Making territory
Diagram 1: This is an artificial situation, but it works for our purpose. Each move A through D is worth one point for White, while the moves E through H are worth one point for Black. Since all positions are symmetric the outcome should be the same no matter if you make territory or take it away.
Diagram 2: Let's see what happens if both parties try to make territory in the sequence through 6. Black 7 is a tricky move. He is really entitled to one point here, but he is trying to make two. If White were to play at 10 immediately, Black would surround two points in the center with 8. Therefore, White doesn't immediately play at 10 but first exchanges 8 for 9 before making the last point with 10. A, B and C are dame points as they make no points for either player. Each player has eight points.
Diagram 3: So what happens if each player prevents his opponent from making additional territory? That is what happens up to move 6. Notice that neither black nor white groups in the center have two eyes. Black sets out to make eyes with 7. White 8 takes away a point before making one with 10. A through I are dame points. Both players end up with five points.
Diagram 4: Black first makes points with 1 and 3 while White destroys his territory with 2 and 4. The tables are turned with Black destroying territory and White making it. In the end, the score is even at six all.
The above diagrams show it does not matter whether you make territory or destroy it as long as you it is worth exactly the same number of points.
Solutions to last week's problems
Solution 1: Black 1 is the best sente move. In other words it requires a response. However, White can get away with 2, which Black must answer with 3 or die, before switching to 4. Black keeps the initiative. Black 9, white 10 and 12, black 15, 17 and 19 are all sente. White 22 is also a kind of sente. However, Black ignores this move and plays at 23, 25 and 27, which becomes gote. This means Black loses the initiative. Black 37 is the last real point, leaving A through H as dame points. If Black plays at 1 first, he will win the game by about six points. If White starts, he should play at 1, which is worth about six points in reverse sente, making the game close. All moves referred to as sente are reverse sente for the other player. Some moves are more forceful than others as they threaten or gain more.
Solution 2: If White plays at 1, Black needs to connect with 2, otherwise White can cut at that point and kill the entire Black group. If Black plays first, he can connect at 1, avoiding having to play inside his own territory with 2. So his territory becomes one point bigger. White 1 is worth one point in sente, while black 1 is worth one point in reverse sente.
Solution 3: If Black plays 1, his territory becomes 6+2 (marked prisoners)=8 points. If White plays first and connects at 1, Black gets only two points as he has to connect at the marked spot sooner or later. So, the difference between Black playing at 1 and White playing at 1 is six points in gote.
Solution 4: If Black plays at 1, he will capture the marked white stones and Black's territory becomes 10 points plus 5 prisoners = 15 points. If White plays at 1, he saves the five stones, and makes territory at the marked spots. This is worth three points while Black has only two points. So playing at A is worth 16 points (15 points for Black and one point for White). However, playing here is gote.
This week's problem
Problem: Black plays first and wins. Think about sente and gote.
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Van Zeijst is a four-time European go champion and European representative at the Fujitsu World Championship.