The Corners Are Even: A Sudoku Masterpiece 

It is utterly *ridiculous* that EVERY Sudoku that appears on this channel is world class. Imagine being able to dine out in your favourite restaurant 365 times a year, ordering different meals every evening and _always_ having the best meal of your life. That's how Simon and Mark must feel about these puzzles.

Thanks for featuring my puzzle, Simon! A pleasure as always! You managed to find almost all column 1/row 1 deductions. For the one which had 9 in the middle, r1c1 and the remaining odd in box 3 (or 7) have to add to 9, so the remaining odd in those boxes are 3 or 5. Due to the 8 in r8c8, r1c8 can be neither. That was hard to spot, so I think you did a nice job working it out through the middle zipper.

Oh, I love Simon's use of the Enligsh language. "That's slightly true... no, that's *jolly* true" I will use that as a gradient for truth going forward

52:11 "please dont be difficult now, I really really just want to fill you in" naughty simon

If it were 6 on the left, you won’t have enough even digits for the corner.

Simon: this is so ridiculously complicated, how does this have only 3 stars? Me: because Simon always picks the most complicated (and beautiful) way to see/prove things? :D

Simon: “If we do X, then y, therefore z, meaning that a, b, and thence c, and so therefore, you cannot place 7 in column 1!! And we now know that X cannot be true.” X: *has five even digits in C1* Simon: “This logic is *so* unusual.”

simpler way of deducing that R1C5 and R5C1 can't be 6 is that it would use up 2,4 and 6 in that row or column and then both square cells in R1 or C1 would both have to be 8

No snakes, no loops, no doubling or halving, no need to design the boxes. Just Sudoku. What a fantastic SUdoku puzzle !!!!

-Simon what is your kryptonite? -Playing sudoku on a sudoku puzzle

Simon, you constantly find beauty and deductions in all your solves. So humble you are that always giving credit to the setter!! The joy you get in solving for us day after day is something special for us.

I just love how sometimes Simon jumps between parts of grid and missing his deductions from before. @16:52 he forget about 9's in row 1/collumn 1 can be placed only at r1c5+r8c1 and r1c8+r5c1, completely removing 9's from center of two zippers.

Hello, I rarely comment on youtube videos but I have to say that those sudoku videos are just a chill time i enjoyr almost everyday. Thanks for these moments :)

So many really clever deductions involved here. It feels like in many of the steps you need to extend the logic by one step further than you'd normally have to in most puzzles. It's not that these two digits see each other so they can't be the same; it's that they each have a counterpart that sees the other's counterpart and if they're the same then so are their counterparts, and that's why they must be different. Lots of that sort of thing going on. Very impressive!

Rules: 04:13 Let's Get Cracking: 05:07 Simon's time: 48m35s Puzzle Solved: 53:42 What about this video's Top Tier Simarkisms?! The Secret: 3x (02:29, 02:44, 05:11) Bobbins: 1x (17:48) Knowledge Bomb: 1x (05:43) Three In the Corner: 1x (00:45) And how about this video's Simarkisms?! Ah: 13x (14:26, 15:17, 15:17, 15:17, 16:00, 33:03, 33:03, 33:07, 35:47, 38:02, 40:35, 47:55, 49:30, 50:28, 50:28) Pencil Mark/mark: 11x (09:52, 14:50, 24:54, 28:26, 34:21, 35:13, 35:28, 37:31, 40:14, 44:28, 48:49) Symmetry: 11x (06:19, 06:50, 06:52, 07:05, 07:20, 07:30, 07:34, 09:40, 36:51, 39:39, 42:09) Sorry: 6x (03:09, 08:07, 08:07, 15:22, 28:06, 30:21) Beautiful: 6x (09:12, 21:28, 33:10, 42:20, 53:55, 55:16) Hang On: 6x (13:37, 30:15, 45:51, 46:15) Cake!: 6x (02:25, 02:37, 02:49, 02:53, 03:18, 03:20) Goodness: 4x (08:04, 08:29, 40:35, 47:24) The Answer is: 3x (05:57, 41:02, 50:00) Brilliant: 3x (01:06, 44:38, 45:20) In Fact: 3x (06:28, 22:59, 27:19) Obviously: 3x (06:43, 12:02, 21:02) Good Grief: 2x (21:28, 38:02) Naked Single: 2x (51:35, 52:58) Shouting: 2x (02:36, 03:45) We Can Do Better Than That: 2x (19:56, 42:38) Wow: 2x (53:46, 53:46) Nonsense: 1x (28:41) Clever: 1x (53:37) Fascinating: 1x (14:18) By Sudoku: 1x (36:46) Surely: 1x (42:09) Puzzling: 1x (04:00) Almost Interesting: 1x (29:43) What Does This Mean?: 1x (41:36) Nature: 1x (38:33) Most popular number(>9), digit and colour this video: Thirty Five (7 mentions) Nine (93 mentions) Green (3 mentions) Antithesis Battles: Low (2) - High (0) Even (34) - Odd (26) Higher (2) - Lower (0) Column (22) - Row (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! Q2: Can you do this for another channel? A2: I've been thinking about that and wrote some code to make that possible. Let me know which channel you think would be a good fit!

Your disentangling the zippers around the edge was fascinating, Simon. Thank you for this great video!

My last deduction from row and col 1 was this: when you know the zippers are 8 and 9, they always have at least 3 odds on them (8 has 4 odds, 9 has 3). This means the row or col with 9 has to have two more odd digits - which cant be in the corners. Together with the fact that the row or column with the 8 has to have a 9 in the light green square (the 5th odd) - leads to the fact that both light green squares are always odd. This disambiguates where 8 and 9 zippers go, because there arent many odd digits available in r1c8.

I love seeing your facial expressions whenever you find a logic deduction. Its like watching a child unpack a christmas present

fascinating how long it took Simon to notice the middle square couldn't be 7. I think his brain works in such complicated mathematical ways these days, he has forgotten to scan.

10:34 "If both of these were 9s..." There's another way besides (and perhaps simpler than) the parity logic Simon gets to shortly to prove this cannot be the case - whichever of the marked 7 positions in box 1 is NOT 7 must sum to 9 with r1c1, since if it didn't its partner would be lonely on the zipper line. As such if the associated row/column 1 zipper line were a 9-sum the digit in r1c1 would repeat in the orange cell

Simon casually understanding that whichever zipper we put the 9 on the other can not have more than 1 even digit on it, and then goes on an entire tyrade about where 7 goes if 6 is in the middle even tho 6 would need 2-4 which he already proved is impossible :D also love it when I make the same progress in 5 minutes as he does in 20, but get stuck for a whole hour after that :D

The eclipse was awesome! Truly awe inspiring. I saw it over a lake in a clear blue sky. It was so quiet....until I heard distant clapping and cheering from the forest all around me from others having the same experience.

Mr. Menace thank you very much for this puzzle. I cannot describe in words the joy I felt logically discovering what number goes where on the grid here. I took double the time than Simon but what a pleasure it was this discovering.

It's lovely to see Simon guiding himself through the puzzle and noticing things he "missed" ^^

25:32 For me, I was so mesmerised by the first row and column it took me 5 minutes before I placed 9 in box 1

Exquisite puzzle, lots of fun deductions. At 38:54 there is another way to deduce how the first column and row go. Simon noticed that whichever digit goes to r1c1, its pair to make 9 is not on the zipper line in box 1. The same holds on the zipper line in row 1 or column 1, whichever has the 9 on the zipper. So in that row or column the pair of 4 or 6 must not go on the zipper. The pair of 4 or 6 is either 5 or 3, so this digit must go to either r1c8 or r8c1 as r1c9 and r9c1 must be even. But r1c8 sees both a 3 and a 5, so column 1 must be the zipper with the 9.

😅I could not have worked this out on my own, but it was easy to follow Simon with his logic, and I enjoyed every one of his moments of insight.

I did this one all by myself, took me only 10 mns more than Simon!! And I filled the 8 and 9 rows without using the middle purple line! I'm a bit baffled actually. I even used all the right logic instead of hammering away at all pencilmarks I can think of. This will be a very good day surely! Thank you mr Menace for this journey in a puzzle, I even giggled at things like "well, both the cells are a one" in row and column one

Though I enjoy every puzzle on this channel, this one was simply spectacular. ❤❤❤❤ this puzzle.

To mute your buzzing phone, click on either of the volume buttons while it is buzzing. It will stop the rettet and the noise!

How can it be that Simon almost instantly jumps to the question "where is the nine in column 1?" and then "where is the nine in row 1?" and next embarks on a far-fetched quest on symmetry without ever going up with the question of the nine in box 1.

22:58 Clever opening that just cascaded into a full grid once the c1 and r1 zippers disambiguate. Beautiful and a pleasure to solve

Twice as quick as Simon!. Ye ha! For once well and truly beaten. Once!. Just once!

Yay managed to solve this one! Took me 1:04:45. Don't usually solve sudokus much but I thought it was a worth a try without watching Simon :) I think this is the first zipper line sudoku I've ever solved but I've done a few odd/even parity ones too. I did get stuck a lot but I pulled through without turning to the video for hints.

It was a fun try, but hard for me. Needed some tips from the watch. Thank you for the solve! 😊

An easy way to determine which way row 1 and column 1 go was to look at the 8th digit in each. They have to be 9 and 5. Then the 5s in box 9 give you which way round that row 1 and column 1 go.

0:53 I always needs to go listen to "Losing my Religion" to cleanse the palette after hearing the "3 in the corner" song. Mark gives it a valiant effort, but is not a singer, and Simon just giggles his way through it each time.

Simmon you already said that one of r1c8 or c1r8 needs to be 9 so this gives you that box 9 center is 8.

The thinner zipper lines look great.

Closes box showing the real time it took to solve puzzle, only to check the recording time while asking how long it took to solve the puzzle - everytime!

I got 58 minutes. Calculating the different values for the zipper lines in my head was a little bit challenging. but it was really fun to do so. This was a great puzzle!

Just wanted to say how much I love the shout outs and happy birthdays at the start of every video. You would think it's something you might skip through but I just love how genuinely appreciative you are of your followers and how lovely you are! Much love

41:21 finish. I had a bit of a snafu in the middle, when I didn't think about what a few of my pencil marks meant. That caused an erroneous chain of events which lasted for a good 5-10 minutes. Fortunately it was an easy fix after rewind, and all of the logic I had done was still sound, just with different numbers. Brilliant!

Some very interesting breakin logic to fill in those middle zipper digits i think 3-4 stars out of 5 is about right. took my just under 40 minutes to complete so certainly not the hardest of puzzles but not easy either

23:49! Solve number 85. Great puzzle!

16:05 for me. What an interesting puzzle, really enjoyed it!!

18:00 you worked out the green cells can't both be 9 so since the only other place in row/column 1 for 9 would see the 89 in box 9 it has to be 8

Aaaaah, no threes in corners, but let's watch anyways ;).

when I made 89 center pairs for the two lines I completely forgot they could either be in either of the sides as a pair, so I took an extra 30 minutes to beat it, the double 3 for the 6 give away the order of 89 pair and the rest was just sudoku, really interesting.

There are a lot of elegant deductions to be made in this puzzle, and I mean a lot. No way is this a 3 star puzzle! That said, I probably did miss something. Very nice though, thanks.

I cracked this one by realising that r1c8 & r8c1 both had to be either 5 or 9 by running through the 8/9 zipper options. Then placed the 9 in r1c8 because of the positions for 5 in box 9.

18:06 for me :) After realizing there always has to be a 1 on the two straight zippers it was easy sailing🎉

So I'm a middle level player with Soduko and I love watching the channel. But for the first time (probably ever) I saw something before Simon. When he was talking about the 9's and was pointing out the middle row 1 or the middle column 1 I saw that affected 8R8C. Whoot whoot !!! I guess I'm getting better (nowhere near the master but still pretty good haha).

I think the simplest path to seeing that the edge zippers take an 8,9 middle is that the nine and all but one even number are used up in the row/column, so the zipper is 1357 and a mystery even-so once you deduce that the even is in the middle, 1+3+5+7 = 2X.

At 10.47 minutes you could already have concluded that R6C6 or R4C4 was a nine, because the 9 cannot be on the zipper. (''Where does 9 go in box 6?'' would have been the right question, I learned from you) At 47.11 min you would then automatically be sure that the 9 was in R6C6, or at 51.27 min, when the 9 was placed in R2C4. As it was, it became the penultimate number that you filled in, at 53.29! It's funny how you sometimes miss the obvious, but I would have missed out on the beautiful deductions that you came up with now. I assume it would have considerably shortened the video. But again....I'm not complaining! Beautiful puzzle, beautiful solve!

Finished in 130:32, but I had to do a lot of mild bifurcation to see what worked and what didn't. Looking forward to watching to see what I missed.

I thought it would be a fun challenge to try to make that zipperline rule more concise. Here goes: The center of a purple line is the sum of pairs of cells equidistant from it.

i thought i heard 'pizza' when he said peter XD but i do want a slice, so that might be why

Finished in 71:41. I'm bad at zipper lines :(. Fun puzzle!

R1C1 could be determined early because of that careful placement of the given 3, which eventually rules out R1C8 and R8C1. Therefore ask how you can put 3 on both the zipper lines?

Thanks Simon! I enjoyed the video as always. 24:25 Once you deduced that there was an even on the opposite zipper from the 9 zipper, I think you could’ve left the deduction of the 89 pair to the fact that the even digit had to go on the center along with 4 odd digits comprised of 1,3,5,7 = 16 / 2 = 8. Or did I miss something?

Nice puzzle! One curious thing is that I got the puzzle completed pop-up despite having one cell still pencil-marked (R7C5). I also got the screen after filling it in correctly and deleting the entry. The preemptive popup went away when I closed the tab and reopened. Not that it affected anything, just thought it was interesting

Only 18:02 for me. Was able to quickly spot a few of the 9 positions. And then in box 1 with an odd total, there had to be 2 more evens on the equal distance lines. From there on the solve wasn't too difficult anymore.

22:00 An easier way of seeing why that couldn't be 6 is because you would have too many even digits in c1 and r1. The corners are even, so that takes up 2 of the 4 even digits allowed. if the middle square is 6, than you would only be allowed 1 more even digit so the sums need to be dual-odds. the only odd numbers that add up to 6 are 1-5 and 3-3, but that last one is illegal.

Another shout at the screen episode where Simon starts a piece of logic then fails to see the obvious implications of it.

This was the hardest puzzle i ever solved, took me about 100 mins. And i solved a few 4 star puzzles before. No way this is 3 stars. Amazing puzzle though.

For unreasons, I get a correct solution without entering a digit in r7c5, or entering any digit at all in r7c5.

23:30 The easier argument against the other center being 6 is that the row/column now has too many even digits. 6 requires 24, and the boxes require two more. 29:50 I bifurcated on 8 vs. 9 using cornermarks and centermarks for the two possibilities. The 5s in block 9 settled the choice.

if 6 was in either of the two green centre fields and 4, 2 was one of the sums adding to 6, plus two even numbers in the corners, that's 5 even numbers between 1 and 9.

43m20s. Not a whole lot to say about this one except that the deductions were delightful as always, and i like zipper lines. Edit: No there is something to say! After having slept on it my mind came back to finding the 89 pair on the zipper centers on R1 and C1 and how that forced the R5C5 zipper center to be 5 or 6 and the feeling of... dread is not the right word, but that "oh gosh, what consequences is THAT going to have?" is a reaction I don't often feel and I cherish it

"This is so complicated" "Only three stars for difficulty" implies "Ah, I must be doing it wrong".... And how can you use a word like "Lacuna" without trying to make a pun with "Coil"...

8:16 I agree, why didn't I see that straight away.

To be clear yes yes make another book :)

For the first time in 3-4 months I manage to solve the puzzle in less time than Simon. Just wanted to flex, I usually take 1.5/2 times of his time

Well Simon is seeing things that I didn't get to so early - so business as usual

Finished in 20:30 by following along with the video.

27:06 for me, nice and simple one today but lovely logic

This is the only sudoku with no chance of a three in the corner

Sigh. I fought with it for over an hour, then realized I was getting the line sums in B1 wrong, treating them like arrows rather than zippers. Unfortunately I don't have more time or energy to spend on this one. Oh well.

16:16 solve time. Zippers still are confusing how they're not adjacent sums, but opposite end sums.

I think Simon got trolled. My first deduction was it is impossible to have 3 in the corner 🤪

12:40 Sorry Simon, R5C1 and R1C5 can't both be nines - or both odd digits for that matter - since your argument proves that both R1C2 and R2C1 will then be odd and that's simply impossible because of the zipper line.

70:34 for me. Nice puzzle!

Also if either is 6 then you run out of even digits for the squares in either row 1 or column 1.

Around 15 minutes in, you're looking at box 9, completely oblivious to what you've just proved when considering box 1. That is, one of the straight lines is a 9, which prevents the other being 9, so one of R1C8, or R8C1 is 9, therefore the zipper in box 9 must be an 8. @ 20:42 - "If it is 6..." - Seconds earlier you explained that the only even digit you can put on the line must be in the centre. Now you're trying to put 2 and 4 on the line as well! Those centre digits are an 89 pair, making the R5C5 either 5 or 6 (despite your best efforts, it could never be 7) Your ability to forget what you've just worked out amazes me. @ 22:04 - "It's so ridiculously complicated" - Only because you make it so. As explained above it's trivially simple. Your "beautiful trick" to disambiguate the 5/6 line wasn't necessary. Sudoku would have given you that. @ 45:18 - "I've run out of colours" - Why have you got any colours? The ones you've used are totally useless. If you can't remember that the digits on the edge form pairs, you really do have a problem. Your utterly chaotic approach to sudoku baffles me. There's just no method to it at all, you just make one deduction, then look somewhere completely different. For instance, you got the 7 in R3C1, and instead of going down the column, where the next cell was a 78, and the one after that was an 89, you jumped to R1C3 and then filled in R1, eventually returning to C1. Even when you've placed a digit, let's say it was 2 at the bottom of the grid, and this resolves a 23 pair at the top, you'll point at the cell which sees the 2, but then click on the other of the pair, making it 2, before returning (sometimes) to click on the cell you originally pointed at to make it 3. You'll then completely forget to look at the second 2 you placed to see what difference it made. Instead, you look at the 3 and are surprised when it gives you nothing. If you first put the 3 in the cell which can't be 2, you can then click in the other cell which cannot now be 3, and then you can see what impact that has, which is quite likely to give you another 2 in a third column, or at least eliminate 2 from other cells in the same column. This is one of the main reasons you end up missing so much, because you jump forward, then step back, breaking the flow. It's not that you miss stuff which bothers me, it's a live solve and you're bound to miss stuff. It's that you miss stuff because of how you work which bothers me. If you were logical and disciplined when filling in the grid, you would miss half of what you do. As you're a fan of logic, I don't understand why you eschew logic when filling in the grid. Sorry for the rant, but this was a very shouty video.

now we need a constructor to make a puzzle with only 3s in the corners :)

Ask yourself where 7 goes in box 5. To help answer that question remember that 7 can’t go on the central zipper. So 7 must be in column. 4 in box 2

Classic Simon using crazy (but sound) logic to work out the middle of C1 or R1 can't be a 6. When in the sentence immediately prior to that logic he says, "If it's a 6, the other cells have to be 1-5 and 2-4." Which soaks up too many even digits. Always entertaining 😊

24:00 for me. with this solve, im up to date again.

Simon, if you press the power button on your phone while it is ringing it will send the call directly to voice mail.

R1 and C1 are a lot simpler than Simon makes out, which is easier to see with case testing and just filling numbers in to see what happens. The middle of the zipper that isn't 9 can't be 6 because we've already worked out that the zipper can only have odd digits so it must be 1-3-5-7 with an 8 in the middle. Very clever puzzle but not too difficult if you just bash some numbers in rather than trying to fold too much in your head, finished in 25 minutes 👍🏻

23:31 for me. I think I did really well on that one!

@45:36 - he makes the claim ".. can't include 2's and 4's" ... but why not? If the grey squares are 2 for example, they're compliments are 4. and r7c3 can be 4 and it's compliment r3c6 can be 2 (while it's neighbors on the upper part are 4's ??) this assuming r8c3 is a 1 and r2c6 is a 5 regardless. But I'm not seeing how he can jump to r7c3 is a 3 so quickly? it could easily be the other 2 or 4 ?

Anyone trouble with the app? I got the right solution but the Sven’s app says “Uh, Oh!”

Column 1 must have a 7 on the zipper (even if it's not box 1). So its value is 8 or 9.

last time i was this early the triangular numbers were a square

Is it even worth doing if I know I'm not going to get a song?

I think Simon got off to a bad start - I used parity blue and orange colors and it never seemed subtle or complicated - solved very quickly

21:49 for me. Super easy, but still fun.

25:23 solve for me. I feel smart