Selinger: Fixed category

2021-09-09T01:53:01Z

Fixed category

Selinger: Created an article on blocking.

2021-09-07T21:05:37Z

Created an article on blocking.

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''Blocking'' means to prevent the opponent from connecting, and is one of the basic Hex skills.

== Common blocking moves ==

Suppose Blue wants to prevent Red from connecting her stone to the edge:
<hexboard size="6x8"
edges="bottom"
coords="none"
visible="area(f1,a6,h6,h1)"
contents="R g1"
/>
The following three basic blocking moves are relatively common:

=== The adjacent block ===

<hexboard size="6x8"
edges="bottom"
coords="none"
visible="area(f1,a6,h6,h1)"
contents="R g1 B g2"
/>

=== The near block ===

<hexboard size="6x8"
edges="bottom"
coords="none"
visible="area(f1,a6,h6,h1)"
contents="R g1 B f3"
/>

=== The far block ===

<hexboard size="6x8"
edges="bottom"
coords="none"
visible="area(f1,a6,h6,h1)"
contents="R g1 B f4"
/>

== How not to block ==

Not all blocking moves work in all circumstances. Adjacent blocks almost never work on their own, as the opponent can just walk around them. Consider what happens when Blue keeps playing adjacent blocks:
<hexboard size="6x8"
edges="bottom"
coords="none"
visible="area(f1,a6,h6,h1)"
contents="R g1 B 1:g2 R 2:f2 B 3:f3 R 4:e3 B 5:d4 R 6:e4 B 7:d5 R 8:e5 B 9:d6 R 10:e6"
/>

Similarly, if Blue keeps playing near blocks, Red can just [[bridge]] to one side, resulting in a [[bridge ladder]].
<hexboard size="6x11"
edges="bottom"
coords="none"
visible="area(f1,a6,k6,k1)"
contents="R g1 B 1:f3 R 2:h2 B 3:g4 R 4:i3 B 5:h5 R 6:j4 B 7:i6 R 8:k5"
/>

Far blocks are also fraught with danger, as it is often a good response for Red to hang back and threaten to go in both directions. Consider this situation:
<hexboard size="5x8"
edges="bottom"
coords="none"
visible="area(e1,a5,h5,h1)"
contents="R f1 B 1:e4 R 2:f2 E *:d3 *:g3 S area(a5,d5,d3,c3) area(e5,h5,h3,g3)"
/>
After Blue plays the far block, Red plays on the 4th row rather than the 3rd row, and can now connect to the edge via either of the cells marked "*" and a [[ziggurat]].

== Some common ways to block ==

Generally speaking, blocking is easier far from the edge than too close to it.

The best way to block very much depends on what is going on on the rest of the board. In many situations, it is a good idea to play a near block followed by an adjacent block, or an adjacent block followed by a near block.

=== Near block followed by adjacent block ===

<hexboard size="6x8"
edges="bottom"
coords="none"
visible="area(f1,a6,h6,h1)"
contents="R g1 B 1:f3 R 2:e2 B 3:d3 R 4:e3 B 5:d5 E *:h2"
/>
Blue plays a near block followed by an adjacent block, resulting in a [[bottleneck]]. Red does not immediately connect to the edge, but instead gets [[ladder]]s in both directions.

This maneuver is often effective, but it also creates a weakness, namely the unprotected hex at "*". Depending on the rest of the board, Red may exploit this, for example by playing a [[ladder escape fork]].

=== Adjacent block followed by near block ===

<hexboard size="6x8"
edges="bottom"
coords="none"
visible="area(f1,a6,h6,h1)"
contents="R g1 B 1:g2 R 2:f2 B 3:e4"
/>
Blue plays an adjacent block followed by a near block, resulting in what is sometimes called a one-sided bottleneck. Red can continue bridging to the left (if there is enough space), but only gets a 4th row ladder on the right.

== See also ==

* [[Bottleneck]]
* [[Ladder]]
* [[Bridge ladder]]

[[category:Basic strategy]]

← Older revision		Revision as of 01:53, 9 September 2021
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	* [[Bridge ladder]]		* [[Bridge ladder]]

−	[[category:Basic ~~strategy~~]]	+	[[category:Basic Strategy]]

Blocking - Revision history

Selinger: Fixed category

Selinger: Created an article on blocking.