Jellyfish

Jellyfish is the four-row, four-column extension of fish patterns. When a candidate in four rows is restricted to the same four columns, it can be eliminated from other cells in those columns.

Technique

1. Find four rows where a candidate appears, with all occurrences in the same four columns.
2. Each row must have 2-4 occurrences of the candidate within these columns.
3. Eliminate the candidate from other cells in those four columns.

Tips

• Jellyfish are quite rare - master X-Wing and Swordfish first.
• Computer assistance is helpful for finding Jellyfish reliably.
• The pattern may not use all 16 intersection cells.