Sudoku Tricks: The Swordfish Pattern 

I think it'd be fascinating to see eye tracking software / technology being used while the puzzle is being solved, to visualise where you're looking at any given moment.

23:25 That 8 at R7 C7 is not possible cause of the x wing you already had. Amazing video. Have to say, your explanations and the way you present your line of thoughts are really clean, makes it so much easier to follow! Congrats and thanks for the upload, keep it going. Cheers from Brazil!

Even though I had to watch this twice, while playing on my own printout, your description of a swordfish pattern made a lot of sense. Thanks!

Sudoku is such a beautiful game. I love watching a high level solver walk through difficult puzzles. I learn so much here.

I've recently gotten back into doing Sudoku, these videos are helping get my game play to another level.

Very much appreciate the explanation of the logic behind the pattern in this video. I would like to see more of that. Some of the other videos on this channel are you guys just blazing through solutions and it does make it difficult follow and resolve the logic for myself at home

@Cracking The Cryptic - I think the possibilities have to be offset in Swordfish puzzles, at least in ones specifically designed to be Swordfish puzzles, due to the simple fact that if the possibilities were aligned then they would be easily eliminated through an X-Wing or standard elimination before you could even get to the Swordfish itself. It looks like a delay tactic in order to force you in to a Swordfish position. I'm willing to be corrected though, it's only my theory.

Have you considered doing a video on alternatives to schneider notation and their advantages and disadvantages? Or are there really no good alternatives.

I just finished a Sudoku puzzle that had a swordfish and yes, it does the little spaced out numbers. Thanks to noticing that, I recognized a swordfish. :) (Like how you were talking about the possible 4s not being in a line and like shifted.)

at 14:52, you could also use a swordfish of 4s in rows instead of columns. Look at rows 1, 5, and 9. They can only place 4s in columns 3, 4, and 8.

I enjoyed the basics of swordfish... I've watched you use it in many solutions. Wish I'd seen this first, but I only found your channel very recently. I've been bingeing!

That was a beautiful puzzle and brilliant explanation! I THINK I got it. Gotta practice more. Keep up the good work, thanks!

I think I finally fully understand the X-wing and swordfish. Great example. Thank you.

Thanks! Best video I've come across to help understand the swordfish pattern.

Thanks. Helpful as always. Working through your Classic Sudoku app and it's good to find explanations of some of the concepts used in the hints there.

I too am learning so much from your videos. It's interesting that I found the swordfish fours but using pairs in rows A,E&I

Thank you for mentioning the sudoku software that you use! ("Duncan's Sudoku Solver") You should consider putting the name of the sudoku software that you use in the description of your videos.

Excellent lesson on the swordfish! Now I get it

At 17:53 if you remove the pencil mark 4 from c8r8 then columns 3 5 and 8 make another swordfish. There was a double swordfish! Even though it adds no extra information as 3 of the 4s are already known, its still pretty cool. Simon said "oh this is nice" and I thought he was about to point it out, would have loved to see his reaction to that.

Fantastic tutorial! Thank you Simon, finally got the swordfish ...

Very good explanation of x-wing and swordfish. Is there any background on those names: swordfish, jellyfish, squirm-bag? Was someone just having fun making them confusing?

Great lesson. Thanks!

7-8 pairs in box 7, box 1! Take out old pencil marks. The x-wing, etc is not necessary if you complete your train of thought.

Doesn't a squirmbag imply a jellyfish? (A sentence I never thought I'd write). Are squirmbags redundant?

Many thanks. These videos have really opened up another level in Sudoku puzzles for me! Before I started learning about XYZ-wings, WXYZ-wings, swordfish patterns, finned X-Wings and swordfishes, etc, I'd pretty much just given up on doing any of the REALLY advanced sudoku puzzles (Aside from getting things down to a two-choice 'trial and error' solution), and just tried to focus on doing the moderate to difficult puzzles without relying on pencil marks, just trying to keep everything in my head. I still have a lot of practice to go as far as recognizing some of the advanced patterns, though. Once they're pointed out, they seem obvious, but I don't notice them right away. But your examples have helped a lot so far!

You spent a fair bit of the puzzle not having placed a 7 in R2C9, and so when you placed the 7 in r7c3 it was more useful than you thought because it would have then placed a 7 in r3c2

Great information, easy to grasp with your explanations. What app do you use for your puzzles?

I am going to have to watch this one a couple of times.

Wow I never would have found this on my own. Trying to lear sodoku and i guess i figured out x-wings on my own but a really neat trick for the harder solves

What software/programme do you use to do your sudokus? I like the way it allows you to not only put pencil marks in but also put colours in. Where can I find it and is it free to use?

Lol around 23:55, "that's huge because it unwinds this 7-8 double...", this whole time you had 3 sevens pointing at the bottom left 3x3 with only 1 slot remaining for the 7... Sometimes you focus so much on patterns and fancy tricks you forget the easy methods.

the problem with this of course is that you went into the puzzle purposefully looking for the swordfish. i wonder if the requester hadn't brought that up, if the swordfish would've still presented itself while solving the puzzle.

You ever play Picross? I love it and am interested in advanced solving logic and heuristics. I think you would like the game if you haven't played it before. :)

It's a lot simpler to think in terms of rows instead of columns and ignore terms such as "swordfish or "x-wing" which are variants of the "lookout puzzle" we all did as kids

I very much enjoy these.

19.30 Column 3 has 7 and 8 pairs. Pencil Marking on Box: D is not needed. Just put 1 which is only missing number on Column 3. I called it Column: c on my notation.

Great 👍

OH I GET IT you treat the 3-xwing as a MASSIVE three that takes up all 4 of the spots in the xwing and in the other corner made up between the xwing and the new row/col pair, you expect to put a three in as well

Awesome, I just wanted to look this up!

late on this one... I got to the same place Simon did where he found the swordfish. I got stuck there. Once I filled in the one square given by the swordfish, I was able to solve the rest w/ basic sudoku logic. Interesting how that one little bugaboo can unlock an entire puzzle...

very nice video.

I think Mark got caught up in looking for teaching moments and notations instead of looking just to solve the puzzle with simple sudoku. He solved the 7 in r7c3 with the 8 x-wing but if he noticed the 7 in r2c9 first it would have unwound the whole puzzle from that moment. When he placed the 7 in r5c8 at 20:50 if he just looked up and placed the 7 in r2c9 he had the puzzle solved.

Can someone tell me how he was able to color all those 4s in green at 14:42? I have downloaded the Duncan software but I don't see how it's done.

what program are you using in this video?

I was slow to understand swordfish because someone explained it as the shape of the swordfish with a bill Which makes no sense at all No...... The Fairey Swordfish was a triple wing airplane, an extension of the xwing bi plane

I don't get why at 17:30 number 5 go into R9C3. It looks like it could still go into R5C3 and R9C2 instead of R9C3 and R5C2 at this point. What am I missing?

Can someone help me out? At 20:10, why are the candidates for 3 in box 8 limited to C4? I'm not seeing it.

What is the name of the computer program that you’re using? What is the name of the computer solving program that tells you the technique required to solve the puzzle? You mentioned this program at 0:55. Thank you

Good please send me more Sudoku primer

no link to follow so I can try to solve.....bye!

Andrew Stuart’s solver (www.sudokuwiki.org/sudoku.htm) picks up a different swordfish on fours, rotated 90 degrees. Isn’t it the case that more than one swordfish on the same number can often be found?

So the times I'm screaming at the screen "PLACE the 7! You know where it goes!" He's live solving?

6:55 And 9 is called an empty sudoku.

What opening song?

where exactly is the snyder notation discussed in depth? i assume you refer to thomas snyder. but see nothing really from him describing any notation? or am i missing something? .

I know I'm very late, but why are the 4's so "interesting " that you chose to focus on them rather than the 5's for example, which were more plentiful in the puzzle. If anyone knows, please help 😊

20:34 You'll always appear stupid at some point...never let that stop you from doing it though.

I really like your videos but the audio quality is really bad. Maybe you might want to consider getting a slightly better microphone? Keep it up!