A Sudoku With No Digits. Impossible??!

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** TODAY'S PUZZLE **
[Apologies for the scheduling error today which resulted in us releasing two videos at the same time. This will teach us for having the temerity to try and take a couple of days off! Hopefully some of you will enjoy this video for an unusual reason - if you go back to June 6, you'll find Mark solved the same puzzle. Many of you have asked how Simon and Mark's styles differ - well now you can see!]
Another sudoku today by the wonderful Joseph Nehme - this one is called Some On Some Off. This puzzle is hard to grade - it depends how quickly you spot the underlying ideas (and whether or not basic sudoku eludes you!). You can play the puzzle at the link below:
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Rules:
Normal sudoku rules apply. Along a main diagonal (marked in blue) digits cannot repeat. Digits along an arrow must sum to the digit in that arrow's circle.
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[@josephnehme7224]

Thank you Simon for the lovely solve. It's nice to see this one get solved by both you and Mark :)

[@CrackingTheCryptic]

Yes, this was an oversight on our part. It was passed on by the testers and we both thought it was recommended to us. I failed to realise Mark had released his solve already - apologies to those with deja vu but hopefully it's interesting to see us attempt the same puzzle.

[@longwaytotipperary]

@@CrackingTheCryptic That's just a bonus!! thank you!

[@goldenknight578]

@@CrackingTheCryptic It's always interesting to see the differences in how you and Mark go about solving puzzles.

[@passerby184]

mark's solve of this puzzle: kzbin.info/www/bejne/hKDUgndoiderjas

[@skid68]

@@CrackingTheCryptic It is good to see both solving the same :)

[@emilywilliams3237]

I started this video with quite a bit of curiosity, because the puzzle looked kind of familiar to me. I wondered if I had solved it on the discord server or something. Then I read the description and saw that Mark had posted a video last month of this same puzzle. Fascinating! So I settled in to watch Simon, and then I went over to re-watch the Mark video of this same puzzle. First, about Simon's solve, I really enjoyed it. I love that the logic seemed very interesting (to Simon, and to me), and that the puzzle seemed to present some nifty opportunities for non-trivial deductions yet was not too awfully hard. And as usual, I love to watch Simon explain and solve things like the contents of the arrows emanating from boxes 1, 9, and 2. So instructive. Thanks for this excellent video, Simon. Now to a couple of comments about the two videos, the one by Mark last month and this one by Simon. Totally interesting that the approaches and the pathways through the solves were very similar, and so were the times to complete. Both colored 1s and 2s early on and used that info to deduce some interesting digits, and even the order in which the arrows were considered was almost the same. I think that is a tribute to the excellence of the setting, actually, as it shows that the constructor had in mind a logical path and was able to lead the solver to discover the right things at opportune times by how the puzzle was put together. The Mark video was one of the ones where I laughed out loud at Mark several times because he is very witty, and in this video by Simon I felt that Simon was more low-key than usual. But both were very interesting and engaging to watch, and the puzzle, of course, is very interesting and provides a lot of scope for good deductions. So, whether it was intentional or not, I very much enjoyed the dual solves of the same puzzle. Thanks for posting them both and drawing our attention to the duplication. So good!

[@inspiringsand123]

Rules: 01:17 Let's Get Cracking: 01:50 Simon's time: 25m28s Puzzle Solved: 27:18 And how about this video's Simarkisms?! Ah: 8x (03:20, 12:20, 15:56, 15:57, 16:00, 23:33, 26:50, 27:11) Lovely: 5x (04:47, 05:55, 18:03, 23:41, 28:13) By Sudoku: 5x (16:01, 16:23, 20:50, 24:47, 26:54) Good Grief: 2x (09:23, 10:17) Goodness: 2x (12:23, 25:47) Clever: 2x (08:06, 27:21) Hang On: 2x (08:50, 17:41) Think Harder: 2x (13:23, 14:42) In Fact: 2x (16:06, 16:16) Progress: 2x (18:10, 18:32) Sorry: 1x (14:38) Out of Nowhere: 1x (21:10) I Have no Clue: 1x (00:42) Beautiful: 1x (00:29) Come on Simon: 1x (09:09) Of All Things: 1x (11:09) Propitious: 1x (20:01) Obviously: 1x (18:46) Wow: 1x (09:02) Losing my Army: 1x (23:58) Have a Think: 1x (19:55) Pencil Mark/mark: 1x (20:54) Most popular digit and colour this video: One (56 mentions) Orange (21 mentions) Antithesis Battles: Low (7) - High (1) Even (2) - Odd (0) Column (6) - Row (2) 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!

[@thedukeminecraft]

Sincicta binding of Issac series would be fun

[@SnowTheJamMan]

Well we finally got Mark and Simon solving the same puzzle

[@Exkajer]

I recall there was a situation like that before, but ctc has way too many videos for me too look for a proof for my statement.

[@wooferzfg]

this happened before with Phistomefel's Sequence Sudoku puzzle - both of their solves were released on Patreon!

[@Exkajer]

@@wooferzfg I'm sure my case wasn't with the patreon puzzle.

[@orkleth]

The other way is for Mark to solve a classic sudoku using bifurication.

[@josephdlist]

Tatooine sunset I believe.

[@santagonewrong]

A simpler way to make progress from where you were at 5:07 without needing to do the whole colouring 1s and 2s thing - because only one of the top circles can have a 9 in it, there's 1 degree of freedom between those arrows combined. And it has to be in the 1-2 pair in row 3, which immediately removes the possibility of the degree of freedom being anywhere else.

[@chocolateboy300]

I finished in 64 minutes. There was a lot of fun logic here regarding the arrows and diagonal lines. It was a lot of fun to calculate in my head the different possibilities of 89s. I finally cracked it with r7c2 and r3c4 being the same and unable to both be 2. I enjoyed this one. Great Puzzle!

[@rpnewlin1221]

Simon, it is joy to spend the hour or so a day I spend with you working through the daily puzzle. A pure joy.

[@johnstipec4853]

Hello Simon. I am a fairly new watcher. (Maybe the last 8 Fridays)? An avid Sudoku solver at a “Hard” level. Likely capable of much more. Sorry I have yelled at you multiple times watching your solutions. (My wife actually videos my reactions to your solves). You are bright, personable and inspirational. I will attempt some of your puzzles soon as we finally moved to a spot with good internet and much less commute time. Thanks for making this game more. Cheers

[@CarlintVeld]

Are you planning to compile some of your reactions into a KZbin video on your own channel?

[@CrackingTheCryptic]

John - welcome to our little corner of the internet and thanks so much for the Super Thanks!

[@R.Daneel]

Let's just give Simon a hand for wearing that fleece hoody when the temperature there was recently close to 40C! I'm surprised he wasn't noticeably smaller at the end of the video.

[@emilywilliams3237]

Hilarious. (I am pretty sure this video was recorded in cooler weather and scheduled to be released this week when Simon was on holiday or something - at least that is how I am explaining his love of that "warm, nerdy" hoodie to myself in these summery days!)

[@SimonJD1000]

Was going to make same comment ...

[@HunterJE]

6:50 There is a way to limit that arrow more at this point - because of the 12 pairs in rows 2 and 3, the second 12 in box 2 has to be in to row one, where it can only be r1c4 and creates a 12 pair in column 4, which therefore gives r5c4 a minimum of 3 and the arrow sum a minimum of 7

[@santisis]

I started to solve it and it was like a deja vu increasing over the solve. Ten minutes into the solving I have an urge to browse the channel history to confirm if that was the same sudoku I've solved one month ago or no. And yes, it was. I'm surprised of my good logic memory remembering the same steps. Last time I was nearly 60 minutes with this puzzle.

[@CarlintVeld]

Can you include a link to the other video?

[@santisis]

@@CarlintVeld "The Martial Art of Sudoku", June 6th, kzbin.info/www/bejne/hKDUgndoiderjas

[@liborkundrat185]

48:39 I'm fairly new to this channel, and doing this one was fun.

[@alienrenders]

18:17 for me. Hadn't done sudoku for a while. I think I landed on a great puzzle to start up again.

[@stevieinselby]

12:40 - that's a bit of a convoluted way of saying that the 8-9 pair in row 1, with each arrow having a maximum of 1 degree of freedom, actually means that the two arrows _between them_ only have one degree of freedom (because they can't both be 9), and _the 1-2 pair in row 3 uses up that degree of freedom_ and so everything else has to be minimum.

[@th.nd.r]

That was lovely! Cool setting and solving, my general impression is that you are correct about the difficulty, I thought it was super clever and satisfying to see each of those little releases in the pressure of the puzzle with every difficult/surprising deduction! Also, you forgot to give the 3 in the corner its song!

[@kevinmartin7760]

Around 13:00, cleaning up the 8/9 pair in the top row is quite simple if you just total all the cells on the two arrows. Totaling up the minima, you get 3+4 in column 6, a 1/2 pair in each of rows 2 and 3, 3 from R3C2, and 1 from R4C3, for a total of 17. The sum of the two arrows cannot exceed 8+9=17 so all the values in column 6, R4C3, and R3C2 must have their minimum values. R1C6 and R2C6 are a 3/4 pair, R3C2 is a 3, and R4C3 is a 1. Which is the 8 and 9 toggle on which way the 1/2 pair turns out in row 3.

[@laszloliptak611]

Excellent puzzle. Solved it in 33:33. At the beginning one can quickly limit the digits on the arrows in boxes 1 and 2 by observing that there is a combined degree of freedom of 1 on the two arrows (as only one of them can add to 9), which is used up by the cells r3c4 and r3c7 (only one of which can be 1). So every other part of the arrows must be minimum, placing 3 in r3c2, 1 in r4c3, and a 34 pair in r12c6.

[@nirmalasokan1687]

At 5:45, you can eliminate 4 from R3C2. If the digits in box one were 1,2,4 then that would make the circle in R1C2 9, with the rest of the arrow digits being 1s. But if that were the case, that would force R2C7 to be 2 and the circle in R1C5 would also have to add up to 9 which is not possible because it would see the 9 in R1C2

[@gunterbosman3250]

Since a couple of weeks I've been finding my way to solving these kinds of puzzles. I'm totally hooked. This one took me a bit more than an hour to crack, but everytime it's just such a beautiful puzzle. I wonder when I will grow tired of them. :p

[@Ashimo]

Quickly wrapped up, well done!

[@jakobpbengtsson3608]

Was stuck a long, long time until I found the same trick for solving r1c5, and then stuck for even longer due to accidentally putting the numbers on the wrong places for r1c6, r2c6. Lovely puzzle (and as someone who isn't that great with more advanced sudoku, this hit the right spot in that regard), and a great video as always. Thanks Joseph for making it and thanks Mark & Simon for making the video!

[@heatherfyffe3618]

Took me over an hour and a half but I got it! I was falling asleep for part of that time so that probably slowed me down haha... I took a break and finished it when I was awake. I got along quite quickly at the start, then was very stuck for a long time, finding only little breakthroughs here and there that didn't seem to get me anywhere. Finally I got a major breakthrough when I finally disambiguated all the 12's, and from then on the rest of the solve was lickety split a piece of cake. NOW I'll watch the video and find out what painfully obvious trick I missed that would have saved me an hour hahaha

[@heatherfyffe3618]

And now I can say that there wasn't anything bleeding obvious that I missed, it just took me a lot longer to find the same connections. I'm content enough with that! And the colouring for the 12s was brilliant and something I should have thought of, it would have made a huge chunk of the middle of my solve go a LOT faster. Oh well, something to remember for next time! :)

[@Coyotek4]

28:05, as I continue to play catch-up with these ... Nice puzzle!

[@mipsuperk]

Coloring numbers after they've been disambiguated seems like pencil marking after you've already written in the number.

[@MathiasE80]

Agreed, would rather see all colors removed after they served their purpose.

[@emilywilliams3237]

@@MathiasE80 I understand, and this has been discussed in comments prior to now - but for me, as a solver, I actually find it helpful if the colors are kept around and completed as the puzzle gets completed because it helps me remember things - logical steps and relationships - that the digits alone might not trigger. I may not be in the majority on that score, of course. Regardless, if Simon (or Mark) likes to use colors and keep them around and it helps them in their solves, then I am entirely in favor of whatever they prefer in these videos.

[@piarittersporn]

Absolutely beautiful puzzle.

[@Worldestroy121]

This was a great puzzle loved the solve through and through and i feel like i actually learned something about how to be a better solver too. This was the first puzzle from CTC that i was able to successfully solve. Thanks for the great puzzle Joseph Nehme

[@rungus24]

At first I thought it was a puzzle inspired by the previous one, which I thought was pretty cool. What's even more interesting is how much further I got into this one before getting completely stuck, as I remembered some of the weird logic from when Mark solved it.

[@Vivo-cp2rb]

46:06 for me. I really struggled with the concept of "1 degree of freedom" and i messed up which way around my 1's and 2's where going but fixed it afterwards.

[@nkorppi]

In my solve, I missed Simon’s simple contradiction of the 89-circle being an 8 leading to both 12-colours representing digit 1. Instead, I ended up conditioning on whether the grid’s middle-cell was a 9 or not, which led to two alternative ways of quickly solving for all 9s and all 4s… one alternative could then be excluded, since it placed digits 4 and 9 in a mutual cell. This solution took much longer to spot… and required using many more colours. But I enjoyed it. ;)

[@BryanLu0]

I know it's been 7 months, but the easier break in is to consider the two 89 arrows together and what the minimum values are

[@zoranocokoljic8927]

38:00 There was unnoticed 3 in bottom left corner.

[@ianoz1]

Thank you Mr Nehme... finally, a solve I did with no hintful helps from Simon.

[@zeynepemelturgay5515]

First solved hard sudoku from this channel🥳 I totally didn't see the option of 4 for r3c2. Glad it it turned out be 3🤦‍♀

[@handlesareanunfortunatefeature]

I like the ones with simple rules much much more than the super complicated ones with tons and tons of rules and restrictors to keep track of.

[@brianagnes]

an easy way to get r4c3 is if r3c7 is 2 then arrow is 9 that makes r1c2 8 and r4c3 =1, if r3c7 is 1 then r3c4 is 2 forcing r4c3 again to = 1. that fixes 1 & 2 in box 1

[@Gonzalo_Garcia_]

That’s very interesting to see you both solve the same puzzle. No time for me today, as I had already done this one before.

[@Coldheart322]

12:50 mark, I did the logic slightly differently. Mainly by showing the 345 cells couldn't actually be a 5, as it would push both arrows to be 9s. But I was impressed I did spot the logic at all. That is the kind of thing that normally evades me and I give up.

[@Coldheart322]

And after watching through to 16:49, I actually spotted a bit more logic and completed the puzzle!?! I really liked this one. Not easy, but just using sudoku experience of asking the right questions I actually managed to win :-D been a while since I've done that.

[@juliadefranco1130]

29:36 (with my husband, it was a joint effort.)

[@Rach881101]

25:04 for me. Lovely puzzle!

[@srwapo]

30:35 with a long break in the middle for my nieces' bday party. Took me forever to see that r1c5 couldn't be an 8, wonder if I missed some logic.

[@Kurgosh1]

51 minutes, which is acceptable for me after being away from these puzzles for a while.

[@Dryltd]

You figured out the 2 and 3 in the different order than me. but I took longer to realize the 1 and 2 relations all over the board. Until I remembered to try the colors.

[@dmcdouga07]

refreshing to see a sub-half-hour video today :) the hour videos are good too, but not every day

[@L83467]

01:36:17 for me, which is a long time, but im actually pretty happy with it because this was the first time that i successfully used colouring all on my own, though i did have to use trial and error one time cause i was very stuck

[@mhelvens]

These clickbait titles though. 😂 You guys solve a sudoku with no digits once a week.

[@DarrenNakamura]

Took me 104:05. I think the opening went pretty smoothly, and the closing did too, but the middle part had me stuck for a while.

[@reubenmckay]

Double serving of Simon tonight? Yes, please.

[@HunterJE]

Since the video was posted (and indeed is relatively short), I'm going to guess the title of this video obeys Betteridge's law...

[@HunterJE]

(Twice over, apparently)

[@mikepictor]

This seems very familiar, hasn't this already been done on the channel?

[@michaels4340]

3:11 Just had an interesting thought: r2c1 can't be 4. (This is because, if there is a 4 in box 1, then r2c1 is a 1, by sudoku. Specifically, r4c3 and r3c4 would both be 1s.)

[@kazetag.3177]

91 mins for me, feels good to solve this things :)

[@jeffreyvannieuwkoop6809]

Good evening to you all.

[@julieannmyers8714]

Once the 8-9 pairs became both green, and then purple on the negative diagonal became 8s, the coloring became meaningless. Great puzzle!

[@ypkoval]

I am sure I've seen a puzzle very similar to this on the channel, solved by Mark. Or this is my deja Vu?

[@333name]

Mark has solved it before. Simon was 1:12 faster

[@maelwys5]

the karate kid link image from last month kzbin.info/www/bejne/hKDUgndoiderjas&ab_channel=CrackingTheCryptic

[@iceberg54321]

@@333name Simon wins!!!

[@reg699]

@@333name can you share the link please

[@333name]

@@reg699 Look for the video called "The Martial Art of Sudoku", early June. Probably can't share the link in comments

[@AdmiralMinell]

Didn't Mark do this puzzle within the last month or so?

[@333name]

June 6th, to be exact. Mark's solve time was 26m40s, so Simon wins!

[@grusbekse]

The amount of time I spent before I saw that the 12 in r7c2 was influenced by the 12 in r3c7 because of the arrows is just embarrassing

[@Nightknight1992]

glad to see simon at least also slightly struggle, still a lot less than me, but at least it didnt seem easy either :D

[@GrahamFirst]

Thanks!

[@GrahamFirst]

So delightful following along (or trying to) as you work through these puzzles. 😁

[@CrackingTheCryptic]

Graham, Thank you so much for the donation, we really appreciate it. Simon & Mark

[@foreverallama]

12:48 I totally missed the possibility of a 5 on the arrow for box 2 and automatically went with a 3-4 pair so I guess my solution was a fluke

[@ceilingfan12345]

So I solved this in a different and, admittedly, kind of cheaty way. I didn't think to color the 1's and 2's and so missed the correlation you noticed at 17:45 . Instead I got to about the same point, but also looked at the last circle/arrow to determine the circle had to be an 8/9 and the arrow digits had to be 4/5's. At that point I realized that the circle in box 5 had to be a 7 because otherwise the puzzle would be left with no way to disambiguate between 6s and 7s. Filling in that meant the end of that arrow had to be a 1 and that filled in all my 1/2s and was able to solve from there pretty easily

[@RupertBruce]

Since @6:06, I have been waiting for you to follow the 9s!

[@RupertBruce]

Finally @21:11...'out of nowhere!'

[@RupertBruce]

Omfg @22:12 TLBR Diagonal!... Now that I've seen you do it, I suspect I may be able to do it in a few hours... I love all the rulesets you use!

[@Tahgtahv]

This is just a bonus solve I guess? We already had a Saturday puzzle posted from Simon

[@JalebJay]

17:09 similar style to the other video in the double feature

[@dmitrymalkov6732]

Look! There's 3 in the corner!

[@Kirbyfan87827]

Finished in 25:33 with help from the video.

[@wanderlustwarrior]

I feel like this puzzle has been posted before... Took me 40:44 even though around the time I started slowing down, I felt more and more familiar with it. EDIT: Ah, a comment pointed out this was indeed posted before under the name "The Martial Art of Sudoku", and solved by Mark in slightly longer time. It seems I broke the puzzle last time, so this is my first actual good solve of the puzzle. Last time I solved it after restarting near the end, so my 28:33 solve time was definitely inaccurate and probably closer to 40-50 minutes.

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

18:48 for me. i played this before.

[@robertcousins2274]

48:18. Got stuck for long time

[@Poet13xRatedRKO]

23:04 for me, I felt like I knew this puzzle before but maybe I am wrong.

[@keithmower921]

A very enjoyable solve whether you watch Mark's or Simon's video. Just a thought, you often get people clamouring to see solves of the same puzzle by each of you, and you have stated that the other of you is often the final test solver (although not in this case). You sometimes also state that you hope that you can solve a puzzle because it should be exhibited for the beautiful and/or unique logic. Would there be a market for a 'bolt on' Patreon category, whereby people can pay to see the final test solve? That way, if the final solve fails for any reason, the puzzle can still be exhibited. I realize that this will be a lot more work, and thus not practical, but if you can fit at least some replicate solves into your busy schedule, there could be a market to recompense your labour. I think that all the reviews of the duplicate solve have been favourable, but then I would expect nothing less from your audience.

[@dpo6311]

Sun up sun down In the way of the samurai

[@bruceh8043]

I finish in 27:34.

[@bristolrovers27]

Nice and cleverly constructed puzzle Simon forced to do sudoku twice in one day, how cruel !!

[@adimeirman2082]

00:39:40

[@chesscube8671]

the merch isn’t in my size 😭

[@spelldaddy5386]

It's definitely telling just between the video titles that mark and Simon used for this video. Simon: A sudoku with no given digits. impossible??! Mark: The martial art of sudoku I also noticed that mark featured this puzzle the day before one of mine. I wonder if Simon is foreshadowing the release of a puzzle of mine tomorrow? I guess it would help if I had published one recently...

[@74marcroy]

"Impossible" Oh good a really had one Checks run time "28:31" Oh not that Impossible then :p

[@RichSmith77]

Apparently, I solved this in 30 minutes the last time it was featured. A little disconcerting that it took me 40 minutes this time. I must more be tired. That's all. 😂

[@otakumonphd742]

No song for 3 in the corner :(

[@oldguydoesstuff120]

Probably already posted, but Mark's solve is here: kzbin.info/www/bejne/hKDUgndoiderjas

[@TurquoizeGoldscraper]

23:49 for me - I'm sure I missed some logic and bifurcated to figure out the arrow with the head in R4C5. I looked at Simon's answer, and I needed to look at the 89 pair in row 1 and figure out that 9-8 wouldn't work.

[@LednacekZ]

24:52 today. I got stuck on the 8 in r1c5 for about 10 minutes. Otherwise there is nothing remotely difficult.

[@jaundice27]

bump

[@heathercrivilare1722]

I’m really interested in how puzzle setting is done. Not even the super complex varieties, just in general. I think it could be cool if Simon or Mark recorded setting a puzzle for one video, and then recorded the other person solving it for a solve-along and uploaded both videos!

[@SirBradiator]

If you go through the channel archives there are plenty of videos from some great setters explaining how they set puzzles

[@HTH565]

Basically, in general you start with some intersting pattern, and you try to solve the puzzle. If the puzzle has multiple solutions or is too hard you add clues to disambiguate, if it is too easy you remove clues, then try to solve it again. Repeat until you are happy with the result.

[@wooferzfg]

search for the videos titled "How I Set Sudoku" on the CTC channel. the ones by clover, zetamath, and Tallcat are some of my favorites

[@emilywilliams3237]

@@wooferzfg Did you do one? Why do I have a memory that you did?

[@wooferzfg]

@@emilywilliams3237 I didn't, but I made a video explaining how to solve the puzzle "Adventure" for CTC a few weeks ago

[@qqleq]

It's frustrating to see what Simon is stuck on for 15 minutes within a minute and _still_ needing 10 minutes more than he.

[@davidh.4944]

Affin gridlock puzzles. They always start out great, then tie you up into a knot of frustration. Three hours of staring at the board, and running straight out bifurcation numbers over and over, and still getting nothing... I'm not one to usually give up, but... I give up. Terrible.

[@xxs_w_o_r_dxx8994]

Do you respond ?

[@MattCurney]

:/ is Simon on vacation? These all feel prerecorded… I miss birthdays and topical information. These feel less personal.

[@nescirian]

Imagine still pretending sudokus with no digits are surprising in 2022

[@lucas411_]

It annoys me how he continues to colour the cells when he’s already worked out what each colour is

[@S_Black]

Come on. You've done countless ones with no digits