(;FF[4]
CA[UTF-8]
GM[1]
GN[Becoming SDK - Lesson 3]
PC[https://online-go.com/review/56290]
PB[Black]
PW[White]
BR[1d]
WR[1d]
OT[Error: time control missing]
RE[?]
SZ[19]
KM[6.5]
RU[Japanese]

(;B[pd]
;W[qf]
;B[pj]
;W[nc]
;B[nd]
;W[md]
;B[ne]
;W[oc]
;B[pc]
;W[od]
;B[pe]
;W[oe]
;B[pf]
;W[of]
;B[pg]
;W[jc]TR[nd]TR[ne]C[Hello. We're going to stick with our theme of opening. Today we'll learn when to capture stones.

Before capturing stones we need to assess whether or not they're valuable. Have a look at these two black stones. How important are they in this case?]
;B[me]C[Sometimes players move these stones out and try to save them. But that's a bad idea.]
;W[le]C[This hane is powerful, and]
;AE[le]
;AW[ld]TR[nd]TR[me]TR[ne]C[This extension is good enough, too. All black is doing is saving 2 stones. And these 2 stones don't influence or threaten White's position at all. They'll simply become a target and suffer from White's attack. Obviously this group can survive, but Black will have to pay dearly for the privilege. In Go you shouldn't create a weak group like this.]
;AE[ld]
;AE[me]C[Given what we just saw, is it necessary for white to spend another move capturing the black stones? No, they have no influence on White at all. There's no need to capture them. ]
;AW[mf]C[It's tempting to capture stones when they're dangling in front of you. However, if you do so you'll waste your moves. ]
;B[ld]C[Later, Black might aim at this sort of aji, so White's unnecessary move can actually help Black. Remember not to touch useless stones! Let's solve another problem below!]
)(;AB[nc]
;AB[nd]
;AB[me]
;AB[mf]
;AB[ng]
;AB[nh]
;AB[oh]
;AB[ph]
;AB[qh]
;AB[qg]
;AW[lb]
;AW[ld]
;AW[md]
;AW[ke]
;AW[lg]
;AW[mg]
;AW[pc]
;AW[ne]
;AW[nf]
;AW[og]
;AW[pg]
;AW[qf]
;AW[rf]
;AW[pe]C[This is problem helps you distinguish between useful stones and useless stones. ]
;B[of]C[Some players might spot this double atari and play there immediately. But this isn't a good move in this case.]
;W[oe]C[White would connect here of course.]
(;B[pf]C[Then Black can capture these two stones. Black, however, captured useless stones.]
)(;AE[oe]
;AE[of]C[Let's go back to the problem.]
;B[oe]TR[ne]TR[nf]C[In this case, this atari is the answer. Then Black can capture these two stones instead.]
;W[of]C[White can't play here because of a liberty shortage. Black will capture all four stones if White does. You need to capture or rescue important stones and leave useless stones alone! ]
;AE[of]TR[ne]TR[nf]C[So these stones can't be rescued. They're much more valuable than the other two. As you can see, Black can save four black stones with this move. Remember to distinguish between important and useless stones! Let's move on to a life and death puzzle.]
))(;AB[sk]
;AB[rk]
;AB[qk]
;AB[ql]
;AB[qm]
;AB[qn]
;AB[qo]
;AB[qp]
;AB[pq]
;AB[or]
;AB[qr]
;AB[rs]
;AB[sr]
;AB[sm]
;AW[sl]
;AW[rm]
;AW[rn]
;AW[ro]
;AW[rp]
;AW[rq]
;AW[rr]
;AW[rl]C[The most important skill in Go is reading. Even if you make good shape, you can't win a game unless you're able to fight. Reading is a key element of Go strength. Solving life and death puzzles is the only way to get better at this.

There's a story about Lee Sedol 9p. Before his father left for work each morning he assigned Lee several life and death puzzles. After he finished work, Lee's father checked his son's answers. And they did it every day. I think this is the reason why Lee's reading is among the best in the world now. I hope you'll solve many puzzles like he did!

This is today's puzzle. Black has to kill white. Eye space matters. Black needs to induce White into making a certain shape. Then Black can capture the group.]
;B[sq]C[Let's look at this move first.
]
(;W[sp]C[If White blocks here,]
;B[sn]C[Black can sacrifice one more stone and capture the whole group.]
;W[ss]C[Even if White captures these two stones,]
;B[sr]C[Black can recapture. Now White's dead. But White won't answer like that. :)]
)(;W[sn]C[Instead of that, White will capture this stone. We need to focus on the liberties now. That's the point of the problem.]
;B[sp]C[To capture, Black has to reduce White's eye space here.
]
;AE[pq]
;AB[qq]C[If this liberty is taken]
;W[so]C[White can't play here because it's self-atari. Black will immediately capture all the stones.]
;AE[so]
;AE[qq]
;B[pq]
;W[so]C[However, white has a liberty here now. Therefore, White can atari and it's not self-atari anymore.]
;B[qs]C[Since Black can't rescue the three stones first, he needs to connect here first.]
;W[ss]C[Then White captures them.]
;B[sr]C[Even if Black recaptures,]
;W[sq]C[White can make another eye like this. Now White's alive. Because of all that, this is a failure for Black. White can rescue her group thanks to the open liberty.]
)(;AE[sq]C[Let's go back to the problem. I guess some of you have already found the answer. :) Here's one basic principle: "the enemy's vital point is your own."]
;AB[sq]C[If black plays here white can live by capturing the top stone.]
;AE[sq]
;AB[sn]C[In this case, sacrificing one more stone here is a wonderful move.]
(;W[so]C[What if White captures?]
;B[sq]C[Then Black reduces White's eye space here. It's no use capturing these two stones.]
;W[sp]
;B[qs]
;W[ss]
;B[sr]C[Eventually, Black can recapture this stone and White's dead. Pretty cool, right?]
)(;W[sq]C[White may try to expand her eye space like this.]
;B[so]C[But Black can capture the group with this move. When solving puzzles remember to look for specific shapes that you know can live or be killed.

This brings us to the end of today's lesson. A house with a good foundation will never collapse. Likewise, fundamental skills will help you improve your strength in leaps and bounds. Thank you!]
;W[sp]
;B[sn]
))))