
Jellyfish 

A Jellyfish is where four columns have a candidate in only four different rows, or vice versa. This is like an XWing or Swordfish expanded into four units. The columns or rows that have these candidates are the primary units, and must only contain the candidates in the other four rows or columns called the secondary units. All other candidates in the secondary units can be eliminated.
Consider the example on this page. Rows 2, 4, 6 and 8 from the top only have 4's in columns 1, 5, 7 and 9 from the left. Thus, all other 4's in columns 1, 5, 7 and 9 (highlighted in green) can be eliminated.
Sudoku Snake gives Jellyfish a skill value of 260.






