(
;
FF[1]
GM[1]
SZ[19]
AP[Jago:Version 4.53]
C[Shygost's public lesson #3

The lesson will focus on the difference between basic moves and changes. While it is normal to play basic moves, this lesson will play change moves normally, only playing basic moves when a group's life is at stake.

If there are any problems with this file, please make note of it at
http://senseis.xmp.net/Shygost/Lessons . More of these lessons, and their audio
components, can be downloaded from http://tengen.bur.st]
GN[lesson-03t]
US[Simon Duff  <simon.duff@gmail.com>]
;
AB[jj]
C[Shygost begins this lecture defining what he means by basic moves and changes.

Black playing here is a perfectly valid move -- but it is not basic.]
;
AB[jc]
C[Playing on the side is also valid, but again, not basic.]
AE[jj]
;
AE[jc]
AB[qd]
AW[pp]
C[Playing in the corner are basic moves.]
;
AB[nq]
C[But Black could play here, rather than the corner. This move is a change, not a basic move.]
;
AE[pp][nq][qd]
C[The objective for today's lesson is to know the basic moves, but to play change moves instead, and see how the game develops.

We will start with a basic move however, R16.]
AB[qd]
;
C[The most basic move for White is D16.]
AW[dd]
;
C[The upper right corner is the best response as thre is an openning at P16.]
AW[od]
;
AE[od][dd]
AW[dp]
C[Lower left is also possible, as this allows development in either direction.]
;
AW[pp]
AE[dp]
C[Q4 is the least biggest of the three remaining corners, so shygost plays here.]
;
C[For Black's next move, D3 and D4 are normal (basic) moves.

O3 is a change move, and is the move the lesson continues with ("A").

P17 is another possible change move ("B").]
AB[nq]
LB[nq:A][oc:B]
;
C[Kyu players must learn to play a basic game of Go, that is, know the basic moves/responses in different situations.

R6 is the basic response for White. Shygost says that a Pro will respond with this move 95% of the time (According to Moyo Go Studio and its 37000+ Pro games, this response occurs XXX of the time)]
AW[qn]
;
C[Shygost analyses why a response at R6 occurs so often.

If White plays at P17, the corner now has one black and one white stones, and the corner is shared between them.]
AE[qn][nq]
AB[dp]
AW[oc]
;
AB[pe]
C[If Black plays in this corner first (for example, Q15), he gets more profit in this corner.

If White plays in this corner first, he would get more profit.]
;
AE[pe]
AB[dd]
C[Black would prefer to play in the last empty corner as there is more profit to be had here.]
;
AW[pe]
C[White can get some profit by playing Q15.

This is all normal, basic behaviour.]
;
AE[dd][oc][pe]
LB[cc:A][dd:B][ee:C]
C["A", "B" and "C" are one-stone finished corners (according to modern play).

When one of these stones is approached, we like to respond -- not because we are weak, but because our opponent gets extra profit if we do not respond.]
;
AW[dd][oo]
AB[nq][qn]
AE[dp]
C[If White does not respond, for example, playing D16, Black can get extra (undue) profit in the lower right corner with R6. This causes White to respond with P5, but allows Black further profit in that corner.]
;
AE[oo][qn]
C[White should respond with R6 as the basic move.

But as a change, White plays D16.]
;
C[In this case, Black's basic move is to punish White for playing away -- by playing R6.

D4 (or some similar corner approach in the remaining corner) would be a change move.]
AB[qn]
;
C[Now, White does not have a choice, he must play the basic move.

If White plays away with D4, Black can surround White with P5, and now White has broken a cardinal rule, "dont get surrounded in sente".]
AB[oo]
AW[dp]
;
AE[oo][dp]
C[White has three choices in responding to B at R6, "A", "B" and "C".

"A" and "C" both settle White.
"B" is a way for White to get sente.

"A" and "C" can be considered basic moves, as they settle, which is what White wants to do.

So lets continue with "B".]
LB[np:A][oo:B][pn:C]
;
AW[oo][dp][mp][mq]
AB[qq][qp][or]
C[Black responds with R3, allowing White to get sente and play away, D4.

At this point, Black's basic move is R4, finishing what Black started. This follows a joseki.

Black gets all the points, White gets nothing. Black also has sente, so this is good for Black. White is OK, but weak.]
LB[qp:1][mp:2][or:3][mq:4]
;
C[Given a board position, White may also want to protect the cut with N6.]
AE[mq]
AW[mn]
LB[qp:1][mp:2][or:3][mn:4]
;
C[R4 is a basic move, but as a change move, Black plays P17, which is also big.

White needs to deal with the right, there is no room for White to make a change, so White continues with Q7.]
AE[qp][mp][mn][or]
AB[oc]
AW[pm]
;
C[The pattern may continue in the same way as the last joseki, but sente has switched.]
AW[qm]
AB[ro][pq]
LB[pm:1][pq:2][qm:3][ro:4]
;
C[White to finish, Shygost doesn't like moving along the side (R11), as Black can limit White's development on the side with S7, which White will follow up with R9.]
AB[rm]
AW[qk][qi]
;
C[A better response by White may be to protect its cut with O8, running out into the center. This is good for the left side as well as the right side, and the center.]
AW[nl]
AE[rm][qk][qi]
;
C[For Black's basic move, F17 is a mistake.

F17 is not in the biggest area. Also, it is played low, on the third line play, which is a finishing move, suggesting "I'm done, I don't want to play here anymore".]
AB[fc]
;
C[If P16 were higher, at P17, then F17 is better. P16, on the fourth line, suggests that Black is not finished in that area, that he is still playing stones there.]
AB[od]
AE[oc]
;
C[Playing on the fourth line means that White can approach, and if Black wants the corner points, needs to play P16 to finish. What is P17 doing then, it is not efficient (a waste of time).]
AW[mc]
AB[oc]
;
AE[mc][oc][od][fc]
AB[oc][cj]
C[C10 is a good basic move for Black. The left side is big, and White is developing the center.]
;
AE[cj]
AB[pj]
C[Q10 is too close to White's thickness, it is not a safe Black stone, as White can attack it immediately with R12.]
AW[qh]
;
C[R10 is safer, as there is a connection underneath, at least with ko.

But all the same, it is still not a safe move.]
AE[pj]
AB[qj][rk][rm]
AW[rl]
LB[qj:1][qh:2][rm:3][rl:4][rk:5]
;
AE[qh][qj][rk][rl][rm]
AB[fp][dq][eq][ip]
C[F10 is a specialty move.

The standard joseki, which finishes on the fourth line, leaves a big whole where White can attack with L3]
AW[cq][cr][dn][kq]
LB[fp:1][dn:2][dq:3][cq:4][eq:5][cr:6][ip:10][ip:7][kq:8]
;
C[White can also attack with M3, and continue wtih P2.]
AE[kq]
AW[lq][or]
AB[jq]
LB[lq:1][jq:2][or:3]
;
AE[or][lq][jq][ip]
AB[jq]
C[So this joseki is almost always finished on the third line.

FInishing on the third line in this case doesn't work well with O3.]
;
AE[fp][eq][dq][cq][cr][dn][jq]
AB[fq]
C[The regular joseki (F3) also doesn't work well with the bottom.]
;
C[The left side is the biggest, and C10 is the basic move.

As a change, Black plays more towards one of the edges.]
AE[fq]
AB[cf]
;
C[White cannot make a change.

The top is small, so the regular response, F17, is not a good response.]
AW[fc]
;
AE[fc]
C[Because the left is the big area, White needs to play there, and elects to pinch.

There are lots of options of how White can pinch.

White is looking forward to eventually playing at move at M3. Because of this, White is more likely to want to pinch on the fourth line (high), encouraging development of the center. An example of this pinch is D11.]
AW[lq][di]
;
C[If only the left was developing, then a low pinch (C12) may be appropriate.]
AE[lq][di]
AW[ch]
;
C[D10 is also a reasonable basic move.]
AW[dj]
AE[ch]
;
C[But D11 is the same idea, but it is bigger, it applies more pressure, so it is doing more.

Possible suggested Black moves from this position include F14, E14, B16, C17 and D13.]
AW[di]
AE[dj]
;
AB[ff]
C[F14 is going too far]
;
C[There is a rule regarding the settling of a group - corner first, then side, then center.

But there is a rule that comes before this -- don't get surrounded.

So if you want to settle the Black stone, it must get out. A move that accomplishes this is E14.]
AE[ff]
AB[ef]
;
C[B16 settles the black group, but leaves it vulnerable to being surrounded.]
AE[ef]
AB[bd]
;
AE[bd]
C[The other option is to not try and settle this group. Black at C17 allows a group to settle locally, sacrificing (giving up) he Black stone at C14.

"A" allows for settling, sacrificing the stone at C14.
"B" allows for settling, not sacrificing the C14 stone.]
LB[cc:A][ef:B]
;
AE[cc][dd][di][cf]
C[D13 is not that effective in the current board setup. If the board position were like this, Black's diagonal play is good.

But it is not usual to play it against the 4-4 stone.]
AW[dc][dh]
AB[df][ce]
;
AE[dh][dc][ce][df]
AW[dd][di][cd][ed][be][ce][lq]
AB[cf][bd][cc][dc][bc][fc]
C[This is a very standard continuation of Black continuing with "A".

Locally, this is good for Black. He has 10 solid points, and life. White has 0 points, but gains sente, which he is happy with as it allows him to play M3.

However, looking at the top, Black's left corner does not work well with the stones in the right corner.]
LB[cc:1][cd:2][dc:3][ed:4][bd:5][be:6][bc:7][ce:8][fc:9]
;
C[A joseki that may work better for Black is this, beginning with Black at F16.

This produces a "high-low" wave for Black at the top, which tends to be more efficient. White gets much better on the left, but Black gets better on top.]
AE[dc][cc][bc][be][bd][ce][cd][ed][fc][lq]
AB[fd][dg][dc][cc]
AW[ce][df][ef][eg]
LB[fd:1][df:2][dg:3][ef:4][cc:5][ce:6][dc:7][eg:8]
;
C[We repeat this joseki, this time after a tight White pinch (C12).

Same idea, slightly different joseki.]
AE[dc][cc][ce][cf][df][ef][eg][dg][di]
AB[cf][dg][cc][dc]
AW[ch][ce][df][cg]
LB[fd:1][df:2][dg:3][cg:4][dc:5][ce:6][cc:7]
;
C[This joseki is common in Pro games, and there is a follow up for Black.

Whenever Black wants to (and is often done straight away), Black can play two sente moves.

In the end-game, Black can play B16.

This joseki is good for Black, and is common in Pro games.]
AB[bf][ef]
AW[be][de]
LB[bf:1][be:2][ef:3][de:4]
;
C[Returning to our decision on how Black can settle in this area, "A" or "B".

We need to determine which side is bigger, the left, or the top -- this will help determine "A" or "B".

In this setup, the left is bigger. This is because of Black's weakness if White plays M3, White is developing the center, and all the White stones are talking left side.

So Black will continue with B.]
AE[dg][ch][cg][bf][cf][ef][df][de][dd][ce][be][cc][dc][fd]
AB[cf]
AW[di][dd]
LB[cc:A][ef:B]
;
AB[ef][gf]
AW[fd]
C[Black continues with E14 ("B"), and White extends  with F16 (a basic move). 

Black's change move could be G14, which creates a miai situation, allowing Black to surround with "A" or attack with "B".]
LB[hd:A][ck:B]
;
C[Black at G14 is not that great a move however, if White continues with H16 and Black attacks with C9. White is almost strong in this area, especially if he  responds with E10, so Black could get in a lot of trouble.

There are too many White stones around here, Black is just begging for an uneven fight.]
AW[ej][hd]
AB[ck]
;
AE[hd][gf][ej][ck]
C[G14 can lead to risky situation.

Why be risky when you don't have too, when Black can just settle with B16.

Black has succeeded in carving out a nice living group in White's area.

Possible White's next basic move include M3, K17, D13, Q12]
AB[bd][bi]
AW[cc]
LB[bd:1][cc:2][bi:3]
;
C[Q12 (and even R12, as in this setup) is in an area that is hard to develop, as it can be undercut by Black. It is very hard to develop an area when it can be undercut.]
AW[qh][rl][rk][rj][sj]
AB[rm][sm][sl][sk]
LB[qh:1][rm:2][rl:3][sl:4][rk:5][sk:6][sj:7][sm:8][rj:9]
;
C[The remaining moves are marked as K17 being "A", D13 being "B" and M3 being "C".]
AE[qh][rj][sj][sk][rk][rl][sl][sm][rm]
LB[jc:A][dg:B][lq:C]
;
C[Starting with "B", this is a very common pattern, played all the time, though there are some slight variations. White gets all this in sente, and may finish it by playing somewhere on the Crosses.

The results of this joseki are that White has forced Black to live - this is not good for White. On the other hand, White has done something on the left. It is vague what white has accomplished though, as black can still invade -- there is still lots of aji for White.]
AB[df][bg][ch][ah]
AW[dg][ci][bj][bh]
LB[dg:1][df:2][bh:3][ch:4][ci:5][bg:6][bj:7][ah:8]
M[dk][dm]
;
C[This particular pattern is most often played by White when the bottom corner is Black's and White is looking for an invasion point.

White may play at C8. This pattern in commonly used in invasions, rather than actual building of territory.]
AE[dp]
AB[eq][cp]
AW[cl]
;
C["C" is nice. Black doesn't want to be surrounded, so may escape with O4. If White attacks Black's weakness with P2, Black can kill it.

O4 is a nothing move however, as it places no pressure on White, and it doesnt get out -- it has almost no purpose.]
AE[bg][bh][ah][ch][dg][df][ci][bj][cl][cp][eq]
AW[dp][oq][or][lq]
AB[np][op][nr]
LB[np:1][or:2][nr:3][oq:4][op:5]
;
C[Black O2 may be a better response.]
AE[np][op][oq][or]
;
C[Another option for Black is to not respond, allowing White some profit. Black then has sente, so is actually able to play two moves somewhere without White responding.

But White is thick in that area now, many White stones there.]
AE[nr]
AW[nr][or][mq]
AB[pr][oq]
LB[or:1][oq:2][nr:3][pr:4][mq:5]
;
C[N3 is possibly the best way to respond to White at M3, as it does it in sente.

White looks reasonable, and would like this.
Black can still play F3, so White does not have all the corner and bottom.]
AE[or][nr][mq][oq][pr]
AB[mq]
AW[lp]
LB[mq:1][lp:2]
;
C[Returning to "A", shygost suggested that this is biggest.

By looking at the desires of the stones, we can determine which area is likely to be biggest.

The only stone with some desire is F16. This stone has a desire to grow.

The stone at "D" is low, on the third line, saying "I'm done, I don't want to go anywhere". So its desire is finished.

White has no big desire to play on the bottom. The D4 stone has a little desire to develop the left, but that can be satisfied somewhat by White playing G3. This is only a single stone's desire, which is no big deal.

In terms of Black, Black has a desire to extend to R13, but White is right there, greatly diminshing its desire.]
AE[lp][lq][mq]
LB[nq:D][jc:A]
;
C[If we look at what happens if Black plays in the upper region (near F16, the "A" region). 

This is bad for White -- his territory is gone, his life is in question. This is because White has a position based on the fourth line.

White will then want to come out, and this is very awkward for White.]
AB[hc][he]
AW[ge]
LB[hc:1][ge:2][he:3]
;
AE[ge][hc][he]
C[White has a strong desire to settle the White group on the upper left.

White can extend to "A" or "E". "E" is often the better choice, ]
LB[jc:A][ic:E]
;
C[If "A", how does White feel about Black playing M17 in sente.

White shouldn't mind this - in fact, White is happy.

This is forcing White to play well]
AB[lc]
AW[jc][je]
LB[lc:1][je:2]
;
AE[oc][qd][lc][je]
AB[pc][qe]
C[If the upper right was like this, K17 would not be as good, as Black has a very promising forcing move.]
;
AE[jc]
AB[kc]
AW[mc][ic]
LB[ic:1][kc:2][mc:3]
C[If White plays at J17, now if Black approaches with L17, White can come in and do almost anything.]
;
AE[qe][pc][mc][kc][ic]
AB[qd][oc]
AW[jc][mc]
C[So because of the direction of Black's shimari (corner enclosure), White can play K17.

If Black plays elsewhere, White can make a two space extension, which is very good for White, taking White's big area and making it bigger.]
;
C[It is important to remember that Black's upper right shimari is finished (a stone has been played on the third line). These stones do have a desire to continue development, down the right side of the board.

So if White trys to remove Black's desire with  R13, White is not really gaining anything, not even territory, as Black can undercut it.

Black can also punish White for ignoring the upper left White group.

The protection of this White group is a 'need', where as the other is a 'desire'.]
AE[mc][jc]
AW[qg]
AB[hc]
;
AW[jc]
AE[hc][qg]
C[Now looking for possible Black moves. F3 is possible, as is C6. Another possibility is C3.

Note that the audio dies for about 30 seconds at this point. While we wait for it to resume, here is a word from our sponsor.

!!! Dont do drugs - Go is hard enough already !!!

And now, back to our regular scheduled broadcast.

"A", "B" and "C" are possible next moves for Black. The "D" area, R13, will be tough to develop because White is right there.]
LB[fq:A][cn:B][cq:C][qg:D]
;
C[Let's beginwith "B".

If we look at the line the Black stones are forming, this is very unpleasent. All the stones are low -- this alone suggests that "B" is not good for Black.]
AB[cn]
TR[ef][cf][cg][bg][bi][bh][cn][bm][bl][bk][bj]
;
AE[cn]
AB[fq]
C["A" is the second possibility.

The bottom is develop-able by Black, but begining with F3 is not the best approach. It is ok, however. It is inefficient, but there is no horrible line like that when playing "B". Many times in Go, you may be forced to do something inefficient -- thats okay. They are not bad moves, they're just not perfect.]
;
C[A similar move, G3, gives White the whole corner. Black gets a little something in return, but it is no comparison.]
AB[jq][gq]
AE[fq]
AW[eq][cn]
LB[gq:1][eq:2][jq:3][cn:4]
;
AE[jq][gq][eq][cn]
C["C" is another alternative for Black.

This is dangerous for Black, because of his weakness when White plays M3. Black forces White to build these walls and get strong.

The result is very nice for White.]
AW[dq][do][lq][lp]
AB[mq][cq][cp][co]
LB[cq:1][dq:2][cp:3][do:4][co:5][lq:6][mq:7][lp:8]
;
C[Because of Black's M3 weakness, the best approach may be for Black to play "A", F3.

White will play the basic response, C6.

Black will continue the basic joseki.]
AE[co][cp][cq][dq][do][lp][lq][mq]
AB[fq][iq][dr]
AW[cn][cq]
LB[fq:1][cn:2][dr:3][cq:4][iq:5]
;
C[C10 is one move for White that is discussed, but it is not a good move. White develops 0 points, Black  gets a few points. White develops a wall that cannot be used, after Black plays G5.

This is White developing an area that can't be developed.]
AW[cj][ck][cl]
AB[bj][bk][go]
LB[cj:1][bj:2][ck:3][bk:4][cl:5][go:6]
;
C[K14 aims to grow the upper left side, but it is already done.]
AE[go][bj][cj][ck][bk][cl]
;
C[M3, trying to invade Black, is too small right now.

If we aim to simply reduce, however, with N4, White is able to grow his area above.

He has made at least 10 points in this exchange, which is more than Black got.

In some cases, reducing is better (more profitable) than invaiding.]
AB[mq][lq][kq]
AW[mp][lp][kp][io]
LB[mp:1][mq:2][lp:3][lq:4][kp:5][kq:6][io:7]
;
C[It is also possible to reduce on the other side, with H3.

The following is a common pattern.
]
AE[mq][lq][kq][kp][lp][mp][io]
AW[hp][fp][go][dk][ho]
AB[hq][gp][gq][ci]
LB[hp:1][hq:1][fp:1][hp:1][hq:2][fp:3][gp:4][go:5][gq:6][ho:7][ci:8][dk:9]
;
AB[ep][fo][fi]
AW[eo][fn]
LB[ep:1][eo:2][fo:3][fn:4][fi:5]
C[Continuing the pattern 

Shygost doesn't like this area for White, very unapealing, very hard to grow.]
AE[fp]
;
AE[ci][fi][dk][ep][eo][fn][go][fo][gp][hp][hq][gq]
C[Comparing the two possible reductions for White, the first is prefered.

The traingled stones on the right have a desire for more stones, and can build well.]
TR[nl][oo][pm][qm]
;
C[On the left, White has one weak stone to help build with.]
TR[di]
;
C[Now, although White has reductions available, these tend to be middle game moves.

And according to Mr Yang, "when in the openning, play openning moves". Therefore it may be better for White to play a move on the right hand side.

The two point extension by White to N17 is also possible, but because the right is so much wider, this may be better.

One possible move on the right is R12. Play may continue in this fashion.

This White area is quite small. Yet Black picked up 3 points at the bottom and at least 6 points on top.]
AW[qh][rl][rk][sk][rh]
AB[qg][rg][rm][sm][sl]
LB[qh:1][rm:2][rl:3][sl:4][sk:5][sm:6][rk:7][rg:8][rh:9][qg:10]
;
AE[qg][rg][rh][rl][rk][sk][sl][sm][rm]
AB[rk][pj]
C[A second variation that may occur after White at R12 is shown here.

White stops Black from connecting under, so Black jumps out and splits White.]
AW[rm]
LB[qh:1][rk:2][rm:3][pj:4]
;
AE[rm][rk][pj][qh]
AW[qf]
AB[qh]
C[White cannot  play any closer, our may be captured by Black.]
;
AE[qf][qh]
AW[qf][je][of][rm]
AB[lc][qh][oh][qk]
C[Black can also use the sente move, and live on the right.

Black is fine, White is weak.]
LB[qf:1][lc:2][je:3][qh:4][of:5][qk:6][rm:7][oh:8]
;
AE[rm][qk][qh][oh][of][je][lc][qf]
AW[mc]
C[N7 is real, gets point, and removes a sente play by Black.]
;
AE[mc]
C[S16 is an excellent move here -- it forces Black to declare what is going on -- does he want the corner, or the side.

If Black wants the top, White can easily develop the side. Its not grand, but it is a positive development in sente for White. 
]
AW[rd][qe][qh][rl][sk][rk][rf][mc]
AB[rc][pd][rm][sl][sm][re][sd]
LB[rd:1][rc:2][qe:3][pd:4][qh:5][rm:6][rl:7][sl:8][sk:9][sm::][sm:10][rk:11][re:12][rf:13][sd:14][mc:15]
;
AE[mc][rc][rd][sd][re][pd][qe][rf][qh][rl][rk][sk][sl][sm][rm]
AW[rd][qc][qb][sc]
C[If Black wants the outside (although there is no point to this, as there is nothing to develop), play can follow like so. White takes the corner and is alive.]
AB[qe][re][pc]
LB[rd:1][qe:1][qc:1][rd:1][qe:2][qc:3][pc:4][qb:5][re:6][sc:7]
;
C[Black could also play this way, but Black's play is passive, for no reason.]
AE[pc][oc][qb][qc][sc][re][qe]
AB[oc][qc][rb]
AW[rc][qe]
LB[rd:1][qc:2][rc:3][rb:4][qe:5]
;
AE[qc][rc][rd][qe][rb]
C[Black can also play this way after White at R16.

At this point, White has several options.]
AW[rd][qe][pd][rf]
AB[re][rc][qc][sd]
LB[re:1][rd:2][rd:1][re:2][qe:3][rc:4][pd:5][qc:6][rf:7][sd:8]
;
AW[od][pf]
AB[nc]
C[One method is to use White's forcing move with P16, then connecting. White is doing well after these moves. Black now has the burden of coming in.]
LB[od:1][nc:2][pf:3]
;
AE[nc][od][pd][qc][rc][sd][re][rf][pf][qe]
AB[qe][qg]
AW[mc][qc]
C[The question arrises is if the probe still works if White exchanegs N17 with R13 before playing S16.

If Black plays this way, White can get the corner.]
LB[mc:1][qg:2][rd:3][qe:4][qc:5]
;
C[But if Black plays an alternate way, it produces a situation with many ladders, more complexity.

Lets avoid this, and play the probe immediately.]
AE[qc][qe]
AB[re]
AW[qe]
LB[mc:1][qg:2][rd:3][re:4][qe:5]
;
AE[mc][qg][qe][re]
C[Go Proverb - "When you don't know where to play, use your sente"

White wants to play on the right side, but is not sure how to. So he approaches with this probe. Black will take the corner, and White will settle with R12.]
AB[rc][pd]
AW[qe][qh]
LB[rd:1][rc:2][qe:3][pd:4][qh:5]
;
C[The question is raised if Black can invade with R9.

White prevents Black from connecting underneath with S8.

Black runs out with Q11.]
AB[qk][pi]
AW[rl]
LB[qk:1][rl:2][pi:3]
;
C[White is weak, which allows Black to run out.

If he wants safety, White will play R11.

Black continues, and White connects.

White will live, Black reduced.

But now Black has a weak group.]
AW[qi][rk]
AB[pj]
LB[qk:1][rl:2][pi:3][qi:4][pj:5][rk:6]
;
AE[qi][pi][pj][qk][rk][rl]
C[Black could also attack the upper right white group.

Let us assume that Black lives at the top.

White can then begin developing a large central moyo. 

The moral is, if Black chooses a difficult invasion such as R9 or H17, Black may get some profit, but so will White.]
AB[hc][hd][ib][jb][fb][db][df]
AW[ge][he][id][kb][kd][dg][fg]
;
AE[db][fb][ge][he][hd][id][hc][ib][jb][kb][kd][dg][df]
AB[lc][hc]
C[If we add a Black stone at M17, now Black's invasion is stronger, and it has purpose.]
;
AE[hc][lc][qe][rd]
C[If a few White stones were removed from the side, Black's invasion is again, stronger, as White is weak.]
AB[qk][pi]
AW[rl]
;
C[End of the lessons, hope you learnt something =)]
)
