LogFAQs > #962365667

Serious Cat posted...

It's an equivalent set like the ring except it's isolating the cages instead of the boxes in the corners and has an extra row, thus an extra set of digits 1-9. I can throw in an extra column and make the two sets equivalent, like this:

https://gamefaqs.gamespot.com/a/user_image/5/4/0/AAPWHiAAC4s8.jpg
The blue set is now equivalent to the red set. The center square sees all of the other blue squares and therefore appears in the red set exactly once, somewhere in column 8.

This is another similar equivalent set:

https://gamefaqs.gamespot.com/a/user_image/5/4/1/AAPWHiAAC4s9.jpg
The blue set is still equivalent to the red set with the column we know contains the red square corresponding to the center digit removed. The center square is still included in the new blue set and can still see all the other blue cells, so the new equivalent sets still have to contain the center digit in red exactly once, this time in column 2.

But like you said, it didn't really get me anywhere. Just noodling in SET theory.

It's an interesting observation, but I think it is captured by the "draw everywhere purple can be" question, because that also observes that purple can only be in those cells in c2 and c8 as well.

Did you want to take a crack at the question of "where is everywhere red can go?" otherwise I'll probably finish the reveal tonight.