Reverse Button Go

Whereas in Button Go the first player to pass gets a "button" (worth 1/2 a point), in reverse button go the last player to pass gets a button (again, worth half a point). Reverse Button Go was first proposed by Herman Hiddema.

Reason for this rule

Under AGA rules, pass stones are used, in combination with the rule that white must pass last, to achieve a score by territory counting that is the same as the score would be by area counting.

The rule that white must pass last is somewhat unpopular it seems, introducing an asymmetrical game end condition (the game ends after either two or three passes, depending on who passes first).

If, however, you end the game after just two passes regardless of color, you get a phenomenon called "pass fights", which go something like:

1. Black pass (pass stone)
2. White ko-threat
3. Black response
4. White pass (pass stone)
5. Black pass (pass stone)

If you compare this with a normal game end:

1. Black pass (pass stone)
2. White pass (pass stone)

Then white has gained a pass stone, and thus a point, by the ko-threat and response exchange. Of course, instead of passing (step 5) in the first sequence, black can also play a ko threat, and get:

1. Black pass (pass stone)
2. White ko-threat
3. Black response
4. White pass (pass stone)
5. Black ko-threat
6. White response
7. Black pass (pass stone)
8. White pass (pass stone)

Which would rebalance the number of pass stones, and hence the score. But again, white need not pass on step 8 here...

The above is what is called a pass fight, and one extra point will hang in the balance depending on who has the most ko threats.

With reverse button go, pass fights are useless, because the outcome will be identical:

1. Black pass (pass stone)
2. White pass (pass stone, button)

Black gets 1 point, White gets 1.5

1. Black pass (pass stone)
2. White ko-threat
3. Black response
4. White pass (pass stone)
5. Black pass (pass stone, button)

Black gets 1.5 points, White gets 2.

1. Black pass (pass stone)
2. White ko-threat
3. Black response
4. White pass (pass stone)
5. Black ko-threat
6. White response
7. Black pass (pass stone)
8. White pass (pass stone, button)

Black gets 2 points, White gets 2.5

So in all cases, white gets 0.5 points more than Black, and there is no incentive to start a pass fight.

With reverse button go, you can use territory counting with pass stones to get an area scoring result, but without the need for White to pass last.

Due to the pass stones, moves inside your own or your opponents territory after all dame are filled do not cost points, so many difficult positions (such as bent four in the corner) can be resolved by play.

Number of passes irrelevant

Reverse button go also has the property that the number of passes used to end a game becomes irrelevant. Examples:

1. Black pass (pass stone)
2. White pass (pass stone, button)

Black gets 1 point, White gets 1.5

1. Black pass (pass stone)
2. White pass (pass stone)
3. Black pass (pass stone, button)

Black gets 1.5 points, White gets 2.

1. Black pass (pass stone)
2. White pass (pass stone)
3. Black pass (pass stone)
4. White pass (pass stone, button)

Black gets 2 points, White gets 2.5

Reverse button go is therefore compatible with whatever number of passes a rules designer deems appropriate to end the game.