Mission Impossible: Sudoku Edition

** TODAY'S SUDOKU **
After Simon solved a relatively straightforward puzzle yesterday, he gets his comeuppance today taking on Frak by zetamath. This is a VERY interesting (and challenging) sudoku. It has a perfect 100% rating on Logic Masters Germany but also merits its highest difficulty rating. Do give the puzzle a try at the link below:
app.crackingth...
Rules:
Place the digits 1 to 9 once each into each row, column and region. Regions need to be deduced by the solver and consist of 9 orthogonally-connected cells. For each blue line, digits on the line have an equal sum N within each region the line passes through. If a line passes through the same region more than once, each individual segment of such a line within that region sums to N separately. Every line must enter at least two regions. A digit in a circle indicates the number of digits on that particular segment of the line within that region. Not all circles are necessarily given.
PS Our cryptic clue on Twitter to this puzzle was:
Once played on the BBC, candid cameraman finally quits?
which is FRANK (candid) - N (final letter of cameraman) and refers to the BBC Micro 1984 game FRAK, which Simon mentions in the video.
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[@HunterJE]

Simon's initial rules example got me thinking how funny it would be if someone set a difficult derive-your-own-irregular-regions sudoku where the regions ended up just being the standard sudoku grid of 3x3 boxes

[@PuzzleQodec]

Haha that would be hilarious

[@SzanyiAtti]

I had the same idea, I thought it would be a nice puzzle for April Fools.

[@kamilbizon8317]

Pretty sure that phistomefel did that with his "seven" puzzle. It was a 6x6 sudoku, but this kinda counts

[@LEEBLISSY]

I've had a similar thought before, I'm not sure if I can explain it well but what if someone set an irregular sudoku with actually irregular regions, but once the puzzle is finished you see that if you look at it as if it was a standard 3x3 sudoku it would still work. like yes, you needed the irregular regions to do all the logic, but if you used the pen tool after the fact to draw all the standard 3x3s the sudoku would still be correct 🤨

[@highpath4776]

@@LEEBLISSY I wonder if it is posslble to draw rules where a set of digits pattern forms the irregular pattern, but the same clues (or same clue structure with different rules) can evaluate to a 3 x 3

[@zetamathdoespuzzles]

Thank you for featuring this one, I'm quite proud of it, and I have more to say than usual, but I'll start by saying you had an extraordinary solve. In particular I was impressed with the near instantaneous realization about the sum of the inner line. I also wanted to offer condolences about whatever bad news you received during the solve. I hope it wasn't too bad! I made this puzzle to celebrate rangsk reaching 1000 subscribers on his KZbin channel where he streams solves of sudoku puzzles like this at least two days a week. He is a good friend, and inspired me to start streaming as well. If you've never seen me stream before and are seeing this comment the day its released, I am streaming all day tomorrow (Wednesday) when I will be doing puzzles submitted by chat that have no 5s in them. Let's see what people come up with! (You can just click my icon here to subscribe if you're interested!) Also, about the title, it is a reference to Battlestar Galactica, the television series remake from about a decade ago where all of the sheets of paper in the universe have their corners cut off, in a shape resembling the border of this grid. As so very often happens with my puzzles, I'm quite impressed by Simon nailing just about every one of my intended deductions! I also really cannot say what a huge compliment it is to be called Phistomefelian two videos in a row!

[@longwaytotipperary]

Wow! Just Wow! 👏

[@davidrattner9]

@ zetamath ..absolutely again amazing puzzle from you!!! Brilliance personified. Extraordinary what you can come up with!!

[@truscottlee5554]

Thank you for your brilliance and dedication 👏

[@gambit3391]

You have put yourself in a category with Phistomefel on this one zetamath. Brilliant puzzle. Please, please, please make a video on how you constructed this puzzle. I would pay to see it!

[@longwaytotipperary]

@@gambit3391 ditto!

[@wixxed]

I have noticed that any puzzle that takes Simon around 30 minutes to complete is my sweet spot. It's challenging enough to make it fun, but not impossible for me. I usually complete those puzzles and then come back to watch the video. I can see this one is almost 2 hours long so I'll just go grab a snack and watch Simon do it.

[@Leyrann]

For me it's a little tough to estimate. The sweet spot is 35-50 minutes, but the issue is that I have completely different solving strengths from Simon. With the right kind of sudoku, I can get close to or even beat his time, even if it's a 50 minute video, but with the wrong kind of sudoku, it can be a 35-minute video, and I just sit there staring at the empty grid for 35 minutes myself and then have to give up. Basically, Simon is incredibly good at finding the logic a setter tried to put in, while I'm extremely bad at it. As a result, I do very well at puzzles with a wider solve path or with more conventional logic (though even in those areas I'm only around Simon's level AT BEST), while I do very badly at discovering completely new logic or just very complicated break-ins (where any comparison between me and Simon would just be silly).

[@taniabn]

I was about to comment the same 😁

[@k1llwizzy]

well, he wasted 30 minutes figuring out that he needed 6 regions of 26 for the outer ring because he kept attempting other shit. 4 regions of 39 means you need to include 2 circles, he got there rather fast, but attempting 12 regions wasted over 20 minutes of the video.

[@TheFreeBro]

Something about the peaceful bird tweeting compliments simon’s occasional silences while he thinks. It’s absolutely beautiful.

[@roiljelly6255]

Simon i hope you give yourself the kind of praises you give to the puzzles you showcase, even if not aloud. You're not slow or stupid just because there are people who can solve puzzles even faster than you can. You're a genius at making these amazing puzzles accessible to someone like me who might otherwise have missed out!

[@HunterJE]

Loved how long the "define the regions" part of the puzzle lasted on this one, so often for chaos construction puzzles reach a point where the regions are either completely done or done but for some small local disambiguation and then it becomes just an irregular sudoku, was nice seeing one where defining the regions was basically the whole solve

[@KombatGod]

Took me a couple days or so but I finally finished this! Phew! The funniest thing about this video is seeing Simon going "no!" every once in a while thinking he broke the puzzle, exactly like I did multiple times during my solve... the only difference being that he was exactly on the right track, while I actually did break the puzzle and had to rewind.

[@ronjohnson6916]

Silly Simon. That was a remarkable solve for all of the minor misses. And we love the misses. Lets us think that we could do the puzzle by the logic of, "I see something Simon didn't, therefore ..." Delusions like that are good for the self esteem.

[@emilywilliams3237]

True. And hilarious.

[@markwizy4661]

I don't expect you to see this. Sincerely, there is no reason to apologize for working through the logic. Take your time and figure it out just like you did for this. I love following your path as you discover the path with you.

[@Playmaker6174]

I remember the day I gave it a try and it's a 2.5 hours tour trip, a very remarkable amount of sheer focus while staring the grid just for a deduction; but once I spotted one, I had to give zetamath an applause because of how stunningly clever it was.

[@G.Aaron.Fisher]

I also took about two and a half hours to solve it when it first came out. At the end of it, I was left feeling like I'd probably brute-forced my way through a few things that could have been beautiful. For instance, I had to bifurcate pretty deeply to figure out which area around the perimeter held the 6th region. Looking forward to Simon's solve to see if I missed a better path.

[@lordclockworks1570]

I missed the clue of the 3-cell region 2 cells must be part of a one region, which caused me to go through heavy multi-step logical elimintaions for shapes of multiple different regions that caused me so much pain. And then I look as Simon goes - the purple 3 can't be here cause purple region already has 4 so we put 3 here and green region's 2-3 are resolved. Was like: "F*k, it was this easy."

[@jtip_bun_bun4104]

I honestly can't believe I solved this one on my own! It took me 169:30 (just under 3 hours) but it was truly a pleasure to work on. My calculator was a lot of help for this one. I'm gonna watch Simon solve it now and see how he tackles this beast!

[@taakotuesday]

fun note: reading the corner numbers gives you 12 and 13, the factors of 156, and also 26, the value needed for the line segments

[@philwheatley5057]

58 minutes for me. Very very happy with that. I worked out the value and split of the outer ring and got the circle values completed within 10 minutes. From there I took about the same time as Simon. First time I have ever completed a difficult puzzle quicker than the CTC boys!

[@willemm9356]

Yes, the whole complicated border-cut thinking at the beginning could be avoided by looking at the minimal value for R5C1 (aided by R1C6)

[@inspiringsand123]

Rules: 02:37 Let's Get Cracking: 08:04 Simon's time: 1h33m34s Puzzle Solved: 1:41:38 What about this video's Top Tier Simarkisms?! The Secret: 5x (09:42, 09:43, 09:49, 10:04, 45:27) Phistomefel: 2x (59:45, 59:50) Knowledge Bomb: 1x (01:41) Three In the Corner: 1x (27:24) And how about this video's Simarkisms?! Ah: 15x (16:26, 26:12, 42:24, 52:42, 56:21, 57:28, 57:48, 1:04:08, 1:12:47, 1:15:47, 1:18:13, 1:24:29, 1:27:11, 1:40:45, 1:40:51) Good Grief: 12x (03:51, 44:01, 50:46, 51:09, 58:28, 58:30, 1:04:24, 1:04:34, 1:14:10, 1:18:29, 1:25:58, 1:27:11) Hang On: 12x (15:40, 19:51, 20:50, 26:12, 37:56, 1:08:43, 1:08:47, 1:12:47, 1:15:07, 1:18:44, 1:28:46, 1:37:13) Sorry: 10x (07:46, 08:49, 31:54, 32:14, 39:20, 44:57, 48:33, 1:24:41, 1:41:31, 1:43:12) Beautiful: 10x (42:24, 42:27, 42:31, 50:10, 56:21, 57:48, 1:25:56, 1:27:11, 1:30:00, 1:42:51) Clever: 9x (56:06, 1:04:29, 1:04:32, 1:09:12, 1:21:49, 1:28:02, 1:41:54, 1:42:00, 1:42:01) The Answer is: 6x (28:26, 56:54, 1:15:12, 1:22:42, 1:27:21, 1:33:30) Obviously: 5x (00:47, 06:48, 10:45, 19:25, 1:13:40) What on Earth: 4x (08:33, 11:32, 34:29, 39:12) Ridiculous: 4x (1:07:27, 1:09:59, 1:10:01, 1:10:09) By Sudoku: 4x (36:08, 36:10, 1:19:03, 1:40:27) In Fact: 4x (04:11, 13:08, 24:28, 33:22) Horrible Feeling: 3x (1:00:10, 1:00:12, 1:14:28) Break the Puzzle: 3x (42:31, 1:12:49, 1:14:30) What Does This Mean?: 3x (43:17, 1:15:47, 1:25:00) Nonsense: 2x (1:02:59, 1:03:01) Lovely: 2x (05:17, 36:23) Surely: 2x (30:35, 1:16:48) Proof: 2x (27:15, 27:16) Alexa: 2x (1:10:15, 1:10:18) Progress: 2x (41:37, 1:34:20) Wow: 2x (1:17:19, 1:23:52) Fabulous: 2x (1:12:33, 1:12:33) Goodness: 1x (49:28) Fascinating: 1x (59:43) Inarticulate: 1x (08:51) Gorgeous: 1x (1:22:22) Our old Friend Sudoku: 1x (1:30:20) Approachable: 1x (01:54) Disappointing: 1x (1:33:16) Phone is Buzzing: 1x (1:18:40) Plonk: 1x (23:30) The Power of Maths: 1x (56:03) Most popular number(>9), digit and colour this video: Thirteen (32 mentions) Four (120 mentions) Red (67 mentions) Antithesis Battles: High (2) - Low (0) Even (13) - Odd (1) Outside (4) - Inside (0) Black (4) - White (0) 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!

[@erinasnow]

Small correction to the computer: the rules start at 2:37

[@inspiringsand123]

@@erinasnow Fixed, thanks

[@noahlyndes4459]

Good robot

[@highpath4776]

Should Impossible be included , or is that too normal

[@highpath4776]

At 59.46 it was Phistomefelphalian ! (which counts, but is extra points)

[@SomethingWellesian]

I have a personal rule that if the video is less than 45 minutes, I’ll attempt the puzzle; anything beyond that tends to be out of my league. So I’m fully in spectator mode for this one. But I thought Simon might like to know that Frak was also adopted by the 2004 Battlestar Galactica TV show as a substitute four-letter word. No idea whether the creators were also referencing the game; I’d never even heard of it until this video.

[@aronlide]

"Frak" was used in the original BSG series from 1978. The game "Frak" was released 1984, and doesn't seem to have anything to do with BSG. The name of the puzzle references the cut corners of papers in BSG.

[@abraxasnl]

I watch these videos using the exact same logic. Short? Try it myself, and progress the video if I get stuck. Long? Get the popcorn.

[@gambit3391]

I am astoundingly proud to say that I was able to solve that in just over 2 hours. I had to backtrack two times for false deductions that I had thought were logical at the time (i.e. breaking the puzzle). That is an amazing sudoku. I can see why it got 10/10. Please, please, please do a constructors video on how zetamath constructed that puzzle. It’s just brilliant

[@perryr4796]

While this puzzle is certainly well out of my league to solve, I'm just satisfied that I was able to understand and follow the logic of your solve. Fantastic puzzle and great job!

[@ArquillWefronic]

Simon, you don't have to apologize about viewers getting bored of watching. If we get bored, we just watch something else. I watched the whole movie :)

[@WormHunter]

The videos above 1.5 hours are always the best ones. Keep the hard puzzles coming!

[@MonkehBuns]

I always watch these long videos before bed, because the fact that it exists means (spoilers) it was solved, so there's no suspense, just the comfortable enjoyment of watching it go. I also feel no need to pause the video and try it myself because I know it would take me a week, or eternity.

[@angelmarie7010]

That’s exactly why I watch this channel, the logic is so far out of my abilities that I know I can just relax and be a total spectator. As much as I like sudoku, I definitely would be stuck on this one for a month at least.

[@longwaytotipperary]

I love to see deliriously happy Simon! Amazing Simon 👏 Amazing Zetamath 👏

[@Coyotek4]

Took me a bit over 75 minutes ... and worth every second of my time. Phenomenal puzzle!!!

[@thesundancekid123]

I'm in awe of your sheer persistence and logic to crack this puzzle! I had the idea about the outer line. And that was it.

[@grahamrskelly6042]

me too. my hope is how many more puzzles I can solve now before I started watching, so I might come back to this one one day.

[@looweeg4229]

I love the birds noises. So relaxing when doing sudoku. It's like the ultimate setup. Good, chair, quiet room, birds signing. Perfect match.

[@aaronwilk1082]

A few weeks ago I commented I wanted to see a region sums puzzle where the regions had to be deduced… it’s here and it’s beautiful!!

[@NeilCrabbe]

That thumbnail immediately brought back some memories. I spent many an hour playing Frak when I was a kid.

[@KayDubs77]

Well done Simon! That was a battle for sure, but you prevailed!

[@BigAsciiHappyStar]

That was one of your best solves. After you got your first digit your solve path was identical to mine, and it was clearly the intended solution. To speed up the initial break-in, let the "equal-sum" in the perimeter be X, which must divide 156. X can't be less than 9 otherwise we cannot place 9 anywhere in the perimeter. X can't be 12 or 13 otherwise r5c1 and r9c5 have no fill. X can't be 39 or more, which you already discovered. Therefore X = 26.

[@th.nd.r]

That’s just a sheerly incredible puzzle and an absolutely brilliant solve. Simon + zetamath is a pair for the ages. Wow wow wow. The ruleset, the deductions, the way the puzzle feels like it’s breaking but finds a way, the way all the sudoku comes so quickly after defining the regions, it’s just beautiful. Take a bow each of you.

[@saurabhbagai5982]

Simon and Mark, please come out with branded CTC popcorn. I need it after this one and the magic you will deliver in the future. Extra butter please

[@sjm6280]

I found Simon particularly brilliant solving this fantastic puzzle, I love these movies

[@HunterJE]

Pretty sure the first two syllables of "Let's imagine" are the trigger words regularly setting off Simon's Alexa...

[@msolec2000]

Makes sense. I think the other time she triggered off of "and exactly..."

[@andrewnelson2525]

This one took me three hours, about 80 minutes longer than Simon. When I started watching the channel (about the time of the Miracle Sudoku) I regularly took five to six hours to solve the difficult ones which maxed out at about 50 minute videos, so I think I must have gotten faster. I was quite pleased that I instantly knew to work maths on the outer border, deduced the 26 sum and then got my first digit. There was a long way to go from there however -- but it was a rewarding journey.

[@MissVindicat]

Lots of people saying they won’t attempt a puzzle that takes Simon this long. But! I’ve found it to be very rewarding to just start trying to solve it for a couple of minutes. Try and see what I come up with, what way my mind goes. And then I come back to see how Simon does it. Makes it way more interesting to follow his thoughts and ideas.

[@AngRyGohan]

In my usual habitat, i usually just watch the rules part because many of them are just confusing ( like this one ) then attempt a go at it. In cases like this one i gave up after 5 minutes because i just dont have a line of thought to start this out even if i gave it 5 hours, but then ! When Simon/Mark gets a bit ahead in the solve i like to pause the video and try to continue myself, even if for a minute if i can follow the same logic as they do for the rest of the puzzle.

[@MissVindicat]

@@AngRyGohan Yes, I sometimes do that too! And this strategy actually taught me a lot about solving these puzzles.

[@joelstevens5670]

I had a go at this puzzle when the video was released but I initially could not get my head around the rule regarding circles. I did eventually reach the conclusion that each circle digit represented the length of the section of line that circle was on (within a single region) but the wording was a little confusing!! It did get better after that mind, as I stumbled across a rather neat opening which I thought I’d share for the benefit of anyone who got stuck like I did and wasn’t fully able to understand Simon’s way in (as clever as it was). The circles on the longest line are the place to start. Consider the circle in row 1. It cannot be a 1 or a 2 due to irregular sudoku rules (there is already a 1 and a 2 in the row) so it must be at least a 3. This implies that the circle is part of a line segment of length three or longer, so the line segment is therefore a minimum of 3+4+5=12 (all three cells would be in row 1). This removes 1 and 2 as possibilities from all the other circles (a 2 in a circle would lead to a maximum total of 2+9=11 for a 2-cell line, which is too small). Now consider the circle in row 9. It cannot be a 3 or a 4 (for sudoku reasons) so it must be at least a 5. The next step is to work out the overall total of the outer line (we can use the secret for a complete row or column and subtract the given corner digits as necessary i.e. 41+42+37+36=156). Simon confirms this to be 156 which can be written as 2x2x3x13. Since we are dealing with equal sum lines, we need to split the long line into sections which add to the same total and this total must therefore be a factor of 156. The minimum sum for a line of length 5 (using the circle in row 9) is 15 (1+2+3+4+5) and we also know that there are at least 5 sections on the line (represented by the fact there are 5 given circles), so the sum must be between 15 and 31 (≈156/5). Thus, the only factor possible is 26 and this also stops the circles on the line from being lower than 4 (3+8+9=20 is also too small) and higher than 6 (the minimum sum for a 7-cell line is 1+2+3+4+5+6+7=28), making the circle in row 9 a 5. The rest of the solve is incredibly clever but it does take a while to get through!! Thanks to zetamath and Simon for the impressive setting and solving respectively!

[@Raven-Creations]

This was absolutely extraordinary. Definitely deserving of both its 100% approval, and 5* difficulty ratings. I love chaos construction puzzles, and this was at least equal to the best I've seen. You called it Phistomefelian, and I agree. There's no higher praise we can give. For the break-in, it's much easier to disprove the region touching twice postulate. You were too focussed on the linear region's ends. You only have to look at what happens to the rest of it as it wraps around. Wherever it is, it makes several single-cell line crossings. While it's possible to have a single-cell segment, there's no way you could get all of them to work, given that you'd have already used 24 or 26 out of the 45 on the outer ring. My order of calculation was somewhat different. Putting numbers in early guided the colouring. After getting that the 4s on top and on the right both needed 9s, the 5 on the right only had one possible fill, thanks to the givens and the possible fills for the 4 in C9, and it needed to dip into R9 with a 9. This gave me the positions and fills for both circles in C9, which in turn gave me the position and fill for the 4 on top. This put 37 into grey, which needed sixteen more, but it couldn't do this in two cells without repeating the 7, so it had to take another cell. It can't reach the 56 because it would need the 3. The 56 is now 5 with 479 in the column, and the grey has 268. Like you, after the elation of completing the outer ring, I quickly had that sinking feeling when contemplating what came next. The way that 14 was the only possible magic number for the inner ring was very nice. Had there been any ambiguity, I may well have thrown in the towel at that point.

[@crystalgehrt8861]

Sometimes, you just wish youtube had a wow button like facebook. And Simon, we never get tired of you!

[@PhilBoswell]

I can't help thinking that the pen tool makes it much easier to re-use colours, since you can remove the colour from a completed region and use it again without fear of confusion…

[@miran248]

But muh colors!

[@BryanLu0]

He nearly colored the grid in 4 colors, so not too bad for Simon

[@gotark]

He could probably benefit form giving all finished regions a light gray colour. Many colours seems to degrades the scanning for numbers.

[@eddiejcc]

Wow, what an astonishing puzzle, it wasn't until 2 minutes left that I realised I had just watched a movie length sudoku solve at normal speed!! Thank you Simon AND Zetamath!!

[@michellew3934]

I think we're all here to watch someone solve a super hard puzzle, we wouldn't begrudge you the time it takes to solve it all! I find it fascinating watching and seeing how someone much cleverer than myself thinks. Don't beat yourself up Simon! You did great!

[@esotericVideos]

I'm an aspiring setter, and I wish I knew how something like this was set. Because to me either working backwards or forwards seems to have way too many ways it would be either 1. Too ambiguous or 2. Unsolvable. If you started from the end and built clues up to get to that end, how would you know what digits to start with at the end? And if you tried to build from the beginning how would you know if any given clue led to an unsolvable grid? I would love for a "making of" video for this puzzle.

[@flobiish]

After a hard day work, it was nice to have a relaxing (for me) long (for Simon) video to enjoy. Now I get to see what Mark's been up to.

[@johnedwards7473]

For once I got to the initial observation quicker than Simon. Since there is a 9 on the the shaded boundary, the size of the segments have to be at least 9 and no more than 45. So 12, 13, 26 or 39. Looking at the circle on the left, it can only have values of 2 or 5 or more. If it was 2 its segment would be at most 11, which is too small. So it is at least 5, which means the segment has to add up to at least 15, which means sizes of 12 and 13 are ruled out. And of course 39 is ruled out because there are 5 circles.

[@johnedwards7473]

And while I was 15 minutes faster on that first part, I would apparently be infinitely slower on the rest of the puzzle.

[@devdog007]

Another proof against 12 and 13 that I first saw is that to add to 12 or 13, you need 2-4 cells, and if you use 2 cells, it can't use a 2, so can't be a circle section and there are 2 circles that can't be 3 or 4, so they'd have no possible number

[@RichSmith77]

I did something very similar, although I didn't think about 9 having to appear on the line on the outer boarder somewhere. Instead I looked at the circle on r1, which sees 1 and 2, so is a minimum of 3. The line through it must be a minimum of 3+4+5=12. I used this to rule out 2 from the circle in c1. But I like your "9" argument too.

[@Gonzalo_Garcia_]

97:28 for me. What an absolute beast of a puzzle that was. I had a big brain fart at one point that almost made me give up, but I soldiered on, found the flaw in my logic and finally managed to finish the puzzle. I’m so happy I solved this one, one of my proudest solves for sure. Awesome puzzle.

[@ardemus]

I liked that puzzle. I'd never have solved it without Simon, but I was able do big chunks, only coming back to the video for the bits I couldn't see. It was a great feeling to come back and see Simon not only get the same answers, but mostly the same way in the same order, and then he'd get stuck the same place. After a time he'd come up with an insight and I'd be running again, often it was enough for him to just point out where he had an insight. Long solve but satisfying.

[@d4r4butler74]

Thank you Simon! Not Boring at all. Thank you Zethmath. Brilliant puzzle.

[@SpeedyBozar]

At first I was really scared of this beast. Then I found some faith and courage to have a deeper look and earned the privilege to see true beauty. Took me 143 mins finishing at 5 am. 100% worth of my time. What I love the most about this puzzle is that until the very end it was not clear to me how the regions are allocated. The whole story was full of twists and surprises.

[@abj136]

I found a different way of starting the border: After figuring the prime factors, Looking at the circles, y,ou quickly see you can’t have all tiny segments. E.g. you can’t have (2) because 2+11=13 will never happen. Thinking through the logic of what’s possible, you realize you must have 4s and must have a 26 total, so 3s are out. Also with 4s and 5s you also realize that there’s gotta be 6 regions to complete the 28 cell loop.

[@jonniboye6399]

What an amazing puzzle! I thought for sure I made a mistake in the bottom right area, but it all worked out! Getting that circled digit in the second line (not the one on the perimeter) was key to working out the rest.

[@Sloth_and_Badger]

I read the rules and my head exploded. Now there is a big hole in Germany

[@MrRevertis]

Oh man, Frak on the BBC Micro. I can still hum the music from that game, can't imagine how long since I last played it. Not sure I ever got past the first level, Chuckie Egg was my jam though. Relevant Calvin and Hobbes cartoon: Calvin worrying that all his present experiences are just doomed to one day become stories with no point that no one cares about.

[@CrackingTheCryptic]

Oh Chuckie Egg was just magnificent - what a wonderful memory. Did you ever play Citadel?

[@heywingliu9085]

90:51 without any help!!! So excited for beating an awfully difficult sudoku by myself.

[@MrCheminee]

Well done!

[@daanschouten2754]

Being in quarantine the last few days, it has been great watching you solve the most insane puzzles! Also, I love your enthousiasm about those puzzles when you're figuring them out! "This is gorgeous!" Is my new favorite english sentence! Thanks Simon!

[@viviencollomb-clerc5526]

Made it!! It took me 2hours and a half XD It was one of the best puzzle i've played. Thanks.

[@leickrobinson5186]

Movie time!!! 🎥🍿🍿🍿

[@ypsehlig]

yessss

[@leeannadimoulas5163]

I love these videos! These weird, complicated puzzles are so fun. Please don't worry about length. I just pause and come back... Sometimes over a couple days! 😆 Thank you for all this great content!!!

[@sanabas1]

Incredible puzzle. Don't think I've ever been 40 minutes quicker than the video before, though I think most of the time difference was the break-in and colouring the outer edge.

[@Talzaroff]

Awesome, right until the end! It never felt "done" till the last minute.

[@FantasyZealot_]

Don’t apologize for the birds chirping, it’s quite nice to hear in early March in Buffalo, NY…. It’s been a while.

[@gregind01]

Holy Frak! Aren't you glad that I warned you to get the popcorn ready. 🍿 Simon I am in awe of your determination and ability to keep finding the tiny morsels of logic to build a solution to this puzzle from! 🤩

[@MrCheminee]

Yay. I did finish it! took me more than five hours! i had to check your video a few times to see if I was on the right track.

[@dontmindme2844]

After finishing it in a little under 2.5 hours, I don't feel so bad given the video length. I missed the initial break in for the longest time, but once I got it, it wasn't that bad.

[@ericpraline1302]

Another brilliant puzzle. I greatly admire zetamath's puzzles because while they are always difficult there is always an excellent logical path through them. I blame a mild hangover for my slowness in places.

[@KnittingbyPhrancko]

What an awesome puzzle and an equally awesome solve! Zeta and Simon, both of you, take... a... bow !!

[@wazzzuuupkiwi]

I did it! :D took a fair bit of your help, but i got the outer ring on my own en then proceded to break my mind over the circle in the inner ring not connecting to either of the two regions on the edge for about 40minutes. So while I got the line had to be divided into 6 regions of 26 waaay faster than you for once, I then slowed down just as much while you smmoothly tackled the second line form the other end. Touché :P Glad IU tried it, was one of the most daunting ones to date to be sure!

[@MasterKnightDH]

So I'm at the 30 minute mark of my own attempt and already I figured out how all of the circles in the perimeter have 4, 5, or 6. Here's the points: -Sum of perimeter line is 156 as you pointed out. -Perimeter line uses 28 spaces and has minimum of 5 regions. 156 is not divisible by 5, of course. -156 divided by 6 is 26, which rules out anything above 6; minimum by 7 would be 28, which is too high. -6 per region x 26 regions can't work because 6 can't use 7 or above which particularly doesn't work on the bottom line. This rules out 2 in the circles because the next lowest per region is 12. Bottom circle is consequently 5 by Sudoku. -12 and 13 are both too low for 5 spaces. That leaves 26 per region for 6 regions, which rules out 3 as a possibility for any of the circles from its maximum of 24. Strengths and weaknesses.

[@dsquirrel]

Very helpful description! I've written it out in a bit more detail below in case that helps others. I also think you meant to say 20 not 24 in the last sentence. Thank you! Let r be the number of regions along the outer blue line, N the total of each such region. 1. rN = 156 as Simon explains at 10:30. Also r>=5 since there are 5 circles, and r

[@markp7262]

1:27:23 finish. I completely understand the title for the puzzle. The first thought I had when I saw it was "What the Frak?!?" 🤣 But such a wonderful puzzle.

[@crazypiikkis]

I played that game on C64! It was the Italian version "L'uomo delle caverne" on Tuttocomputer cassette set. Good times.

[@emilywilliams3237]

Several commenters have compared the length of a Simon video to the likelihood that they would attempt, let along solve, a given puzzle. I agree - anything that takes Simon over an hour is totally a spectator sport for me. And what a game it was - down to the final bell. I usually notice time passing while watching videos, but for this one I was totally absorbed and did not. Thanks so much for this video, for this excellent puzzle, Zetamath - and for leaving your window open so that we could enjoy springtime in England. Even here in North Carolina, USA, the birds are not yet as vociferous as by your house.

[@iabervon]

I often see things immediately that you take ages to work out, but I also often see things immediately that turn out not to be true, so I think you're spending that time ruling out realistic options I didn't even think to consider.

[@kaldeathar3462]

Simon: "I think I solved this puzzle... only took me 100 minutes" Me: so thats why I ran out of popcorn

[@JasperJanssen]

Nothing to add about the puzzle but I wanted to share how much I liked the game back in the day.

[@monosoloq]

I do think Simon wasted 30 mins on determining the sum of the outer ring. First, ruling out 39 is easy. Then you’re left with 2,3,6,12,13,26. 2,3,6 are not possible since you always have to put 7,8,9 in some of the lines. Then look at the circle in the bottom line, it can only be 1,2 or 5 (since you can’t go for 7 as the triangular number of 7 sums to 28) and 1,2 aren’t possible either for apparent reasons. So the circle in r9c5 is 5, which means the length of thar section is 5. So that the regional sum can’t be 12 or 13.

[@sunriselg]

Not intending to try this at all. But found something very interesting fairly quickly. Gonna continue to watch the video now.

[@nickellis999]

Superb puzzle. Excellent solve. Bravo!

[@mstmar]

Really great puzzle. loved the solve. i did find a more robust way to start the puzzle. like simon said, the sums or regions on the outer border need to be a divisor of 156, i.e. 1-6, 12-13, 26 or 39+. if the sum is 1-6, you wouldn't be able to put the high digits anywhere on the border, so they're out. 39+ simon explained away the same way i had, that 2 circles would need to share a region, and so be the same digit. if the sum is 12 or 13, then each circle could be at most a 4; in particular, the bottom one, which sees a 3 and a 4, would need to be a 1 or 2. this would mean making 12 or 13 with either 1 cell that is a 1, or 2 cells that contain a 2. both are impossible. this leaves only 26 as the sum

[@xOscarAx]

i usually follow logic very well, even on your longer 2 hour phistomefel videos. but for some reason i could not wrap my head around the break in of this puzzle. i dont know what math you did to arrive at your conclusions. but after you got all the borders colored and started going inwards into the rest of the puzzle i was able to follow more comfortably. i just dont understand your break in, this was WAAAY out of my league but i enjoyed your solve either way.

[@grahamrskelly6042]

I had no idea how to start, I got that the outer ring had to be the start but my poor math part of my brain just couldn't come up with an answer... so I started watching to get the hint from simon but got mesmerized and watched the whole video. at the start of my CTC I could not solve many of the puzzles that I can solve today, so maybe in the future I can come back to this one and have a go.

[@davidstorrs]

Simon, you always beat yourself up about "I'm sorry this took so long." Please don't. The fact that you can solve these leaves me in awe and you should take pride in your skills. On a separate topic, I'm now worrying about whatever that bad news was that you got over the phone. I hope everything is okay.

[@abraxasnl]

Simon, please open the windows more often. I loved the soothing songs of the birds. Of course, during trampoline wars, please do close the windows and hide underneath your desk.

[@danielauto3767]

Simon, don't be sorry about the long videos. They are the best!

[@paulparker9593]

I couldn't begin to get started on the puzzle, but I think I did solve the Alexa mystery. Simon said "let's imagine..." and I think the lets-i was enough to catch Alexa's attention.

[@gc2009able]

This one took me a very long time (2.5h) but I got almost all the logic on my own. Simon got me going with the *very* beginning logic of each of the two outer lines, and I made a couple of silly sudoku-logic errors late in the puzzle and had to backtrack, but other than that I found my way through! Given how difficult it is, I'm quite proud I was able to wrap my mind around the logic.

[@rohitraghunathan]

Frak was very close to my response on reading the rules of this puzzle

[@MarushiaDark316]

Something tells me the title of "Frak" is meant to be a more-family-friendly version of another 4-letter word starting in 'F', as in one you'll likely want to say as you struggle to solve this puzzle.

[@S_Black]

It's a reference to Battlestar Galactica. The remake used in endless variations. Would have been fun if Simon recognized that and went along with it.

[@andrewzmorris]

Pretty much. They wanted to get swearing past the censors on Battlestar Galactica, so they invented the new word "Frak" for the characters to say when things get rough.

[@Donrafa189]

You may have thought you knew that red wasn’t green…but you didn’t!!! LOL The stuff that comes out of this man’s mouth!

[@carlossosa2907]

Not only do we learn great logic techniques, but also that Orange is not the new black 😅

[@Hephaestus_God]

I'm gonna be honest here. I have a better chance of randomly filling in the circles and drawing random shapes than I am to understand the first 40 min of this video haha... Was a fun watch though

[@cptroot]

A solid 127:35 by me. What a great puzzle!

[@seanmcdonough2683]

That puzzle well earned its 5 stars

[@darreljones8645]

Alexa's interruption at around the 1:10:00 moment in this video is why I refuse to buy a PDA for myself. :)

[@pouletbelette]

What the frak!?

[@benreadingbooks]

Surely 'frak' is a reference to Battlestar Galactica. In the show lots of things (papers and the like) have the corners cut off and so look a bit like the shape made by the longest line in this puzzle.

[@pelahnar4]

zetamath mentioned in his comment that that is exactly the reasoning for the title

[@sarahclark9256]

It’s a joke that got out of hand (the prop department did it once as a protest against having to “cut corners” and the producers decided they liked it.)

[@S_Black]

@@sarahclark9256 Eventually it became a huge issue. It started with simple things like sheets of paper. But later they had to regularly cut whole books.

[@AllenBaranov]

Simon: "Six, Seven, One" Alexa: "Yes?"

[@identity5481]

the puzzle took me literally 6 hours but it's also the first time I've solved one of these on my own. it was so fun honestly

[@mallomon]

My first guess was it was going to have to be 6 borders with segments of 26, but I had no idea how to show that. So I'm glad you did!

[@joekerr3638]

Ohhh wonderful, an early birthday present.

[@CameronFerstat]

😂😂 I also remember the old Frak game, even including the little tune it used to play before displaying the word Frak when you lost a life.

[@aldergreen]

Loved watching this, but as a discalculic person who struggle to add up and subtract even small numbers to eachothers this is a total hell! The maths for solving are way too complicated for me... Good job on explaining, you're crystal clear as always, though!

[@kaldo_kaldo]

Phistomefel watch out, zetamath is coming