Diabolical sudoku: Sashimi & Finned X-Wings

We revisit the Diabolical Sudoku we solved a couple of days ago and note other ways of making progress!

[@JohnRandomness105]

3:00 Oops, I found a finned X-wing in 8s different from the one you described. It ruled out the same 8, though. 5:40 Okay, the Sashimi X-wing is what I found. The way I figure it is that an X-wing (swordfish, jellyfish, finned or not) works perfectly fine if the digit is barred from a cell in the device. (In each column, the digit is still restricted to one of the particular cells of the position.) 9:40 As for the 4s position, I found it as an empty rectangle rather than a finned X-wing. Again, the same 4 was eliminated. It seemed rather useless. However, now with the 8 occupying a remaining 4-cell, maybe not.

[@wossaaaat]

Ah, sashimi... that's what I've been loosely calling 'that finned thingy' in other videos.... My sudoko app throws them at me all the time. They're dead easy to spot with highlighting turned on. I can sometimes spot them after staring at the pencil marks for a while, and usually directly searching for them. Without pencil marks, or with the limited pencil marks of snyder, I find it veeeery difficult to spot. Probably because I have the memory of a goldfish, so unless it's a couple of Rs/Cs restricted down to 2 or 3 empty squares with the same candidates, chances are I'll miss them....

[@madchris47]

there is another way to say that 8 can only go at 5 - 9 , if we supposed that 8 go at 5-4 we can see that the only position that 8 goes is 9-4 and this can be, so we can eliminate 8 (5-4) so we can eliminate 8(6-8) PS sorry for my english

[@discountdadgaming340]

I know I'm very late to this, but couldn't you also eliminate the candidate 8 in r8c6 because of the skyscraper using r9c5 and r8c8, leaving only the 8 at r9c5 alive?

[@javabeanz8549]

I would give it a second thumbs up if I could, just for the pun ;o)

[@Adam-hs4de]

Simon, it seems as though there should be other "rules" or "restrictions" to the fin x or sashimi fin x. Yes it all starts w a candidate locked in 2 positions in a row or column, but what about starting in a row/column in same box and then scanning to another box for the pattern? Imagine please locked 7s R9C7C9, scanning to sashimi value of 4 in R3C7 and a 7 candidate at R3C9 to make degenerate x wing; 7 candidate in R3C8 being fin. There's 1,7 pair in R1C7. By sashimi fin, I should eliminate that 7 thus solving 1 for that spot. It was wrong. I ran it w 7 as the value and it solved puzzle. Hence my opening statement of other rules/restrictions and everywhere I read online or other videos don't explain it. And I'm a smart guy so something is lost? Please help!

[@JohnRandomness105]

Okay, these are the requirements for your situation: row 9 can have 7s only in columns 7 & 9. Row 3 can have no 7s outside of columns 7, 8, and 9. (You placed a 4 in R3C7, but the requirement is still satisfied.) In that situation, we can ignore row 9, and just focus on box 3. The 7 in row 3 is in box 3, so R1C7 must be a 1. It it were a 7, then row 3 could have no 7. The only way a 7 could be in R1C7 is if another cell in row 3 outside of box 3 could take a 7. The requirement must be violated.

[@glidermike1]

had perfect X on 4s witth C2 R2 & C7 R2 aligned with C2 R9 and C7 R9. You eliminated C7 R9 destoying my X, What is the presidence of one over other does finned trump X and how do you apply it. Totally confused