Table of Eyeshapes

The following table summarizes the status of various eye shapes.

Legend

• # to kill is the number of times that opponent must play within the eyeshape in order to effectively reduce it to a single eye, hence kill the (single eyed) group (assuming alternating play after that point). Similarly # for seki". A '-' for "# to kill" indicates that the group can only be killed by capturing it outright. Of course, these values are merely of academic interest in some cases.

• Status is the status of a group which is surrounded, and has a single eyespace of the indicated size and shape (assuming alternating play with opponent first), with no opponent's stones within the eyespace. "Unsettled" means that the status depends on who plays first (depends on sente); this is the case when "# to kill" is exactly 1.

• # libs is the effective number of liberties (in the second sense) that the eyespace yields in a capturing race; see BigEyeLiberties. This assumes that life cannot be made immediately (or else the value is '-'), and does not count the stones inside which are used to prevent life from being made. Note that seki is as good as life for a capturing race.

• Note that some of these shapes (most notoriously the Bent Four) have different properties in the corner. See also Big Eyes Can Be Small In The Corner.

Table

  Size       Shape    Status # to kill # for seki # libs
     1           -      dead         0          -      1
     2           -      dead         0          -      2
     3 ThreeInARow unsettled         1          -      3
         BentThree unsettled         1          -      3
     4 SquaredFour      dead         0          -      5
          BentFour     alive         2          -      5
       PyramidFour unsettled         1          -      5
             other     alive         2          -      5
     5 CrossedFive unsettled         1          -      8
         BulkyFive unsettled         1        (3)      8
              ****
                *      alive         2        (3)      8
               ***
                *      alive         2        (3)      8
                *
               *
               ***     alive         2        (3)      8
                *
             other     alive         -          3      8
     6 RabbittySix unsettled         1          -     12
             other     alive    varies        2–4     12
     7                 alive    varies        1–5     17
     8                 alive         -        2–6      -
   n>8                 alive         -     varies      -
                             (no more than n-2)

See also

• Eyes collection
• Eye shape
• A library of eyes in Go II: Monolithic eyes, page 7 a.s.o. by Thomas Wolf are related.