Two-Space Notchers
Keywords: Life & Death
Two-space notchers are groups that consist of a chain on the second line, interrupted by a notch of two empty spaces on the second line and two stones on the third.
The term was invented by James Davies.
See also Notchers, One-Space Notchers and Three-Space Notchers.
![[Diagram]](../../diagrams/40/af6a80974c941cb8bb2c9b709fd03edc.png) | Two-space notcher |
The rule for two space notchers is, depending on how you want to formulate it, either "Five die, Seven live" or "Six is unsettled". For the time being we'll leave proof of the two extremes to you and demonstrate the unsettled case.
![[Diagram]](../../diagrams/37/f2165648d125a7ca46eae8ef97b33bc4.png) | Black goes first and lives |
If Black goes first, he can live. White is again rather stubborn to keep trying with 2 and 4, but after 5 Black has completely constructed the two eyes he needs to live.
![[Diagram]](../../diagrams/11/15c73974e8044dc464ea68f7a2d6b023.png) | White goes first and kills |
White can start her attack with a hane at 1.
(Reducing your opponent's eye space like this should always be the very first option you consider when examining the status of one of his groups, by the way. See also the article on approaching a life and death problem the right way.).
Even if Black were to resist, White can keep his group dead.
unkx80: See also Two Space Notchers Not Fully Connected.
Classification
![[Diagram]](../../diagrams/8/0024086ab527161e0ced8d3c77970b4c.png) | Two-space notchers |
Marked spots: possible weaknesses
Marked stones: legs
Classification...
211
![[Diagram]](../../diagrams/43/617b19144b99bc6362749f7e53896a25.png) | 211WW |
![[Diagram]](../../diagrams/29/0383e11a1797b35a62aed52d66491f19.png) | 211WN |
![[Diagram]](../../diagrams/44/037bb6a0d2d0b7e42ad70e98b8d27c96.png) | 211WS |
![[Diagram]](../../diagrams/19/c392ad3f19823567519c7fc24ffa4147.png) | 211NN |
![[Diagram]](../../diagrams/9/168bd79550b7b82dab3ec6cf2bece88a.png) | 211NS |
![[Diagram]](../../diagrams/20/1fe97684d39a251095b3c9d5c0734e3a.png) | 211SS |
All of the 211xx are dead
212
![[Diagram]](../../diagrams/50/cdec50646f855b6d6aaa5e45ab04ef1b.png) | 212WW |
![[Diagram]](../../diagrams/45/1329b2f2c0733f7c03673bfb37bc3107.png) | 212WN |
![[Diagram]](../../diagrams/28/4559ab92a901c86349adaf3cd6ca2569.png) | 212WS |
![[Diagram]](../../diagrams/17/5b5795c265faa3b43e7af013c8cecee7.png) | 212NW |
![[Diagram]](../../diagrams/19/e72b246b9f365361e1b14dab38f383ad.png) | 212NN |
![[Diagram]](../../diagrams/5/801e0b9758b9af66d46e93d4c9ffee35.png) | 212NS |
![[Diagram]](../../diagrams/52/5f58b88020b28e68054d20a4930c5b5c.png) | 212SW |
![[Diagram]](../../diagrams/33/9073bdabfaebceb2601919c15e21bd0e.png) | 212SN |
![[Diagram]](../../diagrams/49/f6a1ca957399eb5e771c615fb7ad7104.png) | 212SS |
All of the 212 are dead
222
![[Diagram]](../../diagrams/38/6e30188a48d1e3ae836a5ac14031846b.png) | 222WW |
aka the flying saucer shape. It is dead
![[Diagram]](../../diagrams/20/c10827f0330daa6675ffc48ba02ea33e.png) | 222WN |
Black can live
![[Diagram]](../../diagrams/37/3977d7b06127bccd317c4f176601e61d.png) | 222WS |
Black can live
![[Diagram]](../../diagrams/24/d9671cbf63ab58e74558adf8a1870e10.png) | 222NN |
Black can live
![[Diagram]](../../diagrams/34/681d457f9696c9bd8454a078fd756454.png) | 222NS |
Black can live
![[Diagram]](../../diagrams/12/04c349874f34a9255cb61e9392cb7fe6.png) | 222SS |
Black can live
All 222 are "Black can live, White can kill" except 222WW, which is dead.
213
![[Diagram]](../../diagrams/36/b06a4194e5ba28acb41199e4cc85eaba.png) | 213WW |
dead
![[Diagram]](../../diagrams/14/ac97751de1e4c7a31373848c0682edcd.png) | 213WW |
Black can live
(...)
All of 213 can make life, except for 213WW which is dead
223
![[Diagram]](../../diagrams/6/3c3236af5edc30e2836dfa56173830a6.png) | 223WW |
Black can live
![[Diagram]](../../diagrams/7/53a29594c4a70ee8e66e5812bc1dc107.png) | 223WN |
Black is alive
(...)
All 223WW are alive, except for 223WW, where Black can live and White can kill.
233
![[Diagram]](../../diagrams/34/d0bec732621a35a4ce669a93611532e0.png) | 233WW |
Black is alive
(...)
All 233xx are alive
Table
See notchers for conventions.
211WW D - 212WW D - 213WW D -- 214WW ? -- 215WW ?
211WN D - 212WN D - 213WN LD - 214WN ? -- 215WN ??
211WS D - 212WS D - 213WS LD - 214WS ?? - 215WS ??
211NN D - 212NW D - 213NW LD - 214NW ? -- 215NW ??
211NS D - 212NN D - 213NN LD - 214NN ?? - 215NN ?
211SS D - 212NS D - 213NS LD - 214NS ?? - 215NS ?
xxxxx --- 212SW D - 213SW LD - 214SW ?? - 215SW ??
xxxxx --- 212SN D - 213SN LD - 214SN ?? - 215SN ?
xxxxx --- 212SS D - 213SS LD - 214SS ?? - 215SS ?
222WW D -- 223WW LD
222WN LD - 223WN L
222WS LD - 223WS L
222NN LD - 223NW L
222NS LD - 223NN L
222SS LD - 223NS L
xxxxx --- 223SW L
xxxxx --- 223SN L
xxxxx --- 223SS L
This is a copy of the living page
"Two-Space Notchers" at
Sensei's Library.
2003 the Authors, published under the OpenContent License V1.0.
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