This was absolutely brilliant mate. Makes me realize there's a level of Sudoku solving I'll never reach. Anywho well done!

I have to say that feel a lot better about my own struggles with Sudoku after watching you struggle with this one Simon. Thanks for all of the great videos and help with Sudoku.

You're absolutely amazing Simon! I picked up two new techniques just by watching you solve this one. =)

Wow... Thanks for working through this. I can follow along, and can maybe hope to someday spot the logical steps that you find. Very much enjoy your posts.

Incredible... I was palm to forehead when you didn't lock in the 3-7, 4-8 pairs in column 6 at the outset (you had a 5-8 in box 8 instead) and then mistrusted the correct notation due to the original omission. Much better now that you can differentiate notation in the current software! Your ability to key into the best weak spots & see the needed strategy is awesome. I have no trouble following your logic... I just can't find the points of attack. This solve was especially impressive.

Very enlightening. I'm learning more here than any other place. Thanks

Now that one was a challenge! Thanks for solving it and posting it, even if it did take you quite some time to finish!

Very nice. The tough ones are the best to watch

Wow! Great solve.

Love these videos. I get stuck with basic Sudoku but I’ll learn. Thanks!

Thanks Simon for doing this puzzle

At the end of initial stage of using regular sudoku moves I found column 1 interesting because only two cells were left. One of these, C1R5, was yelling out to be an 8 because, if you adapt Mark's method, you will readily see that an 8 there creates a lot of havoc elsewhere. The 8 turned out to be correct and the rest of the puzzle crumbled. Happy Valentine's Day Mark, your approached led me to the 8 that cracked the cryptic. Seems to me that the harder the puzzle, the more poignant the vulnerable cell, in this case C1R5. I then sat back and enjoyed Simon's Solve, again a very humbling experience. Well done, Simon and Happy Valentine's Day to you too!

I am very new and unexperienced in solving hard sudokus. I started learning on this channel about 2 weeks ago and with this tecknique of snyder pencil marking I honestly couldn't solve a single puzzle. Then I shifted to just stupidly filling in every possible pencil mark and working from there and since then I solved 8 out of 9. And even this one was relatively easy because it was not so hard to spot numbers that could be eliminated from rows, columns and squares. It still took me a bit longer than him but given I have no practice I consider this one of the easier "hard puzzles"

I had never heard of Sue-de-coq until a couple of days ago, now I see them everywhere lol

He ... I'm no beginner at Sudoku, but chains of THIS length is a bit (way!) too steep for me at this point! Hat's off! ;O)

In column 1, putting either 6 or 8, all other numbers can be checked. If row 2 is 6, you get all numbers correct.

7:20 I'm curious to see if you spot the Y-wing of R7C6 (37), R9C4 (23 you just penciled in), and R9C3. As far as I could tell, it was useless. 8:40 You found it. Also, I reversed the order of the 237 triple and 89 pair: found the triple first, to place the pair.

Excellent, I learned 3 techniques.

Great video!! At 26:20, you could have eliminated 2 and 3 from H4 because of the single solution rule. Also, the 8 on C5 could be eliminated early on with a finned skyscraper in columns 6 and 9.

Instead of doing the open rectangle on 5s in box 8, doing it on 7s in box 9 gives even more quickly the same result, starting with proofing that r3c4 = 3. However, the initial Sue the Coq and other rectangle I did not spot so easily....

As a pencil-and-paper solver, I circle all "Bi-Value Cells" while still using Snyder. It obviously gets around wondering later "Is that 3 and 7 in the cell indicating ONLY 3 or 7 can go there? " Too bad the software doesn't seem to allow that indication. Nice solve! I doubt I ever would have got it, but I practice every day. The LA Times "diabolical" is usually not all that hard - a finned X-wing and a Turbot Fish or something and boom, that's it!

19:45 I think i will never get into multi number chains, just because it seems so arbitrary where to start or what to look for. might as well guess with pencil at this point.

I know I've come late to this one, but did anybody else solve this without reference to NY times logic, y-quadruples, empty rectangles or long chains? Well I did, and I don't think I made any assumptions as Simon inadvertantly did on that alleged 3-7 pair in the bottom middle box. Looking back, I think I did more complete Snyder notation and the odd trick of my own on skew triples within a box. I soon had more rows and columns with 6 or 7 digits in (including pairs) and my longest chain was a 3. This is the first puzzle I've finished significantly quicker than Simon did. Not to knock you, Simon - you often crack puzzles I get absolutely nowhere with.

While it took 62 minutes to solve this puzzle, I used all the basic techniques, including your Sneider technique with swordfish.

I fear anything at a difficulty of 28 or above. This was a 75! #FEAR.

What is the system you use above the puzzle

Could you please add the link to this puzzle for us to try? Thanks!

How does a bent quadruple work? Sometimes you do advanced logic methods, but I don't understand when they do/don't work

At 09:32, consider a 4 in row 5 column 7, which implies a 4 in row 3 column 4. But the former implies a 7 in row 7 column 7 and the latter implies a 3 in row 1 column 6. The two taken together rule out all the possible assignments for row 7 column 6. So, a 4 in row 5 column 7 must be ruled out. By applying (mostly) elementary rules, eliminate the 9 in row 7 column 8 and the 5 in row 1 column 3. Next, consider a 6 in row 2 column 8, which implies a 6 in row 4 column 1. The former implies a 9 in row 1 column 8, the latter an 8 in row 5 column 3. But these rule out the remaining two possibilities for row 1 column 3. So, a 6 in row 2 column 8 must be ruled out. The solution now follows from elementary rules. In each case, the pattern consists of a pair of cells in a column or row that contain the only two possibilities for a "6" or "4", respectively (I call this configuration a "two-way", you call it a pair), coupled with a further cell in a shared row or column which contains a possibility for the "number", a sort of partial X-wing pattern. Is there a name for this pattern?

Very helpful walk through! Just wondering how did you highlight/color the cells in Duncan's Sudoku Solver?

Just wondering why you didn't complete the Snyder notation for at least the 5s and the 4s. I'm guessing that things are different when you're recording and attempting a fast solve.

My Sudoku program says there are multiple solutions to this puzzle/

What software do you use for solving sudoku?

@ 19:41 you have reached a contradiction which resolves row 9 column 3 as 7 - isn't it the case?

This guy plays 4D sudoku

It is not possible for an usual human to find the chain at 20:03 )))

To anyone that is trying to learn how to start... 1-9 and mark only where 2 of those numbers can be.

Stop apologizing! I stare at the screen a lot longer than you do! LOL

well I never

It's a good thing they moved on from this software. It's awful for this puzzle.

You are borrowing