Intrusion - Revision history

Selinger: /* Bad intrusion */ fixed a link

2023-10-01T21:03:23Z

‎Bad intrusion: fixed a link

Selinger: Added another "see also"

2023-10-01T15:24:40Z

Added another "see also"

Selinger: Added category

2023-10-01T15:21:53Z

Added category

Selinger: /* Invalid intrusion */ copy-editing

2023-10-01T06:52:48Z

‎Invalid intrusion: copy-editing

Selinger: /* Good intrusion */ Better response to intrusion H.

2023-10-01T06:48:08Z

‎Good intrusion: Better response to intrusion H.

Selinger: copy-edit

2023-10-01T06:39:36Z

copy-edit

Selinger: New article

2023-10-01T06:35:12Z

New article

Selinger: Redirection for "intrusion"

2020-07-05T21:14:28Z

Redirection for "intrusion"

New page

#REDIRECT [[strong connection]]

@@ Line 77: / Line 77: @@
    contents="R a1 b1 a3 E A:a2 B:b2"
    />
-If Blue intrudes at A, Red's response at B actually [[dead cell|kills]] Blue's stone. Therefore, such an intrusion does not help Blue at all, but helps Red instead. See the article on [[bolstered templates]] for more details.
+If Blue intrudes at A, Red's response at B actually [[dead cell|kills]] Blue's stone. Therefore, such an intrusion does not help Blue at all, but helps Red instead. See the article on [[bolstered template]]s for more details.
 == Invalid intrusion ==

← Older revision		Revision as of 15:24, 1 October 2023
Line 106:		Line 106:

	* Some intrusions are [[peeps]].		* Some intrusions are [[peeps]].
		+	* Some intrusions can [[dominated cell\|dominate]] others. See [[Dominated_cell#Star_decomposition_domination\|here]] for an example.

	[[category: Intermediate Strategy]]		[[category: Intermediate Strategy]]

← Older revision		Revision as of 15:21, 1 October 2023
Line 106:		Line 106:

	* Some intrusions are [[peeps]].		* Some intrusions are [[peeps]].
		+
		+	[[category: Intermediate Strategy]]

@@ Line 88: / Line 88: @@
    contents="R d1 E A:c3"
    />
-If Blue tries to intrude at A, Blue does not even threaten to disconnect Red, because in addition to two different ziggurats, Red is also connected by [[edge template III1b]]:<hexboard size="3x5"
+If Blue tries to intrude at A, Blue does not even threaten to disconnect Red, because Red is still connected by [[edge template III1b]], threatening to play one of the two cells marked "*":
    coords="none"
    edges="bottom"
    visible="area(c1,a3,e3,e1)"
-   contents="R d1 S area(c1,a3,e3,e1)-c3 E A:c3"
+   contents="R d1 S area(c1,a3,e3,e1)-c3 B 1:c3 E *:b2 *:e2"
    />
-An intrusion, by definition, must threaten to disconnect Red. Therefore, playing at A is not be a valid intrusion at all. Instead, it is likely a [[irrelevant move|wasted move]].
+By definition, an intrusion must threaten to disconnect Red. Therefore, the move at A is not a valid intrusion at all. Instead, it is likely a [[irrelevant move|wasted move]].
 One situation where an invalid intrusion can be beneficial is [[losing play#Feinting|feinting]].

@@ Line 48: / Line 48: @@
    contents="B a3 R c2 S area(c2,a4,d4,d2) E D:d3 F:b4 B 1:d3 R 2:b4"
    />
-However, not all intrusions along the template's outsides are good in all circumstances. For example, if Blue tries to intrude at H, Red may respond at A, forming [[edge template III2a]] and leaving Blue with only a 2nd row escape:
+However, not all intrusions along the template's outsides are good in all circumstances. For example, if Blue tries to intrude at A, Red may reconnect at D, forming [[edge template III2e]] and again leaving Blue with only a 2nd row escape:
 <hexboard size="4x6"
    coords="none"
    edges="bottom right"
-   contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:d4 R 2:d2"
+   contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:d2 R 2:d3"
    />
-Similarly, if Blue intrudes at A, Red may reconnect at D, forming [[edge template III2e]] and again leaving Blue with only a 2nd row escape:
+If Blue intrudes at H, the situation is even worse for Blue: Red can respond as follows, [[captured cell|capturing]] the entire corner and leaving Blue with nothing useful at all:
 <hexboard size="4x6"
    coords="none"
    edges="bottom right"
-   contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:d2 R 2:d3"
+   contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:d4 R 2:e2 S red:area(c2,a4,f4,f2)"
    />
-If Blue intrudes at C, the situation is even worse for Blue: Red can reconnect at A, leaving Blue with nothing useful at all:
+If Blue intrudes at C, Red can do the same thing, again leaving Blue with nothing:
 <hexboard size="4x6"
    coords="none"
    edges="bottom right"
-   contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:c3 R 2:d2"
+   contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:c3 R 2:e2 S red:area(c2,a4,f4,f2)"
    />
 Thus, Blue must carefully choose the best intrusion for the given situation.

@@ Line 42: / Line 42: @@
    contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:b4 R 2:d3 B 3:d2 R 4:c3"
    />
-On the other hand, if Blue intrudes at D (near the edge of the template), Red reconnects at F, and Blue gets a 3rd row ladder escape:
+On the other hand, if Blue intrudes at D (near the edge of the template), Red reconnects at F, and Blue gets a 3rd row ladder escape. This is better for Blue.
 <hexboard size="4x6"
    coords="none"

← Older revision		Revision as of 06:35, 1 October 2023
Line 1:		Line 1:
−	#~~REDIRECT~~ [[~~strong~~ connection]]	+	An '''intrusion''' is a move that threatens to disconnect a [[virtual connection]] of the opponent. The most common kind of intrusion is a '''template intrusion''', which is a move inside the carrier of one of the opponent's [[templates]].
		+
		+	By definition, a template or a virtual connection can always be defended, and therefore, intruding into a template does not actually disconnect the opponent (unless the opponent [[tenuki\|declines]] to defend the template). Nevertheless, a well-played intrusion can be to the benefit of the intruding player. For example, the intruding player may gain a bit of [[territory]] or a [[ladder escape]].
		+
		+	Choosing which one of several possible intrusions is the most advantageous is one of the most difficult skills in Hex.
		+
		+	== Examples ==
		+
		+	=== Bridge intrusion ===
		+
		+	The most basic template is the [[bridge]]. It has two potential intrusions: at A or at B.
		+	<hexboard size="3x2"
		+	coords="none"
		+	edges="none"
		+	visible="area(b1,a2,a3,b2)"
		+	contents="R b1 a3 E A:a2 B:b2"
		+	/>
		+	If Blue intrudes at A, Red may defend the bridge at B (or [[tenuki\|play elsewhere]]). If Blue intrudes at B, Red may defend the bridge at A. Either way, Blue gains a bit of [[territory]] on one side of the bridge (but not the other). Blue is faced with the choice of which side of the bridge to intrude upon (if any).
		+
		+	=== Ziggurat intrusion ===
		+
		+	In the [[ziggurat]], there are 8 potential intrusion points A–H:
		+	<hexboard size="3x4"
		+	coords="none"
		+	edges="bottom"
		+	visible="area(c1,a3,d3,d1)"
		+	contents="R c1 E A:d1 B:b2 C:c2 D:d2 E:a3 F:b3 G:c3 H:d3"
		+	/>
		+
		+	== Good intrusion ==
		+
		+	Which of several possible intrusions to play is a difficult question that depends on what else is going on on the board and what the intruding player would like to achieve. But generally speaking, it is usually better to intrude along the outside of a template, rather than in its center. A typical situation is the following:
		+	<hexboard size="4x6"
		+	coords="none"
		+	edges="bottom right"
		+	contents="B a3 R c2 S area(c2,a4,d4,d2) E A:d2 B:b3 C:c3 D:d3 E:a4 F:b4 G:c4 H:d4"
		+	/>
		+	Suppose Blue wishes to intrude into Red's [[ziggurat]]. If Blue intrudes at F (near the center of the template), Red reconnects at D. By further intruding into Red's bridge, Blue gets at most a 2nd row [[ladder escape]] along the right edge:
		+	<hexboard size="4x6"
		+	coords="none"
		+	edges="bottom right"
		+	contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:b4 R 2:d3 B 3:d2 R 4:c3"
		+	/>
		+	On the other hand, if Blue intrudes at D (near the edge of the template), Red reconnects at F, and Blue gets a 3rd row ladder escape:
		+	<hexboard size="4x6"
		+	coords="none"
		+	edges="bottom right"
		+	contents="B a3 R c2 S area(c2,a4,d4,d2) E D:d3 F:b4 B 1:d3 R 2:b4"
		+	/>
		+	However, not all intrusions along the template's outsides are good in all circumstances. For example, if Blue tries to intrude at H, Red may respond at A, forming [[edge template III2a]] and leaving Blue with only a 2nd row escape:
		+	<hexboard size="4x6"
		+	coords="none"
		+	edges="bottom right"
		+	contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:d4 R 2:d2"
		+	/>
		+	Similarly, if Blue intrudes at A, Red may reconnect at D, forming [[edge template III2e]] and again leaving Blue with only a 2nd row escape:
		+	<hexboard size="4x6"
		+	coords="none"
		+	edges="bottom right"
		+	contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:d2 R 2:d3"
		+	/>
		+	If Blue intrudes at C, the situation is even worse for Blue: Red can reconnect at A, leaving Blue with nothing useful at all:
		+	<hexboard size="4x6"
		+	coords="none"
		+	edges="bottom right"
		+	contents="B a3 R c2 S area(c2,a4,d4,d2) B 1:c3 R 2:d2"
		+	/>
		+	Thus, Blue must carefully choose the best intrusion for the given situation.
		+
		+	== Bad intrusion ==
		+
		+	Some intrusions are actually counterproductive. One example of this is intruding on the wrong side of a [[bolstered template\|bolstered bridge]], or more generally, of a [[bolstered template]]. For example, consider this situation.
		+	<hexboard size="3x2"
		+	coords="none"
		+	edges="none"
		+	visible="area(b1,a1,a3,b2)"
		+	contents="R a1 b1 a3 E A:a2 B:b2"
		+	/>
		+	If Blue intrudes at A, Red's response at B actually [[dead cell\|kills]] Blue's stone. Therefore, such an intrusion does not help Blue at all, but helps Red instead. See the article on [[bolstered templates]] for more details.
		+
		+	== Invalid intrusion ==
		+
		+	When intruding into one of the opponent's templates or virtual connections, a player must be careful to take into account all of the possible ways in which the opponent is connected. For example, consider the following situation.
		+	<hexboard size="3x5"
		+	coords="none"
		+	edges="bottom"
		+	visible="area(c1,a3,e3,e1)"
		+	contents="R d1 E A:c3"
		+	/>
		+	If Blue tries to intrude at A, Blue does not even threaten to disconnect Red, because in addition to two different ziggurats, Red is also connected by [[edge template III1b]]:<hexboard size="3x5"
		+	coords="none"
		+	edges="bottom"
		+	visible="area(c1,a3,e3,e1)"
		+	contents="R d1 S area(c1,a3,e3,e1)-c3 E A:c3"
		+	/>
		+	An intrusion, by definition, must threaten to disconnect Red. Therefore, playing at A is not be a valid intrusion at all. Instead, it is likely a [[irrelevant move\|wasted move]].
		+
		+	One situation where an invalid intrusion can be beneficial is [[losing play#Feinting\|feinting]].
		+
		+	== Intrusion vs. blocking ==
		+
		+	An intrusion is not the same thing as [[blocking]]. By definition, an intrusion is into an area where the opponent is already [[virtual connection\|virtually connected]]; therefore, the opponent can always re-establish the connection. By contrast, the goal of a [[blocking\|blocking move]] is to disconnect the opponent. As mentioned above, intrusions are often best played on the outside of the connection, whereas blocking moves are best played near the inside. Thus, attempting a blocking move when the opponent already has a virtual connection is often catastrophic; conversely, attempting an intrusion when the opponent actually could have been blocked is also catastrophic. For this reason, it is very important to be able to [[reading\|read]] whether the opponent is already connected or not. The corresponding [[proverbs\|proverb]] is: "''Don't defend the indefensible.''"
		+
		+	== See also ==
		+
		+	* Some intrusions are [[peeps]].