Proven Sudoku
Franken Fish
Also called Franken, Frankenfish.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
A fish where a box is allowed to join in with the rows and columns. That lets the pattern bend round corners it could not reach before.
The exact rule, for stronger players
The rule, stated exactly: A fish where base or cover sets may include boxes as well as lines, but all sets of one role stay within one orientation plus boxes.
What it removes: Remove d from cover cells outside the bases, subject to fins.
Why it works: The set-cover counting argument never required the sets to be lines. Any collection of houses works provided the count balances.
Worked examples
None yet. This pattern does not turn up in our daily boards, so there is no real example to show. We would rather wait than draw a fake one.
Learn these first
- Complex Fish (rank framework)The fish idea, but boxes are allowed to join the rows and columns.
- Endo-FinA spare square that sits inside two parts of the pattern at the same time.
Related complex fish
- Kraken FishA fish that does not quite work.
- Mutant FishA fish where rows, columns and boxes can be mixed freely on both sides.
- Sashimi FishA finned fish that is missing a corner.
- CannibalismWhen a square belongs to both halves of the fish at once.
- Finned FishA fish pattern with one extra square hanging off it.
How often does it come up?
Our rough estimate: rare outside hard puzzle collections.