What Are The Differences Between Japanese, Chinese, & New Zealand Rules?

I am passionate about, and spend a fair amount of time pursuing, educating brand new players about Go. I also run the New Zealand Tournament Group. As a byproduct of these endeavors, I am regularly asked to comment on the differences between Japanese versus Chinese, and Chinese vs New Zealand rule sets. I have posted this as an easy reference for anyone considering or fielding such questions.

Table Of Contents

  1. Introduction
  2. Japanese vs Chinese: Technical Discussion
  3. The Role Of Human Perception
  4. The New Player Perspective
  5. Chinese vs New Zealand
  6. An Example Of An Advanced Concept For Rule Sets: Superko
  7. A Note Concerning Japanese Rules
  8. In Conclusion

 

Introduction

There are many Go rule sets used throughout the world today, seven of which are currently widely used; Japanese, Korean, Ing, Chinese, AGA, New Zealand, and Tromp-Taylor. Among the seven, each allows you to play the game in almost the same way. The exact wording of the rules differs, but the gameplay that each rule set creates on the board is 95% identical; regardless of which rule set is being used. This 95% is the core of Go gameplay.

However, the manner in which these rule sets are worded can and does change how the game handles certain types of rare board configurations. It is worth pointing out that most of these situations are almost exclusively encountered in Dan level gameplay. The rare stuff is difficult to understand, unless your knowledge of Go is rather advanced, and really has no bearing at all to a Kyu level player. For that reason, I won’t be discussing the aspect of rule set wording here.

Although, I will provide one example later (Superko), just for fun. If you are interested in learning about how the wording of rules can create these sorts of situations, Robert Jasiek analyzes the 1989 Japanese rule set in exhaustive detail. Here he provides one of the best known examples of why wording matters in a Go rule set.

 
 

Japanese vs Chinese: Technical Discussion

The Internet is full of discussions comparing these two rule sets. Most folks will tell you that there is almost no difference between Japanese and Chinese rules. And for the most part, they are technically correct. The differences between Chinese and Japanese rules really comes down to three separate areas:

  1. The technical rules which describe how the game is played.

  2. How score is calculated.

  3. How rare board configurations are handled.

The primary difference between Chinese and Japanese rule sets is going to be the way that scoring is handled. Chinese uses Area Scoring and Chinese Counting. Japanese uses Territory Scoring and Japanese Counting. Essentially, this is how scoring works:


  • :white_circle: Chinese, a live stone = +1 point (for you)
     
    :black_circle: Japanese, a live stone = 0 points (for you or opponent)
     
     
    Note: At the end of the game, each stone you placed, that is not currently located in enemy territory, is considered “live”.

  • :white_circle: Chinese, a captured stone = 0 points (prisoners are not counted during scoring)
     
    :black_circle: Japanese, a captured stone = +1 point (for each prisoner stone you possess)
     
     
    Note: When stones that you have placed are fully surrounded by your opponent’s stones, they are considered “captured”. Captured stones are immediately removed from the board and placed into a separate “prisoners” pile on your opponents side of the board.

  • :white_circle: Chinese, a dead stone = 0 points (for you or opponent)
     
    :black_circle: Japanese, a dead stone = 0 points (for you), +1 point (for your opponent)
     
     
    Note: At the end of the game, each stone you placed that resides in enemy territory, is considered “dead”.
     
    Chinese Note: Dead stones are removed from the board and placed back into your opponent’s bowl of stones.
     
    Japanese Note: Dead stones are removed from the board and placed in your opponent’s prisoners pile.

  • :white_circle: Chinese Scoring: Territory + Stones + Komi = Score
     
     1. All Dame should be filled prior to scoring.
     
     2. Live stones you placed on the board = +1 point each.
     
     3. Prisoners you captured = 0 points.
     
     4. An unoccupied intersection inside your territory = +1 point each.
     
     5. Calculate the total number of your Territory and Live stones and add them together. Then add the value of Komi to that number. This is your final score.
     
     
    :black_circle: Japanese Scoring: Territory + Prisoners + Komi = Score
     
     1. Unfilled Dame = 0 points.
     
     2. Live and Dead stones you placed on the board = 0 points.
     
     3. Prisoners you captured = +1 point each.
     
     4. An unoccupied intersection inside your territory = +1 point each.
     
     5. Calculate the total number of your Territory and Prisoner stones, and add them together. Then add the value of Komi to that number. This is your final score.

Under normal circumstances, it is mathematically provable that scoring under each rule set is 100% equivalent. If you are curious how Japanese Scoring might be more difficult for a beginner to grasp, you may refer to this simple example. Also of potential interest, are the differences between Territory and Area Scoring (basic, advanced).

 
 

The Role Of Human Perception

Note: The following section is not necessary to understand the technical differences between each rule set. You can safely skip this section, if it does not interest you :wink:.

I feel that it is important to address the role human perception plays when learning Go, in hopes of raising awareness. If you are currently struggling, know that you are not alone. The struggle faced when beginning Go can feel demoralizing, frustrating, and confusing. Too often now, I have heard experiences recounted by others in conversation, personally witnessed, or read about online, stories where a new player’s exploration of Go has ended with them giving up and walking away.

I believe that understanding the viewpoints of new players and discussing the potential for struggle, is important and helpful for everyone involved in this hobby. Especially concerning the efforts of established players to offer empathetic support. If the questionable opinions and viewpoints of fresh players, like those about to be shared, are dismissed, misunderstood, or ignored by experienced players, I worry the only result can be furthering their insecurity with playing Go. Hopefully, this information will be helpful to some of you.

To help you understand the topic better, I would like to share my personal experience and interpretations with you. During the first two months of my introduction to Go, I compared my combined experiences with each rule set; recording my thoughts on the frustrations I was experiencing. These are not meant to be a comprehensive list of all potential perceptions possible. But rather a window into the mind of a new player struggling to understand the differences between two rule sets.

What follows is an article I wrote three months after beginning Go. I was still researching rule sets and wobbling between 17K and 20K. At the time, these words were true to me; though my mind has since changed. Nothing here needs to be refuted by anyone. I realize that no matter what rule set I use, playing well is determined by logic and making the best move possible on any given turn.

 
 

The New Player Perspective

What I am about to discuss is subjective. This seems to be something a person can either perceive, or it isn’t. Many of these observations might be considered small enough to not be worth mentioning. However, the grand sum of these differences add up to something substantial. And that is worth talking about. Your own experience and interpretations may differ. And that is okay. What is clear, is that people seem to be divided on this topic.

On the surface, the technical differences between both rule sets may seem like two approaches, that arrive at the same conclusion. Different, but simple and not worth thinking too much about. Most folks agree that Chinese Rules, and really any rule set that utilizes Area Scoring, are easier for beginners to comprehend. Those in favor of Japanese, tend to dismiss this argument, most commonly citing they feel the gap between them is truly insignificant.

Nonetheless, there are many people who argue that Japanese rules are unquestionably more complicated. Cyberspace is full of players who claim that when you are playing, each rule set provides a different feeling at the table. Leading to, or requiring, a slightly different mindset while playing. They attribute this to a shift in their perception of how to play wisely under each rule set. This is especially true of the reports from beginners.

  1. In Japanese games, the way the game will be scored is constantly on my mind. I stress more each turn, because I am tracking and weighing the consequences of more elements of gameplay. I remain on edge, worried about potential failures and what they might cost me.
     
    When I play with Chinese rules I feel noticeably more relaxed. For whatever reason, the gears in my head do not turn the same way. As if any move that I make is acceptable. I feel more free and safe to explore any path that I desire, no matter how seemingly futile. And in doing so, I often learn new strategies and move possibilities that I would have otherwise missed out on.
     
    Obviously I can make a foolish move or a smart move, but I don’t stress out as much worrying over how the game will be scored at the end. I am only ever considering where to place my stones for the greatest effect on the current turn.

  2. Under Japanese, each turn I examine the board, trying to figure out how things might progress. I worry that the stone I place now, despite it being a good move at this moment, might become a dead stone in the near future.
     
    The game could theoretically progress in one of many different ways. Since my opponent could surprise me with an unexpected move at any time, there simply is no way to be certain how the gameboard will evolve. And therefore, no way to protect myself against placing a potential dead stone.
     
    However, under Chinese rules, I don’t have to worry about dead stones. The only thing I ever have to consider when placing a stone, is if it makes sense within the framework of the current board configuration. If it dies later, it will be regrettable. But making that mistake doesn’t carry the same emotional weight or worry, since dead stones do not affect my score.

  3. In a Chinese game, I am more likely to try to let one of my groups be captured, in order to gain a strategic advantage on the board. I focus only on the end result of my maneuver, which is the board position after my group is captured. It is either advantageous or it isn’t, but I don’t think twice about the score, since Prisoners aren’t worth any points to my opponent.
     
    Under Japanese, I find myself trying to prevent captures of my stones. As losing or giving up stones intentionally, will cost me points. Often, the positional advantage an intentional sacrifice provides me, isn’t worth the number of points my opponent earns, as a result of my suicidal maneuver. Subsequently, I find myself playing overly defensively and considering sacrificial behavior far less.

  4. Japanese rules require extra consideration when managing the boarders of your territory. Placing a stone inside your own territory will cost you a point. When it comes time to fill dames and shore up these vulnerable points, emotionally I feel like a wreck. I constantly consider whether it is necessary to play it safe, by reinforcing positions.
     
    I stress a lot because I am still learning which points could leave me vulnerable, and which are safe to ignore. There have been many games where the score estimator said I was winning towards the end of the match, but after this final phase of the game, I end up losing by 0.5 to 2.5 points. These losses can feel extra frustrating and demoralizing.
     
    Largely because, at that stage of the game, there really isn’t anything I can do to fight back. Considering that I am well aware of the problem and can see that this situation is occurring to me repeatedly, I still cannot fathom how to protect myself by playing differently throughout the game. Once again, I find myself trying to compensate by playing overly defensively.
     
    Under Chinese rules I do not hesitate to reinforce a wall or to close a gap, because playing in my own territory doesn’t cost me a point. I often ponder this aspect between the two rule sets, and it seems that if I were using Chinese for those 0.5 to 2.5 point loss games, that I simply would have won.
     
    Because I occasionally do lose small groups in Japanese games, on account that I didn’t reinforce a crucial point along my boarder at the very end. Specifically, because I had it in my mind that doing so would cost me a point.

  5. Many claim that Japanese rules are better for beginners, because the scoring encourages you to play in certain ways. As a direct result, the rules foster good habits, which lead you to becoming a stronger player. Whether this viewpoint is true or not, is another debated topic.
     
    The right way to play, the path with the best chance of achieving victory, does seem to be different for each rule set. I personally feel that Japanese rules are formulated in such a way, as to require that I change certain aspects of how I play; in comparison to how I naturally would wish to play the game.
     
    However, the idea that I am being led to behave in any particular fashion, is an issue for me. I value having the freedom to place stones wherever I like. I prefer to learn in a whimsical and exploratory manner. Eventually I will learn good habits on my own. Naturally, in an organic fashion, and as a direct result of trial and error.
     
    How and when that takes place should be led my own desires and choices. By comparison, I do not feel the scoring under Chinese rules encourages any particular type of play style. For better or worse, how I play is entirely self led.

  6. I really appreciate how simple the scoring is to understand under Chinese. Even more so, I love how I never have to fear paying for an attempt to invade inside enemy territory. Invasions under Japanese rules are utterly possible, but they require a different approach, which makes gameplay strategy more complicated.
     
    I need to make sure I behave in a certain manner, handle my board moves in a specific order, and that I’m on top of all the potential dame positions (the bigger the board the harder this becomes). Also, it is wise that I fill in all the dame first, before making my invasion attempt, which does limit my strategy options in some cases.

  7. I like how I don’t even have to think twice about changing the way I play the game when I’m playing with Chinese. Chinese has a more natural feel to it. And by natural, I mean that I don’t have to add new layers of complexity into my strategy or increase the amount of information that I’m tracking on the board. This frees up brain power to concentrate on other aspects of the match, which I feel leads to less stress and better performance.
     
    For example: I’m in a match that is seemingly entering the Endgame phase and my opponent begins filling dame’s, while I decide to instead prioritize something else. Which potentially rewards me with greater returns or a stronger advantage; i.e. capturing stones, invasion attempt, creating eyes, resolving/baiting them with a ko threat, or denying strategic/tactical gains they have temporarily overlooked. There are often actions you can take on a board that award greater gains than filling dame’s alone would have.

  8. Sometimes you have your opponent running or feeling the pressure and you want to invade right now, striking while the mental stress your opponent is experiencing is at its greatest. If my attempt fails while they chose to fill in dame’s I was unable to get points for, then yes, it is a bad move. But I have the option to take this chance and my score will not be affected by as many points lost, since dead stones do not count during the scoring phase.

  9. I understand that mathematically, both rule sets balance out during scoring in an equal fashion. However, despite them being equal, how each rule set calculates points differently can affect the way the game is perceived by the players. Both how they prioritize and respond to different situations. And, at times, the strategies and tactics they use.
     
    Depending on the board configuration and point of progress in the game, playing in certain ways in one rule set, could be risky or unwise in another. The two easiest examples are territory re-enforcement and invasion attempts in high risk (for you) situations.
     
    If a person does not perfectly understand how scoring works, which appears to be rather common, then they are sure to make mistakes in their reasoning of how the score is calculated. They evaluate the board, respond to what they see, and what they think they see affects the player’s understanding of what is possible, what is risky, and what is wise. I see comments and frustrations expressed regularly that showcase this.
     
    Judging by how many of the Chinese vs Japanese threads there are throughout the World Wide Web, I’d say this is actually a significant number of Go players. If you shop around, a lot of these threads include high ranked players, who possess great skill but lack an understanding of how the rule sets actually differ, much less how they mathematically balance out.
     
    So, I maintain the belief that how each rule set handles scoring does in fact affect how games feel to players and how they behave in a match.
     

  10. The beauty of Chinese rules is that I feel uninhibited. I play where I want to play, I never worry about dead stones, I focus only on the gameplay and building my Go skills. Scoring never enters my mind, unless I am considering how an opponents moves are quickly reducing my chances of winning.
     
    Under Japanese I find myself fretting over the score and the different elements of gameplay that are linked to it. A group being swallowed by enemy territory often yields a heavy heart under Chinese; as potential stones just perished and my world got a lot smaller. But this is doubly true under Japanese, because I know his score just saw a big boost thanks to those dead stones.
     
    Emotionally I find Japanese more draining. Cognitively, I find Japanese stretches me thinner as I consider more aspects of gameplay than I normally do under Chinese. Towards the end of a game with Chinese I feel like I know where I stand. Under Japanese I feel like I have a good idea of where I stand. The results of this difference is that I can still be surprised that I lost with Japanese.
     
    It may not mean a lot in the eyes of most other players, but if there are scales during a game that represent my happiness vs sadness, emotional weight vs emotional freedom, and mental clarity vs mental haze, then all of them are tipped towards the negative when I play Japanese games. These effects are there and it is tangible to me. And I know that I am not alone.

As players grow in skill, they are less likely to hold these perceptions. Because as we grow, our understanding of, and familiarity with Go, increases. Our experiences and ever expanding knowledge of game board configurations, grant us the benefit of hindsight. We learn to recognize the good moves from the bad and the safe from the risky. As a result we tend to play in a more reserved fashion and are less likely to perceive the same obstacles we did when we started out.

 
 

Chinese vs New Zealand

In 1978 The New Zealand Go Society adopted the Chinese rules of Go, originating from an article written by James Davies. Later these rules were decided to not be rigorous enough and so the rules were rewritten using recursive definitions. Over time, some additional changes have occurred to the rules based on the group’s evolving views and experiences. Bill Taylor, co-creator of the Tromp-Taylor rule set, which are themselves based on the New Zealand rules, stated:

“The NZ rules are the simplest version of Chinese-style rules around.”

Concerning Chinese rule sets, he adds:

“Let me just re-iterate the motivations for wanting to adopt Chinese-style rules. They are by far the simplest, most elegant, most easily worded, and most easily umpired of the main rule sets. The matter of when the game finishes, and what is dead/removable, in particular, is far more logical and simple than in the Japanese variants…
 
It is of particular concern that the rules be made as ‘natural’ and comprehensible as possible for beginners, so that they not be turned away from the game by puzzlement or outrage, notably at the unfair-looking ‘free removal’ of scoring prisoners at the end of the game. Many of us have known this to happen with promising beginners. Western countries especially cannot afford this kind of wastage of recruits.”

Fun fact, 5 of the 7 widely used Go rule sets today are Chinese based (Chinese, New Zealand, Tromp-Taylor, AGA, Ing). The two remaining are Japanese and Korean, which are nearly identical. So, what are the specific differences between Chinese and New Zealand rules?

  1. Komi: New Zealand is 7, versus 7.5 for Chinese, which means that draws are possible. Although, on OGS, a bare minimum Komi of 0.5 is added to all matches to ensure that ties are not possible.

  2. Suicide: Chinese doesn’t allow it. But one aspect that distinguishes New Zealand rules from several other rule sets is the lack of an additional rule that forbids suicide. In other words, you can fill the last liberty of a group of your own stones, resulting in self capture. This can be relevant. For example, a player can suicide two stones to make a three-space, which must be responded to, because it creates an extra ko threat. For a comprehensive discussion of these differences, see Suicidal Tendencies and Positions With A Good Suicide.

  3. Game Position Repetition: Chinese uses Positional Superko, New Zealand uses Situational Superko, and Japanese doesn’t use Superko at all. To understand the difference check out: Superko, Positional Superko, Situational Superko, and the example below.

  4. Game Conclusion: Chinese games are concluded when two passes are made in a row. New Zealand games end with a verbal agreement by both players. The game is finished when both players agree that there are no more worthwhile moves. ‘Dead’ stones may then be removed from the board by mutual agreement. If they cannot agree which stones are dead, then they must play on. If they cannot agree who shall move next, all stones stay on the board (are alive) and are counted. If you are curious, the first part of this post discusses how the Agreement Phase works in depth.
     
    Note: It is believed that this can be exploited under the right circumstances. Read more about that here: Possible Exploit / Loophole in the NZ agreement phase handling. However, this potential loophole is not possible in the OGS implementation of New Zealand rules, thanks to the stone agreement phase.

  5. Handicap Games: Under Chinese rules, Black gives White compensation for handicap stones, so that the area which they occupy is not counted. Where N stones are given, N÷2 is added to White’s score and N÷2 is subtracted from Black’s score. Under New Zealand rules, no such compensation is given. The effect of this is that an N stone handicap under NZ rules is N points larger than under Chinese rules. Under NZ, White passes the first N-1 moves, where N is the size of the handicap. And Komi is not to be used.
     
    Note: It is worth mentioning, that there is no mention of handicap in the official Chinese rules. However, this is how Handicap is most commonly implemented when utilized. Although, on OGS, a bare minimum Komi of 0.5 is added to all matches to ensure that ties are not possible.

 
 

An Example Of An Advanced Concept For Rule Sets: Superko

Many may wonder what that 5% difference between the seven widely used Go rule sets looks like. While I cannot briefly explain them all, I do have a visual aid to showcase one of these differences, which I find interesting. The 5% is full of little differences like this :hugs:.

The Basic Ko Rule prohibits immediate recapture of a single stone that has just captured a single stone.


This rule does not prevent longer cycles. Different rule sets have different rules for dealing with longer cycles, but all rule sets prevent basic kos. Superko rules prohibit recurrences of an earlier board position under certain circumstances. The recurrence of such positions could be caused by long cycles, such as Triple ko, Eternal Life or Round-Robin ko. Let’s take a look at the Superko rule for Japanese, Chinese, and New Zealand rule sets, followed by an SGF showcasing these different approaches to Superko in action.

 
Japanese: No Result

Most commonly it occurs due to repeating whole board situations such as Triple ko, Quadruple ko, or, more rarely, Eternal Life. Such a repeating position becomes a no result, if the players agree; usually meaning the game must be replayed.

 
Chinese: Positional Superko

Prohibits a board play from repeating a whole board position, regardless of whose turn it was when that position was first reached.

 
New Zealand: Situational Superko

Prohibits a board play from repeating a whole board position, unless the active player is different when the identical position reoccurs. So if the position first occurred on White’s turn, and then reoccurs on Black’s turn, SSK is not violated. But if it is White’s turn when the identical position reoccurs, then that would violate SSK.

 
Let’s take a look at these principles in action:

 
If you are wondering why Japanese rules allow such behavior in the above example, it is because they use Territory Scoring; as opposed to Area Scoring for the Chinese and New Zealand rule sets. An aspect of Territory Scoring is that one player may have a way to prolong the game, but can only do so while losing points. The same situation under Area Scoring would cost the prolonging player nothing, thereby allowing them to extend the game indefinitely. Positional and Situational Superko rules prevent this from happening. For another example of this sort of situation, check out Sending Two, Returning One.

 
 

A Note Concerning Japanese Rules

One thing that is almost never disputed is that the current 1989 Japanese rules need to be revised. I’ve been doing some searching to see if what seems like nonsensical wording, to me, makes sense to those who have attempted to truly decipher the possible loopholes the wording might inadvertently create. The most complete analysis I could locate is Robert Jasiek’s Commentary on the Japanese 1989 Rules. Jasiek’s analyzation of the rules is impressively thorough.

For those who do not know, in 1993 Robert Jasiek began attempting to understand the Japanese 1989 Rules. Starting in 1996 he became a Go rules researcher and in 1997 he began making more serious attempts to understand the 1989 rules. From the beginning of July 2003 to May 2004 he worked on the Japanese 2003 Rules as a full time hobby. In June 2004 he created the New Amateur-Japanese Rules. And in late 2007 he created the Commentary on the 1989 Japanese rules. He is a 5 Dan, author (14 of those about Go), publisher of Go books, a Go teacher, and a game designer by profession.

Without a doubt, he is one of the greatest living authorities on Japanese rules today. Concerning Japanese Rules, he has made a couple of strong comments. First, from the Commentary for the New Amateur-Japanese Rules he states:

“Area Scoring rule sets: One of the great advantages (other advantages shall not be discussed here) of Area Scoring rule sets is that there is a direct correlation between the visual appearance of the (played-out) final-position and the score. This can never be achieved by Territory Scoring rule sets like Japanese style rule sets, regardless of how or how far they might be simplified.”

“The Japanese 1989 Rules: Currently they are the rules used by the Japanese professionals, however, they are illogical, cannot be applied as rules, cannot be understood, and are not suitable for amateurs.”

He added this later in his Conclusion section of his 1989 Japanese Rules Commentary:

“There is only one reason in favour of the Japanese 1989 Rules: They are the valid rule set for the Japanese go associations. Reasons against the rules have been discussed elsewhere in great detail, so here is just a summary: Countless easy / easier alternatives of high design quality are available and some of them are even very close to the Japanese 1989 Rules’ strategic consequences. The rules contain many mistakes and gaps. They are too difficult for almost all players. The rules are inapplicable as rules because a correct application would demand arbitrarily much time for its execution.”

A number of attempts have been made by fans, including Jasiek himself, to address issues with the rule set. If you are a fan of Japanese rules, who is curious about such approaches or are curious about other Japanese-based rule sets, Jasiek discusses many of them, in a short and simple manner, at the end of his 1989 Rules Commentary.

 
 

In Conclusion

Please note that I do occasionally play Japanese games with my friends. I simply have a personal preference for Chinese over Japanese, and Area Scoring in general. If anyone is curious, Tromp-Taylor is my absolute favorite rule set; with New Zealand being a close second. I think Go is both beautiful and wondrous. Because the rules are so simple, yet the situations they produce on the board are so profoundly complex. No matter the rule set being used, I am always eager and overjoyed to be playing Go. I hope this explanation has helped you to understand the differences between Go rule sets a little bit better :wink:.


NOTE: This thread was composed of information sourced from previous forum topics and my own personal research. External links have been provided wherever possible, when considered relevant. For reference, OGS threads that were sourced include:

  1. Discussion: Which rule set do you think is better, Chinese or Japanese?

  2. Lets Talk About New Zealand Rules

  3. New Zealand Rules Are Actually Closer To Tromp-Taylor (on OGS)

3 Likes

Another significant difference exists between various area scoring rule sets and the Japanese rules in how life and death status is settled in various uncommon situations.

Under area scoring rule sets, any dead group can be proven to be dead by continuing play (while applying the same ko rules) and actually capturing them (without affecting the score at the end of the game). Hence, any disputes can and should be settled by continuing play.

However, under Japanese rules, continuing play to capture dead stones would not only change the score (since a player would be filling in their own territory, while the other would pass), but also, there are positions that are actually dead but cannot be captured during normal alternating play (without paying some price elsewhere).

3 Likes

even though i started with J rule and it is more popular in the world, here is how i see the relationship between J and C rule:

C rule is much simpler, there is no confusing ad hoc judgement, no ambiguity.

The ambiguity of J rule, to me, arises out of the attempt to use a different set of rule to TRY TO REPLICATE THE SAME RESULT OF C RULE.

if they are willing to accept that a different set of rules can result in different result, then most of the ambiguity is easily resolved. if one side needs to fill in his own territory to kill the opponent’s group, then let it be. but because J wants to replicate C result, and the maths don’t add up when you have to fill in your territory to kill, so they set up ad hoc rules to decide which one is alive and which is dead. this is the root of the problem.