Learn / Specialty reference
Sudoku technique · Specialty reference · reference
Kraken fish
Inference chains can connect fish fins to a target that does not directly see every fin.
How to spot it
Replace direct fin visibility with a proven implication for every relevant fin case.
The common mistake
One successful fin chain does not cover the other possible fin cases.
Learn this first
Finned fish and AIC.
Further reading: hodoku.sourceforge.net