudoku rules until the vid gets to the rules part and then pause the vid. And sometimes that means skipping to the rules part on the vid cuz there's nothing to place or pencil in with normal sudoku rules. lol

[@TheThomasites]

28:18. It was the 39 below the 23 23 pair as a knights move rulling out the 3 in that cell.

[@eithanschonberg1768]

Realised that at 25:36. It was painfull to watch after that...

[@Scalemailmailmail]

This is like the first time i spottet something faster than Simon. Achievement unlocked! I'm guessing it's 6 months until next time :-)

[@jaguh9069]

It's funny seeing how Simon can spot ridiculously hard to spot techniques but always missed these very obvious right at your face clues XD

[@Scalemailmailmail]

@@jaguh9069 Well, that stings :-O

[@batdowg]

I was talking to him about that for about 5 minutes :D

[@strandvaskeren]

So the aprils fool part was when Simon deliberately steered well clear of that 39 that knight moved those 23's, he saw it right away but let us all yell at the screen for a good 5 minutes before solving it some other way - well trolled, Simon! :)

[@beqwtanddrv]

My wife, explaining why she left me: “Because of the knight’s move constraint.”

[@diegode966]

27:56 I actually didn't see the move Simon made, I was screaming waiting for him to make another realization. The 39 in C1R7 (column 1, Row 7)! The 3 sees both the 23 pairs in C1R5/C2R5, so it must be a 9 in C1R7, causing a chain reaction. Either way, fun puzzle. I'm glad to say this is really teaching me how to look at these puzzles.

[@TheKingsRook]

I was doing the same thing.

[@wolfgangwalk337]

Actually I was laughing. He sometimes doesn't see the obvious, only to arrive at the same solution after some detour. Same with the 5 in r7c7, that immediately erases the possibility for a 5 in r6c9, thus giving you the 5 in r4c9. Having said that: In 99% of the cases he sees things I wouldn't have seen in 3 hours.

[@JakeRoeder]

Paraphrasing: "Make sure you don't overlook all of the new information you've gained." Simon: I will promptly ignore the 2 that can be placed in box 6.

[@alasyon]

YES!! 😂

[@MarioSpiteri]

Hello Simon, I worked this is 1h25m One suggestion please. In each web pages of the puzzles, can you also put the rules please? Also, it would be nice to have a list of puzzles in the main page where the user can click to play a puzzle and maybe put a small description for each, for example: Puzzle 0001 - Normal Sudoku, Knights Move, Difficulty 3 Puzzle 0002 - Killer Sudoku, Difficulty 4 Puzzle 0003 - Normal Sudoku, Magic Square, Difficulty 3 Thanks and keep up the great work :)

[@davidh.4944]

Some fans have built a spreadsheet page detailing all of their puzzles. There's a link in the description box of every newer video. (For any new viewers reading this.)

[@mallechilie]

That spreadsheet doesn't show links to the puzzles directly right? Any idea when CTC started putting the links in the description?

[@vctrsigma]

love at 16:00 that second "it can't be anything Ack!"

[@NicknotNak]

Me every time I try to do anything and realizing I messed up.

[@P4T098]

*screams in pain*

[@ChrisConnett]

28:35! That wasn't so hard. What's that? We're supposed to finish the *whole* puzzle? But you said one digit…

[@The_Cali_Dude_88]

Lol...

[@florianzellmer8735]

Congrats Simon on solving this monster! I tried it 3 times, but I couldn't find the step in. You make it look very easy. When you're spotting something, I can see it at once, but when I am on my own, I just can't

[@Wecoc1]

14:00 Hard to see, but the 6 can only be in one place in row 7. That also locks a 6 in the first box and makes things a bit easier in that point.

[@mikkokormann6814]

Wecoc1 nice Spot!

[@aradhyamn6950]

Superb , u spotted right 😍

[@eve_the_eevee_rh]

2:52:39 after having a friend help out and also a hint for the first digit. Damn, Simon's pretty smart

[@RandomBurfness]

Despite having solved literally all of the anti-knight's move sudokus in your Chess Sudoku app, I stared at the grid for 17 minutes without getting in a single digit. It was exposure to anti-knight's move sudokus like these that made me believe I couldn't do them ever, and just as I had built up some courage to try one of this calibre again I now see I am still as horrible as ever at the variant. Bleh.

[@johangt90]

That 3,9 pair vs 2,3 pairs made it hard for me to breathe.

[@doctorwhouse3881]

He missed some very obvios clues in this one.

[@LPdragonfly1989]

@@doctorwhouse3881 Maybe that was the april fool :D he missed them so that we can shout at the video "YOU OVERSEE [insert number] AAAHH" xD

[@angelmendez-rivera351]

Doctor Whouse He misses some very obvious clues in every video he makes. He even misses the nonclues, such as when a row already has 8 digits in it and then he promptly opts not to fill the final cell. I do find it a little irritating, because I have OCD, but I don't entirely blame him, though I do wish he was more careful, because this type of issue just makes the lessons more confusing and also a little more painful to watch than they should be.

[@P4T098]

@@angelmendez-rivera351 Just imagine a baby seal getting sucked by a jet engine

[@MyNarsa]

this WAS an April Fool, the puzzle made a joke out of me for almost an hour :O

[@RoderickEtheria]

That was quite a struggle. Took me about an hour just to find a way in, and then another hour and about 12 minutes to solve. I observed the 69 as a switch with a 15(69) triple in the middle box. And actually if we start it and think we cannot get anywhere, it's not your fault, the Aad's are just stacked against us.

[@hitdoctor24]

I love seeing how giddy he gets when he solves certain squares. In addition to these videos being fascinating, it's also the most wholesome content on the entire damn internet

[@grudley]

Huh, the skill difference between you and me is not so much that you can spot more than I can, but that you can find what's relevant much more easily than I can. That gives me ideas for how to improve :)

i subscribed to the patreon membership now, because of the high quality of this channel. Keep goin...

[@lakarto19]

01:19:38 solve time today // Wow, I feel like an idiot. I managed to get the first digit (the same 9) in seven minutes or so, but got majorly stuck in placing the 1 in box 3 (r3c7), not realizing that it was seen by the 9 in the center box. Sometimes with variants, there seems to be one of those moments when the ability to transition fluently between the variant rules and 'normal sudoku rules' just deserts your brain, your mind just goes blank and you don't spot something really obvious for a long, long time...

[@lavenderwalrus9875]

love the video as always :D although it was a bit painful when at 10:33 simon inputs a 2 whilst saying to make sure to use all the information it gives him then misses that he can easily put a 2 in the middle right box because of his pencil marks XD

[@glennmelven3414]

I spotted that cell R2 C4 was restricted but I didn't realize the implication of it. So, I spent a lot of time staring at the grid with nothing going in.

[@Socialdogma]

That was my first digit but I missed the challenge, getting it at about 6 mins.

[@MorningNapalm]

Me too, other than whisky of course, that went in quite well.

[@samtravis4822]

Couldn’t even get a single digit. It’s these puzzles that keep me humble!

[@WatermanViolinStudio]

Solved it! Interesting that we diverged in our approach in the middle somewhere. I enjoy watching you work!

[@cobba42]

This puzzle is a beautiful and brilliant demonstration of how the constraint was used to full potential. Incredible!

[@kraljevo8]

I stumbled upon this channel by accident, but the way you explain the logical steps you take to solve these puzzles hooked me. I do have some suggestions for your web app, though. Perhaps you could add a pause feature in the app and a clear explanation of any additional constraints on each puzzle so that anyone opening the app from an external link won't need an explanation to understand the special rules (i.e. I send the links to my wife from time to time). Excellent content. Keep up the good work!

[@bristolrovers27]

I had an enjoyable 15 minutes staring at this before I gave up and watched the video

[@toddschaefer5488]

Fun solve. Loved the ending. R7C1 was resolvable well before that by the 23 pair above it. Loved watching the "what fixes this scan" at the end when I caught that when I placed the 39. Great puzzle.

[@Birchbayaromatics]

Could not get it started until I watched you find the first clue with the 6's. then I got the hang of it. Very difficult and mind-bending. It is easy to waste clues. also very enjoyable. Please keep bringing more horse puzzles.

[@sarahcicconetti6826]

Here's what I do when watching one of Simon's videos: Step 1- Smile as I listen to the intro. Step 2- Listen intently to the directions. Step 3- Attempt to start the puzzle while the video is paused. Enter no more than 2 or 3 digits (if my brain is working that day). This step takes me 20 to 30 minutes. Step 4- Watch how Simon gets started. Step 5- Make another attempt with the additional information. Step 6- Start the video again because I've gotten stuck again. Step 7- See the obvious information that I had marked down but somehow ignored but luckily Simon never judges me. Step 8- Work on the puzzle, sometimes to conclusion. At this point an hour or longer has passed. Sometimes multiple hours. Step 9- Watch the rest of the video and get frustrated at the obvious thing Simon is not marking down (see step 7). Step 10- Reach the end of the video so that I can hear Simon praise the video because my day isn't complete with it.

[@lucio8947]

I laughed my ass off when he marked a square that was restricted to a 6 or a 9 and he said "That's still very nice"

[@kleozyn4179]

4:59 for me for the first digit! Ofc it was wrong but i had to guess :)

[@Dennis-vh5hm]

KleoZyn loooool

[@Novas12390]

atleast you got a digit under 5 minutes

[@stevfusion]

I haven't done a sudoku in a while. This was a mean one to come back to.

[@ItsSansom]

You know Simon's starting to panic when he squarks (16:07)

[@nathanmahady6484]

He is definitely overestimating how smart I am. I would have fallen for an april fools joke

[@TimDroz]

That 2 pencil-marked at the bottom of column 8 drove me crazy, but I could only keep telling myself that I couldn't have even figured out that a 2 ought to have been penciled in there at all at any time.

[@DougCube]

At 9:21, a way to make progress without using that tough knight strategy is to notice that placing a 6 in r2c6 creates a a locked-quad of 1348 in column 6 (from r6c6 to r9c6) which exposes a 69 bi-value cell in r3c6. The locked-pair of 69 in box 2 then contradicts with the 6 in r2c6. Therefore, r2c6 is not 6. Then could make a tiny bit more progress before realizing that it's impossible without using an advanced knight-based strategy.

[@luke8558]

*adds a 6 and a 9* "Now that's really nice"

[@thomasosborne894]

The end was killing me!!! Lol I saw the 3/9 in column 1 row 7... that couldn’t be a 3 because if knights move! :)

[@ThomasJohnsen2]

Wow I struggled with this one - 45:52. It had a lot of "doooh" moments for me, where I didn't spot something obvious for a loooong time.

[@DougCube]

At 25:34, you put 39 as candidates for r7c1, but the 23 locked-pair in row 5 eliminates 3 from that cell.

[@avishagkelhamer]

I am soo happy rn!! after a lot of puzzles i tried solving with you that i made mistakes in and gave up i actually succeeded in this one!! ngl i did watch a little bit of the video when i got stuck but it was mostly me solving:) im new to the "not regular sudoku" world and i made it in 35 minutes!

[@jonathanhensley2079]

You, my good sir, are a monster. Keep it up, I learn more every time.

[@GeneralYouri]

I found a different first digit, but using the same 69 pencilmark. Pencil 2s, 4s, 6s, 9s into box5; they each have two options except for 4s which have three options. Now because of r2c4 being 69, you can only have one of 69 into c4 of box5. Therefore the other of 69 in box5 forms a pair with the 2, taking the place of two 4s pencilmarks and thus placing 4r6c6.

[@58209]

i haven't tried solving one of your puzzles myself yet. i'm just a novice bingeing your videos. but it felt really good when i spotted the logic at 28:24 with the 3 a couple minutes before you did. :D

[@freezzerriss]

"So this square is massively restricted now, this can't be anything... aaaaarghh!!!!" Died laughing.... :D

[@KAF128]

26:58 You ask what resolves the 2:3 pair ? Answer: the 3 in the box below it. I am starting to enjoy the knights move element to these puzzles - nice one !

[@gordonglenn2089]

This was a good challenge. A good variation that makes a "standard" sudoku almost as much fun as a killer sudoku ;-)

[@chrisvaughn4399]

17 minutes to get the first number. Trapped myself once and had to backtrack a couple numbers. 44 minutes to solve this one. I greatly enjoy how these knights move restriction puzzles conspire to give concealed hints where none would normally be.

[@davidh.4944]

This one murdered me. 5 minutes? Try 120, before finally giving up and watching the vid. I had eventually managed to deduce all of the other available eliminations that Simon found in his first minute, but just could not spot that one pivotal 6 that broke the puzzle open. On the other hand, I always feel a sense of bemusement when I see Simon (or Mark) so often finding a digit or useful pattern and then not fully following up on their ramifications before moving on. @12:00 he used the 15 pair to fill out the trivial r5c2 cell, but he then failed to immediately apply the same logic to the important naked single 4 in r3c4 (although he did come back to it later). He could also have used them to fill in r4c7 (an 89 pair) and r6c3 (789) while he was at it.

[@Polymeron]

I found this to be fiendishly difficult. It took me in fact more than an hour to place the first number (same one you found, of course), and many more false starts with errors before I finally got it right. Great puzzle.

[@garyha2650]

Maybe you could add a feature to your software, something like blinking a number in a box when pencil marks would indicate it is the only choice left, or another where pencil marks would blink when they are no longer valid :)

[@batdowg]

10:35 "Must be careful to use all the information"... 15 seconds later, ignores that the 2 in box 6 can only go in one place now...

[@MsBestPilotEver]

Yeah, it annoys my autistic brain that he skips from number to another without looking all of the boxes 🙈

[@angelmendez-rivera351]

JuuGelis BuuGelis SAME. Finally someone who understands. And I don't mean any offense by this, but while I do understand that mistakes can be made, I think that (1) this can very easily avoided if he was just more careful, and to make matters worse (2) whenever he is teaching a lesson, his lack of care results in him overcomplicating the puzzle and just making the lesson a lot more confusing than it needs to be, and also less enjoyable. Don't get me wrong, I still like the videos at the end of the day. But this is a notable flaw that I seriously think they should eventually address, because I know I'm not the only one with issue. And it's not a matter of style either. Like I said, just being careful could make lessons less confusing. And on a somewhat related topic, I noticed that he is also pretty bad at scanning the board, probably because he isn't systematic at all when he does it. And again, this makes the lessons less than optimal, because it makes the puzzle harder when he doesn't scan for all the possible areas where he can pencil mark. In the first place, all of these lessons are about learning things about X-wings, empty rectangles, skycrapers, and other such advanced techniques, but how are we supposed to apply them correctly if we're not even pencil marking the board the best that we can? Like, very often, he will be given the chance to pencil mark three eights from the very beginning, but then he doesn't actually do it until after it's no longer useful to do so.

[@ItsCalico]

It was funny when you always says "I'm sure you at home or poiting out what I'm missing" and I'm always like nope. But, for the first time, at 27:03 I saw what resolved the 23 pair. In the bottom left box where the 39 pair was, if a 3 was there then a 3 couldn't be in either of the two spots in the 23 pair, making it a 9! I feel like I'm actually learning when I watch this channel 😂

[@TheTalkoftheStreetPodcast]

Always amazes me how much thinking is required so late in the game.

[@AdiM-lq4bp]

That pencil marked 6 at the top left corner annoyed me so much!! (Time stamp 19:52 )

[@DrMattCS]

9:26 pretty happy with myself for being 3/4 bottle of wine in...paused the video, gave it a shot, and found the logic :). Love Simon and these videos!

[@steezymtb5876]

Column 1, row 7. Could have easily solved it earlier when you were "stuck", because of the 2/3 pair on the box above. The 3 would've eliminated both squares, therefore must be 9. Got there though, such a beautiful puzzle. I really love these knight move sudokus.

[@jampishon]

We wish more savage level sudoku from you to get through this quarantine period!

[@l3igl2eaper]

I pencil marked in every single possible number in every cell and removed all the values that they could not be from 1-9. I found the initial 69 but did not see the next step in using that. Crazy puzzle.

[@angelmendez-rivera351]

This is easier if you systematically scan the grid by digit. For example, look at every 1 in the grid and look at how they interact with every single box in the grid. Pencil mark accordingly. Then proceed with a 2. And so on. As you do this, obtaining new digits will come more easily, and then you can scan again until you've exhausted the possible pencil marks with Schneider notation. Once this is done, then you can start looking at techniques to apply per classic sudoku rules, and this does the job. It's still harder than classic sudoku, being an antiknight sudoku, but doing it systematically makes a little easier than otherwise. And I get that it's a little annoying because you have to do the scanning twice or thrice, at least, but it gets the job done instead of not scanning carefully and being stuck on a clue that, in retrospect, should have been very easy to spot if you had scanned properly. Remember, sudoku is all about logic, and logic is all about rules and systematic deduction. If you are not being systematic, then you are not using logic optimally.

[@lokinakor1]

You shouldn't feel dumb for not catching the 9 early on, that was nasty. The dummy move was adding the 6 to the top right square of the bottom center cell when the 6 above rules it out with the knight's move. I sat here for ten minutes screaming SIX!!

[@vicktorus847]

At 13:27 when you place the 4 and 5, cause this box can't be 168, you have been lucky cause, F7 can't be a 6, cause knight move of the 6 at D6. The 6 on H6 saved you.

[@msolec2000]

At the end you did it a bit of the hard way. If R7C1 was a 3 then box 4 becomes devoid of threes, and again that collapses everything. But very nice solve. I couldn't do it. :)

[@vicktorus847]

At 20:40, you put a 5 in G7, but if i'm not mistaken it could be G8 too. You have been lucky. the 5 was at G7. :) :)

[@micheltordoir7734]

45 min for the first digit and an hour after that for the sudoku. I have to go slowly to be concentrate and scan all knight moves. So easy to forget one. Very nice puzzle.

[@jenniferdouglas3295]

Took about 10 minutes on the third attempt to place the right digit in that 6 and 9 square, and 42 minutes to solve. That was a good puzzle.

[@jrbos]

21:25 You resolved a 7, yet you still had a seven penciled in on row 6. What was the reasoning?

[@Brian-nx3yp]

Had the same question, but now see he used the 26 pair in the column to narrow the box to 37 and the knights move eliminated the 3. He often gets in a hurry and skips explaining his work.

[@dannyzhang6336]

just buy sudoku rules that box can only be a 3 or a 7, knights move makes it so that it has to be a 7, its just not explained

[@darciestimpson8904]

9:04 - this square can only be a 6 or a 9, that’s really n i c e

[@colleenscottcarmello5103]

my goodness.. brain on fire.. ha.. I did manage to get ahead of you on some squares, and also made a few mistakes from not catching the Knights square,, ugh lolol. lots of fun.. =D

[@RengarAlgerad]

1:53:47 -- took 15 minutes to find the first digit, then I messed up and had to start over. One of the toughest puzzles I was actually able solve.

[@dwmoll]

Great puzzle. Long solve and I had to rewind a mistake with 7 numbers remaining, but very satisfying. I would have been faster with a negative pencil mark option (what cannot be there).

[@JaggerG]

This one destroyed me. Absolutely not my A game. Finished in 4:24:44. I’m usually only a couple minutes behind Simon/Mark on chess sudoku, but after missing that R3 constriction on 6, I just penciled in every possibility like a mad man, finding logic chains and junk and trying to boil those chains into simpler rules. I had a disjointed bent triple on the 269 at the very start that actually gave me the central 4 as my first digit, 33 minutes in. Didn’t resolve that 69 until like an hour later. Even the 8 restriction in r3c7 didn’t occur to me until several efforts at logic chaining. Big oof. But at least I spotted that 23 at the end resolving the 39. Lol

[@Rangar1997]

I'm reminded of what someone posted on Steam about the Knight's Sudoku, and how it would make solving the puzzles easier . . . yeah . . . . . . . .

[@tomekduresov706]

Challenge failed

[@Jonasz314]

Had some problem taking off, but managed to spot patterns to solve it in ~20 minutes.

[@tashkiira7838]

It usually takes me more than 5 minutes to simply fill in the digits that can be in the various cells, so I didn't think I'd get the challenge done. but I acquired the 7 in the right-center square at 4:58.

[@eg14000]

So I paused the video. Fired up my brain to find the why the square wasn't a 6. But was then waiting in agony after seeing the same logic worked on the other side of the puzzle with 6 and he didn't see it for 5 minutes.

[@harstar12345]

Knight Sudoku is so quaint! It's the best variant of sudoku in my opinion.

[@harkelin]

Thank you for these videos.

[@yudhispokemon]

More than 1 solution to this? I just solved it and last few numbers a different 😱

[@Robin19358]

Saying that something isn't an April fool's joke, is equal to reminding them of April fool's and how easy it would be to trick someone with this title

[@Newbrict]

21:12 How did you rule out the 7 from the lower right corner? I don't understand...

[@Cristalman0]

The seven he placed was the last possible number for this square.

[@Lisa.H.]

Took me 1 hour and 17 minutes, had to do it with a bit of your help, was fun though!

[@liiiinder]

3:24:46 ... I took out paint and made colored notation on all possible digits... Got to remove that 6 in box two (R2C4) really quick but it took me almost 2 hours to realize it was a 69 pair to place the 9...

[@AlexanderLeset]

It took me 5 hours and 24 minutes to get my first number. I ended up quitting about 8 hours in after just getting 9 numbers. I ended up following the same steps you did, just much, much slower, and I feel like an idiot for getting stuck where I did because it was really obvious, I was just too tired by then

[@alienrenders]

Only took me 5 hours and 16 minutes to finish it. Gonna watch the video and see how you did it. Ah, I didn't get that first 9 right away. I was able to fill in 3's and 5's in the middle and use that to eliminate tons of possibilities and finally I got the 9. You did in 10 minutes what I did in 3 hours. First knight's move sudoku. They're a little odd for me.

[@calmeilles]

Wow! That doesn't become conventionally solvable with an unique solution until you place the 9 in r1c7 at 28:46 - *ten seconds* from the end!

[@OffishallyDedd]

Can anyone help me understand why can't there be any 6's in row 1 at the 10th minute mark? He makes the assumption at 10:11 that there could be only a 6 or 9 in that box, and he rules out the 6 based on what it would mean for row 3. But I can't understand why is the 1st row left out.

[@mikesummers-smith4091]

I placed the 9 in about 4 minutes; and followed up with the filthiest bifurcation I've ever done, from 21 digits fixed. I got lucky; but it wasn't exactly plain sailing even after that.

[@1981stonemonkey]

3:53 a.m. Started out by corner-marking those numbers are IMpossible for every square, then slowly central-marking that were possible for some squares. Big jumble of numbers all over the place, slowly converting and eliminating. Got 'stuck' more than once, 'peeked' to discover where I had lost overview, then continued on. Got it after 3 hours... 8-J Let's give it another go tomorrow... * yawn * Good night.

[@angelmendez-rivera351]

Harmen Westerhof Marking the numbers that cannot appear in a cell is typically a very bad idea in most sudoku variants, and it's bound to eventually cause a headache, or worse, an anneurysm. It's easier to just Schneider notation, although I admit that Schneider notation, by itself, is not optimal. Usually, a hybrid of Scheneider notation and only-or notation can get you the solution to even the hardest sudoku in less than 20 minutes.

[@songbird7450]

It looks so easy... then I try it and break the Sudoku twenty times in a row before giving up.

[@owlman145]

Was not able to get the first digit without Simon's help, but after that was more or less straightforward (if you abuse knight moves).