These anti-quads are so anti-everything that their antipathy needs to be spread out across four different cells to avoid overloading a digit. They might only list the digits they’re most against, but they don’t want any other digits doubling up, either.

The last puzzle I published with “anti-quadruples” fully filled each anti-quad circle, providing maximum information about what wasn’t there. This time, a few digits seem to be missing, and most of these circles eliminate very few candidates each.

What do arrows do? They point! Arrows in Sudoku puzzles don’t often point anywhere in particular, though. They just point out that some puzzles do require arithmetic skills, to wit: summing up a series of single digits to a single-digit total.

That thermometer in the center, it is 23 cells long, and yet still contains only digits between 1 and 9 inclusive. 23 cells is one of the longest slow thermometers possible within a standard 9x9 Sudoku grid, although I’ve heard rumors of even longer. I think to be longer, the thermo has to cross itself, which can lead to some confusion. There are a few different ways to arrange such long thermometers, and this is one.

I looked up a few temperature scales to use for puzzles involving “slow” thermometers like these, and there are some odd ones. It’s nice to live in a world in which such things are settled, in which we have two settled temperature scales oriented around humans, and easy math to convert between them. Team Fahrenheit and Team Celsius don’t apply here, though. Here, temperatures rise very, very slowly, or sometimes not at all.

It could have been named “Son of DoubleDoku” or “2 Double 2 Doku” or even “DoubleDoku: Folie à Deux,” but whatever it’s called, it’s a sequel to DoubleDoku.

More of these combo cages that act as “German Whispers” lines. In this case, some of them are square, and adjacent digits means orthogonally-adjacent, since there’s no way a square would work otherwise. For extra fun, very few of the cages have totals.

These cages are the color of “German Whispers” lines as a reminder that each cage functions as just such a line. Even the two-cell cages function as if they were two-cell green lines. Imagine that they’re green lines, but I’ve helpfully provided the total for all of the digits along the line.

Sometimes I think I should create a separate tag for puzzles so full of cages there’s no other constraint. Like Predator 6, and this one. If I ever do, I should update this text, since it will no longer apply.

Every digit is given twice, and yet it still seems like it might not be enough. Except these are unfriendly digits, keeping away from their closest relations. Can’t we all just get along?