View source for FIFI25 vs. murasawa, October 2021

== Game information ==
* Size: 11x11
* Red: FIFI25
* Blue: murasawa
* Result: 1-0 (Red won)
* Comments: Eric Demer
* Location: [[Board Game Arena]], table [https://boardgamearena.com/table?table=212776246 212776246]

== Coordinate conversion and directions ==

This game was played with BGA's old hex implementation, so its coordinates and board orientation are different from what's shown on this page.  I apply a small rotation to show move coordinates and positions on this page:

(11;11) -> a11     (1;11) -> a1     (1;1) -> k1     (11;1) -> k11


References to the "left" and "top" etc. work for ''this'' page's orientation and the default hexworld.org/board orientation, but ''not'' for the orientation shown at the boardgamearena.com link by Location under Game Information.  (In particular, the left edge goes from a1 to a11 inclusive, and the top edge goes from a1 to k1 inclusive.)






== Moves and comments ==







You can see the diagram for each move by following along at  [https://hexworld.org/board/#11c1,,a11f6e6e4g7f5h5h4c4c3d3c5e5e8j3h3f4j2b4b3g2d8c8b9c9d7b7:rw this HexWorld link] .


FIFI25 plays  1. a11

murasawa does ''not'' swap, and plays  2. f6


<hexboard size="11x11" contents="R 1:a11 B 2:f6"/>




----





3. e6     good   This works with the swap piece, since normally play towards an obtuse corner would favor whoever is on the [[short diagonal]], but a11 means it would favor Red here.


4. e4


5. g7     h7 would normally be better ([[joseki]]), but g7 is good here, since if Blue connects to the right with   6. h5  ,   then  [[Peep|7. g5]]  works well with f6, due to [[Edge_templates_everybody_should_know#Fifth_row_edge_templates_with_two_stones|the edge template that f5+g5 would form]].


6. f5


<hexboard size="11x11" contents="R a11 3:e6 5:g7 7:h5 9:c4 B f6 4:e4 6:f5 8:h4 10:c3"/>


7. h5     8. h4


9. c4     good ([[joseki]])   Blue is fairly strong towards the left, so Blue will probably connect to the left edge.  That means Red will probably need to ladder along the top, and c4 will be quite helpful with such a ladder.


10. c3   [[joseki]] again





----





11. d3   12. c5       This ends the [[joseki]].


13. e5   This seemed fine  to me until I saw Blue's response :-).  Due to that response, Red should've tried j3 instead.  (j3 would create a ladder along the top towards the left and a ladder along the right towards the bottom.)


14. e8     This wins for Blue, though Blue did ''not'' keep the win:   Due to c3, Blue can keep c5 connected ''and'' serving as an escape for height-3 ladders (Red can't [[Foiling|foil]]), so Blue connects left via f4 or c9.  For the right, h4 gives Blue either a height-2 ladder plus a [[Switchback#Switchback_threat|switchback threat]] or a height-3 ladder, and either of those is enough to [[Climbing|climb]] to e8.


15. j3


<hexboard size="11x11" contents="R a11 e6 g7 h5 c4 11:d3 13:e5 15:j3 17:f4 19:b4 B f6 e4 f5 h4 c3 12:c5 14:e8 16:h3 18:j2 20:b3"/>


16. h3   This is locally good — Blue is being [[Tidiness|tidy]] before laddering along the right — and keeps Blue's win, but was not necessary:  i4 wins more efficiently than h3.   See [[#Blue's Connection Right|the variations for that]].


17. f4   h3 reconnected Blue to the right, and f4 threatens Blue's connection left, so Blue should keep Blue's win by defending Blue's connection left, with c9.


18. j2   Instead, Blue wastes a substantial fraction of a move, since Blue was already connected right.  (See [[#Blue's Connection Right|the variations for that]].)  Now, not only am I no longer able to prove that Blue wins, but I in fact prefer Red.


19.  b4

b5 was better ([[Minimax|minimaxing]]):     It gives Red a [[ladder escape fork]] at b2, so the only advantage b4 might have over b5 is avoiding a potential [[peep]] at e2.   However, that is almost-always much less important than the extra strength b5 gives along the left.   Furthermore, in this case, since Blue has e4 and e3,f2,g1,h1 are all empty, that peep provably achieves nothing:  Red can just answer with e2 with d2, and f2+g1 will still be [[Captured cell|red-captured]].

However, even b5 is almost-certainly not enough here:  If Blue responds in the cell Blue plays for 22, then the situation becomes the same as just after Blue plays 22 in the game.   I would've played b9 instead of either of  b4,b5 ,  due to Blue's strength towards the right.   See my explanation of [[#the Situation on Top|the situation on top]].


20. b3     If Blue was playing this as a timesuji [https://senseis.xmp.net/?TimeSuji], then I think Blue should've played g2 instead, so Blue would have more of them left.  Otherwise, this was bad because redD2 [[Captured cell|captures]] e1+d1, and thereby [[Dead cell|kills]] b3.  Red ''might'' play b7 to try punishing b3, but I would probably instead neutralize b3 with a move near the top.





----





21. g2     simple and fine, since this makes  20. b3  completely useless to Blue


22. d8     Very Good:   Before I saw Blue play this, the position looked good for Red.  With this move, I am almost-certain that Blue wins.  (Blue does ''not'' keep this almost-certain win.)


23. c8     Red's only chance   c8 has a connection to the top, and c5 is an escape for ladders under c8, so the upward direction is [[settled region|settled]].


24. b9     blunder; now Red wins   ''Red'' keeps this win for the short rest of the game.

Blue needed to [[#the Ladder Along the Bottom|defend along the bottom]], either immediately with b10 (simpler), or after threatening to cut through near the middle of the left edge (b8 is faster).


<hexboard size="11x11" contents="R a11 e6 g7 h5 c4 d3 e5 j3 f4 b4 21:g2 23:c8 25:c9 27:b7 B f6 e4 f5 h4 c3 c5 e8 h3 j2 b3 22:d8 24:b9 26:d7"/>


25. c9   forced


26. d7   Blue has a height-4 ladder.  If Red just pushes, then Blue will connect to c5 which will then ladder to b9.


27. b7     Instead, Red [[Ladder_handling#Defending|yields]], winning.   I also give [[#the Final Move|more explanation regarding this move]].


28.  Blue resigns     b7 connects to the top via c6 or a6.


<hexboard size="11x11" contents="R a11 e6 g7 h5 c4 d3 e5 j3 f4 b4 g2 c8 c9 b7 B f6 e4 f5 h4 c3 c5 e8 h3 j2 b3 d8 b9 d7 S area(e5,d5,b7,b8) f4 h1 area(g1,d1,d3,g3) c4 area(b4,a5,a7,b7) c7 b8 c8 area(c9,c11,a11)"/>









== Variations and more explanation==







=== Blue's connection right===



As stated in the main comments,   16. i4   was winning for Blue,

<hexboard size="11x11" contents="R a11 e6 g7 h5 c4 d3 e5 j3 B f6 e4 f5 h4 c3 c5 e8 E 16:h3 *:i4 17:f4 S red:f4 blue:h3"/>

and after   16. h3  ,   i4 meant Blue was connected right.

<hexboard size="7x7"
 visible="- (e1 d1 area(c1,a1,a3) a4 d7)"
 edges="right"
 coords="none"
 contents="R c5 c4 d3 f1 B a6 b4 b3 d2 e2"
 />

The above diagram shows the area Blue uses to connect right without h3.


Blue defends

<hexboard size="7x7"
 visible="- (e1 d1 area(c1,a1,a3) a4 d7)"
 edges="right"
 coords="none"
 contents="R c5 c4 d3 f1 a5 c2 B a6 b4 b3 d2 e2 b5 c3"
 />

both bridges.


If Red pushes three times, then Blue just pivots and [[Climbing#3rd_row_ladder|climbs]],

<hexboard size="7x7"
 visible="- (e1 d1 area(c1,a1,a3) a4 d7)"
 edges="right"
 coords="none"
 contents="R c5 c4 d3 f1 a5 c2 1:f2 3:f3 5:f4 7:e5 9:d5 B a6 b4 b3 d2 e2 b5 c3 2:e3 4:e4 6:e6 8:d6 10:b7"
 />

and Red [[Ladder_handling#Defending|yielding]] instead of Red's last push doesn't help Red.

<hexboard size="7x7"
 visible="- (e1 d1 area(c1,a1,a3) a4 d7)"
 edges="right"
 coords="none"
 contents="R c5 c4 d3 f1 a5 c2 1:f2 3:f3 5:g4 7:g3 9:f5 B a6 b4 b3 d2 e2 b5 c3 2:e3 4:e4 6:f4 8:f6 10:e6"
 />

Blue doesn't need the 6,7 exchange here; that is simply shown to make clear why Red does not respond to the diagram's 8 further left than the diagram's 9.


If Red instead [[Ladder_handling#Defending|yields]] immediately, then

<hexboard size="7x7"
 visible="- (e1 d1 area(c1,a1,a3) a4 d7)"
 edges="right"
 coords="none"
 contents="R c5 c4 d3 f1 a5 c2 1:g2 3:g1 5:f3 B a6 b4 b3 d2 e2 b5 c3 2:f2 4:e4 6:e3"
 />

Blue gets the same thing as if Red pushed twice.


That leaves Red pushing exactly once and then [[Ladder_handling#Defending|yielding]], in which case Blue's 1 gives Blue a [[Switchback#Switchback_threat|switchback threat]], which lets Blue still [[Climbing#2nd_row_ladder|climb]].

<hexboard size="7x7"
 visible="- (e1 d1 area(c1,a1,a3) a4 d7)"
 edges="right"
 coords="none"
 contents="R c5 c4 d3 f1 a5 c2 1:f2 3:g3 5:g2 7:f4 B a6 b4 b3 d2 e2 b5 c3 2:e3 4:f3 6:f5 8:d6 S b6 a7 b7 c7 c6 d5 d4 e4 e5 e6 g5 g4"
 />

Again, Blue doesn't need the 4,5 exchange here; that is simply shown to make clear why Red does not respond to the diagram's 6 further left than the diagram's 7.





===The situation on top===



Between   18. j2   and   19. b4  ,   but Blue cutting Red off there would just give Blue a height-3 ladder along the left.

<hexboard size="11x11" contents="R a11 e6 g7 h5 c4 d3 e5 j3 f4 B f6 e4 f5 h4 c3 c5 e8 h3 j2"/>


<hexboard size="5x9"
 visible="-(f5 g4 area(g5,i5,i3) i2)"
 edges="top left"
 contents="R c4 d3 e5 f4 B e4 c3 c5 h3"
 />

The above diagram shows the relevant area, and the below diagram shows the sequence.

<hexboard size="5x9"
 visible="-(f5 g4 area(g5,i5,i3) i2)"
 edges="top left"
 contents="R c4 d3 e5 f4 2:b5 4:d5 B e4 c3 c5 h3 1:g2 3:f3 5:d4 E *:b2"
 />

f2 is ''locally'' better than f3, but that doesn't matter here, since Red would still be connected in the upper-left due to the [[ladder escape fork]] at "*".





===The ladder along the bottom===



<hexboard size="11x11" contents="R a11 e6 g7 h5 c4 d3 e5 j3 f4 b4 g2 c8 B f6 e4 f5 h4 c3 c5 e8 h3 j2 b3 d8"/>

Here, Red played b9, which loses because c8 is still connected to the top.  The below diagram shows the start of the ladder that ''should'' have occurred instead.

<hexboard size="11x11" contents="R a11 e6 g7 h5 c4 d3 e5 j3 f4 b4 g2 c8 2:d7 4:c9 6:d9 B f6 e4 f5 h4 c3 c5 e8 h3 x:j2 b3 d8 1:b8 3:b10 5:c10"/>

Blue played  18. j2  when Blue was ''already'' connected right, thereby giving up a guaranteed win.     Furthermore, if Red had responded with   19. b9  ,   then I would've preferred Red.     However, j2 ''does'' mean Blue's center group connects right ''without'' using any of the lower-right, so Red has no useful forcing moves.     As a result, I am ''almost'' sure that Blue wins here.





===The final move===



<hexboard size="11x11" contents="R a11 e6 g7 h5 c4 d3 e5 j3 f4 b4 g2 c8 c9 *:b7 B f6 e4 f5 h4 c3 O:c5 e8 h3 j2 b3 d8 b9 d7"/>


Against "O", "*" is the same defense as if a height-4 ladder is pushed too close to an a3 swap piece:  In that case, the attacker might be anticipating a [[Foldback|foldback underneath]], but if the defender [[Ladder_handling#Defending|yields]] just before the attacker's push makes a bridge to the swap piece, then instead the the original ''defender'' gets a height-2 ladder.


<hexboard size="5x4"
 visible="-(b5 c5 d5 d4)"
 edges="top left"
 contents="R c4 1:c3 3:c2 5:a2 7:a3 9:a4 11:a5 B c1 d3 2:d2 4:d1 6:b2 8:b3 10:b4 12:b5"
 />

If Red pushes with c3, then Blue gets a [[Foldback|foldback underneath]].  Red should instead [[Ladder_handling#Defending|yield]] with b3, so that instead ''Red'' gets a ladder.

<hexboard size="5x4"
 visible="-(b5 c5 d5 d4)"
 edges="top left"
 contents="R c4 1:b3 3:c2 5:c3 7:d2 B c1 d3 2:(b1 a2 b2) 4:b4 6:d1"
 />

To avoid this, Blue should [[Ladder_handling#Attacking|pivot]] sooner.











[[Category:Game record]]