Edge template V1b

Edge template V1b is a 5th row edge template with 1 stone.

The validity and minimality of this template has been checked by computer. The template was mentioned on 2016-05-19 by the user shalev in this Little Golem thread, but likely predates that post.

Defense against intrusions

Reduction

Red has 3 main threats. Using the ziggurat:

Using edge template III1b:

And using edge_template_IV1d:

For a blocking attempt, Blue must play in the overlap:

Intrusion at a

If Blue intrudes at a, Red can start by forcing a 3rd or 2nd row ladder like this

or like this:

Red's continuation will be discussed below.

Intrusion at b

If Blue intrudes at b, Red can start by forcing a 3rd row ladder like this:

Red's continuation will be discussed below.

Intrusion at c

If Blue intrudes at c, Red can start by forcing a 2nd row ladder like this:

Red's continuation will be discussed below.

Continuation after 3rd row ladder

If Red achieved a 3rd row ladder after intrusions a or b as shown above, Red continues as follows.

Now Red is connected by Tom's move for 3rd and 5th row parallel ladders.

Continuation:

Now Red threatens to play at "*":

so Blue must play in the shaded area.

the top 3 of those cells

Now Blue must play in one of the 3 shaded cells. ​ If Blue plays in the left 2 of those 3, then Red connects via IV-2-b. ​ Otherwise, Red connects via Tom's move.

... 5. e4

Yet to come ...

... 5. f4

Yet to come ...

... 5. g4

Yet to come ...

... 5. e5

Yet to come ...

... 5. f5

Yet to come ...

... 5. g5

Yet to come ...

... 5. d6

The group with 2 is connected to the top in two non-overlapping ways (see area marked with +) and to the bottom with IV-2-b.

... 5. e6

Red can respond here:

Continuation:

Now Red has two threats:

and

Blue must play in the overlap:

7. f2

7. g2

7. f3

6 is now connected to the left and to the bottom by Tom's move.

7. e4

4 is again connected to the left and to the bottom by Tom's move.

7. f4

Blue must go on one of the 3 marked fields. However, d6 can't be any better than 35, so it's enough to look at e5 and g6. Let's have a look at g6 first:

4 is now connected to the bottom and to the left in a similar way as in Tom's move. (Just the piece on g3 is connected to the left in a slightly different way.)

The other possible move was e5:

Red 2 is connected to the left by two non-overlapping ways and to the bottom by a 5th row template that has yet to be added to this wiki.

7. g4

Once again 6 is now connected to the bottom and to the left in a similar way as in Tom's move.

7. e5

And Tom's move at the end again.

7. f6

Red 2 is connected to the bottom and to at least one of the red pieces in the middle by Tom's move. Red now has three threats to connect both these pieces to the top:

and

Blue must play in the overlap:

First move:

Second move:

... 5. f6

Red can start like this:

Red now has these threats:

and

using IV-2-e.

Blue must play in the overlap:

First move:

You get the the defense against the other move by just swapping 1 and 2 in the diagram above.

... 5. g6

Note that 2 is safely connected to the top, so 3 is forced.

Continuation after 2nd row ladder

If Red achieved a 2nd row ladder after intrusions a or c above, Red continues as follows.

Now Red connects in essentially the same way as Tom's move.

Continuation:

Red has these threats:

The overlap in which Blue must play is:

Four of these five possible moves can be analysed in one line. In the following diagram assume Blue has played 1 on any of the fields marked with +:

After Red 2 that group is safely connected to them bottom, now matter which of the pluses Blue chose before.

That leaves only one Blue move to deal with:

Note that Red 4 connects to the bottom with IV-2-b.