Jellyfish (4x4 Fish)

Difficulty

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Description

The Jellyfish is the 4x4 variant of the X-Wing. A Jellyfish brings nothing new to the table. It behaves exactly like an X-Wing or Swordfish, except that it is based on 4x4 cells.

See the X-Wing and Swordfish pages to learn more about how (and why) the Jellyfish technique works.

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You don't need to look for bigger fish

In standard Sudoku (9x9), you only need to look for X-Wings (2x2), Swordfish (3x3) and Jellyfish (4x4). For every fish that is 5x5 or bigger, there would always be a complementary fish, that is smaller in size, so you don't need to look for the bigger one.

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Jellyfish Examples

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Very common for Jellyfish

What is seemingly very common for Jellyfish is that there is a complementary Jellyfish. So for every Row-to-Column-Jellyfish there seems to be a Column-to-Row-Jellyfish.

That is a bit weird. Usually we would expect the complementary fish to be 5x5 in size. (9 rows/columns of the Sudoku grid minus 4 rows/columns of the Jellyfish). Strangely, I haven't found a single Jellyfish that doesn't have a complementary Jellyfish.

Here are some examples for complementary Jellyfish:

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