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If memory serves (it's been a while since I did this one), the logical step is (SPOILER - highlight below):

The two 7's in row 9, columns 6/7 force one of the two sevens in that column (R15C6 or R16C7) to be black, which forces the 13 in R15C7 to be white.

From the point in the spoiler, I made a good amount of progress in a couple of minutes (although I'm tired, and hitori isn't my strong suit), so I'm pretty sure that was the logical break in.

Honestly not sure how I missed that guys. My apologies! I swear I had logic that disproved that (and somehow used the same incorrect logic two to three times in the process of solving to verify it myself). As Puss-N-Boots in a Shrek movie so aptly puts it, "I have shamed myself"

Hopefully I'll get this one back into circulation soon!

It doesn't make you a bad person, don't worry

If you look at the big picture, this one can be solved without uniqueness/guessing. It's a tough one but good logic throughout (and quite fun).

Shvegait wrote:

Well, couldn't you incorporate that subtraction/division rule for >two-cell regions without causing any confusion? As it is, there won't be any puzzles with subtraction or division in >two-cell regions, so there's no conflict. You wouldn't need to allow Snyder variants to expand just that one rule, that would be a separate question. Maybe I'm missing something, though...

You're right that there (currently) aren't any puzzles with subtraction/division in a 2-cell region. However, it actually can screw up the operationless puzzles. For example, if you have an L shaped region of size 3 with a given 2, under the current rules you know that's multiplication:

Code:

 21
 1

However, as soon as you enable multi-cell division and subtraction, the following is possible:

Code:

 62
 2

So that's the current issue in a nutshell. Multicell division/subtraction really only affects puzzles with no (or limited) operations, but the basic assumptions dramatically change when 3+ cell regions are addition/multiplication only.

That's what I've been doing, pretty much. Sometimes knowing a number exists helps you to place other key squares, and so the + helps a lot (or for that matter, when a puzzle ends up having all of the squares as yes without you realizing it).