Life In 19x19

This is a position from Dosaku v/s Chitetsu game. During the video analysis here and in sgf file, A is considered heavy play while B is light. Why it is so?

Here is the position:

I think that it's in comparison with move 28 that A is heavy.

"Light" means that White wants to escape quickly, and is ready to sacrifice a few unimportant stones, so doesn't necessarily want to save both M16 and L17. A move at K16 would be slower, and wants to connect M16 with L17. In addition, it would give Black a forcing move (peep) at L15.

I suppose the hanging connection is heavy because then if black peeps and white connects (probably white shouldn't but push up on left) then black can one point jump out with the stone to the left. The peep, if answered with connect, makes white's shape poor (spot the empty triangle) whilst the black stone is running out faster. It's not important to save the white stone on the 4th line, white wants to attack the black stone on the top side whilst taking care of his group.

Thanks for the replies, though I don't understand everything few concepts are clearer than before now. Thanks again.

I think keeping the goal of the stones in mind is important.

The move at A says "I want to keep the black stone on the upper left isolated by forming a group of my own in between it and the stones on the right."

The move at B says, "I want to keep the black stone on the upper left isolated, but I don't care about any of these stones in particular."

Both moves look at cutting off the black stone, but B lets white give up any stones that are not necessary to do so as the fighting evolves. A makes white invested in keeping all of those stones alive.

xoxox wrote:...though I don't understand everything few concepts are clearer than before now....

That is the state of affairs for most of us.

jeromie wrote:
The move at B says, "I want to keep the black stone on the upper left isolated, but I don't care about any of these stones in particular."

Any of these stones means L17 and M16, right? I mean P17 is not part of the plan.

In the following position black played at A, is that a heavy move?

No it's not, because Black wants to keep his stones connected, and the corner is big in terms of points.

Generally speaking, you want to play light when your are in your opponent's sphere of influence, and since you are outnumbered you are not sure that you can save all your stones. In the last game you posted, Black is close to the edge/the corner so is safe and has no reason to sacrifice any stones.

P.S. Maybe that wasn't clear. A group of stones is considered as heavy when it becomes a burden, and here it is not the case.

xoxox wrote:

jeromie wrote:
The move at B says, "I want to keep the black stone on the upper left isolated, but I don't care about any of these stones in particular."

Any of these stones means L17 and M16, right? I mean P17 is not part of the plan.

Yes, it is. If Black ignores the hane, White lives with the P-17 stone. It's part of what makes the hane light play. Without it, we would consider the hane to be thin, as it leaves two cutting points behind. But with the P-17 stone, the hane is sente, and then White can play more strongly against the Black H-17 stone.

To add to what jlt said: I think of stones as being heavy when they will have to run to live. That may be too restrictive, but I think it’s usually right.

hyperpape wrote:To add to what jlt said: I think of stones as being heavy when they will have to run to live. That may be too restrictive, but I think it’s usually right.

Yes, I think this is more true about already settled groups, though my knowledge is very limited I might be wrong totally.

xoxox wrote:

hyperpape wrote:To add to what jlt said: I think of stones as being heavy when they will have to run to live. That may be too restrictive, but I think it’s usually right.

Yes, I think this is more true about already settled groups, though my knowledge is very limited I might be wrong totally.

Already settled means dead or alive. A group that has to run to live is unsettled. Generally speaking, stones that are not yet alive but cannot afford to be thrown away are heavy. There is also a heavy/light continuum, so that a play or sequence of play may be considered heavy or light by comparison with other plays or sequences of play. It takes experience and judgement to fully understand the terms, heavy, light, thick, and thin.

Light stones:
.... can live easily, often because:
........ of flexible shape
........ not all of the stones have to live i.e. you can sacrifice parts of the group and it will still survive
.... even if they do die, they often do not cost any points
.... often have a big impact for their size

Light stones are like a light sharp sword.

Heavy stones:

.... can die easily
.... often cost many points, forcing you you to try to live with a group struggling for eyes.
.... is the perfect target for your opponent to attack whilst making profit. Remember! Attack not to kill, but to gain profit. If your group is heavy, it has a negative impact on the game by giving free points to an attacking opponent.

Heavy stones are like a sword you cannot lift— a burden.

Take the above with a grain of salt— hopefully it gets the simple things across.

Go is essentially creating spaces in which to make living groups, and whenever you make a group anywhere, always think of if wether it will survive or become captured.