Expert technique

Swordfish: The X-Wing’s Bigger Sibling

Swordfish is the three-row version of the X-Wing.

A Swordfish is an X Wing grown by one: three rows, three columns, and six cells that close into a loop. All three columns are taken.

A board with nothing left to place

BEFORE

Another stuck board. No cell shows a single color and no color has just one place left, so there is nothing to place. Pick a color and look at it on its own.

Look at one color

Only the Turquoise dots are showing now. Nothing has been erased, this is the same board with one color kept and the rest set aside. Eighteen cells can still take Turquoise.

Three rows that share three columns

Three of the rows have only two cells left for Turquoise. Look at which columns those cells sit in: between the three rows, only three columns ever come up. Trace the six cells and the path closes into a loop.

All three columns are taken

Those three rows each need a Turquoise, and the only columns open to them are the three in the loop. Three rows, three columns, one Turquoise each. However they settle, all three columns are used up, so every other cell in them loses Turquoise.

Read what that opened

AFTER

Look along the top row. Turquoise had two cells it could go in, and one of them sat in a locked column and just lost it. Only one cell is left, so place Turquoise there. Same as the X Wing: the loop only cleared space, and a much simpler technique finished the job.

Cells being readColor tints match the color being followed

Key Insight

Two rows sharing two columns is an X Wing. Three rows sharing three columns is a swordfish, and the reasoning does not change: as many rows as columns means every one of those columns is taken. The trouble is that a swordfish is much harder to see, because no single row tells you anything on its own. Find the rows where a color fits only two cells, list the columns each one uses, and look for three rows whose lists add up to only three columns.

If you’re stuck on a puzzle, see what to try next, in order.