- Board and stones general description: (no change)
- Placement of handicap stones: A matter for tournament rules or
personal agreement, not the rules themselves, but once they are placed
and the game started they are considered the same as stones previously
placed during the game in regard to liberties life/death etc.
- Black first unless special agreement such as fixed handicap,
alternating: (no change)
Intersection = where the lines cross or meet (including edges and
Group = maximal orthogonally-connected set of stones of the same color
(a single stone not connected to any others counts as a group).
Group of the played stone = the group containing the stone that was
just placed = the stone that was just placed, and any other stones
which are now part of the group containing that stone (i.e. all the
stones of groups of the same color having at least one stone adjacent
to the stone that was just played).
Breathing space (for a group) = empty spot orthogonally adjacent to any
stone of the group.
- Capturing: If any group of one color has no breathing space (because
it had only one breathing space but that space has now been occupied by
a stone of the other color that was just placed), ALL the stones of
that group are immediately (before it is the next person's turn to pass
or place a stone) removed from the board (i.e. the group is captured).
If several groups of the same color satisfy this no-breathing-spaces
condition, ALL of them are immediately captured (all the stones of all
the captured groups are immediately removed).
- Legal moves: (Japanese/American rules, no suicide, but with SuperKo
mostly per Lasker's original statement):
Whenever it is one player's turn to play next, that player may pass, or
may place one of his stones on one of the intersections of the board
subject to the following restrictions:
The intersection must have just-previously been empty (no stone on it).
Either the group of the placed stone must have at least one breathing
space, or at least one group of the other color must be captured (per
the earlier condition, no breathing space) thus creating breathing
space for the group of the placed stone.
The resultant position (after placing the stone and removing the stones
of any thereby captured groups of the other color) must NOT repeat the
exact whole-board position at any previous time (at the end of a play)
with the same person to play.
- Prisoners and supply of stones: During the first stage of the game,
there is an unlimited supply of stones of both colors to use, one at a
time, for placing on the board. Captured stones (stones removed from
the board when their group is captured) are put in a special storage
area that is empty at the start of the game (except that by special
arrangement a number of prisoners of one color or the other may be put
there to compensite for differing skill of the players and/or to
compensite for the advantage of the first move). During the second
stage of the game, stones are taken not from the unlimited supply but
from the storage area for prisoners. If during the second stage the
prisoners storage area becomes empty of one or the other color of
stones, an equal number of stones of each color is put into the
prisoners storage area to allow play to continue from that source of
- Ending regular play: When the two players pass consecutively, the first
stage of the game is ended and the second start begins. When the two
players pass consecutively AFTER the first two passes, the second stage
is ended and the counting begins.
- Final life/death and counting: All stones on the board at the end of
the second stage are ruled alive for the purpose of counting. Any
maximal orthogonally-connected sets of empty intersections which touch
(have at least one empty intersection touching) only one color of
stone, not the other, count as territory for the player who was placing
stones of that color. Each stone still in the prisoner storage area
counts against the player who was placing stones of that color. (An
adjustment to this score may be agreed-upon before the game began, for
example a half point in White's favor to avoid draws.)
- Early resolution: At any time the two players may agree to fill
neutral points in parallel, or that certain groups are to be removed
immediately without actually capturing them, and to end the game with
these agreements before carrying out the full two stages specified
above. (In timed games, some agreement must be specified whose clock
will run under what circumstances when players are negotiation towards
such an early resolution of the game.)
- Equivalence: Any method of play mathematically equivalent to the
above can be substitued, such as a computer program that doesn't
actually place stones on a board but merely updates its memory and its
display of its memory, and keeps track of the number of prisoners and
stones played during the two stages separately and combines the
sub-totals in an appropriate way at the end of the game.
- Comment: The score here is equivalent to Japanese score, but without
the fiat rules about what's alive and what's dead. Playing stage two
from the prisoner's storage is equivalent to deciding what's alive and
what's dead by the Chinese or Lasker "kill it, or else it's alive"
rule, without screwing up the essentially Japanese score. Therefore
score is in 1-point increments instead of the 2-point increments of the
Chinese subtract-whole-territory counting method. As a result komi can
be meaningfully adjusted in 1-point increments to have a 50% chance of
better matching the diffence in skill and advantage of first move.