Lesson 31

Jellyfish

The rule

When a number's candidates in four rows all fall within the same four columns (or in four columns all fall within the same four rows), that candidate is removed everywhere else in those four crossing lines.

Step by step

1. In each base row, 5 is a candidate in 2, 3 or 4 cells. Taking the four base rows together, every 5 candidate sits in one of only four columns. This is a Jellyfish!
2. The Jellyfish means we can remove the candidate 5 from the four columns that hold it, in every cell outside the four base rows.