Swordfish
The three-line version of the X-Wing: a digit confined to three rows and three columns.
What it is
A Swordfish uses three rows in which a digit has two or three candidate cells, all falling within the same three columns. Because each of the three rows needs the digit and only those three columns are available, the three columns are fully claimed. The digit can be removed from all other cells in those columns. Rows and columns can be exchanged for the transposed pattern.
How to spot it
For each digit, list the rows where it has two or three candidates. Take combinations of three such rows and check whether their candidate columns fit inside three columns in total. The cells do not need to form a neat grid — gaps are allowed, which is what makes Swordfish harder to see than X-Wings.
Worked example
Step through the reasoning below. Each step adds one layer: first the position, then the pattern, then the candidates involved, and finally what can be eliminated.
Step 1 of 4: The starting position
- Pattern cells
- 1/2, 1/5, 1/6, 4/2, 4/5, 4/6, 6/2, 6/5, 6/6
- Digits
- 3
- Eliminations
- 3/2, 2/5, 2/6
Press a marked square to point it out on the board above.
Why it matters
Swordfish handles positions where an X-Wing does not quite fit. It is a genuine step up in difficulty, mainly because the pattern is often incomplete: recognising a Swordfish with missing cells is the skill that separates advanced solvers from intermediates.
Practise now
Solve a puzzle where this technique decides the game
Frequently asked questions
How is a Swordfish different from an X-Wing?
Size. An X-Wing uses two lines with two cells each; a Swordfish uses three lines whose candidates fit inside three cross-lines. The elimination logic is identical.
Do all nine cells need to hold the candidate?
No, and they rarely do. Each of the three rows needs at least two candidate cells, and all of them must fall within the same three columns. Missing cells are normal.
Is Jellyfish the next step?
Yes. A Jellyfish uses four lines and four cross-lines. Beyond that the patterns stop being useful, because a five-line fish always has a smaller equivalent.
Put it to use
Where you will meet it
Expert grids are the only place this pattern regularly decides the solve. Bring your notes.
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