dailysudoku.com

[nataraj]

Trying to solve today's nightmare, I came across this position:

[Asellus]

In my opinion, it's best to see it as a Medusa Wrap. I haven't found any simpler way to "see" it.

I can't follow your chain as you've marked it. I see two different XY Chains, each involving 6 cells, that link R3C8 with R9C4 and give the implications you mention. In any case, your assignment conclusions require use of ALS's and/or strong links in C8 and in R9 that are independent of those chains. The nice thing about Medusa is that it takes all those things into "consideration."

[Asellus]

If you want to avoid coloring, your grid is solvable as follows:

(1) Sashimi X-Wing in R19 removes <7> from R7C1
(2) XY Wing removes <3> from R9C2
(3) A long XY chain with pincers at R6C3 and R9C2 removes <7> from R9C3

No doubt there are other ways.

[nataraj]

Asellus, I am not trying to avoid coloring at all. Especially Medusa and even "extreme" coloring are great methods to make one aware of certain possibilities that exist in the grid. But in the end, when the coloring leads to results like the elimination of a candidate or even (as with color wrap) of a whole lot of candidates, I don't feel comfortable with just saying "well, guys, I did some magic. The magic is great. It even has a fancy name. I solved the puzzle". I like to be able to point to a part of the grid and to say: "look here, this is why r9c8 must be 3".

I am aware that equivalence marks ("r" and "g") are just as valid once you've "bought into" the concept, but for communication purposes I prefer to steer clear of these. The reason might be that once I got into a nasty (and completely unnecessary) argument with someone who just didn't trust the colorful arguments ("why red" "why green" "you're making these up" ...).

Actually I was hoping to have found some well established and well understood pattern (like "xy-wing"), that can be used as a kind of shorthand, so one doesn't have to go through the individual proof every time.

[nataraj]

I like the "sashimi"...

Just to make sure I understand this fishy business: the sashimi is like an "almost-skyscraper" (poor critter needs some serious growing, I'd say) :

If r9c3 is NOT "7", then we'd have a skyscraper in 7 (r1c1=r1c8-r9c8=r9c2), either way, the 7 in r7c1 is toast.

Thx.

[Asellus]

Since it's nearly 2am here, I can't digest all of your posts right now. But, as regards "Sashimi" fish: they are finned fish with a piece of the fish missing. (Presumably, some high priced diner is munching away on the missing piece.)

So, while a Sashimi X-Wing can be seen as an "almost Skyscraper" (or, in some cases, an actual Skyscraper), it is more true to the concept to say that it is an "almost finned fish" ... in this case, an "almost Finned X-Wing."

PS: I only offered the non-coloring route for those who eschew coloring. Me, I'm very colorful.