Basic Fish
Points.
All fish are single digit patterns. Basic fish like XWings and Swordfish have
equal numbers of rows and columns. For an XWing, it is either 2 row truths
and 2 column links or 2 column truths and 2 row links. A Swordfish is the
same with 3 truths and 3 links, Jellyfish are 4, and Greatfish (Squirmbags)
are 5. The patterns below examples of each fish. In real fish except XWings,
it is not necessary to have all possible candidates. See XWings, Swordfish,
Jellyfish, and Greatfish.
XWing Pattern. The
pattern to the right shows an XWing pattern made of two (red) truths in
rows 3 and six. The candidates in the two rows see each other (linked green)
in columns 3 and 6. The yellow candidates show all the locations where
candidates can be eliminated. An XWing, link all basic fish, is rank 0.


Swordfish Pattern. This
Swordfish pattern has 3 truths covered by three links as opposed to an XWing
with 2 truths and 2 links. The logical reasoning is the same as the XWing,
if all the candidates in 3 truths are contained in 3 links, then no other
candidates in the links can be true, and can be removed.


Swordfish Pattern, Minimal.
This pattern shows a swordfish with the smallest possible number of
candidates. If the center candidate is removed, the logic is still valid
but it's called an XCycle. Only one example elimination is shown.


Jellyfish Pattern.
This Jellyfish is the size 4 member of the basic fish family. Only
one example elimination is shown.


Greatfish Pattern.
A Greatfish has a size of 5 but it is sometimes argued that they are not
required as other, smaller patterns should exist along with the Greatfish.
A Greatfish is more commonly referred to as a Squirmbag. Only one example
elimination is shown.


