Missing that column 6 1-9 pair was so painful from 55:11 until the end... Would've made the ending so much easier without that 3-7 coloring rollercoaster
@@abbybose7671My thoughts exactly. It's easy to armchair criticize Simon and Mark, but could I do these 60+ minute puzzles myself? Almost certainly not!
Well, if he just looked further into the x-wing on 5's, he wouldn't have started on the 3/7 coloring and have found the 5 in r7c6 way earlier, it was the only possible 5 in r7 :/
@@whelmking6497That was not the only thing Simon missed, but indeed once you know one 37 cell in box 2 looks down column 5 you get the 5 in r7c6, the 19 pair in column 6, the 4 in r2c6 and 2 right of it and then much more, without tracing further 37 cells. I saw 159 triples and more... It was quite natural to concentrate on 5s once you know a lot of 10 pairs, but then the 6 or 14 sums you need neighboring the tens is only giving you a pencilmark of all digits except 3 and 7. That just tells you two of the five 10 sums that are in many borders are 37s in both orientations, which doesn't yield much in itself. It was quite natural to look for 37 pairs, though, in defense of Simon. You're still punished with not seeing the 42 6 sum gap from box2 to box3.
He came sooo close to looking there so many times as well. "Oh, that put a bunch of even digits in the row", so where can you slot the odd numbers? Any that interact with the X's? And several times he was looking at row 6 and I was waiting for him to just drop down one more row. It was fun just waiting for the inevitable
I was YELLING at my screen forever. He did aknowlege his brain doesn't work in traditional sodoku ways. Half the time his pencil marks violate sodoku and he just doesn't see it, but he still solves puzzles I could never lol
(spoiler that helps a tiny bit in the solve) Once you've marked all the X on the box borders and found the 8224 square, it is interesting to ask where the 5s go along those borders. It turns out that having four 5s on rows 3, 4, 6 and 7 are forcing a 5 into r6c4! Same logic applies later to find the 5 in r7c6. And again later in the solve, ask where the 37 pairs go on the border? Forces one in r6-7c7. There's probably a ton of other tricks like that around the puzzle!
Yes he had established that he needed two 3-7 dominos in each of rows 3/4 and 6/7. In the top such rows there are only 3 options for these 2 dominoes, each of which would knock out 2 options in the bottom such rows. So the ‘x’ in row 6/7 that is not sitting below another x, the one that is sticking out the bottom of the gray square, must be a 3-7 domino. That fairly straightforward bit of logic (in my opinion, only a couple steps beyond what Simon worked out early on) plus the 1-9 pair in column 6 that sat for a long time, would have helped him out a lot. A really neat puzzle either way.
That was one bit I was proud of. It's not often I find a bit of logic Simon doesn't use, but I worked out early that 5 was restricted, and had to show up on the Phistomefel ring - and that's the only spot it could.
Oh, what a treat, a second Phistomefel in a week! Cannot wait to watch you have a go at it, Simon, it's always such a pleasure to see you work through the logic
Just another masterpiece by the great man himself!! Loved your description Simon of where Phistomefel sits starting at 10:55. Fabulous solve from you!!
One of the best puzzles. I think this was the first hour long video that I sat through and watched it in one go. Thoroughly enjoyable. I usually run out of patience when the videos are so long. Have so many incomplete videos. But not this one. This was probably one of the best videos.
The missing that the 5 was the only place that it could go in row 7 and then subsequently missing the blank 19 pair in column 6 afterwards only to use a very convoluted 3/7 puzzle wide paring to untangle it all is a certified Simon classic. Sometimes the man just forgets to Sudoku and I'm here for it.
The way the grey square works looking at it upwards and downwards.. this is genius... I think Phistomefel has closed the gap so much with his holy grail puzzle which includes the least amount of constraints and ruleset while still solves beautifully.. this is just beautiful..
As I get better, purely thank to this channel, I'm flipping between wonder at the brilliance of finding the break in and wondering when he's going to notice there's only one place for a 5 in row 7 And the wonder again at the brilliant logic he uses to prove it an entirely different way
There's an X-wing on fives in rows 3467 that gives the 5 in r6c4 early on, and then later there is a 19 pair in column 6 that quickly gives the 4 in r2c6.
also an x-wing on fives in columns 2 and 8 that, along with the "X" dominoes, gives a 5 in r7c6 right away. But that's doing it the easy way, so not applicable here.
An X-wing spanning four rows is called a Jellyfish, just as one spanning three rows is called a Swordfish. Simon is usually good at spotting jellyfish, but never noticed this one.
Lovely like always! Buuuut, missing the 1/9-pair in col6 during the last 20 minutes took you unnecessarily over the 1 hour mark. Not complaining though! Simon and Phistomefel is always a treat, and two times in such a short amount of days..? TREAT DELUXE!
Awesome puzzle as always. I saw a few things that helped with my solve. first, there was a much simpler way to get the 5 at 55:00. that is, asking where 5 goes in row 7. it can't be on any of the xs and pencil marks leaves only 1 cell that can the 5. The second involves jelly fish. if you look as we started asking about the non 10 dominoes. they have to add to 6 or 14 and so none of them can have contain 3 nor 7. in rows 3, 4, 6 and 7, the 3s and 7s form a pair of jellyfish. at 28:22, when we get rid of the top 2 jellyfish cells in col 7, we can write in a 37 pair. Once the red digit comes out at 57:00, we can use that 37 pair to quickly whittle down the locations for 3s and 7s.
1:16:40 I'm *very* surprised that Simon didn't use his colour tricks here. I he had done so, painting the other 37 in (say) yellow, the yellow digit in box one can only be in R2C2. So in box three it's in R3C9.
68:47 for me. A very satisfying solve! A couple of big (jellyfish-sized!) things that Simon missed, which would have made this solve quite a bit easier: 1) As soon as the Xes are placed, there's immediately a jellyfish on 5s. (The 5s in rows 3, 4, 6, and 7 can only go in columns 2, 4, 6, and 8.) That would have made placing the 5s easier, because each of those columns needs exactly one 5 in one of those rows, and there are no other 5s in those columns. 2) At the 31:23 mark of the video, when Simon is stating how horrific all of those pencil marks are, one could note that they don't contain 3s or 7s (as will be the case with any pair that can only add to 6 or 14), and this creates jellyfish on both 3s and 7s. (Those digits in rows 3, 4, 6, and 7 can only go in columns 1, 5, 7, and 9.) This would have made placing the 3s and 7s much easier, knowing that each of those columns must have exactly one 3-7 pair.
This is one of those rare days where I solved a puzzle before Simon, which means I get to immediately sit back and watch him solve it without having to do any Sudoku first. Hurray!
55:00 Simon, your capacity to construct elegant mathematical logic to complete a sudoku puzzle without scanning is a marvel. You've eliminated 5 as a possibility from 36 squares through the use of X dominoes, and having roughly placed 5s in r3-4 have ruled it out of 8/9 of row 7, and you manage to prove not that r7c6 is the only valid location for 5, but that it can't be 4.
I think the 5 in r7c6 at 55:12 could have been placed by the x-wing at 40:12, which combines with the ten-dominoes to make it the only possible position for the 5 in row 7? (There's a jellyfish on 5s as soon as those ten-dominoes are discovered, I think...)
I was more than a little upset when Simon removed those x-wing markings because he didn't think they were of any use. That x-wing on 5s in r3/4 directly places the 5 in r7! EDIT: rows, not columns
I just love how Simon does everything on his power to avoid looking at the arrow in box 7. Immediately after he pencil marked the 37 on that arrow he could have checked if 3 even could be on that arrow and unwind the whole puzzle at that time. Even when he got the 2 on the arrow he didn't see the 5 in the box which would again make 3 on the arrow impossible and instead goes on pencil marking the whole grid. I really love watching Simon doing Sudoku but sometimes... 😉
Wow wee what a ride. Had to come back to this several days after starting and was very slow to spot some things but eventually had a lightbulb moment. Another incredible concept from Mr P.
Just gave it a try, what a clever puzzle! I realized a little less than halfway through what the bottom left arrow was going to be used for, and the anticipation of finally reaching it to polish everything off was a lovely bit of pacing. Pure elegance on Phistomefel's part.
This is a truly beautiful sudoku. It took me 59:59. And while I spent a lot of that time struggling to find some pairs and triples in my pencil marks, I never felt stuck at any point.
Phistomefel is such a genius! Love his puzzles, though this was too hard for me. Very much enjoyed Simon's solve. (Though I had to do some shouting, too.)
They do overlap - but they have to work as individual 2x2 squares, also. Simon explains this (pretty well, I thought ) as he works through the possibilities with the shifting of colored 2x2s toward the beginning. (If you look at the completed puzzle you will see that the 2x2s do overlap.)
An excellent puzzle. It's always interesting when you have a different chain of logic to deduce similar bits of information. Your way of placing the 3/7 pairs was almost completely different from mine which is absolutely wild to me.
The only thing thing to think about after he set up all the sets of 10, was where does 5 go. Not only in rows 3,4,6,7.(just much more obvious with the Arrow) but then also in columns 3,4,6,7. Classic Phistomefel ring as well.
@41:20 We prove ridiculous things here all the time, so this is normal. Where else have we proven that Yellow is Purple or 7 is not equal to 4 or that a Domino must be a Red 5 pair?
34:53 Ingenious concept with a surprisingly straightforward resolution after a little thinking on the maths of it. Stunning how empty the grid and ruleset can get.
Finished in 47:34. Lovely logic for the break-in. I must admit though, when solving for the middle box I just plugged in the various numbers and tried it out and went down the road of "solving" it for one of the two solutions. I thought I had reached an impossibility for the correct path in box 7, so I tried the other number and found that that lead to an impossibility immediately so my previous "impossibility" must have been possible. And I again went down the correct path and solved it from there. Fun puzzle!
You know, a practically bare grid and a fairly simple rule - this was wonderful. I was very impressed with your figuring out how the columns of 2x2s worked, and the positioning of the X-dominoes. I am amazed at how your brain works, Simon.
I got a lot of traction on by coloring where the 5s could go, which made a swordfish that allowed me to narrow the 5s down enough to get that R7C6 was a 5 much earlier. Later coloring the 19 pairs took me around to the arrow which disambiguated them.
Just the amount of info that comes from such a tiny ruleset and the moment you realize how insanely restrictive it just is.......mindboggling, just a stunning puzzle. I started with evens and unevens which helped me later on to find the pairs. bit longer route I think but in the end you all follow the same logic. Just a fantastic puzzle.❤
Phenomenal puzzle! Solved it in 98:16. One small correction at 43:00: 19 pairs in cells r15c67 would not form a deadly pattern because they go across boxes. Each pair needs to be in a box to form a deadly pattern.
OW, my head hurts……Great video though. Can you imagine a collaboration between Phistomefel and Icy Fruit, likely the answer would be 42 and despite a few chocolate teapots and bobbinses Simon would ultimately reveal the question. Can’t wait for that video.
1:13:50 I was really hoping Simon would look at the arrow before backing into resolving it. spoiler catcher.... If red is three, the circle cant be 4,5 or 6 because of the digits in the box, but also cant add up to 7,8 or 9 because it would require the 4, 5 or 6! thus red is 7.
I got through this more smoothly by recognizing that the dominoes between the 10-dominoes have to be 6 mod 8 (ie, 6 or 14) and filling in all possible values for all the dominoes, across all 4 dividing lines between boxes. Lots of pencil marks but relatively easy to zip through them and eliminate impossibilities one by one. Messier board but cleaner logic, I daresay
This was such an awesome puzzle to solve. I did it in about 40 minutes, but I did do a bit of dodgy notation near the end that caused me to have one wrong digit. Easily corrected though. Phistomefel continues to amaze!
What a fun puzzle - happy to have solved a Phistomofel without watching the video. Now I can go and watch Simon and see how much I missed that slowed me down ...
Amazing puzzle! I got the main (astonishing) break-in reasonably efficiently, but got a bit bogged down later. Still managed to finish, and well worth it.
My favorite part was near the end when you were talking about how the arrow would solve the puzzle, not realizing the arrow was solvable until several minutes lager lol.
This was one of those puzzles where I need a few Simon nudges to break into the logic, then I can fly ahead with sudoku. I found it very helpful to colour all of the x pairs, but it does make for quite a busy grid.
One way to get the "8" in the quadruple containing the arrow right away (after placing the Xs) would have been the following: call the digit not on the arrow "x". Then the digits on the arrow are "10-x", and the bulb is "20-2x". Overall the quadruple sums to "40 - 3x", which has to be a multiple of 8. This means that 3x has to be a multiple of 8, but since 3 is coprime with 8, then x must be a multiple of 8. Therefore, x = 8 :) By the way, I love your channel! Especially as a mathematician, I find it amusing, entertaining and instructive. Keep up the good work!
I started when he first found it, and then in the middle of his "37" stretch, when looking at the r67c7 pair, saying "if you use the 19-pair, this must be 3-7, since r2c7 is a 2!
I had an interesting thought. When filming, Simon should have a little smart reminder set to go off every 10 minutes of the solve that gently says “remember to scan and do sudoku”.
Loved the puzzle, but needed Simon's help to get me started, or indeed anywhere at all, so I certainly have no right to complain about the solve. It's just that Simon never fails to take the difficult route over the easy ones. 52:00 and a few minutes on: S: "I'm so sorry if you've all spotted what I'm missing..." Me: "Don't worry about it." S: "These two are the same." (1/9) Me: "Yes, you noticed." S: "Is there anything clever we can do with that and Sudoku?" Me: "Yes, you can." S: "No, don't think so..." Me: "Oh, no..." S: "Well, that digit... Can we do anything with that and Sudoku?" Me: "Oh, yes! Back on track!" S: "Don't know... Or are there X-dominoes that I've undermarked?" (points to row 6 and 7). Me: "Oh, yes! You've got this Simon...!" S: "Well, I can do something about this domino, but it's indirect..." Me: "No, it's very direct. Just think about the other X's in the same rows, and the only place you can place a 1 or 9!" S: Continues doing something very indirect while I give up on trying to tell him through my screen and resort to venting in the comment section instead. : )
I did the same coloring as you did, but with 19 instead of 37, and the circle sum in box 7 resolved the ambiguity (it was yellow as a 1 or 9 and couldn't be a sum).
The hard earned 19 pair in column six was crying for Simons attention, at least in my brain. Way, way out of my solving skills. I still do not fully understand how you got the x'es at the start.
Around 55:00 I'd already been asking "where's the 5 in row 7?" for ages (but Simon never hears me...). The combination of X's, solved/centre-marked digits, and the x-wing on 5's in columns 2 and 8 have meant that R7C6 has had to be a 5 for ages as it was the only place available in row 7.
Maybe next puzzle we al tune our minds in the afternoon, (moment of recording) and beam "Simon, Do Sudoku" simultaneously. Maybe he wil finally hear us call to him!
When Simon put 1,1,6,2 in the example, and you could see from his expression that his brain was rejecting it, even though he couldn't see why immediately 😂. Brains are funny things, sometimes...
I am genuinely asking.. does he intentionally try to put off sudoku for the end for the added challenge? Or is it just by mistake that he misses simple scans? It's funny and entertaining on occassions but today I am just confused lol
I took a slightly different approach. I saw that 5 would be more restricted than most digits, and worked out early on that it had to be on the Phistomephel ring, and could only be on the ring in one spot. That made a few points easier to clear up.
At about the 45 minute mark, this puzzle had 5 minutes left to solve tops. Simon is very detailed and loves to prove the obvious, like the X-wing on 5's and why that box in row 7 could not be a 4. As soon as he had the X-wing on 5s (which he admits was found much more easily with the X dominoes), then there was only one place for a 5 in row 7. Then chase down the 1-9 pairs and bam, puzzle iss solved. Now - it would have taken me 2 years to solve without his jump starting me the first 45 minutes! But hey, I always love to watch and learn.
1:07:22 Simon takes the longest way round to get the 4 in r2c6 that he could have gotten 12 minutes earlier if only he'd used his fair weather friend, Sudoku.
well the 5 pattern gives you two fives right away, but the first one that is on the ring and has to be a 5 because without it there is no hope of placing the 5s is the greatest thing ever.
while wathing the solve ive had an idea on how to nearly resolve which of those dominoes had to be 37 pairs fairly quickly. at some point you had three possible placements in rows 3 and 4, and four in rows 6 and 7, three of which were in the same columns as the ones above them. knowing that two of those possible placements in rows 34 are definitely occupied by a 37 pair we can deduce that two of those three placements directly underneath them will not be able to contain a 37 pair. therefore only one of those 37 pairs in rows 67 can be in dominoes directly underneath the dominoes in rows 34, and the other one has to be in column 7. then you could use that to place the 37 pair in the bottom of column 6 and so on. that being said i could never have solved this puzzle on my own, that was just one hopefully inteligent idea ive had
I started off much the same as you. The difference was that I did sudoku. @ 39:35 - "I was thinking this couldn't be a 4, but it absolutely can be" - actually it can't. Where does 5 goes in R7? This one deduction was the critical thing you were missing. With that, you get a 5 and a 19 pair in C6, which makes R2C6=4, R2C8=2, and this eliminates many options. The rest just flows very smoothly and you can finish the rest in under five minutes. @ 55:29 - Even after getting the 5 in R7C6 by the most circuitous route imaginable, you still didn't get the 4 in R2C6. There's a 19 pair in the column, and you never even checked. What's the point of saying "what's that given me?" if you don't even look? @ 58:33 - Musing about which pair in R5 is a 37 pair. It's easy. If it's the pair on the right, what happens in box 4? You end up with a 37 in both R4C1 and R6C1, but they each need another 37 on the opposite side of their X. This video should have been half an hour shorter if you'd considered the restriction with 5s, and then done some proper sudoku with the result, rather than made a token gesture. You even pencil-marked 5s in the pairs in R3/4 at one point, and you'd already pointed out that 5 can't go on an X. You gave yourself every opportunity to spot this. It's really not clever trying to solve a sudoku without doing sudoku unless you really can't avoid it. I find it's disrespectful to the phenomenon which has provided you with your current career, and if you care about showing your viewers how to solve sudoku, avoiding sudoku is hardly the way to go about it. You should be doing sudoku at every step, religiously. Sure, sometimes the deductions come quickly and you don't have chance to check them all, but in that case, once the flow has ended, do a complete audit of every row, column and box and look for doubles, triples, etc. Check whether you can eliminate some pencil-marks, or whether you've got a solitary corner-mark remaining for a digit in a box. Almost every time you say that a deduction gave you nothing, it's because you've not looked properly. I don't know where you are looking, but you're clearly never looking in the right places. When you placed the 5 and 19 in C6, the obvious thing to do was to check the column, but all you did was remove a solitary 5 candidate from a single cell, when you could have removed three out of four candidates. For a Phistomefel puzzle, I was surprised that it yielded so easily after the break-in. His puzzles usually have more staying power.
For 15 minutes I was waiting for Simon to work out that a 37 went into the bottom right corner of the grey square. You could compute this a lot easier than Simon did by determining that there were three Xs in rows 3&4 where a 37 pair could go. In rows 6&7 there were 4 places. The extra place in rows 6&7 were in column 7. If column 7 didn’t have 37 pair in it then you’d of had an overlap.
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25:36 "Two of these three squares have to be filled with three sevens" is a pretty great line out of context.
me after twenty minutes: now i have four digits!
me after forty-five minutes: now i have four digits and lots of pencil marks!
same, but change 45 to 90
same, but change 45 to 70 and four digits to zero (I just came back to watch Simon do it)
I'm glad there are others that struggle as much as I do😅
Missing that column 6 1-9 pair was so painful from 55:11 until the end... Would've made the ending so much easier without that 3-7 coloring rollercoaster
Came here looking for this comment! A few other things also. Ofc he still solved it much faster than I could ever hope to, lol
@@abbybose7671My thoughts exactly. It's easy to armchair criticize Simon and Mark, but could I do these 60+ minute puzzles myself? Almost certainly not!
Well, if he just looked further into the x-wing on 5's, he wouldn't have started on the 3/7 coloring and have found the 5 in r7c6 way earlier, it was the only possible 5 in r7 :/
The 19 pair wouldn't have given much more than the 4 and 2 under it... The 3-7 coloring still went a long way in unwinding the grid.
Another example of the genius of Simon in finding consequences of new rules, but failing simple scanning.
Yeah, this one was especially bad. Probably could have pulled the time down to 30 minutes with some simple scanning.
MIssing the 1-9 pair in column 6 almost felt like an intentional oversight.
Yes, this is one where Simon found the break-in faster than me, but then I could zoom ahead with sudoku
Sodoku scanning is far too simple for Simon’s brain. It’s always searching for the hard stuff.
@@whelmking6497That was not the only thing Simon missed, but indeed once you know one 37 cell in box 2 looks down column 5 you get the 5 in r7c6, the 19 pair in column 6, the 4 in r2c6 and 2 right of it and then much more, without tracing further 37 cells. I saw 159 triples and more...
It was quite natural to concentrate on 5s once you know a lot of 10 pairs, but then the 6 or 14 sums you need neighboring the tens is only giving you a pencilmark of all digits except 3 and 7. That just tells you two of the five 10 sums that are in many borders are 37s in both orientations, which doesn't yield much in itself.
It was quite natural to look for 37 pairs, though, in defense of Simon. You're still punished with not seeing the 42 6 sum gap from box2 to box3.
For over 10 minutes I kept asking Simon "Where can 5 go in row 7?" I guess he just kept getting distracted from the Sudoku of the Sudoku puzzle.
And after he found that in a complicated way, it was the 19 pair in column 6
@@d95mnAt least he acknowledges the 19 pair might have been there for ages when he does spot it!
He came sooo close to looking there so many times as well. "Oh, that put a bunch of even digits in the row", so where can you slot the odd numbers? Any that interact with the X's? And several times he was looking at row 6 and I was waiting for him to just drop down one more row. It was fun just waiting for the inevitable
Had the same flow :-)
I was YELLING at my screen forever. He did aknowlege his brain doesn't work in traditional sodoku ways. Half the time his pencil marks violate sodoku and he just doesn't see it, but he still solves puzzles I could never lol
(spoiler that helps a tiny bit in the solve)
Once you've marked all the X on the box borders and found the 8224 square, it is interesting to ask where the 5s go along those borders. It turns out that having four 5s on rows 3, 4, 6 and 7 are forcing a 5 into r6c4! Same logic applies later to find the 5 in r7c6. And again later in the solve, ask where the 37 pairs go on the border? Forces one in r6-7c7. There's probably a ton of other tricks like that around the puzzle!
Yes he had established that he needed two 3-7 dominos in each of rows 3/4 and 6/7. In the top such rows there are only 3 options for these 2 dominoes, each of which would knock out 2 options in the bottom such rows. So the ‘x’ in row 6/7 that is not sitting below another x, the one that is sticking out the bottom of the gray square, must be a 3-7 domino. That fairly straightforward bit of logic (in my opinion, only a couple steps beyond what Simon worked out early on) plus the 1-9 pair in column 6 that sat for a long time, would have helped him out a lot. A really neat puzzle either way.
Came to the comments for this. Though I like to see that Simon finds another deduction for it, showing there are multiple paths to the solve
That 5 in row 7 was sitting there with simple Sudoku for a very long time. Always nice to spot something missed by someone 1000 times better than me.
That was one bit I was proud of. It's not often I find a bit of logic Simon doesn't use, but I worked out early that 5 was restricted, and had to show up on the Phistomefel ring - and that's the only spot it could.
Oh, what a treat, a second Phistomefel in a week!
Cannot wait to watch you have a go at it, Simon, it's always such a pleasure to see you work through the logic
Just another masterpiece by the great man himself!! Loved your description Simon of where Phistomefel sits starting at 10:55.
Fabulous solve from you!!
One of the best puzzles. I think this was the first hour long video that I sat through and watched it in one go. Thoroughly enjoyable. I usually run out of patience when the videos are so long. Have so many incomplete videos. But not this one. This was probably one of the best videos.
The missing that the 5 was the only place that it could go in row 7 and then subsequently missing the blank 19 pair in column 6 afterwards only to use a very convoluted 3/7 puzzle wide paring to untangle it all is a certified Simon classic.
Sometimes the man just forgets to Sudoku and I'm here for it.
The way the grey square works looking at it upwards and downwards.. this is genius... I think Phistomefel has closed the gap so much with his holy grail puzzle which includes the least amount of constraints and ruleset while still solves beautifully.. this is just beautiful..
I could have stared at this puzzle for a year and never figured out the virtual "X" domino's...Well done Simon...
As I get better, purely thank to this channel, I'm flipping between wonder at the brilliance of finding the break in and wondering when he's going to notice there's only one place for a 5 in row 7
And the wonder again at the brilliant logic he uses to prove it an entirely different way
There's an X-wing on fives in rows 3467 that gives the 5 in r6c4 early on, and then later there is a 19 pair in column 6 that quickly gives the 4 in r2c6.
also an x-wing on fives in columns 2 and 8 that, along with the "X" dominoes, gives a 5 in r7c6 right away. But that's doing it the easy way, so not applicable here.
An X-wing spanning four rows is called a Jellyfish, just as one spanning three rows is called a Swordfish.
Simon is usually good at spotting jellyfish, but never noticed this one.
Lovely like always! Buuuut, missing the 1/9-pair in col6 during the last 20 minutes took you unnecessarily over the 1 hour mark. Not complaining though! Simon and Phistomefel is always a treat, and two times in such a short amount of days..? TREAT DELUXE!
Awesome puzzle as always. I saw a few things that helped with my solve.
first, there was a much simpler way to get the 5 at 55:00. that is, asking where 5 goes in row 7. it can't be on any of the xs and pencil marks leaves only 1 cell that can the 5.
The second involves jelly fish. if you look as we started asking about the non 10 dominoes. they have to add to 6 or 14 and so none of them can have contain 3 nor 7. in rows 3, 4, 6 and 7, the 3s and 7s form a pair of jellyfish. at 28:22, when we get rid of the top 2 jellyfish cells in col 7, we can write in a 37 pair. Once the red digit comes out at 57:00, we can use that 37 pair to quickly whittle down the locations for 3s and 7s.
Glad you didn't miss this! This is absolutely wonderful!
Glad you enjoyed the music, video was great as per usual!
1:16:40 I'm *very* surprised that Simon didn't use his colour tricks here. I he had done so, painting the other 37 in (say) yellow, the yellow digit in box one can only be in R2C2. So in box three it's in R3C9.
I've had a pretty awful day pain wise. There is nothing like a Phistomephel puzzle to help cheer me up.
I hope your pain goes away soon, or atleast lessens.
You obviously aren’t solving a Phistomefel. That usually causes pain in my brain. Feel better.
I hope tomorrow comes with less pain
I think something similar everytime I have a bad day.
"I hope at least the sudoku is good"
Maybe tomorrow be much better! 🙏🏻
68:47 for me. A very satisfying solve!
A couple of big (jellyfish-sized!) things that Simon missed, which would have made this solve quite a bit easier:
1) As soon as the Xes are placed, there's immediately a jellyfish on 5s. (The 5s in rows 3, 4, 6, and 7 can only go in columns 2, 4, 6, and 8.) That would have made placing the 5s easier, because each of those columns needs exactly one 5 in one of those rows, and there are no other 5s in those columns.
2) At the 31:23 mark of the video, when Simon is stating how horrific all of those pencil marks are, one could note that they don't contain 3s or 7s (as will be the case with any pair that can only add to 6 or 14), and this creates jellyfish on both 3s and 7s. (Those digits in rows 3, 4, 6, and 7 can only go in columns 1, 5, 7, and 9.) This would have made placing the 3s and 7s much easier, knowing that each of those columns must have exactly one 3-7 pair.
This is one of those rare days where I solved a puzzle before Simon, which means I get to immediately sit back and watch him solve it without having to do any Sudoku first. Hurray!
This is a really astonishing puzzle!!! Beautiful rule set requires one to invent a new solving path. Superb idea for this one.
55:00 Simon, your capacity to construct elegant mathematical logic to complete a sudoku puzzle without scanning is a marvel. You've eliminated 5 as a possibility from 36 squares through the use of X dominoes, and having roughly placed 5s in r3-4 have ruled it out of 8/9 of row 7, and you manage to prove not that r7c6 is the only valid location for 5, but that it can't be 4.
I think the 5 in r7c6 at 55:12 could have been placed by the x-wing at 40:12, which combines with the ten-dominoes to make it the only possible position for the 5 in row 7? (There's a jellyfish on 5s as soon as those ten-dominoes are discovered, I think...)
I was more than a little upset when Simon removed those x-wing markings because he didn't think they were of any use. That x-wing on 5s in r3/4 directly places the 5 in r7!
EDIT: rows, not columns
I just love how Simon does everything on his power to avoid looking at the arrow in box 7. Immediately after he pencil marked the 37 on that arrow he could have checked if 3 even could be on that arrow and unwind the whole puzzle at that time.
Even when he got the 2 on the arrow he didn't see the 5 in the box which would again make 3 on the arrow impossible and instead goes on pencil marking the whole grid.
I really love watching Simon doing Sudoku but sometimes... 😉
Wow wee what a ride. Had to come back to this several days after starting and was very slow to spot some things but eventually had a lightbulb moment. Another incredible concept from Mr P.
Just gave it a try, what a clever puzzle! I realized a little less than halfway through what the bottom left arrow was going to be used for, and the anticipation of finally reaching it to polish everything off was a lovely bit of pacing. Pure elegance on Phistomefel's part.
This is a truly beautiful sudoku. It took me 59:59. And while I spent a lot of that time struggling to find some pairs and triples in my pencil marks, I never felt stuck at any point.
First time I solved a Phistomephel puzzle using a Phistomephel ring that Simon did not use in his solve.
So excited! This puzzle looks crazy!
Phistomefel is such a genius! Love his puzzles, though this was too hard for me. Very much enjoyed Simon's solve. (Though I had to do some shouting, too.)
An amazing puzzle and an incredible solve. Kudos to both you and Phistomefel.
Such a fresh idea. Loved the break in 🎉
I got the 3-7 breakthrough using swordfish logic. Great solve!
@Simon There is a feature called "Follow list" and a check box for email-notifications, when a new puzzle gets published, on LMG.
I was under the impression that the 2x2 squares could overlap. What was the immediate clue that they don't?
They do overlap - but they have to work as individual 2x2 squares, also. Simon explains this (pretty well, I thought ) as he works through the possibilities with the shifting of colored 2x2s toward the beginning. (If you look at the completed puzzle you will see that the 2x2s do overlap.)
An excellent puzzle. It's always interesting when you have a different chain of logic to deduce similar bits of information. Your way of placing the 3/7 pairs was almost completely different from mine which is absolutely wild to me.
The only thing thing to think about after he set up all the sets of 10, was where does 5 go. Not only in rows 3,4,6,7.(just much more obvious with the Arrow) but then also in columns 3,4,6,7. Classic Phistomefel ring as well.
@41:20 We prove ridiculous things here all the time, so this is normal. Where else have we proven that Yellow is Purple or 7 is not equal to 4 or that a Domino must be a Red 5 pair?
35:11 for me, pencilmarking really was your friend in this puzzle.
34:53
Ingenious concept with a surprisingly straightforward resolution after a little thinking on the maths of it. Stunning how empty the grid and ruleset can get.
Happy to see another new Phistomefel puzzle!!
You and me both!! 😁
@@davidrattner9 😃
Me three!@@longwaytotipperary and @davidrattner9
I solved a phistomefel puzzle by myself!! That's the first one i've managed without tips from simon!
Finished in 47:34. Lovely logic for the break-in. I must admit though, when solving for the middle box I just plugged in the various numbers and tried it out and went down the road of "solving" it for one of the two solutions. I thought I had reached an impossibility for the correct path in box 7, so I tried the other number and found that that lead to an impossibility immediately so my previous "impossibility" must have been possible. And I again went down the correct path and solved it from there.
Fun puzzle!
You know, a practically bare grid and a fairly simple rule - this was wonderful. I was very impressed with your figuring out how the columns of 2x2s worked, and the positioning of the X-dominoes. I am amazed at how your brain works, Simon.
I got a lot of traction on by coloring where the 5s could go, which made a swordfish that allowed me to narrow the 5s down enough to get that R7C6 was a 5 much earlier. Later coloring the 19 pairs took me around to the arrow which disambiguated them.
Shout out to all the row 7 homies chilling with 5 when Simon arrived.
Just the amount of info that comes from such a tiny ruleset and the moment you realize how insanely restrictive it just is.......mindboggling, just a stunning puzzle. I started with evens and unevens which helped me later on to find the pairs. bit longer route I think but in the end you all follow the same logic. Just a fantastic puzzle.❤
Phenomenal puzzle! Solved it in 98:16.
One small correction at 43:00: 19 pairs in cells r15c67 would not form a deadly pattern because they go across boxes. Each pair needs to be in a box to form a deadly pattern.
OW, my head hurts……Great video though. Can you imagine a collaboration between Phistomefel and Icy Fruit, likely the answer would be 42 and despite a few chocolate teapots and bobbinses Simon would ultimately reveal the question. Can’t wait for that video.
I have the flu. I have binged CtC for nearly 4 days! I still suck at variant Suduko but Simon and Mark beat the hell out of Netflix and Hulu ❤
Back in the early days, I learnt to scan up and down when new information is added and to remove colouring once it's served its purpose.
1:13:50 I was really hoping Simon would look at the arrow before backing into resolving it.
spoiler catcher....
If red is three, the circle cant be 4,5 or 6 because of the digits in the box, but also cant add up to 7,8 or 9 because it would require the 4, 5 or 6!
thus red is 7.
It always amazes me the Simon can do the most mind bending logic yet miss the simplest sudoku thingies.
I got through this more smoothly by recognizing that the dominoes between the 10-dominoes have to be 6 mod 8 (ie, 6 or 14) and filling in all possible values for all the dominoes, across all 4 dividing lines between boxes. Lots of pencil marks but relatively easy to zip through them and eliminate impossibilities one by one. Messier board but cleaner logic, I daresay
This was such an awesome puzzle to solve. I did it in about 40 minutes, but I did do a bit of dodgy notation near the end that caused me to have one wrong digit. Easily corrected though. Phistomefel continues to amaze!
What a brilliant new idea. The fact that Phistomefel does not interact in person with the community much adds to the mystique.
What a fun puzzle - happy to have solved a Phistomofel without watching the video. Now I can go and watch Simon and see how much I missed that slowed me down ...
Amazing puzzle! I got the main (astonishing) break-in reasonably efficiently, but got a bit bogged down later. Still managed to finish, and well worth it.
My favorite part was near the end when you were talking about how the arrow would solve the puzzle, not realizing the arrow was solvable until several minutes lager lol.
Impressive solve! I stared at it for a while but couldn't figure it out. Still not convinced with the x's ;-)
This software is really well done, btw!
53:17 finish. So much fun! All of those hidden Xs that you need to find to do the puzzle. Another amazing challenge!
Sometimes when Simon misses an obvious 5 and spends 10 minutes finding it's not 4....I do yell at the screen...and he missed a 19 pair!!
This was one of those puzzles where I need a few Simon nudges to break into the logic, then I can fly ahead with sudoku. I found it very helpful to colour all of the x pairs, but it does make for quite a busy grid.
One way to get the "8" in the quadruple containing the arrow right away (after placing the Xs) would have been the following: call the digit not on the arrow "x". Then the digits on the arrow are "10-x", and the bulb is "20-2x". Overall the quadruple sums to "40 - 3x", which has to be a multiple of 8. This means that 3x has to be a multiple of 8, but since 3 is coprime with 8, then x must be a multiple of 8. Therefore, x = 8 :)
By the way, I love your channel! Especially as a mathematician, I find it amusing, entertaining and instructive. Keep up the good work!
49:31 for me. Over the moon to have cracked the great man's two latest offerings!
Very interesting puzzle. I didn't unterstand und rule completely, so I had to watch Simon for a while to make it possible for me to start solving.
Am i the only one screaming for that 1 9 pair? :)
No, I was screaming too 😉
I started when he first found it, and then in the middle of his "37" stretch, when looking at the r67c7 pair, saying "if you use the 19-pair, this must be 3-7, since r2c7 is a 2!
Simon: These arrows must be there to disambiguate. Also Simon: puts first digits on the arrow :)
I had an interesting thought. When filming, Simon should have a little smart reminder set to go off every 10 minutes of the solve that gently says “remember to scan and do sudoku”.
I almost can't believe how I clicked with this puzzle. So good!
Loved the puzzle, but needed Simon's help to get me started, or indeed anywhere at all, so I certainly have no right to complain about the solve.
It's just that Simon never fails to take the difficult route over the easy ones.
52:00 and a few minutes on:
S: "I'm so sorry if you've all spotted what I'm missing..." Me: "Don't worry about it."
S: "These two are the same." (1/9) Me: "Yes, you noticed."
S: "Is there anything clever we can do with that and Sudoku?" Me: "Yes, you can."
S: "No, don't think so..." Me: "Oh, no..."
S: "Well, that digit... Can we do anything with that and Sudoku?" Me: "Oh, yes! Back on track!"
S: "Don't know... Or are there X-dominoes that I've undermarked?" (points to row 6 and 7). Me: "Oh, yes! You've got this Simon...!"
S: "Well, I can do something about this domino, but it's indirect..." Me: "No, it's very direct. Just think about the other X's in the same rows, and the only place you can place a 1 or 9!"
S: Continues doing something very indirect while I give up on trying to tell him through my screen and resort to venting in the comment section instead. : )
I did the same coloring as you did, but with 19 instead of 37, and the circle sum in box 7 resolved the ambiguity (it was yellow as a 1 or 9 and couldn't be a sum).
The hard earned 19 pair in column six was crying for Simons attention, at least in my brain. Way, way out of my solving skills. I still do not fully understand how you got the x'es at the start.
Around 55:00 I'd already been asking "where's the 5 in row 7?" for ages (but Simon never hears me...). The combination of X's, solved/centre-marked digits, and the x-wing on 5's in columns 2 and 8 have meant that R7C6 has had to be a 5 for ages as it was the only place available in row 7.
Maybe next puzzle we al tune our minds in the afternoon, (moment of recording) and beam "Simon, Do Sudoku" simultaneously. Maybe he wil finally hear us call to him!
When Simon put 1,1,6,2 in the example, and you could see from his expression that his brain was rejecting it, even though he couldn't see why immediately 😂.
Brains are funny things, sometimes...
I am genuinely asking.. does he intentionally try to put off sudoku for the end for the added challenge? Or is it just by mistake that he misses simple scans? It's funny and entertaining on occassions but today I am just confused lol
Astounding! Loved that
I took a slightly different approach. I saw that 5 would be more restricted than most digits, and worked out early on that it had to be on the Phistomephel ring, and could only be on the ring in one spot. That made a few points easier to clear up.
At about the 45 minute mark, this puzzle had 5 minutes left to solve tops. Simon is very detailed and loves to prove the obvious, like the X-wing on 5's and why that box in row 7 could not be a 4. As soon as he had the X-wing on 5s (which he admits was found much more easily with the X dominoes), then there was only one place for a 5 in row 7. Then chase down the 1-9 pairs and bam, puzzle iss solved. Now - it would have taken me 2 years to solve without his jump starting me the first 45 minutes! But hey, I always love to watch and learn.
Simon is so into those incredibly complex deduction that he completely overlooks the obvious 19 pair in column 6 for 20 minutes.
you are smart and nice, i enjoy your videos
1:07:22 Simon takes the longest way round to get the 4 in r2c6 that he could have gotten 12 minutes earlier if only he'd used his fair weather friend, Sudoku.
Phistomefel is such a genius. How the hell did he come up with this?!
well the 5 pattern gives you two fives right away, but the first one that is on the ring and has to be a 5 because without it there is no hope of placing the 5s is the greatest thing ever.
It is funny that I don't have an idea how to start a puzzle like this, but I am always shouting to Simon do sudoku!!! 😅
Wonder how long Simon leaves that hard won 19 pair in C6 unused. It does some handy work.
while wathing the solve ive had an idea on how to nearly resolve which of those dominoes had to be 37 pairs fairly quickly. at some point you had three possible placements in rows 3 and 4, and four in rows 6 and 7, three of which were in the same columns as the ones above them. knowing that two of those possible placements in rows 34 are definitely occupied by a 37 pair we can deduce that two of those three placements directly underneath them will not be able to contain a 37 pair. therefore only one of those 37 pairs in rows 67 can be in dominoes directly underneath the dominoes in rows 34, and the other one has to be in column 7. then you could use that to place the 37 pair in the bottom of column 6 and so on. that being said i could never have solved this puzzle on my own, that was just one hopefully inteligent idea ive had
What Simon missed was that there is a double jellyfish on 3s and 7s in rows 3, 4, 6, and 7, which immediately places a 37-pair in (R6C7, R7C7).
Simon's phone vibrates once - "Phone is going nuts"
That's a brilliant puzzle holy shit. Also the mental image of the sauron tower that was cool too
41 minutes to solve, so it is most certainly worthy of the 4 star rating.
76:45 for me, super fun solve! Felt so satisfying to see how the puzzle worked while solving
I started off much the same as you. The difference was that I did sudoku.
@ 39:35 - "I was thinking this couldn't be a 4, but it absolutely can be" - actually it can't. Where does 5 goes in R7? This one deduction was the critical thing you were missing. With that, you get a 5 and a 19 pair in C6, which makes R2C6=4, R2C8=2, and this eliminates many options. The rest just flows very smoothly and you can finish the rest in under five minutes.
@ 55:29 - Even after getting the 5 in R7C6 by the most circuitous route imaginable, you still didn't get the 4 in R2C6. There's a 19 pair in the column, and you never even checked. What's the point of saying "what's that given me?" if you don't even look?
@ 58:33 - Musing about which pair in R5 is a 37 pair. It's easy. If it's the pair on the right, what happens in box 4? You end up with a 37 in both R4C1 and R6C1, but they each need another 37 on the opposite side of their X.
This video should have been half an hour shorter if you'd considered the restriction with 5s, and then done some proper sudoku with the result, rather than made a token gesture. You even pencil-marked 5s in the pairs in R3/4 at one point, and you'd already pointed out that 5 can't go on an X. You gave yourself every opportunity to spot this. It's really not clever trying to solve a sudoku without doing sudoku unless you really can't avoid it. I find it's disrespectful to the phenomenon which has provided you with your current career, and if you care about showing your viewers how to solve sudoku, avoiding sudoku is hardly the way to go about it. You should be doing sudoku at every step, religiously. Sure, sometimes the deductions come quickly and you don't have chance to check them all, but in that case, once the flow has ended, do a complete audit of every row, column and box and look for doubles, triples, etc. Check whether you can eliminate some pencil-marks, or whether you've got a solitary corner-mark remaining for a digit in a box. Almost every time you say that a deduction gave you nothing, it's because you've not looked properly. I don't know where you are looking, but you're clearly never looking in the right places. When you placed the 5 and 19 in C6, the obvious thing to do was to check the column, but all you did was remove a solitary 5 candidate from a single cell, when you could have removed three out of four candidates.
For a Phistomefel puzzle, I was surprised that it yielded so easily after the break-in. His puzzles usually have more staying power.
For 15 minutes I was waiting for Simon to work out that a 37 went into the bottom right corner of the grey square.
You could compute this a lot easier than Simon did by determining that there were three Xs in rows 3&4 where a 37 pair could go. In rows 6&7 there were 4 places. The extra place in rows 6&7 were in column 7. If column 7 didn’t have 37 pair in it then you’d of had an overlap.
Simon and us make a great team. He cracks it and we can scan and fill in the rest.
haha yes, he certainly missed a few easy sudoku-based eliminations this time
Note to Rocky Roer - the cake needs lots more frosting!!!! 🤔
We would never skimp on frosting. 😋😋😋😋
@@davidrattner9 right!!
Wow!! Two in such a short time span? Amazing