(;CA[Windows-1252]AB[qp][rp][pr][pq]AW[or][oq][op][oo][po][qo][ro][mr][rm]C[there are  a few standard shapes of a dead  carpenters square, a black failure allows the creation of one of those 

1) a big eye\:
 an answered hane is needed for that, else the room is too big

2) a capturing race\:
 no outside liberties are needed and white must get an eye in the corner

3) shortage of liberties on the original carpenter's square\:
no liberties needed and the main variant has both white hanes

4) connection out 
thousand of variants, most obvious and the main threat of all plays, but not complicated, if not with threat of 3)

other things i noticed\:

- a main defensive threat of black is that she gets both plays on the 2-3 points

- white plays on the 2-3 points have two aims\: a) threatening connecting under (also if already haned) b) create big eye 




]
AP[MultiGo:4.4.4]SZ[19]AB[pp]MULTIGOGM[1]
;W[rr]
(;B[sr]C[main move]
(;W[ps]C[main answer threatening to connect]
(;B[qr];W[qs]C[main line];B[rs]C[ko so if white loses this ko black takes at p1 and white can defend outside, so i prefer the main line to sensei libs main line, but could be wrong])
(;B[qs]C[failure  leading to big eye; answered bnarrows eye space and makes big eye possible, which is achieved by threatening connecting under]
;W[rq];B[sq];W[qr];B[os];W[rs]C[big eye])
(;B[rs]C[white can connect];W[qr]))
(;W[sq]C[this one bothers me,its threatening to connect under and the answer stone. 

i considered two main options for black\:

1) stopping the connectionand let white take the 1-2 stone

2) immediate ko at the other 1-2 point leading to direct ko, but with an internal ko threat

]
(;B[rq]C[this move would be the answer for an white hane at  t4, so maybe it also works,  

white has the option of taking the stone and exchange  something on the other side threatening to connect out]
;W[ss]C[now black must stop connection else white can connect under]
(;B[sp]C[now black would live with the other 2-3 point and white must answer in this area

1) at the 2- 3 point for an two stag approach move ko for the possibility for killing with ignoring three black ko threats

2 at the hane for black living within double ko]
(;W[qr]C[threatening connection under or making an eye with ko defect

black can 

1) step down to force white into the two stage approach move ko

2) hane for a white approach move ko

3) take the ko now and die cause white connecting and killing]
(;B[ps]C[white now can 

1) complete his defect eye and make two stage ko, in which he has to ignore 3 black ko threats

2) fill an outsiede liberty with the effect that he has to complete the defect eye later also having to ignore three black ko threats]
(;W[qs];B[sr]C[its a two stage ko  and white still needs two outside approach moves- Because black can retake after the second appraoch move white   has to ignore three black ko threats]
;W[om];B[pm];W[sq];B[mp]
(;W[so];B[lp];W[os];B[sr];W[ol];B[pl];W[sq];B[mq];W[qq])
(;W[sr];B[qq]))
(;W[os]C[black now can

1) take the ko forcing white to an one approach move two stage ko
 and white must ignore three black ko threats

2) play inside at r 1 for an shape similar to the hane branch  with an white approach move ko 
white has to ignore two ko threats this way ]
(;B[sr]C[white  muatr in the end fill his defect eye which brings forth an  two stage ko ]
;W[qs];B[rs];W[om];B[pm];W[ss];B[mp];W[so];B[pl];W[ol];B[rs];W[ok];B[pk];W[ss];B[mo]
;W[sq];B[lp];W[qq])
(;B[qs];W[so];B[sr];W[om];B[pm];W[sq];B[mp];W[rs];B[sr];W[ol];B[pl];W[sq];B[mo]
;W[qq])))
(;B[qs]C[stopping the defect eye,

1) if white connects the ko its a seki 

2) if he fills outside liberties black takes the ko first and white still needs an approach move at p1 while its direct ko for black

3) an exchange s1 for q1 or p1 for q1 which doesnt change the situation so reverts to option 2


 for white so worse than main line, ]
(;W[so];B[sr];W[pm];B[om];W[sq];B[mp];W[os]C[ black must connect else white has to answer one less ko threat]
(;B[ps];W[rs];B[sr];W[pl];B[ol];W[sq];B[mo];W[qq]C[white needs to ignore two ko threats])
(;B[sr];W[ps];B[rs];W[ss];B[rs];W[qs]C[one unanswered ko therat]))
(;W[rs];B[ps];W[so];B[sr];W[om];B[pm];W[sq];B[mp];W[os];B[sr]C[wh];W[ol];B[pl];W[sq]
;B[mo];W[qq]C[approach move ko white needs to ignore two black ko threats])
(;W[os];B[ps];W[so];B[sr];W[om];B[pm];W[sq];B[mp];W[rs];B[sr];W[ol];B[pl];W[sq]
;B[mo];W[qq]))
(;B[sr];W[ps]))
(;W[ps]C[black lives in a double ko];B[qs]C[black threatens living at the 2-3 point]
;W[qr];B[os];W[rs];B[qq];W[ps];B[sr]))
(;B[qs];W[sp];B[rs];W[sr])
(;B[qr];W[sp];B[qs];W[sr]))
(;B[rs]C[now white options are

1) fighting the ko immediately
gives him an internal ko threat at t4

2) connecting under
takes away this ko threat and starts direct ko]
(;W[ss]C[black can not evade this ko by stopping the connction at t4 or by another way, do he plays a ko threat at p7]
(;B[om];W[pm]C[ko threat];B[sr]C[now white has internal ko threat at t4];W[sp];B[rq]
;W[ss]C[and black cannot evade this ko again]
(;B[ol];W[pl];B[sr];W[mp];B[qr]C[Black has to ignore one white ko threat - direct ko, but white has an internal ko threat 

so worse for black than mainline])
(;B[qr];W[qs];B[ps])
(;B[qs];W[sr]))
(;B[sp];W[ps]C[white connects under with oppsite hane];B[sr];W[qr])
(;B[rq];W[sp];B[qr];W[qs])
(;B[qr];W[sp];B[rq];W[qs])
(;B[qs]
(;W[sp]C[he connects under and black lost all]
(;B[sr];W[rq])
(;B[rq];W[sr]))
(;W[sr];B[sp]C[seki])))
(;W[sp];B[rq];W[ss]C[the exchange at t4 is bad for white, it becomes direct ko and white lost an internal ko theat]))
(;B[sp]C[an white anser at aking the ko reverts to the main line];W[ss]
(;B[rq]
(;W[qr];B[ps];W[os];B[sr];W[om];B[pm];W[sq];B[mp];W[qs];B[sr];W[ol];B[pl];W[sq]
;B[mo];W[so];B[sr];W[ok];B[pk];W[sq];B[lp];W[qq]C[whiite has to ignore three black ko threats after this two stage approach move ko])
(;W[qs];B[ps];W[qr]))
(;B[ps];W[qs];B[rq];W[qr];B[sr];W[so];B[mp];W[om];B[pm];W[sq];B[mo];W[os];B[sr]
;W[ol];B[pl];W[sq];B[lp];W[qq])))
(;W[sp]C[wrong direction allows seki];B[rq];W[qr];B[qs]C[now black can play this hane as big eye possiblity is erased by the beforehand exchange]
;W[rs];B[ps]C[seki])
(;W[rq]C[just an exchange that doesnt alter main line and can be played anytime,]
;B[sq]
(;W[ps]
(;B[qr];W[qs];B[rs]C[the main ko again])
(;B[qs]C[answered hane is big eye time];W[qr];B[os];W[rs]C[big eye]))
(;W[qr];B[ps]C[alive in big seki]))
(;W[qr]C[according to senseis lib the main line for no outsied liberties, im not so sure cause of next play]
(;B[ps]C[this stone has outside influence, so why prefer this to the main line?]
;W[sp];B[rq];W[qs];B[rs];W[ss]C[also a ko in the end])
(;B[qs];W[rs];B[ps];W[rq]))
(;W[rs]C[threatening to connect but only leading to seki];B[qr]
(;W[rq];B[sq];W[ps];B[qs])
(;W[sp];B[rq];W[qs];B[ps])
(;W[sq];B[rq];W[ss];B[sp])))
(;B[qr]C[failure leading to capturing race cause white is allowed an sente 2- 3 play and can so make an eye in the corner]
;W[rq]C[threat to connect must be ansewered]
(;B[sp];W[rs]C[capturing race]
(;B[sq];W[sr];B[qs];W[so]C[capturing race lost for b])
(;B[sr];W[sq]))
(;B[sq];W[sr];B[sp];W[rs]))
(;B[qs]C[dumb play for completeness; i just reviewed one method];W[sp]C[threatening connectin under]
(;B[rq];W[sq]C[connected])
(;B[sq];W[rq]C[two answered hanes make big eye easy];B[so];W[rs]
(;B[sr];W[qr])
(;B[qr];W[sr]))))