Proven Sudoku
Kraken Fish
Also called Kraken Fish pattern.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
A fish that does not quite work. You check each way it could fail. If they all point at the same square, you can rub the number out anyway.
The exact rule, for stronger players
The rule, stated exactly: A finned fish where, instead of restricting eliminations to cells seeing every fin, each fin is followed by a chain to a common conclusion.
What it removes: Remove the candidate that both the exact fish and every fin branch exclude.
Why it works: Case split on the fin: either the fish is exact, or the fin is true and a chain from it reaches the same elimination.
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
- Finned FishA fish pattern with one extra square hanging off it.
- KrakenTake a pattern that nearly works.
Related complex fish
- 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.
- 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.
How often does it come up?
Our rough estimate: rare.