Congratulations Simon, another lovely solve! I'm glad to see this puzzle on the channel, because it showcases a technique that I think is easier to figure out on one's own through example than to have explained, namely that of Multi-Sector Locked Sets. I think a lot of people get scared away by the name and the notion that it's some super hyper advanced classic technique. That's why I'm so happy to hear comments from people who had never seen the idea before, but were still able to develop it from scratch in order to solve this puzzle. Indeed, one of the reasons I made this puzzle was to help solidify my own understanding. You're also absolutely right that someone could blow through this puzzle in half an hour if they got lucky enough. After entering all the eliminations from MSLS (and there are a lot), a solver will fly through with mostly hidden singles and pointing pairs. I tried to make the puzzle not too hard after the break-in, which is why I think so many people were able to grind through it, but it still ended up being quite the beastie. As you noticed, it's not quite in my style to include unnecessary clues -- partly because I'm always scared that they will shortcut cool logic. The name of this puzzle is actually not X, but ✖ (the thick multiplication symbol), due to the outline roughly formed by the given clues. There is no inherently logical reason the single-digit quads all end up in the centers of their boxes. Rather, after all the main logic is exhausted, I was left with the task of disambiguating a lot of deadly pairs around the edges of the grid, with almost no information in the "phisto" 2x2s. Quads that alter those cells was therefore the natural choice. Speaking of the phisto trick, I think this might be the third puzzle that has been featured where it unintentionally shows up as a red herring, which I find rather amusing.
Gliperal...another fascinating, wonderful puzzle from you. Your logic and techniques in setting is extraordinary. Always thrilled and excited to try one of your puzzles. Look forward to the next one from you. Keep on setting and thank you again for this beauty!!
I love that you comment with your thoughts and insights, as well as answering questions from the video. I would love it if more setters would do this too!
i could never get to the point in the solve where im seeing the things he's missing, but once he gets there i see it, so i never feel frustrated cause i know i can only spot the things when he does the first 20 minutes of solving XD
@@alexgordon7312 In all honesty, it's quite a good moment for self improvement. Learning to feel better about these things. It's so trivial in the grand scheme, or even compared to most trivial schemes...
Don't know about you, but I didn't realise that the sum of any row, column, or box of the grid always equals 45 until he taught me. Sorry... that should have come with a spoiler alert. Too late now! 😂
I'm starting to really, really appreciate the way Simon explains each and every time how to follow his reasoning. It meant when I was new I could jump right in.
I started watching the channel in January, and I largely started with the backlog. I actually really hate the overexplaining, personally. As a new viewer I felt much more intrigued when I had to think a little bit to understand. Obviously some logic merits explanation, but I think the current explanation level just leads to passive viewing, and longer videos.
@@MineRoyale. Long comment, TL;DR at the end… that is the Problem of all channels line this: we, as experienced viewers, don‘t need things like Phistomephel explained for the 20th time, or an X-wing, swordfish or the sudoku secret. However, any new viewer would need it, and not all viewers start with the backlog. So, as a creator, you have to find the sweet spot between several factors: 1, you want to make entertaining videos; 2, you want to satisfy your existing community; 3, you want to attract new people and 4, (a bit special to the sort of content on ctc, as it is highly focused on Simon and Mark), you need to be as natural and authentic as possible. I, even though I don’t need those explanations over and over, don‘t mind, because Simon just seems to explain automatically and it sometimes even helps him to spot another bit of logic. Quite some time ago, I suggested that Simon just records a series of very short instructional videos explaining recurring techniques and just link them in every video needed. My rationale was the same as yours. By now, I‘m not that convinced, because it‘s just authentic Simon. If you don‘t like excessive explanation, just watch Mark‘s videos. I, personally, mainly (if not exclusively) watch Simon. His enthusiasm about small bits of logic, his little imperfections, his whole personality simply grew on me, whilst Mark is a bit too perfect, brilliant and fast for me to enjoy a video. TL;DR: You have a point, but not really due to the way UA-cam works.
The truth is, almost no one starts with the backlog, and I can't blame them. I don't mind the repetitive explanations, personally. It's easy to skip 10, 20 or 30s ahead on youtube.
I have been a fan of CTC for over a year now, but the past few days the channel has been so helpful for me. I had my baby a week ago and yesterday i was diagnosed with preeclampsia. I have been stuck in the hospital alone while my husband is at home caring for our kids. CTC has really helped cure my boredom and loneliness while i try to stabilize and get over this hurdle. So many thanks, to you and Mark. ❤️
@@jpryan90 Tatooine Sunset had 21 given digits. And only classic rules. Yet that was a monstorous hard puzzle and break in. Horses for courses. It's astonishing to me how many different setters and approaches to setting (both for insanely hard, and 'approachable' but still amazingly beautiful puzzles) have developed over such a short space of time. I wonder if the people who came up with the concept of the first sudoku are looking on and thinking, "Bobbins! What the heck did we unleash into the world?"
Simon: uses advanced set theory & words like recalcitrant, solves puzzle. doesn’t see why it’s called ‘X’ Me: can’t make heads or tails of puzzle, fails miserably. Has to google recalcitrant. Sees the X shape immediately We are two very different people
@@andrewflynn113 No, it’s a law. It’s a summarized observation, not an explanation of why this is. Andrew’s Theory of Sudoku Difficulty would be why 5 as the center square makes it hard.
37:20 My scream of the night: the 1 in column 3 wants so badly to be placed in row 3. Simon somehow has abandoned his earlier quest for 'saturated' digits. The full quorum of 1s in the green has been accounted for, so once the 1s in the other boxes rule out columns 1 & 2 in box 1, the only non-green cell in column 3 is the only place 1 can go in box 1. This relatively easy low-hanging fruit remains outside Simon's cortex for the next 20+ minutes. I hasten to add that this is ultra-cheap kibitzing. I completely and utterly stand in constant amazement of the brains at work on CtC. I am just *also* amazed at the sort of blindness these brains suffer from. The lesson assuredly is that none of us should be too sure she sees the truth, the whole truth and nothing but the truth. Next time you have jury duty, this is something to remember. [edit] 58:57 Yes, Simon has forgotten that he has been sweating blood to ascertain the full complement of all digits in green and purple. He hasn't leveraged that treasure to account for digits that cannot any longer appear in colours because their quota has been spoken for. At this stage that *must* be the vice that cracks the puzzle's nut. [further edit] *I cannot believe it* !!! Simon found logic that avoided using the 'full quota' logic. How differently wired is this man. I love his brain, every fricking synapse of it.
Agree with everything you said here. I'm reading a few more comments saying the same and I left a similar comment. Once you have the full quota of numbers, the puzzle is actually quite easy. I have no idea why Simon had so much trouble with it but his brain is just not wired correctly for this type of puzzle. The way he solved the 8's for example blew my mind. I'd ask Simon to go rewatch that part because I think even he would admit he wasn't in top form on that one. You can't put 8's in the green unless the circle has an 8. But no... that's too easy for box 3. Let's go through all sorts of other logic to get that 8. lol
This might be my best solve ever. Finished in a time of 1:03:07, and successfully used 'set theory' along the way without guessing. I am *ecstatic* at how I did on this one. Fantastic puzzle!
@@Coyotek4 Hey, coming from someone who really cant' get very far in most of these puzzles, you've done awesome anyways! Also, being that far along to be able to do this puzzle that quickly, you'll get those other ones no worries
I really do wish Simon knew just how much we appreciate him. When I look at these videos it feels like sitting down with a friend to solve some puzzles. His company is a huge part of the fun. So each time he apologizes for “missing something” I want to smack him because it’s not about the efficiency. It’s about the fun, you lovable fool ❤️
Hello Simon, it may have been stream of consciousness or frustration at the puzzle, but please don't apologise for taking a while with these difficult puzzles. It takes as long as it takes and if we try to force it, it simply takes longer.
i know what you mean, i spotted the fact that 1 could only be in one spot in column three at least 20 minutes before simon because i kept doublechecking the colours
Lovely! Sorry about the misleading evaluation of 3-4 stars! I was too excited after the early solve, but this sudoku is genuinely difficult. Every deduction was challenging
If its THAT diffecult its more fun to watch someone solve it instead of trying it yourself, because otherwise I would go crazy... And it would take like 6 hours of hard brainstorming
@@theunwelcome well, you should take breaks when trying a hard puzzle above your normal skill level. I find that it works surprisingly well when you get back at it the next day. So in realtime I would spend 6 hours, sure.. But over the span of 2 days f.e. Knowing when to stop when you're stuck is quite important for the time consumption that these puzzles tend to have.
"I'm so sorry I've wasted all your time" I'm not a solver or a setter but I watch someone solve Sudoku on UA-cam. I spend my time the way I want to. Keep up the great work!
Another brilliant solve, Simon! I couldn't even get started, then I saw you draw your green and purple bars, paused the video, and I was off to the races! Two things I did slightly differently. First was to notice that the purple and green barely intersect (one 1 and the 5), and that the purple had the 4679's and the green the 1238's. Knowing this, it was clear that the green cells in row 5 had to come from the 4679 set and needed to all be different because they shared the row, so...4679. Likewise the 1238 in purple's column 5. After that I was focused on placing the remaining 6679 from the purple in the green 2x2s and the remaining 2338 in the purple 2x2s. That seemed to make keeping track of things easier. The second thing I did was make a third set of the four central 2x2s, which had a full set of 1-9, plus 2556789. That helped push me to look for places to put all those 5s! Nevertheless, my solve was not faster, and was not without an error and restart about half way through. It continues to amaze me that you can keep those sets straight in your head, while filming and narrating your solve. Remarkable.
47:20 "There must be a digit I can place" ... ignores the 6 from the clue you could just write in, deduces an 8 ! And then ignores the 8 clue in Box 1 forced into column 2. Those single digit clues look so useless but sit the smirking, holding the key!
I come here to learn how to work through logic and deductions, so its never a waste of time to hear how you go through all your ideas on how to do it. The ones that don't pan out are still interesting and useful! Thank you!
I just followed along, here and there stopping the video to attempt a stint on my own. And yes! I found the digit in the center, and all the domino mirrors radiating rectangularly away from the center. Thank you very much for an insanely beautiful puzzle, Gliperal - and an extremely educational video, Simon!
Quote of the day: 25:59 "... And sort of ... then look at other places that are affected by the greens and the purples and where we know those digits can't go to force those digits onto places where we never knew those digits were in the first place ... that is a summary of madness ..." Listening to that I must admit I feel very much like Pooh bear ...
Found the same break-in as Simon (funnily enough, I used the same colours the opposite way round) and then saw a bit of logic which Simon missed... As soon as you place the 5 in the middle (at 18:00 in the video), you get a 38 pair in column 6 in the central box. This is because in column 4, the numbers 3 and 8 have to be in one of the green squares. Then, once you rule out the 4s from r5c4 and r5c6 (at 19:40), you can place the 4 in the central box by the same logic (4s in row 4 have to be in one of the red squares). After that, I got stuck and needed help from the video to get me back on track. Brilliant puzzle and indeed very hard!
A month ago I hadn't done a sudoku in years. Now I'm doing sudokus and watching your videos all the time. Thank you Simon. I've learned killer sudokus thanks to you and they're so much fun!
Beautiful puzzle! One of the things I love most about watching Simon solve these is that he's able to teach me techniques I would never have thought of. I was quite happy with the progress I was able to make after Simon pointed out the geometry. Simon, I had tremendous sympathy for you as you repeatedly failed to notice the 8 forced into R4C1. It seems to be consistent that you don't really trust your corner pencil marks - the "679" that you placed in R4C4, even though you had 6's corner-penciled into Row 5 in Box 5, the "179" that you placed in R3C9 even though you had 7's corner-penciled into Column 8 in Box 3, etc. I wonder if you've partly trained yourself to ignore the corner pencil marks because you so often leave them in even after placing the real digit in the box.
I don't know if it's helpful to the solve, but when mentioning Phistomefel, there was a clever equivalence that the 4 Phistomefel corners are equivalent to the 4 unshaded 2x2 boxes that got cancelled in your original purple/green set theory due to the extra region that was created instead of using box 5 as the extra digits 1-9. This might be why the puzzle is called X.
When Simon was stuck at the end and apologizing, I noticed that he had almost all of the Green and Purple squares filled in. Since he knew all the digits in those colors, he knew which digits the remaining cells could've been. Combined with Sudoku, I bet he could've gotten all those digits right away. I know he would've gotten at least one digit because I saw one green cell with two center marks, one of which was impossible from the green logic.
I've had this puzzle open for several days now, occasionally staring at it, trying to figure out a break in and getting nowhere. I'm usually too stubborn to give up and watch the video, but eventually it got unbearable and I gave in. 5 and a half minutes in, Simon started highlighting rows and I managed to at least figure out on my own where he was going with it, paused the video and finally smashed through this cursed thing. Feeling pretty good about myself now even if I did need a nudge in the right direction.
I did it in 26 minutes... on the third try using information from my first 2 tries spending over an hour on each. I love how Simon is able to both understand and explain the geometry in about the first 5 minutes, when that part took me about an hour of messy cell-gebra.
Thanks for your awesome videos. Most of the time I have to watch them twice a day coz I normally watch them to fall asleep but in the morning I want to know how you solved the puzzles👍🏼 Ceep on Cracking 😘
I went on a wild goose chase of using the circle pairs to eliminate numbers from rows/columns trying to find a pattern for like 20 minutes before giving up and watching. As soon as Simon layed out the purple and green equivalency, something clicked in my head so I opened up notepad and made that discovery that the green/purple circles together revealed exactly all 20 digits that could go in each purple and green and went on to solve it (albeit slower than Simon as usual lol). This is probably the closest I've been to solving one of the >1 hour long video sudokus without any hints, I feel like I both have made a lot of progress while still demonstrating how much more I could improve (especially with break ins). Regardless, it was still very satisfying near the end of my solve being able to drop in all of the 12 pairs and 79 pairs that had been piling up.
I would never have got that break in, but I did quite enjoy being about 10mins ahead of Simon on a fair number of deductions. Did a great job battling through it.
This is maybe the first time I’ve got frustrated - the last 20 minutes would have been much more straightforward if Simon had remembered the number distributions in the colours! To be fair, I could have stared at the blank puzzle for days and not broken in.
You deduced much earlier that you can't have a 1 next to the 38 circle because there are only three 1s in green, but left it as an option there anyway.
At 5:17, when Simon said, "It must be geometry madness," I closed the other tab (the one with the puzzle open on it), and resigned myself to the fact that today's puzzle was one I was going to watch, and not one I was going to solve.
This is one I decided to live vicariously through Simon. Some puzzles are nice outings where you get a lot of quick satisfying deductions that lead you to a conclusion like that wonderful kakuro yesterday and some puzzles make you peel back the veil and roll for SAN loss for your digits. This is the latter. Well done to Simon and all the others for taking this on.
I think the ending might have been a little smoother if Simon had noticed at 54:05 when he pencil marked R2C4 that the two 79 squares in R3C6 and R4C4 must be different digits to not break the 479 quadruple in those rows, and they both see R2C4 so it can only be 6.
54:26 This just goes to show that CTC is more than just a sudoku channel, it also improves our vocabulary. This is the first time I’ve heard the word “recalcitrant” which means uncooperative. Good to see uncommon words being used. Thank you Simon!
Really interesting solve to watch - something I did notice during the 'shout at the screen' stage of the solve was that you seemed to forget your key deduction from the break-in a few times - That the colour with the larger amount of each digit couldn't have more of that digit. Which I suspect is a property of how long the solve took more than anything.
Definitely not a waste of my time to watch you solve. It's actually very reassuring to see you hesitate every now and then (that's what you call grinding to a halt and being stumped -- for me being stumped is staring at the screen for ten solid minutes). I felt like there were portions of this puzzle that I raced through that you plodded, but you STILL solved in half my time overall. I did not think the set theory break-in was telegraphed, but once I got that I felt the eventual solve was never in doubt.
At 51:48 Simon placed an 8 in R3C7, which he could have done at 48:40, when he pencil marked 8's in box 3. He missed that he couldn't add any more 8's in the green squares. Similarly he could have put 1 in R3C3, because the 1's in boxes 4 and 7 forced a 1 in box 1 column 3, where it couldn't be in the green cells.
_"Why is it called X?"_ => because there is an X-tra set of 1-9? It seems awfully weird to me that you're apologizing for "wasting time". If I had tried to solve this on my own, *that* would have chewed up at least a week of my time. I didn't even *attempt* to do this myself, but even just watching it I had to pause the video a few times just to give my brain a rest so I could keep up with the logic which you were figuring out in a live solve! Very impressive puzzle, and impressive solve, IMO!
I always love with the long puzzles how Simon tends to find the most important clue in the beginning then periodically forget it throughout the puzzle (understandably so). We knew the exact composition of Purple/Green which means we get a lot of somewhat naked singles by virtue that they can't be in the colored portions of the grid. I wrote down the composition at the start of this one just so I could keep track and with 8's and 6's it kept being a thing.
i love how Simon figures something out, explains it enthusiastically for like 2-3 minutes, shows the conclusion and tops it off with "which does nothing!" lolol see example 38:08 and the famous line at 39:57
Really loved this solve! I think trying to keep the 20 numbers that green and purple had to have might have helped juggle those numbers a bit more (for example, I think it puts 1 into box 1 a bit quicker when you realise there are already three 1s locked into the green, so it could only be in r3c3) but I think it's a testament to Simon's incredible ability that he conquered this puzzle so effectively. Bravo!
What a stunning construction. The way the quads worked together to completely define the composition of both sets was brilliant (I'm pretty certain that was the intended break-in). For a moment, I thought this would make the rest easy, but that notion was quickly dispelled. I think Simon was hampered early on by not spotting that the 38/138 quads created a 38 pair in the right hand corners of box 5. This meant that the 3 on the 123 quad was in C7. Similarly, the 456/479 quads pushed 4 into R6C4. This provided quite a bit more traction than Simon was working with. By the time he found the 38 pair, it was too late, which is why it seemed useless. When Simon corner-marked 8s in box 7, C3, he failed to notice that the 8 quad now had to be in C2, which resolved the horizontal kropkis. This is Simon's biggest failing - not fully checking the results of deductions. He usually checks deduction A, which gives him B, but then he never checks what B gives him, and C is often crucial. In a puzzle like this, where you have to fight for every minor gain, this is even more important. He later corner-marked 1s in C3 box 1, but forgot that the 1 couldn't go in the green. This placed the 1, and also placed a 2 in R3C8, fixing the other 3 cells of the quad as 479. Since R3C9 couldn't be 4 or 7, this was 9, giving a 47 pair in R4. I found it useful also to work out the composition of the 16 cells that were removed from the sets at the start. This all made it a bit easier than Simon found it, but it was still by no means a pushover. I can't remember who rated it 3, but perhaps he should put up a video talking us through his solve. Maybe we missed some magic key that made it fall apart.
Great puzzle as always. I got through the late solve much faster than Simon did, which is very unusual for me; I think what made the difference was that I wrote down what digits the purple and green 2x2 boxes each needed (and therefore, which digits could NOT be added into them). Made the eliminations much easier.
Excellent solve, Simon! Your ankles thank you. I couldn't get the break-in, but super proud of figuring it out after you provided me with the idea. Absolutely didn't solve it in 30m.
I used your guidance stepwise, after testing out some excessive pencil marking approaches. After you marked the 8 regions plus +, I paused the video and had the idea to count number occurences myself, and came to the right conclusion from there, too. But in the central box, there was no 38 (@ 18:10) and this pair could only go into the corners, and since there are two circles (38) and (138) looking at column 3 and 4, they had to go to column 6 right from the beginning. Which made the 4 in column 4 (still box 5) a pretty easy find. But later I got stuck and needed the idea of the 5 in phistomefels regions of box 1 and 3. At some point in time, I had an original idea: There was no 3 in the purple 4x4 regions, only one in the vertical plus part, so there where 2 threes to place, but ruled out from 3 regions, which forced both 3s in the same region. Still 161 minutes.
25:45 "..pick digits..where we do know where they go in the Greens and the Purples and then...look at other places affected by the Greens and Purples and where we know those digits can't go, to force those digits into places we never knew they were in the first place.." The stress of this solve has Simon channelling Alice in Wonderland...
@@Varksterable Alright, for you: Twas bobbins, and the palindrome Did gyre and gimble in the cage All jolly were the kropki dots And Phistomefel outgrabe
No need to apologize, Simon. I think it's much easier to spot things watching someone else than it is when you're doing puzzles yourself. It was amusing/frustrating to see you finally spot the 8's noted in box seven to give you the 8 in box one, only to overlook those same notated 8's in box seven then giving you an 8 in box 4. A lot of us wouldn't get far enough to see these things without your notes and explanations, though. So, well done. Enjoyable to watch.
If you've done the Phistomefel ring logic, you've realized that the 2x2 'outer boxes' and the 2x2 'inner boxes' contain the same digits and combined with 5 they make X , also i think it would give you some more digits, there was something I saw with 8s while watching the video... however very good puzzle and very good solve.
I make no claim to having a better solution than what Simon showed. However, I think in a puzzle like this, where every indicator is that it will be brutally hard, a play aid should be used. Here, it will dramatically reduce the solve time. The first step is to recognize the two subsets (green/purple). This step is entirely beyond me, although Simon gets there almost immediately. However, having started on that path, it should be followed to its logical conclusion, which is obtained by simply counting the missing digits. If you do this, you quickly realize that you have to add 1: 2 -> P 2: 2 -> P 3: 3 -> P 4: 3 -> G 5: none 6: 2 -> G 7: 2 -> G 8: 2 -> P 9: 2 -> G Summary: you have to add 9 digits to each of the purple and green subsets, and that count is exactly right, so you're on the right track. Now write that chart down, and keep referring to it, otherwise you will have to rederive it multiple times, or memorize it. Right away, you should be able to see that the cross in the middle needs the two quadruples, 1238 and 4679, with 5 in the middle. Simon does this between 7:15 and 18:15. Just by using the play aid, you should be able to knock about 5 min off that time. To continue, refer to the chart again, and ask the question "What can I add to the two subsets?" You can see that you can't add ANY 5s, so that's a good place to start. This quickly gives 3 more digits, and a bunch of pencil marks. Ask the same question about 6s, and that gives 2 more digits. You can also bifurcate now by trying a 1 in r5c9 to get a couple more digits, but that's not necessary. Anyway, this takes you through to about 30:30 of the video, and should save at least another 5 min. After that, Simon's solution is probably the most efficient one, except that the play aid will still prove useful as following. You have already added one of each digit to the g/p subsets, and you should keep track of each new digit added. As a specific example of the use of the play aid in the later game, look at the position at 28:05. Checking the play aid, you see that you can't add a 6 to the purple subset. Therefore, in box 6, the only place 6 can go is r4c7. The next 6 can be found in box 9 beside the single-digit circle. A general example of the use of the play aid can be seen at 56:15. At this stage of the game, who will remember that you can't add a 1 to the green subset?
Crazy puzzle. Simon, when you grind to a halt, think back to the last digit you placed in the grid. It's almost always there where your ADHD took you off on an amazing and fascinating tangent.
I think there maybe was a smoother way to coninue after the break-in: Simon seemed to have abandoned those sets after the break-in, but they were still useful, e.g. to place a 1 in box 1.
Yes, I do wish he had written down the numbers that Green and Purple were made of, and looked at it occasionally. I would have pencil marked everything and then started to take them away as needed. But that would be assuming that I could get that far by myself... and I am not there yet.
And also please don’t apologize too much.. We know it’s a hard puzzle and seeing you solve a difficult puzzle while trying to explain to us how the logic goes is an incredible feat.
24:40 (still watching) In the central square, we still need 3,4,8 and one of 7 or 9 in the corner. But 3 and 8 have to be a pair in column 6, and the 4 has to be in r6c4 because of that. I wonder if Simon will see that at around 24:45? or in ten minutes? 39:12, almost 15 minutes. And boy was that explanation complex.
39:48 Could have seen the 38-pair in the center box already at 20:50, if you notice that "green" 3s and 8s in columns 3 and 4 are used up. Similarly "pink" 4s in rows 3 and 4 is used up leaving only one position for the 4 in the center box.
47:00 Once you know R3C6 is a 79, you know that it can't be the same as R4C4 via the purple 479 circled cells in box 3 and 6 if you think about it. So if you look in box 5 that 79 must go in R4C5! That means the 6 is resolved in box 5 (R5C6) and box 8 and in box 7 then box 1. And a whole bunch of other stuff too. F.e: 68 pair in box 2 etc.... I thought that was the next step but I guess you dont necessarily need to see that for solving the puzzle.
1:08:35 If you have to sneeze at a very important moment (like 1 minute before finishing your video), just put your tongue to your palate, and you won't sneeze!
I love it when I'm internally screaming, when you see a digit for half an hour, and it comes back around to it xD The 8s being disambiguated on the left side, imo, helped get things going.
Incredible puzzle, great solve, I would have never been able to solve it myself. I'm sure somebody has already pointed it out, but you could have pinned down the 1 in Box 1 a lot sooner if you had remembered that all of the 1s in green were accounted for, so it couldn't have appeared in green. I think it would have helped you nail down Box 3 sooner.
When you were getting closer to the end you could have save a few minutes, by putting 1 in row 3 column 3 , cuz you concluded that no more ones in the green cells as they are only 3 ones and you got them 36:40 & 56:10.. this kept me wondering how did you miss that 😲. Never mind, You have done a great work👌 , l enjoy watching you almost every day cracking difficult sudoku.. thank you for time 😍
Somewhere close to 30:00, Simon, you could have placed a 1 at r3c3 because, no more 1s on green. Shortly after, you could have placed the 6 at r8c8. Afterward, it would have helped you progress in box 3 , particularly when you see 7 could not go in r3c9 because of the 7 in the quad inside box 3. That being said, it would have taken me at least two hours+ to figure out that green and purple had the same digits so ... i still can't solve a puzzle in less than twice the time it takes you!
52:38 Simon can deduce that 3 in box 6 has to be on row 6, because if it joins the 4s on row 4 then it will make a 79 pair above for the circle clue which will break the 79 in box 2. That then places a 3 in box 5
At 16:49. Simon has a 3-8 in r3c5. The quad 8 clue in box 1 pushes the 8 in column 4 into box 2, resolving that 3-8. Simon does some genius logic from 38:50 onwards to put a 38 pair in box 5, still ignoring that logic that was available just after the break in. It finally resolves at 42:04 but not through the easy way. Sorry to give you this comment Simon, but that 3-8 thing did my head in.
Sorry, I don't think that's quite right. The 8 quad in box 1 doesn't push the 8 into column 4 in box 2, since an 8 in r2c3 could satisfy both the 8 quad clue and the 3,8 quad clue simultaneously.
Aww Simon you are too cute and funny. Your phrases crack me up and make watching these so much more enjoyable added to the pure pleasure of your incredible logic and the magic of sudoku. My new favourite channel
Wow!! Really quite hard, but i loved it. I don't think i've seen the combination of quadruples with SET before, that's marvelous! And i find it fascinating how you need to care more about which "purple digits" _can't_ be in certain sections of purple, than where the "green digits" have to go in purple. It tripped me up a good couple times cause i'm not used to thinking like that.
The 1 in box one could've been placed much earlier if Simon hadn't forgotten his earlier logic that he already knew that there wasn't another 1 in the green areas.
A fairly easy start would have been to fully pencilmark box 5 after limiting the arms of the "extra region". The two left green quadruples forces 3-8 as a pair in R2C6 and R6C6. This leave only one place for 4 in box 5. After placing the 3 5s in the Phistomefel ring, an easy deduction would be that R6C1-3 must be 6-7-9, as you cannot put 4, 6, 7 or 9 in a purple quadruple unless it is already there by the given clue, which affects the lower bottom purple quadruple and thereby forces the 6-7-9 triple in box 4.
That was a really great puzzle! When you said "it's magic", cracked me up xD Great explaining as usual, though I will never be as patient as you, Simon (:
8 quadruple in box 1 could have been used to resolve the 3/8 in col 5 as soon as they were placed. Also fascinating to watch Simon solve it without leveraging the impact of the 7 quadruple in box 3 on the 479 quadruple to force a 7 into col 6. That said, that's the only logic I solved for myself in the whole puzzle lol. Loved the solve!
I consider myself relatively intelligent, or at least conversationally so. The mind-boggling thing about these videos of more difficult puzzles is catching a glimpse into the minds of both setters and solvers who are far more intelligent than me, at least in the types of intelligence needed to set and solve these puzzles. It reminds me of finding an old pulp fiction sci-fi book and, upon reading it, wondering at the madness of the mind that created it, except instead of creative madness, it's a type of intelligence that I can only marvel at. Sure, I guess practice is part of what makes someone so good at setting and at solving, but that doesn't change how impressive it is, just like seeing a magic trick is no less impressive even if you know that there had to be a trick, like some sleight of hand, that made it possible. I'll make a cup of coffee before carrying on watching the rest of this, as I think I might need it.
That was phenomenal. While watching I tried to follow along and spot things that could be done next. The majority of the time I found something before Simon I later found out I made a mistake, so I was quite content just watching and not trying it myself.
It amazes me that brains are wired so differently in different people. I can't come close to solving most of these puzzles, but I have read many comments from people in addition to Simon who can't see why the puzzle is called X. The origin of the name is clear if you stop thinking about sudoku and think of it as a connect the dots puzzle. Just put your pencil on a dot and draw lines to adjacent dots until you get back to the starting dot.
Man this one took me forever. Eventually I was able to break in by coloring Rows 3-7 green, cols 3-7 yellow, clearing the common cells, and noting the remaining 20 yellow cells and 20 green cells had to match. From there I was able to determine the exact quantities of each of the digits 1-9 in the sets (one 5, three of each digits 1, 3, and 4, and 2 of each of the remaining 5 digits. ) Some Phil. Ring magic, circle hints, and traditional sudoku techs allowed me to fill in about 7 cells and isolate candidates to particular rows, columns, or regions, but I eventually hit a brick wall. ... and then I realized I could repeat my original technique, this time with cols 3, 4, 6, 7 being red, and rows 3, 4, 6, 7 being purple. That allowed me to fill in the 5 in the middle, eliminate candidates from the white dots, create a 3-8 pair, and the rest sort of fell into place after a few hours of further work. Brutal puzzle.
Congratulations Simon, another lovely solve! I'm glad to see this puzzle on the channel, because it showcases a technique that I think is easier to figure out on one's own through example than to have explained, namely that of Multi-Sector Locked Sets. I think a lot of people get scared away by the name and the notion that it's some super hyper advanced classic technique. That's why I'm so happy to hear comments from people who had never seen the idea before, but were still able to develop it from scratch in order to solve this puzzle. Indeed, one of the reasons I made this puzzle was to help solidify my own understanding.
You're also absolutely right that someone could blow through this puzzle in half an hour if they got lucky enough. After entering all the eliminations from MSLS (and there are a lot), a solver will fly through with mostly hidden singles and pointing pairs. I tried to make the puzzle not too hard after the break-in, which is why I think so many people were able to grind through it, but it still ended up being quite the beastie. As you noticed, it's not quite in my style to include unnecessary clues -- partly because I'm always scared that they will shortcut cool logic.
The name of this puzzle is actually not X, but ✖ (the thick multiplication symbol), due to the outline roughly formed by the given clues. There is no inherently logical reason the single-digit quads all end up in the centers of their boxes. Rather, after all the main logic is exhausted, I was left with the task of disambiguating a lot of deadly pairs around the edges of the grid, with almost no information in the "phisto" 2x2s. Quads that alter those cells was therefore the natural choice. Speaking of the phisto trick, I think this might be the third puzzle that has been featured where it unintentionally shows up as a red herring, which I find rather amusing.
Gliperal...another fascinating, wonderful puzzle from you. Your logic and techniques in setting is extraordinary. Always thrilled and excited to try one of your puzzles.
Look forward to the next one from you.
Keep on setting and thank you again for this beauty!!
Thanks for your insights!
I love that you comment with your thoughts and insights, as well as answering questions from the video. I would love it if more setters would do this too!
Please don't overlook this fact, Simon: A lot of us are only able to spot the things you missed because you've been so damn good at teaching us.
I spot a load of things he misses, and get frustrated. Then realise I'm actually wrong... :-/
i could never get to the point in the solve where im seeing the things he's missing, but once he gets there i see it, so i never feel frustrated cause i know i can only spot the things when he does the first 20 minutes of solving XD
@@alexgordon7312 In all honesty, it's quite a good moment for self improvement. Learning to feel better about these things. It's so trivial in the grand scheme, or even compared to most trivial schemes...
Don't know about you, but I didn't realise that the sum of any row, column, or box of the grid always equals 45 until he taught me. Sorry... that should have come with a spoiler alert. Too late now! 😂
Underrated comment
I'm starting to really, really appreciate the way Simon explains each and every time how to follow his reasoning. It meant when I was new I could jump right in.
It helps me when I'm doing puzzles, I find myself asking the same questions Simon asks when he's solving one of these.
I started watching the channel in January, and I largely started with the backlog. I actually really hate the overexplaining, personally. As a new viewer I felt much more intrigued when I had to think a little bit to understand. Obviously some logic merits explanation, but I think the current explanation level just leads to passive viewing, and longer videos.
@@MineRoyale. Long comment, TL;DR at the end…
that is the Problem of all channels line this: we, as experienced viewers, don‘t need things like Phistomephel explained for the 20th time, or an X-wing, swordfish or the sudoku secret.
However, any new viewer would need it, and not all viewers start with the backlog.
So, as a creator, you have to find the sweet spot between several factors: 1, you want to make entertaining videos; 2, you want to satisfy your existing community; 3, you want to attract new people and 4, (a bit special to the sort of content on ctc, as it is highly focused on Simon and Mark), you need to be as natural and authentic as possible.
I, even though I don’t need those explanations over and over, don‘t mind, because Simon just seems to explain automatically and it sometimes even helps him to spot another bit of logic.
Quite some time ago, I suggested that Simon just records a series of very short instructional videos explaining recurring techniques and just link them in every video needed. My rationale was the same as yours. By now, I‘m not that convinced, because it‘s just authentic Simon.
If you don‘t like excessive explanation, just watch Mark‘s videos.
I, personally, mainly (if not exclusively) watch Simon. His enthusiasm about small bits of logic, his little imperfections, his whole personality simply grew on me, whilst Mark is a bit too perfect, brilliant and fast for me to enjoy a video.
TL;DR: You have a point, but not really due to the way UA-cam works.
I'm curious how often you use 'the secret'. I use it almost daily.
The truth is, almost no one starts with the backlog, and I can't blame them. I don't mind the repetitive explanations, personally. It's easy to skip 10, 20 or 30s ahead on youtube.
I have been a fan of CTC for over a year now, but the past few days the channel has been so helpful for me. I had my baby a week ago and yesterday i was diagnosed with preeclampsia. I have been stuck in the hospital alone while my husband is at home caring for our kids.
CTC has really helped cure my boredom and loneliness while i try to stabilize and get over this hurdle. So many thanks, to you and Mark. ❤️
Get well soon 😊
I hope you feel better soon!
My mum had that when I was born. Spent ten days in a coma. Get well soon.
@Andy Kay @D4r4 Butler @Andrew Grant thank you for the well wishes!
Congrats on the new arrival Kayla. I hope your health improves quickly and you can get home to your family. All the best from Mark and me.
It's the year 2022, CTC just released a 3 hour long video titled: A short one for a change.
@@jpryan90 Or that first one where no digits were provided and Simon thought he was getting trolled.
@@myles6557 now it seems that no digit puzzles have an even harder break in then 1-5 given digit puzzles
@@jpryan90 Tatooine Sunset had 21 given digits. And only classic rules. Yet that was a monstorous hard puzzle and break in.
Horses for courses.
It's astonishing to me how many different setters and approaches to setting (both for insanely hard, and 'approachable' but still amazingly beautiful puzzles) have developed over such a short space of time.
I wonder if the people who came up with the concept of the first sudoku are looking on and thinking, "Bobbins! What the heck did we unleash into the world?"
Simon: uses advanced set theory & words like recalcitrant, solves puzzle. doesn’t see why it’s called ‘X’
Me: can’t make heads or tails of puzzle, fails miserably. Has to google recalcitrant. Sees the X shape immediately
We are two very different people
I was also thinking X being the Roman numeral for ten as Simon points out, it could be referring to the tenth “region” of the sudoku
Andrew's Law: The harder the sudoku, the greater the chance that the centre square is 5.
haha
Well it's a theory, not a Law.
But Law sounds better tbh.
@@andrewflynn113 That’s why they change theory to theorem. Andrews theorem sounds pretty good ngl
@@esperiandawn155 oh yea that's lit tbh. I like that.
@@andrewflynn113 No, it’s a law. It’s a summarized observation, not an explanation of why this is. Andrew’s Theory of Sudoku Difficulty would be why 5 as the center square makes it hard.
I am watching a man solving puzzles on the internet for hours an he is apologizing to me for wasting my time? Quite astonishing, I must say.
This is one of those puzzles that I was content with watching you and avoiding the migraine. As always, you are an absolute wizard.
37:20 My scream of the night: the 1 in column 3 wants so badly to be placed in row 3. Simon somehow has abandoned his earlier quest for 'saturated' digits. The full quorum of 1s in the green has been accounted for, so once the 1s in the other boxes rule out columns 1 & 2 in box 1, the only non-green cell in column 3 is the only place 1 can go in box 1. This relatively easy low-hanging fruit remains outside Simon's cortex for the next 20+ minutes.
I hasten to add that this is ultra-cheap kibitzing. I completely and utterly stand in constant amazement of the brains at work on CtC. I am just *also* amazed at the sort of blindness these brains suffer from. The lesson assuredly is that none of us should be too sure she sees the truth, the whole truth and nothing but the truth.
Next time you have jury duty, this is something to remember.
[edit]
58:57 Yes, Simon has forgotten that he has been sweating blood to ascertain the full complement of all digits in green and purple. He hasn't leveraged that treasure to account for digits that cannot any longer appear in colours because their quota has been spoken for. At this stage that *must* be the vice that cracks the puzzle's nut.
[further edit]
*I cannot believe it* !!! Simon found logic that avoided using the 'full quota' logic. How differently wired is this man. I love his brain, every fricking synapse of it.
Agree with everything you said here. I'm reading a few more comments saying the same and I left a similar comment. Once you have the full quota of numbers, the puzzle is actually quite easy. I have no idea why Simon had so much trouble with it but his brain is just not wired correctly for this type of puzzle. The way he solved the 8's for example blew my mind. I'd ask Simon to go rewatch that part because I think even he would admit he wasn't in top form on that one. You can't put 8's in the green unless the circle has an 8. But no... that's too easy for box 3. Let's go through all sorts of other logic to get that 8. lol
I just had to like and comment so he reads this...
@@blacksarlacc91 Who is the he in your comment?
@@amoswittenbergsmusings Simon
This might be my best solve ever.
Finished in a time of 1:03:07, and successfully used 'set theory' along the way without guessing. I am *ecstatic* at how I did on this one.
Fantastic puzzle!
Legend
I wish I was this good at these solves 😂 good job!
@@joshuapr999 Well, I completely struck out on the 'Mark' puzzle of the next day. I'm not always so good at these.
@@Coyotek4 Hey, coming from someone who really cant' get very far in most of these puzzles, you've done awesome anyways! Also, being that far along to be able to do this puzzle that quickly, you'll get those other ones no worries
I really do wish Simon knew just how much we appreciate him. When I look at these videos it feels like sitting down with a friend to solve some puzzles. His company is a huge part of the fun. So each time he apologizes for “missing something” I want to smack him because it’s not about the efficiency. It’s about the fun, you lovable fool ❤️
Hello Simon, it may have been stream of consciousness or frustration at the puzzle, but please don't apologise for taking a while with these difficult puzzles. It takes as long as it takes and if we try to force it, it simply takes longer.
simon stopped checking what numbers could go on green and purple after a while. for once i spotted quite a few numbers faster than him :D
The 679 in green in the row 5 left 6789 as the last four green and finishing the rest of column 3 was a pushover.
i know what you mean, i spotted the fact that 1 could only be in one spot in column three at least 20 minutes before simon because i kept doublechecking the colours
Lovely! Sorry about the misleading evaluation of 3-4 stars! I was too excited after the early solve, but this sudoku is genuinely difficult. Every deduction was challenging
If its THAT diffecult its more fun to watch someone solve it instead of trying it yourself, because otherwise I would go crazy... And it would take like 6 hours of hard brainstorming
I'm not sure I'd have solved it in 6 days...
@@theunwelcome well, you should take breaks when trying a hard puzzle above your normal skill level. I find that it works surprisingly well when you get back at it the next day. So in realtime I would spend 6 hours, sure.. But over the span of 2 days f.e.
Knowing when to stop when you're stuck is quite important for the time consumption that these puzzles tend to have.
@@ocaly Taking notes also helps. Especially when you need to take breaks.
@@57thorns I'm always amazed by how much Simon and Mark can hold in their heads. I'm often scribbling away.
You know Simon is stressed when he fails to make his “3 in the corner” joke lol. Well done sir!
"I'm so sorry I've wasted all your time" I'm not a solver or a setter but I watch someone solve Sudoku on UA-cam. I spend my time the way I want to. Keep up the great work!
Another brilliant solve, Simon! I couldn't even get started, then I saw you draw your green and purple bars, paused the video, and I was off to the races! Two things I did slightly differently. First was to notice that the purple and green barely intersect (one 1 and the 5), and that the purple had the 4679's and the green the 1238's. Knowing this, it was clear that the green cells in row 5 had to come from the 4679 set and needed to all be different because they shared the row, so...4679. Likewise the 1238 in purple's column 5. After that I was focused on placing the remaining 6679 from the purple in the green 2x2s and the remaining 2338 in the purple 2x2s. That seemed to make keeping track of things easier. The second thing I did was make a third set of the four central 2x2s, which had a full set of 1-9, plus 2556789. That helped push me to look for places to put all those 5s!
Nevertheless, my solve was not faster, and was not without an error and restart about half way through. It continues to amaze me that you can keep those sets straight in your head, while filming and narrating your solve. Remarkable.
47:20 "There must be a digit I can place" ... ignores the 6 from the clue you could just write in, deduces an 8 !
And then ignores the 8 clue in Box 1 forced into column 2.
Those single digit clues look so useless but sit the smirking, holding the key!
I believe it is called "X" because when you connect the circle clues with lines you get an outline of the letter "X."
I come here to learn how to work through logic and deductions, so its never a waste of time to hear how you go through all your ideas on how to do it. The ones that don't pan out are still interesting and useful! Thank you!
I just followed along, here and there stopping the video to attempt a stint on my own.
And yes! I found the digit in the center, and all the domino mirrors radiating rectangularly away from the center.
Thank you very much for an insanely beautiful puzzle, Gliperal - and an extremely educational video, Simon!
Quote of the day:
25:59 "... And sort of ... then look at other places that are affected by the greens and the purples and where we know those digits can't go to force those digits onto places where we never knew those digits were in the first place ... that is a summary of madness ..."
Listening to that I must admit I feel very much like Pooh bear ...
Found the same break-in as Simon (funnily enough, I used the same colours the opposite way round) and then saw a bit of logic which Simon missed... As soon as you place the 5 in the middle (at 18:00 in the video), you get a 38 pair in column 6 in the central box. This is because in column 4, the numbers 3 and 8 have to be in one of the green squares. Then, once you rule out the 4s from r5c4 and r5c6 (at 19:40), you can place the 4 in the central box by the same logic (4s in row 4 have to be in one of the red squares). After that, I got stuck and needed help from the video to get me back on track.
Brilliant puzzle and indeed very hard!
A month ago I hadn't done a sudoku in years. Now I'm doing sudokus and watching your videos all the time. Thank you Simon. I've learned killer sudokus thanks to you and they're so much fun!
Beautiful puzzle! One of the things I love most about watching Simon solve these is that he's able to teach me techniques I would never have thought of. I was quite happy with the progress I was able to make after Simon pointed out the geometry.
Simon, I had tremendous sympathy for you as you repeatedly failed to notice the 8 forced into R4C1. It seems to be consistent that you don't really trust your corner pencil marks - the "679" that you placed in R4C4, even though you had 6's corner-penciled into Row 5 in Box 5, the "179" that you placed in R3C9 even though you had 7's corner-penciled into Column 8 in Box 3, etc. I wonder if you've partly trained yourself to ignore the corner pencil marks because you so often leave them in even after placing the real digit in the box.
I don't know if it's helpful to the solve, but when mentioning Phistomefel, there was a clever equivalence that the 4 Phistomefel corners are equivalent to the 4 unshaded 2x2 boxes that got cancelled in your original purple/green set theory due to the extra region that was created instead of using box 5 as the extra digits 1-9. This might be why the puzzle is called X.
Plum
Plumber
Plumbest
Best plum
When Simon was stuck at the end and apologizing, I noticed that he had almost all of the Green and Purple squares filled in. Since he knew all the digits in those colors, he knew which digits the remaining cells could've been. Combined with Sudoku, I bet he could've gotten all those digits right away. I know he would've gotten at least one digit because I saw one green cell with two center marks, one of which was impossible from the green logic.
There were many instances of this
I've had this puzzle open for several days now, occasionally staring at it, trying to figure out a break in and getting nowhere. I'm usually too stubborn to give up and watch the video, but eventually it got unbearable and I gave in. 5 and a half minutes in, Simon started highlighting rows and I managed to at least figure out on my own where he was going with it, paused the video and finally smashed through this cursed thing. Feeling pretty good about myself now even if I did need a nudge in the right direction.
I did it in 26 minutes... on the third try using information from my first 2 tries spending over an hour on each.
I love how Simon is able to both understand and explain the geometry in about the first 5 minutes, when that part took me about an hour of messy cell-gebra.
Thanks for your awesome videos. Most of the time I have to watch them twice a day coz I normally watch them to fall asleep but in the morning I want to know how you solved the puzzles👍🏼
Ceep on Cracking 😘
I went on a wild goose chase of using the circle pairs to eliminate numbers from rows/columns trying to find a pattern for like 20 minutes before giving up and watching. As soon as Simon layed out the purple and green equivalency, something clicked in my head so I opened up notepad and made that discovery that the green/purple circles together revealed exactly all 20 digits that could go in each purple and green and went on to solve it (albeit slower than Simon as usual lol).
This is probably the closest I've been to solving one of the >1 hour long video sudokus without any hints, I feel like I both have made a lot of progress while still demonstrating how much more I could improve (especially with break ins). Regardless, it was still very satisfying near the end of my solve being able to drop in all of the 12 pairs and 79 pairs that had been piling up.
I would never have got that break in, but I did quite enjoy being about 10mins ahead of Simon on a fair number of deductions.
Did a great job battling through it.
Simon: Sorry for wasting so much of your time.
Me: I wish you could have wasted more of my time.
i am honest. seeing you how you solve soduko is so relaxing that i fell asleep from it yesterday. now i try to look at the solution again
I love puzzles that take Simon a good hour to solve. Makes him seem more human and less math wizard. Great job!^^
This is maybe the first time I’ve got frustrated - the last 20 minutes would have been much more straightforward if Simon had remembered the number distributions in the colours! To be fair, I could have stared at the blank puzzle for days and not broken in.
I'm just about following the geometry but wouldn't dare attempt this myself!
You deduced much earlier that you can't have a 1 next to the 38 circle because there are only three 1s in green, but left it as an option there anyway.
At 5:17, when Simon said, "It must be geometry madness," I closed the other tab (the one with the puzzle open on it), and resigned myself to the fact that today's puzzle was one I was going to watch, and not one I was going to solve.
This is one I decided to live vicariously through Simon.
Some puzzles are nice outings where you get a lot of quick satisfying deductions that lead you to a conclusion like that wonderful kakuro yesterday and some puzzles make you peel back the veil and roll for SAN loss for your digits. This is the latter.
Well done to Simon and all the others for taking this on.
I think the ending might have been a little smoother if Simon had noticed at 54:05 when he pencil marked R2C4 that the two 79 squares in R3C6 and R4C4 must be different digits to not break the 479 quadruple in those rows, and they both see R2C4 so it can only be 6.
Me when I see the clues: I suspect colours will be involved today
54:26 This just goes to show that CTC is more than just a sudoku channel, it also improves our vocabulary. This is the first time I’ve heard the word “recalcitrant” which means uncooperative. Good to see uncommon words being used. Thank you Simon!
You, sir, are an awesome wizard visiting from a logically superior parallel universe. We mere mortals salute you. Well done!
Really interesting solve to watch - something I did notice during the 'shout at the screen' stage of the solve was that you seemed to forget your key deduction from the break-in a few times - That the colour with the larger amount of each digit couldn't have more of that digit. Which I suspect is a property of how long the solve took more than anything.
Definitely not a waste of my time to watch you solve. It's actually very reassuring to see you hesitate every now and then (that's what you call grinding to a halt and being stumped -- for me being stumped is staring at the screen for ten solid minutes). I felt like there were portions of this puzzle that I raced through that you plodded, but you STILL solved in half my time overall. I did not think the set theory break-in was telegraphed, but once I got that I felt the eventual solve was never in doubt.
At 51:48 Simon placed an 8 in R3C7, which he could have done at 48:40, when he pencil marked 8's in box 3. He missed that he couldn't add any more 8's in the green squares. Similarly he could have put 1 in R3C3, because the 1's in boxes 4 and 7 forced a 1 in box 1 column 3, where it couldn't be in the green cells.
"I know more about you than you think I know." Simon 2021
This may be the most threatening thing he has said so far
@52:45 "It's so strange, you feel you're making real progress and then you find that actually you've hardly done anything."
Tell me about it.
_"Why is it called X?"_ => because there is an X-tra set of 1-9?
It seems awfully weird to me that you're apologizing for "wasting time". If I had tried to solve this on my own, *that* would have chewed up at least a week of my time. I didn't even *attempt* to do this myself, but even just watching it I had to pause the video a few times just to give my brain a rest so I could keep up with the logic which you were figuring out in a live solve!
Very impressive puzzle, and impressive solve, IMO!
I always love with the long puzzles how Simon tends to find the most important clue in the beginning then periodically forget it throughout the puzzle (understandably so). We knew the exact composition of Purple/Green which means we get a lot of somewhat naked singles by virtue that they can't be in the colored portions of the grid. I wrote down the composition at the start of this one just so I could keep track and with 8's and 6's it kept being a thing.
i love how Simon figures something out, explains it enthusiastically for like 2-3 minutes, shows the conclusion and tops it off with "which does nothing!" lolol
see example 38:08
and the famous line at 39:57
A rainy evening with hot cocoa, chocolate, and an 1 hour long CtC video is as perfect as can be in my eyes, and I have all 3!
I liked it before the dislike bot could do anything :) Gliperal is an excellent setter, so this should be awesome!
Really loved this solve! I think trying to keep the 20 numbers that green and purple had to have might have helped juggle those numbers a bit more (for example, I think it puts 1 into box 1 a bit quicker when you realise there are already three 1s locked into the green, so it could only be in r3c3) but I think it's a testament to Simon's incredible ability that he conquered this puzzle so effectively. Bravo!
What a stunning construction. The way the quads worked together to completely define the composition of both sets was brilliant (I'm pretty certain that was the intended break-in). For a moment, I thought this would make the rest easy, but that notion was quickly dispelled.
I think Simon was hampered early on by not spotting that the 38/138 quads created a 38 pair in the right hand corners of box 5. This meant that the 3 on the 123 quad was in C7. Similarly, the 456/479 quads pushed 4 into R6C4. This provided quite a bit more traction than Simon was working with. By the time he found the 38 pair, it was too late, which is why it seemed useless.
When Simon corner-marked 8s in box 7, C3, he failed to notice that the 8 quad now had to be in C2, which resolved the horizontal kropkis. This is Simon's biggest failing - not fully checking the results of deductions. He usually checks deduction A, which gives him B, but then he never checks what B gives him, and C is often crucial. In a puzzle like this, where you have to fight for every minor gain, this is even more important. He later corner-marked 1s in C3 box 1, but forgot that the 1 couldn't go in the green. This placed the 1, and also placed a 2 in R3C8, fixing the other 3 cells of the quad as 479. Since R3C9 couldn't be 4 or 7, this was 9, giving a 47 pair in R4.
I found it useful also to work out the composition of the 16 cells that were removed from the sets at the start.
This all made it a bit easier than Simon found it, but it was still by no means a pushover.
I can't remember who rated it 3, but perhaps he should put up a video talking us through his solve. Maybe we missed some magic key that made it fall apart.
Great puzzle as always. I got through the late solve much faster than Simon did, which is very unusual for me; I think what made the difference was that I wrote down what digits the purple and green 2x2 boxes each needed (and therefore, which digits could NOT be added into them). Made the eliminations much easier.
Excellent solve, Simon! Your ankles thank you.
I couldn't get the break-in, but super proud of figuring it out after you provided me with the idea. Absolutely didn't solve it in 30m.
The application of SET is fascinating! I love it!
I used your guidance stepwise, after testing out some excessive pencil marking approaches. After you marked the 8 regions plus +, I paused the video and had the idea to count number occurences myself, and came to the right conclusion from there, too.
But in the central box, there was no 38 (@ 18:10) and this pair could only go into the corners, and since there are two circles (38) and (138) looking at column 3 and 4, they had to go to column 6 right from the beginning. Which made the 4 in column 4 (still box 5) a pretty easy find.
But later I got stuck and needed the idea of the 5 in phistomefels regions of box 1 and 3.
At some point in time, I had an original idea: There was no 3 in the purple 4x4 regions, only one in the vertical plus part, so there where 2 threes to place, but ruled out from 3 regions, which forced both 3s in the same region.
Still 161 minutes.
25:45 "..pick digits..where we do know where they go in the Greens and the Purples and then...look at other places affected by the Greens and Purples and where we know those digits can't go, to force those digits into places we never knew they were in the first place.." The stress of this solve has Simon channelling Alice in Wonderland...
twas brillig, and the slithy toves
did gyre and gimble in the wabe
all mimsy were the borogoves
and the mome raths outgrabe
@@Felixr2 "Twas bobbins..." FTFY
@@Varksterable Alright, for you:
Twas bobbins, and the palindrome
Did gyre and gimble in the cage
All jolly were the kropki dots
And Phistomefel outgrabe
@@Felixr2 Excellent work. 😁
No need to apologize, Simon. I think it's much easier to spot things watching someone else than it is when you're doing puzzles yourself. It was amusing/frustrating to see you finally spot the 8's noted in box seven to give you the 8 in box one, only to overlook those same notated 8's in box seven then giving you an 8 in box 4. A lot of us wouldn't get far enough to see these things without your notes and explanations, though. So, well done. Enjoyable to watch.
If you've done the Phistomefel ring logic, you've realized that the 2x2 'outer boxes' and the 2x2 'inner boxes' contain the same digits and combined with 5 they make X , also i think it would give you some more digits, there was something I saw with 8s while watching the video... however very good puzzle and very good solve.
I make no claim to having a better solution than what Simon showed. However, I think in a puzzle like this, where every indicator is that it will be brutally hard, a play aid should be used. Here, it will dramatically reduce the solve time.
The first step is to recognize the two subsets (green/purple). This step is entirely beyond me, although Simon gets there almost immediately. However, having started on that path, it should be followed to its logical conclusion, which is obtained by simply counting the missing digits. If you do this, you quickly realize that you have to add
1: 2 -> P
2: 2 -> P
3: 3 -> P
4: 3 -> G
5: none
6: 2 -> G
7: 2 -> G
8: 2 -> P
9: 2 -> G
Summary: you have to add 9 digits to each of the purple and green subsets, and that count is exactly right, so you're on the right track.
Now write that chart down, and keep referring to it, otherwise you will have to rederive it multiple times, or memorize it.
Right away, you should be able to see that the cross in the middle needs the two quadruples, 1238 and 4679, with 5 in the middle.
Simon does this between 7:15 and 18:15. Just by using the play aid, you should be able to knock about 5 min off that time.
To continue, refer to the chart again, and ask the question
"What can I add to the two subsets?" You can see that you can't add ANY 5s, so that's a good place to start. This quickly gives 3 more digits, and a bunch of pencil marks.
Ask the same question about 6s, and that gives 2 more digits.
You can also bifurcate now by trying a 1 in r5c9 to get a couple more digits, but that's not necessary.
Anyway, this takes you through to about 30:30 of the video, and should save at least another 5 min.
After that, Simon's solution is probably the most efficient one, except that the play aid will still prove useful as following. You have already added one of each digit to the g/p subsets, and you should keep track of each new digit added.
As a specific example of the use of the play aid in the later game, look at the position at 28:05. Checking the play aid, you see that you can't add a 6 to the purple subset. Therefore, in box 6, the only place 6 can go is r4c7. The next 6 can be found in box 9 beside the single-digit circle.
A general example of the use of the play aid can be seen at 56:15. At this stage of the game, who will remember that you can't add a 1 to the green subset?
Crazy puzzle. Simon, when you grind to a halt, think back to the last digit you placed in the grid. It's almost always there where your ADHD took you off on an amazing and fascinating tangent.
I think there maybe was a smoother way to coninue after the break-in: Simon seemed to have abandoned those sets after the break-in, but they were still useful, e.g. to place a 1 in box 1.
Yes, I do wish he had written down the numbers that Green and Purple were made of, and looked at it occasionally. I would have pencil marked everything and then started to take them away as needed. But that would be assuming that I could get that far by myself... and I am not there yet.
And also please don’t apologize too much.. We know it’s a hard puzzle and seeing you solve a difficult puzzle while trying to explain to us how the logic goes is an incredible feat.
24:40 (still watching)
In the central square, we still need 3,4,8 and one of 7 or 9 in the corner. But 3 and 8 have to be a pair in column 6, and the 4 has to be in r6c4 because of that.
I wonder if Simon will see that at around 24:45? or in ten minutes?
39:12, almost 15 minutes. And boy was that explanation complex.
Simon forgetting that he has a limit on numbers in Purple/Green is driving me nuts :p
39:48 Could have seen the 38-pair in the center box already at 20:50, if you notice that "green" 3s and 8s in columns 3 and 4 are used up. Similarly "pink" 4s in rows 3 and 4 is used up leaving only one position for the 4 in the center box.
"1s in relation to Green look like they're restricted"
ahhh such a classic cracking the cryptic quote
47:00
Once you know R3C6 is a 79, you know that it can't be the same as R4C4 via the purple 479 circled cells in box 3 and 6 if you think about it.
So if you look in box 5 that 79 must go in R4C5! That means the 6 is resolved in box 5 (R5C6) and box 8 and in box 7 then box 1.
And a whole bunch of other stuff too. F.e: 68 pair in box 2 etc....
I thought that was the next step but I guess you dont necessarily need to see that for solving the puzzle.
1:08:35 If you have to sneeze at a very important moment (like 1 minute before finishing your video), just put your tongue to your palate, and you won't sneeze!
I love it when I'm internally screaming, when you see a digit for half an hour, and it comes back around to it xD
The 8s being disambiguated on the left side, imo, helped get things going.
Incredible puzzle, great solve, I would have never been able to solve it myself. I'm sure somebody has already pointed it out, but you could have pinned down the 1 in Box 1 a lot sooner if you had remembered that all of the 1s in green were accounted for, so it couldn't have appeared in green. I think it would have helped you nail down Box 3 sooner.
I couldn't solve this myself in a million years, but I was screaming when Simon wouldn't see the 8 in Box 4 for minutes on end!
This puzzle (and solve) are truly jaw dropping. One of my favorite videos from the channel!
When you were getting closer to the end you could have save a few minutes, by putting 1 in row 3 column 3 , cuz you concluded that no more ones in the green cells as they are only 3 ones and you got them 36:40 & 56:10.. this kept me wondering how did you miss that 😲.
Never mind, You have done a great work👌 , l enjoy watching you almost every day cracking difficult sudoku.. thank you for time 😍
46:27 finish. This was definitely slow going at first, but at a certain point, things just started clicking and fell into place. Excellent puzzle!
Beautiful puzzle - beautiful solve! Please don't apologize for wasting our time - this was the highlight of my day!
+1
When you see him say this Puzzle is Quite Difficult it is likely an understatement.
Somewhere close to 30:00, Simon, you could have placed a 1 at r3c3 because, no more 1s on green. Shortly after, you could have placed the 6 at r8c8. Afterward, it would have helped you progress in box 3 , particularly when you see 7 could not go in r3c9 because of the 7 in the quad inside box 3. That being said, it would have taken me at least two hours+ to figure out that green and purple had the same digits so ... i still can't solve a puzzle in less than twice the time it takes you!
Genius break-in! Well done Sir! and the invisible 8 in box 1.
52:38 Simon can deduce that 3 in box 6 has to be on row 6, because if it joins the 4s on row 4 then it will make a 79 pair above for the circle clue which will break the 79 in box 2. That then places a 3 in box 5
I'm screaming, "how many ones in green". "How many eights in green" "check the quad number"
Sometimes these videos give a kind of "blue's clues" or "Dora the explorer" vibe, haha
At 16:49. Simon has a 3-8 in r3c5. The quad 8 clue in box 1 pushes the 8 in column 4 into box 2, resolving that 3-8. Simon does some genius logic from 38:50 onwards to put a 38 pair in box 5, still ignoring that logic that was available just after the break in. It finally resolves at 42:04 but not through the easy way. Sorry to give you this comment Simon, but that 3-8 thing did my head in.
Sorry, I don't think that's quite right.
The 8 quad in box 1 doesn't push the 8 into column 4 in box 2, since an 8 in r2c3 could satisfy both the 8 quad clue and the 3,8 quad clue simultaneously.
Simon: You feel like you’re making real progress and then you find out you’ve hardly done anything
Me: Mood
Simon at 0:55 "A puzzle by the terrifying Gliperal"
Simon at 69:19 "Gliperal, you are terrifying"
Aww Simon you are too cute and funny. Your phrases crack me up and make watching these so much more enjoyable added to the pure pleasure of your incredible logic and the magic of sudoku.
My new favourite channel
Wow!! Really quite hard, but i loved it. I don't think i've seen the combination of quadruples with SET before, that's marvelous! And i find it fascinating how you need to care more about which "purple digits" _can't_ be in certain sections of purple, than where the "green digits" have to go in purple. It tripped me up a good couple times cause i'm not used to thinking like that.
The 1 in box one could've been placed much earlier if Simon hadn't forgotten his earlier logic that he already knew that there wasn't another 1 in the green areas.
A fairly easy start would have been to fully pencilmark box 5 after limiting the arms of the "extra region". The two left green quadruples forces 3-8 as a pair in R2C6 and R6C6. This leave only one place for 4 in box 5. After placing the 3 5s in the Phistomefel ring, an easy deduction would be that R6C1-3 must be 6-7-9, as you cannot put 4, 6, 7 or 9 in a purple quadruple unless it is already there by the given clue, which affects the lower bottom purple quadruple and thereby forces the 6-7-9 triple in box 4.
That was a really great puzzle! When you said "it's magic", cracked me up xD Great explaining as usual, though I will never be as patient as you, Simon (:
8 quadruple in box 1 could have been used to resolve the 3/8 in col 5 as soon as they were placed. Also fascinating to watch Simon solve it without leveraging the impact of the 7 quadruple in box 3 on the 479 quadruple to force a 7 into col 6. That said, that's the only logic I solved for myself in the whole puzzle lol. Loved the solve!
I consider myself relatively intelligent, or at least conversationally so. The mind-boggling thing about these videos of more difficult puzzles is catching a glimpse into the minds of both setters and solvers who are far more intelligent than me, at least in the types of intelligence needed to set and solve these puzzles. It reminds me of finding an old pulp fiction sci-fi book and, upon reading it, wondering at the madness of the mind that created it, except instead of creative madness, it's a type of intelligence that I can only marvel at. Sure, I guess practice is part of what makes someone so good at setting and at solving, but that doesn't change how impressive it is, just like seeing a magic trick is no less impressive even if you know that there had to be a trick, like some sleight of hand, that made it possible.
I'll make a cup of coffee before carrying on watching the rest of this, as I think I might need it.
That was phenomenal. While watching I tried to follow along and spot things that could be done next. The majority of the time I found something before Simon I later found out I made a mistake, so I was quite content just watching and not trying it myself.
It amazes me that brains are wired so differently in different people. I can't come close to solving most of these puzzles, but I have read many comments from people in addition to Simon who can't see why the puzzle is called X. The origin of the name is clear if you stop thinking about sudoku and think of it as a connect the dots puzzle. Just put your pencil on a dot and draw lines to adjacent dots until you get back to the starting dot.
Man this one took me forever. Eventually I was able to break in by coloring Rows 3-7 green, cols 3-7 yellow, clearing the common cells, and noting the remaining 20 yellow cells and 20 green cells had to match.
From there I was able to determine the exact quantities of each of the digits 1-9 in the sets (one 5, three of each digits 1, 3, and 4, and 2 of each of the remaining 5 digits. )
Some Phil. Ring magic, circle hints, and traditional sudoku techs allowed me to fill in about 7 cells and isolate candidates to particular rows, columns, or regions, but I eventually hit a brick wall.
... and then I realized I could repeat my original technique, this time with cols 3, 4, 6, 7 being red, and rows 3, 4, 6, 7 being purple.
That allowed me to fill in the 5 in the middle, eliminate candidates from the white dots, create a 3-8 pair, and the rest sort of fell into place after a few hours of further work.
Brutal puzzle.