I'm new to Go, but I've been a chess player for a long time. Not a great chess player, mind you, but I like to play. One thing has me confused on Go, and I'm trying to figure out whether it's something I really don't understand, or the free Go game I have on my Droid phone is buggy.

I thought I had captured a significant region of the board, but the phone kept playing pieces within it. At the end, it claimed everything within its pieces. Other times, if I play, all my pieces are captured when it seems like a nearly identical scenario, I had a region of the board, it had a border of pieces around mine, and at the end everything inside its border was his. How does the hierarchy work as far as claiming territory? It makes sense that if you made a border around 1/4 of the board, then the other 3/4 doesn't become yours, but how does it really work?

How much do you know about go? Are you familiar with the concept of eyes?

A group is alive, and claims territory, if it cannot be taken off the board in any way...which means it's still there at the end of the game. The most simple (and by far the most common) way for this is for it to have two eyes. I'm not sure where the best material about this is, but http://playgo.to/iwtg/en/ is a popular tutorial that includes this concept.

Assuming the computer is correct in what it's telling you, the difference is probably in whether the groups in question have two eyes or not. However, this is probably quite confusing, especially since the computer may well be wrong (computers aren't necessarily very good at getting this stuff right). I'd strongly suggest giving us an example of what you mean, either via an sgf file (you can create and link to a game at http://eidogo.com/) or image. That will allow someone to illustrate the problem.

Thank you amnal, here's the scenario my phone had that really had me puzzled (I was black):

Click Here To Show Diagram Code

[go]$$
$$-----------
$$|...OOX...|
$$|....OX...|
$$|....OX...|
$$|.OOOXX...|
$$|OOXXX....|
$$|XXX......|
$$|.........|
$$|.........|
$$|.........|
$$-----------[/go]

Yes, I have read up on the concept of eyes, and why two eyes are important. I had figured that since I had defined the territory, the white pieces would be dead, but at the end, the phone declared everything within his row of white pieces as his. Like I said, it seems like in similar scenarios, I would have had my pieces declared dead at the end.

You might want to try starting with this.

http://playgo.to/iwtg/en/

In this case the white stones are alive.

Click Here To Show Diagram Code

[go]$$
$$-----------
$$|...OOX...|
$$|..2.OX...|
$$|.4..OX...|
$$|.OOOXX...|
$$|OOXXX....|
$$|XXX......|
$$|.........|
$$|.........|
$$|.........|
$$-----------[/go]

If white plays and , there are two eyes and you can see that white is alive for sure.

Could black play inside and prevent white from making two eyes? It's actually a little tricky to see. You can try playing it out if you're uncertain. If black could play inside and prevent white from making two eyes, we say the position is unsettled, and either Black should kill white or white should play inside to make two eyes. If white can't make two eyes no matter what, then white is dead.

So Black is dead unless he either has two eyes or he can play inside and kill white.

_________________
When you think your opponent has made a mistake, that's when you should be the most cautious.

Hey sparkydave, welcome to Go!

Go was originally a game about how many of your own stones you can get on the board. To accomplish that, of course, you need to create zones where if your opponent plays a stone, you can kill it; at the end of the game, you can fill those zones that you control with your own stones. Eventually we stopped bothering with filling in the territory surrounded by friendly stones, and even later we started only counting the territory (and subtracting captured stones, which makes it come out the same).

So the question you're asking is essentially: "Have I created a zone here where if my opponent plays a stone, I can kill it? Or not?" And for now, the only way to know the answer is to play it out to the bitter end.

Here's a chess analogy that you may find useful:

Actually, not sure if white is alive with points if black plays first - seems like seki at least for black if he plays 1 as below? 2 seems like strongest resistance to avoid seki, but then black 3 and white can't seem to avoid seki without a ko.

Click Here To Show Diagram Code

[go]$$
$$-----------
$$|.3.OOX...|
$$|.21.OX...|
$$|....OX...|
$$|.OOOXX...|
$$|OOXXX....|
$$|XXX......|
$$|.........|
$$|.........|
$$|.........|
$$-----------[/go]

This is a fun little problem actually,

For example, this results in a direct ko with 1 internal ko threat for w

Click Here To Show Diagram Code

[go]$$
$$-----------
$$|.34OOX...|
$$|.21.OX...|
$$|....OX...|
$$|.OOOXX...|
$$|OOXXX....|
$$|XXX......|
$$|.........|
$$|.........|
$$|.........|
$$-----------[/go]

Not a beginner problem at all


But in answer to the original poster, something is only territory if it can be protected. If your opponent wants to dispute whether or not it's territory, he/she may play in there, it is then your job to:

A) Kill it
B) Ignore it (if you think you can still kill it even after he makes another move) This will pay you off by letting you play somewhere else and/or getting an extra prisoner for your trouble.

Think of it like this, having a piece of territory is a bit like having a King-Bishop-Knight vs. King endgame. Technically it's a win for you, but if your opponent is stubborn, you may be forced to prove it.

_________________
Let my comments be as eggs thrown on stones... explosive and hard to wash.

Yeah, I was looking at the corner and realized I wasn't sure if it was alive or dead, so I punted.

But I think that's why the best advice is to test it out when you're unsure.

_________________
When you think your opponent has made a mistake, that's when you should be the most cautious.

what jts says about the evolution of the game is good.

but here is your particular confusion... you've learned the simple rule "surround to capture", but there are multiple definitions of the word surround.

in one sense, yes you have surrounded the white stones.

but in another sense, you have not yet surrounded them.

in Go, they have to be completely surrounded -- what I like to call suffocated

Click Here To Show Diagram Code

[go]$$ these white stones have now been suffocated - no liberties
$$-----------
$$|..XOOX...|
$$|...XOX...|
$$|.XXXOX...|
$$|XOOOXX...|
$$|OOXXX....|
$$|XXX......|
$$|.........|
$$|.........|
$$|.........|
$$-----------[/go]

otherwise, in your diagram, the white stones themselves surround their own open territory (aside from the stronger player's analysis of whether or not they are still killable)

Ko threats matter, but this is more or less normal play in this corner when Black plays first.

Click Here To Show Diagram Code

[go]$$
$$-----------
$$|a37OOX...|
$$|521.OX...|
$$|9648OX...|
$$|.OOOXX...|
$$|OOXXX....|
$$|XXX......|
$$|.........|
$$|.........|
$$|.........|
$$-----------[/go]

OC, threatens ko. threatens a snapback at 8. makes seki. (Under AGA rules "a" is a point for Black.)

_________________
Sheik Yerbuti -- if that really is your name --

Dave, since other posts go more into detail, let me just add three non-deep comments:

1) For a group to be alive, you don't need to make actual eyes. You only need to be able to make two eyes. As the other posts have shown, this isn't always trivial to see.

2) Something that may be totally obvious, but was a real eye opener (slight pun) for me when I learned the game: As long as your opponent responds, you can always try and invade an area that is "controlled" by him. Even if your invading stones get killed and you failed to make a living group, the score remains the same, if your opponent makes the last move during the invasion/defense sequence. (Because they play in their own territory.)

3) There will be a moment very soon where you suddenly start "seeing" these things more clearly. I can't describe it any better, but I recall that after a few weeks after learning the game, something "clicked" and I started to "see" eye space and potential eye "spots" better.

Thanks all, I think I got some of it sorted out. It turns out when I lost pieces in what seemed like the same situation, there wasn't space to make an eye. In the case I gave above, there was plenty of space. I went through some of the puzzles on the playgo.to site, and it's making a little more sense.

You can study for a long time and still get surprised at a point where you think you make eyes, but they disappear! It is sort of the 'heart' of the game. If you could tell without fail, what stones are safe, you would be a very good player.