The Most Incredible Sudoku Rules EVER

[@KNT_puzzle]

Congratulations on the solve! I admit, I did not expect to see this on the channel. While I tend to typically set larger non-sudokus which may *seem* harder just by the vastness of the grid sizes, I definitely think this is one of the most challenging puzzles I have created, so once again, well done on finding a logical path through it. The core of the idea when setting, admittedly, was to create a scenario that just felt broken, but was not. That idea in specifics was having a region that is not of index 1 or 9 (i.e. a region with both an entrance and an exit along the path) have to get its region number from a bizarre and unexpected location, which happened to be yellow getting its region number at R1C8. The quad-arrow at R4C3 was my way to trivially (ok, maybe not so trivially) create a huge wall near the edges, forcing regions to pass through narrow channels (which turned out to be R1, R2, C1). Settling on where to put this wall took some consideration, and afterwards the arrows in R2 took some fiddling to give me the result I wanted. The path of least resistance through the first half I quite like, and would be happy to formally write up elsewhere for those curious, though I do know of several different ways to get through the start, from both my wonderful testers, and a handful of great solvers. I think, taxonomically, difficult puzzles fall primarily into two classes: ones where you're supposed to figure out The Thing and then afterwards the puzzle drastically decreases in difficulty, and ones that feel a bit more like a video game: an onslaught of miniature challenges and obstacles that must be overcome to reach a goal. I tend to value the latter quite a lot, since that's what i find fun, and "fun" is the characteristic I value most when creating a puzzle. I try to figure out rulesets or combinations of rulesets that allow me to maximize clue usability or reusability, without ever forcing the solver to feel like they're missing a big picture idea. While I think you're very limited in that regard on a 9x9 grid, this ruleset does capture what I like in a puzzle: lots of little things interacting in unexpected ways, and all that's needed to solve is logic and logic alone. Thank you for this gift, Simon :)

[@davidrattner9]

Masterpiece from you!! Thank you so much for a little bit into your brain in how you constructed this and what your thought process was. Absolutely loss for words for what this phenomenal piece of art is!!

[@StephaneBura]

Simply amazing. Bravo! :)

[@crazypantaloons]

I feel R2C2 really was the key unlocking this puzzle. It either had to be the exit of a region, or you have to go around. Honorable mention to the ridiculously empty right side of the grid! I almost didn't find the 3 for region 2, and thought I broke the puzzle at the very end!

[@KNT_puzzle]

@@crazypantaloons I tend to agree about R2C2. I'll break down the general big ideas for the top left, from the start. 1) The quad arrow must contain the four diagonally adjacent cells, and travel through them in an efficient square - any detour would make the region 10 cells large, at minimum. The path also cannot travel through the quad arrow cell, because it would then break the thermo. 2) R4C4 is always a 2, and R4C5 would always be 2 if it belonged to the quad-arrow region. Therefore R4C5 and R4C1 are the same region, and that region travels "under", because of the clue at R2C4. R2C4 also is in same region as R3C3, generally fixing most of the path and loop of the quad arrow region. 3) R2C2, R2C4, and R2C5 are all part of the same region, R2C2 must be a 1. R2C4 cannot be a 4, because that would put a "1" in the middle of a thermo. This 3 looks down and fixes the entire thermo of the quad-arrow region, putting 9 in R3C2. 4) If the quad arrow region was _not_ region 9, then R3C1 belongs to the quad arrow region, and is not on the path. The path must then continue (as it is not region 9) into the R2 clues region, but then either the path in the next region goes "backwards" (it ascends into the 1 in R2C2), or goes around the 1, and traps itself in the top left corner. 5) This means the quad arrow region is region 9, and R3C1 is a new region. Once again, it's a new region because if it were in the same region as the R2 clues, either the path goes through the 1, or it goes over it, making the region too big. This new region at R3C1 fully completes its shape immediately, the R2 clues region is then region 8, and must get its 8 at R1C8, the top leftmost region is region 7... etc. I hope this is interesting!

[@davidrattner9]

@knt2562 very interesting and logical to understand!!

[@tezcharold]

I like how Simon starts the puzzle with a joke, "Do have a go." Yeah, nah, I don't think I will. Haha

[@Autoskip]

I had a go (and solved it) - it was quite fun, but I don't blame you for skipping it in the least. ...admittedly, I only even click on these videos if I'm planning on having a go - which unfortunately means I'm not watching as many of these as I'd like.

[@CaptainSpock1701]

When he said "Have a go" he meant "Have a go at watching the video!" At least that's what I do!

[@allgreatfictions]

Simon at the beginning: "I can't conclude anything from this" Me: "I'm as smart as Simon"

[@inspiringsand123]

Rules: 02:49 Let's Get Cracking: 10:25 Simon's time: 2h25m33s Puzzle Solved: 2:35:58 What about this video's Top Tier Simarkisms?! Bobbins: 2x (20:12, 2:07:33) Goodliffing: 1x (55:43) And how about this video's Simarkisms?! Ah: 23x (11:16, 15:33, 18:18, 38:15, 40:15, 52:48, 55:07, 56:21, 57:16, 1:02:54, 1:18:25, 1:19:25, 1:24:29, 1:29:04, 1:47:03, 1:47:05, 1:55:39, 1:58:09, 2:01:17, 2:03:46, 2:06:44, 2:29:23, 2:29:30) Hang On: 22x (06:31, 08:14, 38:11, 1:07:51, 1:07:53, 1:07:53, 1:30:22, 1:30:22, 1:30:22, 1:34:15, 1:36:27, 1:36:44, 1:37:01, 1:37:01, 1:37:12, 2:03:25, 2:03:27, 2:11:53, 2:11:53, 2:11:53, 2:17:05, 2:28:52) Sorry: 14x (00:35, 06:31, 13:34, 37:17, 1:10:14, 1:10:16, 1:13:49, 1:20:19, 1:31:24, 1:31:24, 1:35:15, 1:43:07, 2:24:41, 2:25:28) In Fact: 14x (14:59, 31:41, 39:10, 39:24, 55:07, 1:09:16, 1:32:10, 1:37:46, 2:07:54, 2:11:36, 2:12:51, 2:15:13, 2:17:55) Wow: 12x (16:11, 28:18, 45:59, 1:18:40, 1:24:33, 1:28:47, 1:43:39, 1:43:39, 2:06:50, 2:06:50, 2:11:19, 2:31:04) By Sudoku: 11x (1:03:18, 1:46:10, 1:46:18, 1:47:58, 1:48:45, 1:49:21, 1:50:06, 2:16:40, 2:31:41, 2:33:29, 2:33:46) Obviously: 10x (03:08, 11:09, 16:46, 24:11, 29:29, 1:23:27, 1:25:43, 1:52:19, 2:25:59, 2:35:37) Nonsense: 9x (15:33, 15:33, 26:32, 50:16, 1:10:16, 1:19:50, 1:19:56, 1:28:15, 1:28:15) Lovely: 5x (03:25, 26:03, 26:05, 1:11:20, 2:09:53) Beautiful: 5x (27:47, 56:45, 1:52:04, 1:52:04, 2:11:19) Good Grief: 4x (1:03:02, 1:11:38, 1:18:28, 2:02:34) Clever: 4x (02:29, 15:36, 21:08, 2:15:59) Surely: 4x (42:28, 50:41, 55:45, 2:32:21) What on Earth: 3x (26:48, 29:12, 2:05:37) The Answer is: 3x (1:47:10, 2:10:09, 2:11:32) Brilliant: 3x (03:10, 03:27, 2:36:13) Break the Puzzle: 3x (1:42:02, 2:03:29, 2:23:19) Nature: 3x (1:52:23, 2:10:05, 2:10:05) Goodness: 2x (2:09:56, 2:35:06) Fascinating: 2x (1:23:01, 2:22:26) Extraordinary: 2x (01:09, 2:35:52) Come on Simon: 2x (1:03:18, 2:33:05) I've Got It!: 2x (03:06, 1:31:24) Baffling: 2x (02:39, 02:39) What Does This Mean?: 2x (24:55, 2:00:33) Symmetry: 2x (23:13, 32:00) Useless: 1x (1:45:17) What a Puzzle: 1x (2:35:46) Out of Nowhere: 1x (2:28:29) Bingo: 1x (2:13:21) I Have no Clue: 1x (02:43) Horrible Feeling: 1x (11:49) Elegant: 1x (1:58:53) Deadly Pattern: 1x (2:34:44) Hypothecate: 1x (1:52:21) Discombobulating: 1x (37:37) Shouting: 1x (00:23) Pregnant pause: 1x (37:17) Progress: 1x (48:29) That's Huge: 1x (57:22) On the Cusp: 1x (1:57:49) Have a Think: 1x (2:25:48) Cake!: 1x (03:10) Unique: 1x (01:18) Most popular number(>9), digit and colour this video: Ten (12 mentions) One (168 mentions) Green (254 mentions) Antithesis Battles: Low (3) - High (2) Even (25) - Odd (0) Higher (14) - Lower (1) Highest (4) - Lowest (0) White (2) - Black (0) Row (23) - Column (22) 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!

[@MisterAwesan]

Rules are actually at 4:51

[@marcelopicheth6111]

I think he didn't mention "even" as an antithesis to odd, perhaps in the meaning of emphasis something, like "this can be a 2 or a 3, or even a 4".

[@marcelopicheth6111]

But thank you for this compilation.

[@SekGuy]

I wonder how many times Simon says loop... When it is a path.

[@ry-guy_]

I love that he only says "Progress" one time.

[@Wecoc1]

This one is longer than the first Harry Potter film (and has more magic 😆)

[@krollic]

wow the first hp is almost 2 and half hours. that's mad

[@danielrhymer1762]

The only HP film this video is shorter than is Chamber of Secrets

[@AcidDotCom]

Every single video on this channel is better than HP :P

[@Vanhalte]

If I had more disposable income, I would rent a screen at my theater to watch this with a few of my friends

[@gauravmitra150]

Especially because Harry didn't perform active magic in the first book.

[@mikedonnan6541]

There are very few things I would instantly agree to committing 2.5 hours of my time to…BUT…a Simon CTC video is absolutely at/near the top of the list…!!! 😆

[@TheClawNinja]

Yep, that's exactly what I was thinking. Settling in now, because I'm just not even attempting this one lol

[@amysteele2488]

Ditto!

[@davidrattner9]

@amysteele2488 Ditto is a great word to use..especially on this channel. 😀

[@timch5227]

The longer the video the more interesting it is

[@BertBergaf]

Yep, I don't watch movies because I get bored. Trying to think along is much more entertaining

[@dumediat_]

I can’t tell you how happy it made me to see “Pathfinder” featured today! A true masterpiece set by a rare genius, worth every moment of the 150+ minute solve. Congratulations KNT, very well deserved!

[@paulcrumley9756]

The circles made it so hard to read the center pencil markings, and early when you thought you might not need them any more, I think you were correct. Otherwise, unbelievable, and I'll bet there are very few who will solve this puzzle on their own.

[@buzzly108]

Yes... I kept wishing that once he drew in the path, he'd remove the circles, because they were redundant.

[@MohamedMahmoud-ey9tj]

If he changes circle to grey they should be visible

[@blcmd]

This was an amazing puzzle (and one of the very few that I’ve completed in less time than Simon). I can’t even imagine how it was constructed. In terms of the solve, it would have really helped to cleanup the circles, as they provided no useful information once the path was drawn in the cell and instead, made it much harder to scan the grid. Simon teased us by almost doing that, then got distracted and instead just kept adding more and more circles.

[@HikingEngineer]

yeah agreed, the circles really made it tough to watch/see

[@angelmendez-rivera351]

Simon doesn't have the greatest clean-up technique. In fact, he rarely ever cleans up his grids, which I think makes his solving methods very confusing. Instead of getting rid of tools that have served their purpose and no longer need to be used as such (like a particular coloring), it would be best to get rid of them, and maybe repurpose them, rather than just continuing to make the puzzle progressively more and more cluttered. Not only does it make the viewer experience far more enjoyable, but it would also actually save him some frustration when solving the puzzles.

[@Mephistahpheles]

Indeed. One thing in particular is that purple could not be region 1 OR region 2.....but the 2 is obscured by the circle. Second thing is the circle vs thermo confusion. Even at 1:45.....he mentions "too much notation", but doesn't do anything about it. Heh

[@niverio8400]

Justice has been restored! This puzzle is awesome, along with pretty much the entirety of KNT's catalogue, and definitely deserves a feature. I am glad you decided to feature this magnificent beast even after the overwhelming support for Embark (which is an amazing puzzle in its own right.)

[@jmrgomes]

What a milestone! We’ve reached the point at which Simon’s video is so long that by the time you finish watching it you can go straight to watching Mark’s which is out by then 😂😂

[@acantilado]

Nice work Simon! What determination-I think you were your own worst enemy keeping those circles in the grid which obfuscated the numbers (making it harder to do sudoku-deductions), but in classic form you found more incredible deductions as work-arounds. I hope you slept much better after this one 😅

[@DarkBeoulve1]

At the end Simon was so focused on finishing that the 3 in the corner didnt get a song

[@mremumerm]

Wow. I also totally missed it so engrossed i was watching the solve

[@ry-guy_]

My favorite part was how you were so mentally fatigued by the end that you were wondering how far the path went into region 1 before seeing the clue and having that "just use the clues Simon" moment. That was an epic puzzle!

[@RichSmith77]

I tried this when it got offered as one of the two puzzles to vote on in a previous video. I'm so glad the puzzle link was posted in advance of today's video, as it took me two days to solve it. But I did solve it! That meant I could watch today's video straightaway. 🙂 Simon, your solve was brilliant, but why didn't you remove the circles after you had drawn the path through those cells!? You even talked about removing them at one point, as you recognised they had served their purpose and were a distraction. But you left them, and then added even more, despite drawing the path immediately through them. They just hindered your scanning so much - you missed that you had 5-6-7 in row 5 already, when looking to see if the path through the green region could visit row 5 (it couldn't). I also don't understand why you only have seven colours on your palette that you are prepared to use? It's been months since Sven gave us the ability to customise the colours. Find nine colours that you are actually prepared to use!

[@Ziboo30]

I managed to solve this puzzle last week by my-self and I was very proud. I learned so much from this channel and you Simon. Thank you very much for sharing and explaining so well your train of though, it helps immensely.

[@shellmichael9665]

The circles were just a way of notating it was a path cell. Once he got the path going through that cell, it definitely would’ve helped to remove the circles. And when he mentioned it and said they were cluttering up the screen, I was hopeful he’d remove them. But, alas, no such luck. What a puzzle though, and what a solve!

[@samlight1387]

Getting the 4 in grey was doable for ages because of sudoku, I’d clear the circles next time Simon it will make it a lot easier to see! Other than that, simply incredible solve. Longest video ever and I enjoyed every minute of it, you’re a wizard!

[@th.nd.r]

That is absolutely incredible. Well set and well solved. Goodness gracious, 2.5 hours!! That takes stamina, proud of you Simon!! My only frustrations: you could’ve taken the circles you didn’t need out of the cells, and the 3 in the corner didn’t get its song. But truly neither of those things is all that important, this is an absolute feat!

[@corsiKa]

So amazed Simon didn't get tired doing this. It speaks to exactly how engaging this puzzle is.

[@captchagod64]

I suspect this video would be significantly shorter if it werent for simons dedication to rigorously proving that you cant draw a region around a nine cell region in less than nine cells. Edit: and also that you can only have 2 "terminal" line cells in each box

[@Urutsini]

And definitively, unquestionably proving X. Then positing if "Not X" then Y . . . But he is still a bloody legend for tackling and solving it, especially when hungover

[@dolf370]

I also think it would have been significantly shorter hadn't Simon been hung over.

[@wraithbow]

I think he also hurt himself keeping circles to define where the path needs to go... after drawing the path through them. Made it harder to read his pencil marks and took longer to see stuff.

[@dolf370]

@@wraithbow Yeah, and weirdly he also when finished circles all the path cells that weren't circled before instead of removing all the circles instead.

[@MAHDON00]

I think Simon wanted to increase the high difficulty of this solve by keeping circles on paths making "simple wins" less visible really nice solution (I would never be able to do myself) although overlooking sudoku (done often on purpose as we know :P) made me almost cry

[@BenRHarsh]

He ignored R7C1 for so long in doing any sudoku but then immediately after he filled in the cells in question he uses it to eliminate a single 5 pencil mark from R7C6... I sometimes think he focuses solely on the pencil marks to do deductions purely to see if it's possible before even considering using known digits.

[@dannstarrjp]

These circles drove me nuts, I understand using them in the very beginning, but afterwards all the did was make it much harder to see the pencilmarks… and the person who struggled the most was not a viewer but Simon, we all could see the sudoku he missed and I’m sure the circles were the main reason. Let alone the fact they look ugly to look at. I really can’t believe especially someone like Simon who is so pedantic and easily confused by visual aspects (like colors that are not distinct enough) left them there through the entire puzzle. I love long videos and hard puzzles but this wasn’t a 2.5h puzzle, it was 1.5h puzzle at most with the other hour being the reason of Simon making the grid impossible to read.

[@davidblake6889]

@@dannstarrjp Yes. I found the black circles very distracting. So did Simon, on more than one occasion.

[@marcelopicheth6111]

@@BenRHarsh When the rules are so convoluting, his mind is "set" on these new rules, he might forget sudoku entirely.

[@yaboyJJJJJ]

he got so close to removing those utterly useless circles too, considered it for a minute and then he got distracted. THE CIRCLES DO NOTHING SIMON TAKE THEM AWAYYYY PLEASE

[@frederf3227]

This is not a puzzle to be tossed aside lightly, but thrown with great force! Simon is a hero for not upon reading the rules and looking at the initial grid simply closing the page and retiring to a Tibetan monastery. I would not think less of him had he.

[@buzzly108]

Me, interacting with this video: Simon: "Can this be not green?" Me: "No." "Let me think about it" "No, Simon, then you'd have 4 endpoints!" "So if I put a pink here and here" "NOOO!" "Then what do we have...?" "4 ENDPOINTS!!!" "...." "PUT THE GREEN IN TWO OF THE CELLS!!!!!!!" "Oh, no... that won't work....

[@Rissper.]

You know to expect nothing but absolute brilliance when you see a video of such length on CtC!

[@pclifton]

To hear S's commentary as if he was talking to someone in the room at the time, rather than recording in isolation shows just how good S is at both the solves but also the instructional manner. An epic puzzle, thank you KNT, an epic solve and fantastic narrative, Thank you S.

[@bryanroland9402]

Wow! Watched this over three days because it was so long - but well worth it. I think those big circles were affecting your scanning because around the 2:10 mark when you were trying to see where the grey 4 region continued, it was easy to see that its region number had to be in row 3 because its top leftmost cell in row 6 contained a 1 and rows 4 and 5 already contained a 4 in other colours. Amazing puzzle and solve.

[@stevieinselby]

At 2:25:45, an interesting point is that you could close the loop in green with the shortest path _and it would be correct_ even if it was also possible to draw a loop wiggling into the cells above. So without a rule that says "Draw the longest possible loop...", we know by uniqueness that it can't go into the cells above, and so there must be a way - either by thermo logic or by making one of those cells into a different region - that stops it from being a possibility...

[@elainedenning]

Brilliant solve. I did have a giggle when you took 5 minutes working out if the green region was 8 or 9, when the answer was sitting there with sodoku! And at that point you could have filled in all the numbers in green, but took another 10 minutes to do so. Even so, I loved every minute of it. Thank you!

[@potatoistic]

My jaw dropped at getting region 8 from R1C8.. gave up there after thinking I've broken the puzzle multiple times.. that was devious.. mad genius of you Simon to catch that. Amazing watch! (PS: Consider removing the circles once lines are drawn.. things might look more clear)

[@CONM0S]

This is simply fantastic. I'm an hour and eleven minutes in and Simon has placed only 5 digits in the grid yet the video still has my full attention. I think I might let the master take this one. Aint no way I'm finishing it.

[@davidrattner9]

Absolutely legendary and amazing that you put this long of a solve on here for us Simon!!

[@emilywilliams3237]

I agree. So much to admire in this, not the least of which is pure resilience and stamina!

[@bruresende]

I was setting things up to watch a movie or something like that to enjoy my Sunday evening, but I wasn't sure about what to watch... So Simon comes to my rescue with a Hollywoodian-length video, and saves me from picking a movie!!!

[@amysteele2488]

Simon's voice weaved it's magic again, and I was asleep within minutes. Woke up briefly to the sound of the outro music, now watching in the wee small hours of the morning

[@davidrattner9]

Indeed..Simon's voice is so addicting , relaxing and soothing. His love and joy for his solves is contagious. Know you love this community and channel as much as me..especially if watching at 240 in the morning. 🙂

[@kookeekwisp]

I feel extremely honored trying this puzzle myself before watching Simon try to solve it, especially after hearing him say this is one of the most complicated rulesets ever featured on the channel. Godspeed Simon! Side note: One thing that made it immensely easier to solve (spoilers) The fact you start from nine and work backwards from finish to start makes it very hard to completely grasp what it means to "come from" a place you're going, so it helps a lot to think of the line DESCENDING from 9 to 1 in region, and strictly decreasing in each region. Since digits in each region cant repeat and region order is fixed, you CAN exactly invert the nature of the rule without breaking any of the logic.

[@AIDcyt]

you could've detected that R6C3 is a grey 4 because it's the only place available for region 4's number (rows 4 & 5 have a 4, and the 4 must be on a higher row than the 1)

[@BleachWizz]

1:19:13 - I like this part because he goes so deep when most things would've been proven by "but purple would have to be box 1"

[@chiphead777]

2 hrs 37 minutes?! I may take a day off work to watch this! Love the channel, please don't stop.

[@kathyjohnson2043]

Good thing that, for most of us, today is a Sunday.

[@dolf370]

Ok, I admit immediately that I would never have been able to solve this one, even if I'd been staring at it for a week without break, I very much doubt I would have manage to even get the first digit. But that said, Simon must have had a horrible hangover, I spotted _many_ _obvious_ deductions _long_ before Simon. I hope he's recovered by now.

[@mvivian100]

I was so frustrated with the redudent circles. So many times digits were just unseen, I'm sure because of the circle.

[@robert-skibelo]

Agreed. Unfortunately Simon does not have a feel for good visual communication. This was a disaster in that sense.

[@peaches760a]

at 2:12:00 ish... easier question: where does Grey get its region number: 4? It can't get it from rows 4 or 5 and if it's any lower row, that cell can't be the region number because of the 1. It's then obvious it must get its 4 from row 3 and R3c6 becomes the only logical place.

[@kevinmartin7760]

At 1:19:55 I though the line marked a definite region boundary (which is how you usually use lines), and an x on an edge forbade the path, in which case the line is valid.

[@profregan6937]

Any solicitor should know about a deed box ! A metal container to preserve important documents often with name of the client painted on the exterior. Another brilliant explanation of everything. The best programme on KZbin ! ❤

[@matt2641]

It is insane to me that you can even start a puzzle like this. I think you are more brilliant than you give yourself credit for. I would have looked at this and noped out before even trying. Hats off to you, sir.

[@crystalgehrt8861]

This was a remarkably enjoyable puzzle. The best you can ask from a sudoku is for it to make time disappear because you're too engrossed to notice its passing, and this one definitely delivered. After the past three puzzle hunts, it didn't feel nearly as hard as it would have a couple of months ago. CTC certainly has a way of developing your sudoku skills! The videos are never too long, in my opinion. Even both solving and watching this is not a waste of time.

[@Seth0326]

Lol, around 47:34, he says he suspects green is 3x3, even though mere seconds earlier, he said one of those cells needed to be yellow. Classic Simon!

[@dannstarrjp]

Yea forgetting some logic you did 10-15min ago can happen to anybody but forgetting something you literally said 5 seconds earlier is quite impressive 😂

[@darkflame4488]

Love love long puzzles. This gonna be so good

[@tjabow195]

First of all, great solve and puzzle! This was really enjoyable. I could not stop watching even though I had a few really important things on my agenda today 🤭 For future reference, I would like to suggest that you remove the circles in the boxes where you have determined the path. Initially, the circle works great to mark the boxes where the path must pass through. Later on, the line does a sufficient job in showing the path, and the circle rather hurt than help here. So when you have a line drawn, please remove the circle. Or at least that is my suggestion. It would make it easier on the eyes and brain 😊 Other than that, great job Simon 👏

[@karsaanita]

This turned out to be way more approachable than I expected based on the length of this video. There's something nice about these puzzles where it's possible to slowly work your way through it instead of having to find a clever break-in.

[@markrusting7944]

CRAZY Solve! It took me a couple of days to fit in watching the video. At first, I could barely follow Simon’s logic, but his on-the-fly explanations really helped. So much so that at 2:05:15, I was able to color most of the rest of the regions, with “simple” logic. 1. With a “1” in r9c1 along with the arrow clue, that was evident that it was Region 1. If it were any other Region#, there would be at least two cells within the path and the clue would be violated. 2. Because Region1 & Region 2 start at oppostie corners of the grid and have to connect to each other, there is only 1 degree of “Region Freedom;” either r9c9 is blue or red. All other eight cells in r1 cells are blue and all other 8 cells in c9 cells are red. The connecting point between Region 1 & Region 2 would be either r8c8 or r9c9; at this point either one could be blue or red. 3. Region 4 (grey) had to grow in c6 to place a “4” somewhere, but r4c6 an r5c6 are eliminated because of Sudoku (eliminating the circles along the known path would have likely helped Simon’s scanning), so r3c6 is grey and a "4". This also means that r4c6 & r5c6 are grey, otherwise those two would be isolated cells from the other regions; at this point Region 4 (grey) has 7 cells. 4. r7c7 could not be part of grey because the arrow clues would pull in two more cells; for a total of 10 cells in the region (Simon used the same logic at 2:13:30). r7c7 could not be blue or red based on the 2nd bullet point, so r7c7 is a different region; along with r6c8 & r8c8. Also, because r8c8 is cannot be blue, r9c9 now had to be blue (per bullet point #2), and the path starts at r9c9 and moves to r8c9. Region 1 (blue) now has 9 cells. 5. r8c7 is now green as it can no longer be blue and r7c7 is now a “2” because the arrow clues no longer relegated only to r6c8 & r8c8 (all the other cells along those diagonals are different regions). 6. Because of the “thermo-nature” of the path, r7c8 is green because there’s no way to reach a “2” value in path cells (Simon used the same logic at 2:18:10). 7. Because the path in Region 4 (grey) has to exit at r6c6 (because of the “1” value), since it cannot go upwards (those cells are also grey), it’s only exit cell is r6c7; making that also green. 8. r3c7 is grey (Region 4), because red (Region 2) cannot reach it (it only has 1 cell of “Region Freedom”) and if it were green (Region 3), that would cut off Region 4 with only 7 grey cells. All told, this leaves all but 5 cells assigned to their region (r3c8, r4c7, r4c8, r5c7 & r5c8) and just a final path connection to be made between r6c7 & r6c8, with Sudoku determining the rest (How DARE we be asked to do Sudoku in a Sudoku puzzle! 😊)

[@joshuashanahan2976]

I just recently came across your videos by happenstance and absolutely love them! I live for puzzles and am so excited that there is a channel that is dedicated to tough puzzles like this!!

[@cjShmoo]

Finally finished watching.. Did it in three sessions. Your endurance to keep up with all those deductions for nearly 160min is incredible!!

[@angeleia]

Loved this. Seeing such a long solve on a Sunday night meant no debating whether to have a go or not! Straight in to watching the master at work. Ate a packet of biscuits and enjoyed it thoroughly ❤

[@prepe5]

Hey great solve, i have been watching your videos for some time now and you got me back into doing some sudoku again. Man my love hate relationship with sudoku will never stop. A few days/weeks ago I found your channel and stated to watch them, because I was curios to what kind of sudokus are possible. I really like how well you explain all your moves, even tho sometimes I feel you "overprove". I just thought this time I leave a comment, because I finally manged to beat you on a solve and that by over 30 minutes, plus this is one of the recently uploaded videos. A few videos ago I started to solve them too while listening to you explaining it. Never managed to beat you up until now. Always got some hints or clues I overlooked. I don't really know if i can be proud of myself for that as you still explain everything in a lot of detail.

[@theia4893]

Really enjoyed this one.. we don't play along (my brain only does basic sudoku), but we love to watch Simon get baffled before a brilliant solve. My 5 yr old loves to watch when you are both on doing games. Keep on cracking guys💕

[@mattbennett3909]

@ 2:33:22 minutes, we have a neglected, undeclared 3 in the corner! Good solve Simon. I enjoy your videos when winding down from my own day full of crunching less interesting numbers!

[@ProBadSing]

The circles made it hard to follow other notation. Loved this puzzle!

[@aksgup1]

Tried solving this one a while back when it was posted on LMD and 1:29:30 is about where I got to at the time. I gave it up thinking I had broken it and had no idea what I did wrong. The fact that you can use R1C8 as the region number for yellow is so extremely devious I'm shaking my head in amazement.

[@HomeoftheWilt17]

While I applaud Simon's dedication in proving R3C6 wasn't red @ 2:13:18, he could have saved himself the trouble by asking where the region number for region 4 went. R6 had a 1 in the far left cell, R5 had a 4 in the purple region, and R4 had a 4 in the green region. Thus, R3 *had* to have a 4 in C6/7/8, but a 4 in any of those other than C6 would have secluded away a different region and thus broken the puzzle

[@wowitscoldout1119]

A nearly 3 hour video with a thumbnail of the most incomprehensible d20 conceivable. Simon's sick the poor lad and I'm here for a great time. Let's GO

[@MariaVlasiou]

2.5 HOURS?!?! Congratulations on getting through it and thank you for the gift!

[@helenpaynter5731]

Amazing solve! We sat down to view it over three evenings, and watched it in a oner! Couldn't switch it off.

[@marcelopicheth6111]

Amazing! I went through all emotions during the course of this video. Congratulations!

[@JASPACB750RR]

Couple thing. 1) Great Solve! 2) I wish the circles were removed once the line segments were determined in each area. They really muddied up the puzzle and made it difficult to see some deductions available 3) see if Sven can add a couple little feature to the software. A little square that would sit in the center of a cell to signify the starting point of a line segment. And a small directional arrow that could be used to show a line segments direction of travel through the grid. I.e. ^ < > v. I think those additions would allow Puzzles like this to be easier to follow and solve. They wouldn’t be as obstructive as those large O that block out most of a cells. And it would allow for setters to have yet another tool in the software for coming up with some more unique puzzle variants that are currently restricted by the softwares capabilities. He could add the small square that could either be starting pint of a line/snake. The arrows to show direction of travel (especially if a line crosses itself diagonally), and a small symbol of some sort that could be used as the snakes head.

[@sloid32]

Amazing. Simply gobsmacking! And given the sheer length of the video, I can forgive the lack of a song for the '3 in the corner'! :)

[@ProstoLyubo]

This is definitelly one of the best and most engaging videos here. Thank You!

[@glum_hippo]

breath-takingly lovely. Hats off to KNT and to Simon. I'm still glad that BOTH KNT's and dumediat's puzzles were featured. Both were ineluctable.

[@srwapo]

This puzzle took me so much time. A few hours yesterday, a little bit after I got in bed, a little bit when I woke up, and finally another 30 minutes after work. But, 24 hours later, I finally finished it. I saw the entire video!

[@victoriam6569]

1:19:00 but why can't path go from R3C2 to R2C2? (And end in yellow region at R3C3)

[@RichSmith77]

Good spot. I think you're the first to comment on it, and it does look like a mistake to me, too. It's not the only time he misinterprets the line he drew between r2c2 and r3c2. He drew it back at 55:05 to indicate that the green region couldn't extend upwards. But both here (1:19:00) and again later (1:35:30) (and possibly other times too), he incorrectly thinks the line between cells is telling him the path cannot cross there. That's not why he drew the line.

[@khoozu7802]

Same reason, R4C1 cannot connect to other cells, it is the starting point in region 1 & also the top left cell of the region, so it has to be region number 1 which will clash with the 1 in R4C5.

[@logiciananimal]

Astonishing! What I find more incredible than almost anything is that this was solved effectively *notes free*. In many highly deduction oriented fields one uses (e.g.) pencil and paper to keep track of matters, and yet here we have a few tentative cell values only.

[@madeking4]

One nice bit of logic you missed about the bottom blue region: Once you knew the bottom left cell was one and counting the line segments. how do you get a line in and out of the bottom row with only 1 line segment? You can't. Therefore a line has to start there so blue has to be region one and to make that its region number the region has to take up the entire bottom row and be flat, and meet up with region 2.

[@RichSmith77]

You're saying this proves blue must take up the entire bottom row, so your starting point must be before we know the entire bottom row is blue, right? But IF blue didn't take up the entire bottom row, then the path could have entered blue from a non-blue region in the bottom row and then immediately turned up, no? The 1 arrow only counts path cells seen in blue in that direction. There could be a second path cell in the bottom row, not in blue, that allows the path to enter and leave the bottom row.

[@maksimilanmel5610]

watched this over a few days. Although I can’t follow your speed of logic at times, it is very entertaining! Keep it up!

[@yadiracamacho499]

at 1:35:40. You know green is not region 1, so the path can't start on it. It has to enter on the cell with the 1, because it's the lowest value. It can only come from the left, so it comes from yellow. Green is either 8 or 9, so yellow is either 7 or 8. The path to yellow can only come through blue, and the path to blue can only come from purple. That means that after green the path has nowhere to go, so green is region 9. at 1:46:36, you know that pair below the 7 corresponds to r1c8 and r1c9. If the 8 goes in r3c1, r2c1 would have to be 9, but that would make r1c9 a 9, which it can't be since green is the region 9. So 8 goes in r2c1 and r3c1 can only be 2 or 5. But the red region can't be region 5, since it's to far away from r6c2 which is the where the path enters region 6. So r3c1=r1c9=2

[@srwapo]

@2:13:22, that was a 4 because every row below that already has a 4 in it, so the 4/gray region has to go up to row 3. If it was a cell to the right, it would isolate that cell and it would have to be gray either way.

[@TrentCairus]

That was epic. Was with you all the way, Simon! Well done indeed!!!

[@mousev1093]

2:12:00 I came to a similar roadblock in my solve trying to figure out Simon's grey region layout as well. The logic I used which I think was a little simpler to spot (and it is likely the converse of what he proved) was that we knew grey was region 4 from the path connectivity. Where could it get a 4 that would also be a region number? All of the grey region already defined at that point was south of the grey 1 which isn't good enough, nothing east of 1 would count either. It means you had to be north of that 1 somewhere but all of the immediate rows were ruled out by sudoku. You had to go to up to that top corner available 4 to do it

[@mikatuomaala1186]

You need to start taking movie ticket fees to watch this length videos >.< (I love these though)

[@rgoyal107]

So many would happily pay. I know I would. They have totally earned it.

[@AgeOfNerds]

Those are my favorites!

[@mikatuomaala1186]

@@AgeOfNerds Yeah, I come here for the long ones! I like that they for real feel like they have their own narrative's and plot twists >.

[@mikatuomaala1186]

@@rgoyal107 Absolutely!

[@buzzly108]

2:14:53 This was always region 1 because the only way the blue region has only one path segment is if it's the start or end of the path. And it can't be the end (9).

[@jonaslinde9330]

That was a brilliant solve. It was a rollercoaster! I really enjoyed it. The whole video was felt way shorter, than it actually was.

[@leojs5673]

my popcorn bucket is ready!! these videos are always the best

[@TheFrogfather1]

However much you ordered it's not going to be enough!

[@BenRHarsh]

2:05:44 I sometimes love and sometimes hate the lengths Simon will go to avoid doing sudoku. I had fun coming up with more and more ways to respond to his comments with "Where's your 4? Region 4 can't get its marker now. Where will the 4 go in gray?" when he hadn't considered where the 4 goes in region 4. Not in R6 because the 1 was on the left, and 4s were already in R5 and R4 so gray had to go up to R3. The path he took about considering connectivity was interesting but damn was that a long road to get there.

[@leeben25]

Great solve! As you mentioned partway through (and I hoped you were going to follow through) the circles should have been removed once the path line was established to de-clutter the grid. It would have been easier to follow as a viewer and easier for you to scan :)

[@emilywilliams3237]

So many things to say ... I'll start at the end. Yes, I did watch the whole video, but in I think three sessions (not because I was not interested, simply because I did not have a long enough stretch of time to watch it all in one sitting). Second, I have not read any comments, but I sure hope that they are all kind because really, Simon, there are no words for the applause you deserve for attempting and completing this puzzle in one sitting without any lunch and with some ... aftereffects, shall we say (though surely the length of time you were with us must have meant that you were feeling better by the end of the video than maybe you were at the beginning). Perseverance alone, not to mention stamina and more than just stamina, but energy were required for this - and your brilliant mind! You mentioned close to the beginning (relatively speaking, anyway) that if you were not on camera you would have had the luxury of playing around with some scenarios rather than proving everything - which was both comforting and a bit surprising for me to hear - but although I value logical solving in myself also, I do "play around with" various things in tough spots, so that's good. I am so glad, however, that you are thorough and careful and complete in your labors in these videos because you demonstrate the value of rigorous application of logic. (I could argue that this lesson can be applied to all of life ...) Thanks so much for this fantastic video - what a victory, and what a puzzle, and what a channel! (It is so much of an anticlimax to mention "replete," "quorate," and ... I had a note from the other day of another great word but my note is missing ... just another aspect of your wonderful brain.)

[@Posiadam.]

I was screaming at the screen and Simon around 2:10:00 because goodness me, you didn’t see that the grey region is the 4th region and that it needs a 4. And how could you put the 4 in this region if there was two 4s in the rows no. 4 and no. 5? The ONLY way was putting it in r3c6, so every other digression wasn’t necessary. Without this that was a great solve, I only got a little bit angry but that’s ok 😂

[@ChrisRemo]

Is there anything in the rules that specifically indicates that the numbers on line segments must increase within regions starting from the lower number at the entry point from the lower numbered neighbouring region? (As opposed to the direction of increase in the internal line being irrelevant to the region numbers themselves.) Simon seems to assume this, and indeed it seems like this assumption is maybe necessary to determine the way in which the line connects regions 8 and 9, but I can’t see how the rules specifically state it. What am I missing?

[@RichSmith77]

Digits strictly increase "along" the path. The fact the path visits regions in a particular order, from 1 to 9, gives the path a direction. I'd say increasing along the path can be interpreted as meaning increasing in the direction of the path. But I can see how someone may disagree. 🙂 [Edit: To add, the example puzzle shown at the start (7:45) also happens to show digits increasing along the path in only one direction.]

[@Vim]

You can get all the way up to here: i.imgur.com/03gEeBD.png without assuming this rule, after which the puzzle ends up having multiple valid solutions. Very frustrating.

[@notthatkindofdoctor5911]

KNT: Pathfinder Simon: Loopfinder Solve: Chainfinder Wonderful puzzle, the popcorn was delicious!

[@Bugonchair]

First time in my life I've been waiting on Simon to figure out a bunch of things that seem obvious to me lol. I've done some of these puzzles where Simon goes through deductions in seconds that took me an hour to understand, but not this time! Excellent solve though, I'll watch Simon struggle through any puzzle for 2.5 hours.

[@zirco77]

I drew a line I drew a line for you Oh, what a thing to do And it was all yellow Seriously, I loved that feature-length film from Simon, as much as solving this puzzle. Amazing set of rules! Thank you for both Simon and KNT for those enjoyable hours. There was a few times though where Simon missed the simple question and went a long way to prove something, such as from around 2:07:00, where the easy question was "where can 4 go in grey", given other 4s already in the grid.

[@boman2000]

Simply phenomenal! Loved watching this all the way through.

[@JayK-wb8fm]

I am lost for words, that was absolutely brilliant work from both KNT as well as Simon for sticking with the puzzle even after realizing how much time has passed with little to no progress (37 mark)

[@adrianp5465]

What a marvellous journey to go on with Simon. Joyful to watch. Stayed up far later than I should have done, but couldn’t turn it off.

[@rigeborod]

When Simon draws a line between c2r2 and c2r3 it was meant to show that green cannot grow there, not that there's a path blockage. But later in the solve he thinks it is a path blockage totally dismissing the possibility for the line to go through the line.

[@starcastle1181]

I saw how long this one was and was popping corn within 5 minutes. Thanks Simon ❤🎉❤🎉

[@spudd86]

1:35:38 Simon misreading his pencil marks! The line there means you concluded that r2c2 wasn't green not that the path can't move through the border between r2c2 and r3c3. Also once you've drawn the path through a cell you *really* don't need the circles, they're just making it harder to see what's happening...

[@RichSmith77]

Good spot! You're right. Fortunately, it doesn't affect the solve. He works out very soon after that since green cannot be region 1, the path must enter green from somewhere, and that can only be yellow. (1:37:50) The circles were driving me mad too.

[@chessburns]

Golly that was the most satisfyingly long video. I cried happy tears wen he solved it. I had to watcb it in parts since i couldnt watch it in 1 sitting. That being said wat a solvr this was. How KNT set this puzzle blows my mind. And Simon how he solved this genuinely maddeninly splendid genius puzzle is beyond me. Does anyone know if this is the longest solve in CTC history? I hope we get to 3+ hr videos in the near future.

[@MCarrington01]

Simon using rigor and not the orange 5 to remove green 5 beginning 2:30:02 and then using it mere seconds later to remove grey 5 shows just how intense this puzzle was. Edit: and no 3 in the corner song confirms it. Amazing solve to watch regardless.

[@Coyotek4]

Not only that: the 3 in the corner begins the path!

[@BrooksMoses]

At 2:08, there is a fascinating bit of logic: Where does the gray region's 4 go? By Sudoku it cant' go in rows 4 or 5, and it must be the region number, which means it can't be in row 6 or below. Therefore it must go in row 3, and to avoid trapping a too-small region, the cell in r3c6 must be gray -- and therefore it must be the 4. Then, since the remaining cells in row 3 cannot be 1, 2, or 3, they cannot be region numbers either, and so r3c7 must be gray and and r3c8 must be gray or red.

[@RoderickEtheria]

Didn't take me long to discover that r4c3 and all its diagonal squares must all be in the same region by the "visits each region exactly once part of the rules. Issue is extending any beyond those 4 diagonally adjacent cells makes a region of more than 9 digits, considering a path touching all 4 diagonally adjacent squares with path already requires 7 cells of path and the central digit, which makes 8 cells accounted for.

[@jsdodgers]

That wall between green and yellow meant that green couldn't extend that way as a region, it didn't have anything to do with the line being able to cross.

[@giantswingallday7001]

You know upon seeing the hour mark of Simon solving a monstrously difficult puzzle, he does not need to apologize for being stuck. We are with him in every step of the way! More power to you, good sir!