View the example grid
A Jellyfish confines a digit’s candidates from four starting rows to exactly four columns. Those columns are needed for the four placements, allowing eliminations outside the starting rows.
An example from the app
In row 2, row 5, row 7, row 9, candidate 9 is confined to column A, column F, column B, column H. There are 4 starting lines and exactly 4 crossing lines.
The 4 required placements of 9 occupy column A, column F, column B, column H. In those lines, 9 is ruled out outside row 2, row 5, row 7, row 9.
These notes are therefore ruled out: A1: 9; A8: 9; F8: 9; H1: 9; H8: 9.
The image shows the candidates relevant to this step. A note being hidden does not mean it has been logically eliminated.
Practice the next step
Not every corner of a large rectangle needs a candidate. Check the complete positions in all four starting rows.
In the app, follow the reasoning in the matching lesson and try a task yourself. With a new puzzle, always start from its actual candidate state.
Questions about Jellyfish
What are the four starting areas?
Four rows or four columns whose possible positions for one digit are together restricted to four cover areas.
Must each starting area contain four candidates?
No. Individual areas can have fewer positions. Their combined restriction to four cover areas is what matters.
What if another position lies outside the cover areas?
This Jellyfish condition is not satisfied. You must not overlook an additional actual candidate.
Where can I eliminate the digit?
In the four cover areas outside the starting areas. The direction depends on whether you began with rows or columns.
Should I always look for Jellyfish first?
Check simpler steps, X-Wing and Swordfish first. Tracking four areas needs complete, current candidates.
Keep practicing in Unisu
Download Unisu for iPhone or Android. Solve a puzzle or work through a guided lesson on the technique.
