Lasker Maas Rules With Long Cycle Rule
These rules are a slight variation on the LaskerMaasRules. Many people dislike superko, and even professional Chinese players do not apply superko literally as written. Motivated by that, these rules keep all the essence of the Lasker-Maas rules, but changing the superko rule.
The basic version is identical to LaskerMaasRules but replacing Rule 4 (positional superko) by the following two simple and intuitive rules:
- Rule 4: The BasicKoRule. It is forbidden to immediately recapture a single stone, that has just captured a single stone.
- Rule 5 (long cycle): If at any time in the game (either the main phase or the second phase) a cycle of repetitions is established and noticed by the players or the referee, and none of the players wants to break the cycle, then:
- If both players pass the same number of times (possibly 0 times) in the cycle (equivalently, if both capture the same number of stones, possibly 0), then it is a balanced cycle and the game is immediately stopped deemed a draw / no result, depending on the tournament rules.
- Otherwise, it is an unbalanced cycle, and the player that is passing more times in each cycle (equivalently, the player that is capturing more stones in each cycle) is immediately declared the winner of the game.
- Triple ko, quadruple ko, eternal life and other "hot" cycles will result in a draw, just like is traditional in China, Japan and Korea.
- SendingTwoReturningOne and similar positions cannot be abused because they are unbalanced cycles, so they lead to losing the game even in the second "area scoring" phase.
- MoonshineLife behaves like a triple ko, as it is a balanced cycle. There are two possible results, "moonshine group lives" or "moonshine group dies". Each player prefers one of those. Like in a normal hot triple ko during the game, if either player has enough of a lead to win the game even if allowing the opponent to get his preferred result, then that player can accept the worse outcome and win anyway. Otherwise, both will prefer to keep fighting the ko (the moonshine player to avoid dying, and the other player to avoid ending the game with the moonshine group living).
- DoubleKoSeki + BentFourInTheCorner behaves exactly the same way as moonshine life: one side can at any time start the attack to kill, creating a triple ko due to the infinite available ko threats. The other side can only wait and hope that the opponent does not attack, and just lets his group live. Under this ruleset, it can become a draw if neither player wants to yield.
Moonshine life has (at least) two properties that set it intuitively apart from triple ko:
- One player can "force their preferred result to be definitely achieved on the board, without waiting for the two passes, or else enter an infinite cycle", but the other cannot: the player defending the moonshine group can force his group to "stay on the board until the game end, or create an infinite cycle", but can never force the situation to be "resolved". Put differently, if infinite phases and resumptions were allowed, the defending moonshine group player can force infinite resumptions, but cannot force an infinite cycle within a single phase, unlike his opponent. In a normal triple ko, both players can force an infinite cycle within a single phase, without this asymmetry.
- It is not a "hot" position: there is no hurry during the main phase to do anything about the moonshine group, as its situation will not change. So it can be left to be resolved at the very end.
To avoid moonshine life and similar positions, then taking advantage of the second property, this version uses the long-cycle rules in the main phase, but use superko only for the second phase. This has the effect of ruling moonshine life dead, but still avoiding superko in the main phase of the game, thus making triple ko and such lead to a draw. Since the second phase will almost never be used in fact, the superko rule will almost never have to be kept track of either.
Still, since this version retains superko, it is likely to be a "compromise solution leaving everyone unhappy": If superko is accepted, simply using original Lasker-Maas might be better, and if it is rejected, then perhaps version 3 or some specific moonshine-life-ruling is better.
The third version is motivated by the desire to rule moonshine life as dead, instead of working like triple ko, but still avoid using any form of superko. That can be done using the previously mentioned properties of moonshine life.
One option is to just state: "When one player can force actual infinite repetition in a balanced cycle, but the other player can only wait, then the forcing player wins the game if the other does not yield the infinite cycle". This of course is not formal but would have to be interpreted by referee. Even though it is a bit more precise than just saying "moonshine life is dead" as a rule, it is still informal. This same rule also makes the bent4 dead, in a bent4 + double-ko-seki situation.
A possible formal way to make that distinction by actual play is to play a full game by variant 1, and then adding more extra phases of play to actually show that the above "only one player can force the cycle" holds.
The rules are:
- Play a full game by variant 1.
- If the second phase of the game ends by two passes (and not by means of the long-cycle-rule), then if any player requests so, the game proceeds as described in the following rules. Otherwise, the result of the game as played by variant 1 is the final result.
- The game position after the second phase is recorded, and two different extra "games" are played, each from that starting position, with the next player to play just as if the final two passes had never occurred. In one of these games black tries to prove that they can force a repetition, and in the other, white tries to prove that it is white who can force a repetition.
- Each of these games has two area-scoring phases, like the second one in the basic Lasker-Maas rules (in which stones are taken from the opponent prisoners and not the bowl). So up to 4 extra phases are played: two consecutive ones for the game where white tries to show that they can force the repetition, and other two for the similar black game. Each phase might end by two consecutive passes, or by reaching a cycle that players do not want to break. Each phase starts right where the previous one ended, keeping the same player order, as always in Lasker-Maas.
- In the game where a player tries to prove that they can force a repetition, their goal is to either win the game, or create a balanced cycle IN THE FIRST PHASE (of the two phases of this extra game). Both losing the game and ending with a balanced cycle in the second phase means failing at the extra game's goal.
- If both players achieve their goal at their respective extra games, or if both fail, then the result of the first two phases of play (played exactly as in variant 1) becomes the final result of the game.
- If exactly one player achieves their goal, then that player wins the game.
- This solves moonshine life because it makes sure that the player that would win the game if all moonshine groups were ruled dead, will have a winning strategy (there might be such groups for both players). In effect, the player can simply let all its own moonshine groups die without defense, in all phases, and thus will be able to pass so that any phase in which he does not want to make a cycle ends without a cycle. The opponent will not be able to prevent this. On the other hand, both in the first phase of their own extra game and in the second phase of the opponent's extra game, the player is encouraged to create a cycle, and then the player can engage in actively killing all the opponent moonshine groups: if the opponent resists, then an infinite cycle occurs and thus the player is deemed winner because he wins his extra game but the opponent loses his. If his opponent does not resist, then both phases end without cycles, but all the moonshine groups have been killed and thus that game is scored correctly.
- This proposal is much more complex than the previous two, for the seemingly only practical effect of ruling moonshine life as dead. Maybe there is an alternative, simpler way to distinguish moonshine life from triple ko while using formal, implementable rules. The strategical similarities of moonshine life and triple ko previously outlined is at the core of the difficulty in distinguishing them.
- DoubleKoSeki + BentFourInTheCorner behaves the same way as moonshine life, and in this variant the attacking side can force the death of the bent-four group. Note that this is even in the case that there are unremovable ko-threats, so maybe a bent4 lives because of unremovable ko-threats, but then adding a double-ko-seki to that position makes the bent4 die. This is very unintuitive, but the chances of such a position appearing on a board are astronomically low (A bent4, an unremovable ko threat of the right size and a double ko seki all must appear on the same board).
jann: Your variant 2 seems similar to a possible alternative for bringing AGA rules closer to Chinese rules. For variant 3, note that moonshine is not the only one-sided-postponeable triple ko (bent4 + double ko seki etc.). Santo?: Changed version 3 thanks to your very helpful feedback, and also included a mention of the similar bent4 + double-ko-seki position.
Santo?: That's a good point, bent4 + double-ko-seki becomes a postponeable HOT ko, unlike moonshine life which is not a hot ko. So once it appears it does behave like a true triple-ko. That position should be even much rarer than the already super rare moonshine life, but the given variant 3 does have in fact an asymmetry between black and white as is written, and the argument about "where to break the cycle does not matter" fails. So the variant 3 does not work as is. I feel that treating such a delayed hot ko as an actual triple ko is correct under the spirit of these rules... after all bent four + unremovable ko threat might be fought and exchanged in game, so then it is only natural for a triple ko to appear and void the game. My preferred option is be variant 1, but I understand that some people really hate the remote possibility of drawing with a moonshine life.