Difficulty: Intermediate   Keywords: Rules


A half-pass is a pass that only hands over half a pass-stone.[1]

See Button Go (which, of course, gave the idea - RP).


To simplify territory rules without changing the score in most cases (switching to area scoring gives Black an extra point in about half the cases), we could use following rules (cycle treatment intentionally skipped):

  • naive territory scoring (neither dead nor seki defined)
  • first and last pass are half-passes; other passes are full-passes
  • each half-pass adds a new captive to the half-pass zone
  • each full-pass hands over a new captive to the opponent
  • a pass that directly follows a full-pass ends the game
  • captives in the half-pass zone only score with half of their value (in practice each player takes one stone from it, no matter which, and, depending on its color, either joins it to his captives or drops it into his supply)

To enable an agreement about dead stones, following may be added:

  • first pass may suggest dead stones
  • if a pass directly follows it, the passing player may choose if it ends the game or not (by using the half-pass zone or not, of course)
  • in the ending case the suggested stones are removed as captives, otherwise the suggestion has no effect


Black wins by one  
  • B5 at B7 were wrong: costs Black a point (first pass therefore nicely sets off clean-up)
  • pass W6 does not end the game because it's not right after a full-pass (however, if pass B5 suggests dead stones, it might end)
Again Black wins by one  


Version 1

If territory scorers play out things after the "end", both players have to use the same number of stones because each costs one point (in most cases, at least):

  • either it decreases own territory
  • or it adds a dead stone to opposing territory
  • or it hands over a captive

The number of stones used in the color-alternating clean-up sequence either

  • is even: first and last stone differ in color and halving them doesn't harm balance
  • or odd: first and last stone are of same color and halving them restores balance

Version 2

If territory scorers use area scoring, but don't want the score to change (in most cases, at least), they can increase komi by half a point and use a half-point button:

  • either Black gets the last "neutral" and White is compensated with button plus komi increase
  • or White gets the last "neutral" and Black makes up for the komi increase by taking the button

They can even mask area scoring with pass-stones: storing captives as usual and handing over a new captive on each pass. However, they have to take care that White hands over an extra stone if the game's last pass was made by Black and that taking the button goes together with a handing over: strange.

Note that the button effectively halves the cost of the "first" pass (actually it just looks like a pass, since half of the stone goes onto the virtual board and only the other half is handed over, but let's sloppily call it so).

What about the last pass? If White made it, deduct the komi increase; if Black made it, balance with the extra stone and be left with the komi increase: komi increase and extra stone effectively halve the cost of the last pass as well!

Author: Robert Pauli


Bill: Sounds half-passed to me. ;-)

half-pass last edited by BillSpight on November 19, 2004 - 17:30
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