Tom's move - Revision history

Demer: /* Bridge-first variant */ added other try by Blue

2025-11-29T16:16:02Z

‎Bridge-first variant: added other try by Blue

Demer: /* Bridge-first variant */ fixed cell reference

2025-11-27T22:07:14Z

‎Bridge-first variant: fixed cell reference

Demer: /* Variants */ removed unneeded cells and stones

2025-11-26T23:48:43Z

‎Variants: removed unneeded cells and stones

Mason: /* Bridge-first variant */

2025-11-23T20:25:45Z

‎Bridge-first variant

Selinger: /* Bridge-first variant */ Copy-edit

2025-11-23T18:53:34Z

‎Bridge-first variant: Copy-edit

Selinger: /* Bridge-first variant */ Added an example where bridge-first variant is the only winning play.

2025-11-23T18:46:00Z

‎Bridge-first variant: Added an example where bridge-first variant is the only winning play.

Mason: Add more info about the bridge-first variant

2025-11-23T06:11:22Z

Add more info about the bridge-first variant

Mason: Add bridge-first variant

2025-11-22T19:01:06Z

Add bridge-first variant

Selinger: /* Alternative connection up */ Added link for "alternative connection up" theorem.

2024-04-20T21:44:44Z

‎Alternative connection up: Added link for "alternative connection up" theorem.

Selinger: /* Tom's move for 3rd-and-5th row parallel ladders */ Added tall variant.

2023-09-13T03:15:42Z

‎Tom's move for 3rd-and-5th row parallel ladders: Added tall variant.

@@ Line 241: / Line 241: @@
 Here is a specific example position where the bridge-first variant is necessary. Red's only winning move is Tom's move (a), and if Blue plays at (b), Red's only winning response is (c).
 <hexboard size="7x7"
-   contents="R d1 b3 b4 a5 B b2 e1--g1 b5 E a:d5 b:c6 c:d3"
+   contents="R d1 b3 b4 a5 B b2 e1--g1 b5 E a:d5 b:c6 c:d3 d:d2"
    />
 == Tom's move for 3rd-and-5th row parallel ladders ==

@@ Line 205: / Line 205: @@
 === Bridge-first variant ===
-If the end of Red's second row ladder is not yet directly beneath the end of their 4th row ladder, Red can opt to play the bridge to "*" first, instead of playing at "*".
+If the end of Red's second row ladder is not yet directly beneath the end of Red's 4th row ladder, Red can opt to play the bridge to "1" first, instead of playing at "*".
 <hexboard size="5x8"
    edges="bottom"

@@ Line 168: / Line 168: @@
 For example, Tom's move works in this situation:
-<hexboard size="6x8"
+<hexboard size="6x7"
    edges="bottom"
    coords="none"
-   visible="-g2 h2 h3 f1--h1 -area(a1,a5,c1)"
+   visible="-(a1 b1 a2 a3 e1 f1 g1 f2 g2 g3)"
-   contents="R arrow(12):b4 b5 c3 B a6 b6 c4 R e4 E b:e2 R d1 B a:d2 R c2"
+   contents="R arrow(12):a4 a5 b3 B a6 b4 R d4 E b:d2 R c1 B a:c2 R b2"
    />
@@ Line 180: / Line 180: @@
 If "d" is empty, there is a variant of Tom's move that does not require a connection via "b", or even for "b" to be empty; it merely requires "c" and "e" to threaten to connect to Red's main group. An example is this situation:
-<hexboard size="6x8"
+<hexboard size="6x7"
    edges="bottom"
    coords="none"
-   visible="-h2 h3 g1--h1 -area(a1,a5,c2,d1)"
+   visible="-(f1 g1 g2 g3 area(a1,a3,c1))"
-   contents="R arrow(12):b4 b5 c3 B a6 b6 c4 R e4 E c:f2 d:g2 e:e3 R e1 B b:e2 R d2"
+   contents="R arrow(12):a4 a5 b3 B a6 b4 R d4 E c:e2 d:f2 e:d3 R d1 B b:d2 R c2"
    />
 In this version of Tom's move, Red's 4 is different than usual (the usual move 4 does not work here). As before, moves 2 and 3 don't need to be played, but make it easier to see how the connection works.
-<hexboard size="6x8"
+<hexboard size="6x7"
    edges="bottom"
    coords="none"
-   visible="-h2 h3 g1--h1 -area(a1,a5,c2,d1)"
+   visible="-(f1 g1 g2 g3 area(a1,a3,c1))"
-   contents="R arrow(12):b4 b5 c3 B a6 b6 c4 R x:e4 R e1 B e2 R d2
+   contents="R arrow(12):a4 a5 b3 B a6 b4 R x:d4 R d1 B d2 R c2
-             B 1:d5 R 2:c5 B 3:c6 R 4:f2 E y:f3"
+             B 1:c5 R 2:b5 B 3:b6 R 4:e2 E y:e3"
    />
 Note that "x" is connected to Red's main group without requiring "y", and "4" is also connected to Red's main group without requiring "y". (However, Red cannot guarantee to connect both "x" and "4" to her main group without requiring "y"). If Blue tries to cut Red off from the edge, Red responds as follows:
-<hexboard size="6x8"
+<hexboard size="6x7"
    edges="bottom"
    coords="none"
-   visible="-h2 h3 g1--h1 -area(a1,a5,c2,d1)"
+   visible="-(f1 g1 g2 g3 area(a1,a3,c1))"
-   contents="R arrow(12):b4 b5 c3 B a6 b6 c4 R x:e4 R e1 B e2 R d2
+   contents="R arrow(12):a4 a5 b3 B a6 b4 R x:d4 R d1 B d2 R c2
-             B 1:d5 R 2:c5 B 3:c6 R 4:f2 E y:f3 B 5:e5 R 6:g4"
+             B 1:c5 R 2:b5 B 3:b6 R 4:e2 E y:e3 B 5:d5 R 6:f4"
    />
 Now no matter how Blue plays, Red can connect to the edge by a sequence of forcing moves. The situation is analogous to the [[Interior_template#The_hammock|hammock template]].
@@ Line 209: / Line 209: @@
    edges="bottom"
    coords="none"
-   visible="-(a1--a3 b2 b1 c1 g1 h1 h2)"
+   visible="-(a1--a4 b2 b1 c1 g1 h1 h2)"
    contents="R arrow(12):c2 b3 e3 1:e1 B c3 a5 d4 E *:f2"
    />
@@ Line 218: / Line 218: @@
    edges="bottom"
    coords="none"
-   visible="-(a1--a3 b2 b1 c1 g1 h1 h2)"
+   visible="-(a1--a4 b2 b1 c1 g1 h1 h2)"
    contents="R arrow(12):c2 b3 e3 e1 2:f2 4:c4 B c3 a5 d4 1:e4 3:f4 S b4 d3"
    />
@@ Line 226: / Line 226: @@
    edges="bottom"
    coords="none"
-   visible="-(a1--a3 b2 b1 c1 g1 h1 h2)"
+   visible="-(a1--a4 b2 b1 c1 g1 h1 h2)"
    contents="R arrow(12):c2 b3 e3 e1 2:e4 B c3 a5 d4 1:f2"
    />
@@ Line 235: / Line 235: @@
    edges="bottom"
    coords="none"
-   visible="-area(a1,a4,d1) h2 h3 g1--h1"
+   visible="-area(a1,a4,d1) a5 h2 h3 g1--h1"
    contents="R arrow(12):c3 b4 e4 2:e1 B c4 a6 1:e2"
    />
@@ Line 241: / Line 241: @@
 Here is a specific example position where the bridge-first variant is necessary. Red's only winning move is Tom's move (a), and if Blue plays at (b), Red's only winning response is (c).
 <hexboard size="7x7"
-   contents="R d1 a2--b2--b4--a5 B a1--c1 e1--g1 b5 E a:d5 b:c6 c:d3"
+   contents="R d1 b3 b4 a5 B b2 e1--g1 b5 E a:d5 b:c6 c:d3"
    />

@@ Line 230: / Line 230: @@
    />
-This variation should be used if you don't want the opponent to get the territory from intruding into the bridge of a standard Tom's move. But what if the opponent plays that move before you do to ensure they get it? In this case it is often good to respond as follows, and use the tall variant to connect "2".
+This variation should be used if you don't want the opponent to get the territory from intruding into the bridge of a standard Tom's move. But what if the opponent plays that move before you do to ensure they get it? In this case it is often good to respond as follows, and use the tall variant to connect 2.
 <hexboard size="6x8"

@@ Line 239: / Line 239: @@
    />
-Here is a specific example position where the only winning move for Red is Tom's move (a), and if Blue plays at (b), Red's only winning response is the bridge-first move (c).
+Here is a specific example position where the bridge-first variant is necessary. Red's only winning move is Tom's move (a), and if Blue plays at (b), Red's only winning response is (c).
 <hexboard size="7x7"
    contents="R d1 a2--b2--b4--a5 B a1--c1 e1--g1 b5 E a:d5 b:c6 c:d3"

@@ Line 174: / Line 174: @@
    contents="R arrow(12):b4 b5 c3 B a6 b6 c4 R e4 E b:e2 R d1 B a:d2 R c2"
    />
 === Tall variant ===

← Older revision		Revision as of 03:15, 13 September 2023
Line 233:		Line 233:

	See [[Tom's move for 3rd and 5th row parallel ladders]] for more details.		See [[Tom's move for 3rd and 5th row parallel ladders]] for more details.
		+
		+	=== Tall variant ===
		+
		+	Tom's move for 3rd-and-5th row parallel ladders also has a tall version. It works in the same way as the tall version of Tom's move for 2nd-and-4th row parallel ladders above, given the appropriate amount of space.
		+
		+	<hexboard size="7x12"
		+	coords="hide"
		+	edges="bottom"
		+	visible="area(d2,b4,b7,l7,l5,j3,g2,f1,e1)"
		+	contents="R arrow(12):e1 d2 c3 b4 b5 B b6 c4 e2 R 1:e4 B 2:d5 R 3:f2"
		+	/>

	== See also ==		== See also ==