Rotation

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Revision as of 05:00, 10 July 2021 by Zircean (talk | contribs) (Making space)
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Rotation is a tactic that can be used to move chain links into a more favorable position, or convert straight chains into corner chains and vice versa. Rotations can be used to improve the compactness of chains, add extensions, fix bad board states, and so on. Effective use of rotations allows the player to make larger chains while keeping the board state from growing too complex.

Basic premise

Suppose we start from this board:

pyggy
y
py
bbrr
gp
ypr

The blue link at the head does not easily admit further extension—the leftmost blue petal is against the wall, and cannot be pushed to the right by another clear. As such, we want to find a way to move this link into a better position so that it can be extended further. However, moving that leftmost petal to the right will trigger the chain, and moving it up or down will put it in a bad position such that it becomes difficult to trigger the chain immediately.

If we can't move the leftmost petal, we must move the blue petal which is currently set up next to the next link in the chain first, then. We can move it left, but that simply clears both blue petals in a basic 1-chain, which is not helpful in this situation. So, we will have to move it up or down. First, let's try to move it up:

pyggy
by
py
brr
gp
ypr

The blue link is now broken, but we can fix it by pushing that leftmost blue to the right now:

pyggy
by
py
brr
gp
ypr

Now our chain is whole again. The blue-to-red link is now a corner chain rather than a straight chain, and both blue petals are away from walls, making it possible to push them via other clears. In this circumstance, the blue petal which is now at the top is adjacent to the green petals which form the tail of the chain. As this chain has a loop structure, we can continue to extend by lining up petals to the left of that green link. For example, using the purple petal in the top left as scaffolding lets us extend with yellows. First we move it down:

yggy
by
py
brr
gp
pypr

Then we can line up the yellow petal at the bottom so it is in the same file as the one at the top:

yggy
by
py
brr
gp
pypr

To connect this to the chain, we can push one of the green petals to the left:

yggy
by
py
brr
gp
pypr

Setting this off from the bottom yellow now results in a 5-chain. We were succesfully able to extend the chain. However, this was not the best option for rotating the blue link, as the chain cannot be extended any further—the yellow petal we use to trigger the chain is now along the bottom wall, and can only be pushed up by the cursor, rather than an adjacent clear. Let's rewind to the initial board state again.

pyggy
y
py
bbrr
gp
ypr

In this instance, we will push the blue petal down instead of up.

pyggy
y
py
brr
bgp
ypr

Now we can move the leftmost blue petal to the right and form a compact link at the head.

pyggy
y
py
brr
bgp
ypr

From here we can move the top yellow petal down if we want to set off the chain right away, which takes the equivalent chain to before in far fewer moves than the upward rotation:

pggy
y
py
brr
bgp
yypr

As the yellow petal we are using to trigger the chain is now away from a wall, we can even extend further using the purple in the top left corner and the one above the red link in the chain on the right. This rotation was not only simpler, but also led to a more versatile form.

Fixing bad shapes

Some shapes have the materials required in a pair, but they are not lined up properly. For example, there is a non-functional structure in the top-left corner of this board called a buried corner.

brrpp
ybp
ypgg
ry
r

We would like to connect the red link along the top to the purple link to its right. If we simply move one of the red petals to the right, then we are left with this:

brrpp
ybp
ypgg
ry
r

The green petal in the center can now be used to trigger a 3-chain, but it cannot be easily extended, as the blue petal which the red link would push to the left is buried behind other petals and not set up in a pair of its own. So, instead, we want to move the entire pair to link up all of these petals in a single chain that moves counterclockwise around the edge of the board.

If we simply try to move both red petals to the right, we trigger a 2-chain and lose what we have been building. So this is a dead end—instead, we must move one of the red petals out of the way so we can manipulate the other one without crashing anything. The red petal on the left is buried behind three other petals and the top edge of the board, so it cannot be moved. As such, we must move the petal on the right. We tried moving it to the right and that didn't really help us, and we can't move it up or left, so we have no choice but to try moving it down:

brpp
ybrp
ypgg
ry
r

From here we have a more familiar double diagonal shape with the red and blue petals in the top left corner. We perform a sequence of moves to convert it into a straight chain. First, we take out the red petal which was formerly buried in the corner by pushing it to the right.

brpp
ybrp
ypgg
ry
r

From this point we have a bow shape, and we can project it against the upper wall by moving up the remaining red and blue petals:

bbrrpp
yp
ypgg
ry
r

Now we have constructed a 6-chain which can be triggered with the green in the center. Even though we did not change the orientation of the red link here, it still changes the order of the red petals in the pair—the red petal which was buried in the top-left corner is now on the right, and is the trigger point for that red link. As such, we have rotated the link 180° rather than 90° as in the previous example.

Making space

Occasionally, a player will find themselves on a relatively full board with little mobility, and a compact link at the head of a chain may be next to a wall, preventing the player from triggering the chain with a double push:

pypgbg
ypxbrb
pyggr
ryxxb
pprryy
xxxbpg

In this instance, the yellow link at the head cannot be easily set off. A double push is not possible as the link is nestled between other petals and the wall of the board. Additionally, other yellows that could potentially be used to trigger the chain are all buried on the left half of the board. In this instance, we rotate the link upwards by moving the yellow petal on the left side of the link up, then the petal against the wall to the left to take its place:

pypgbg
ypxbrb
pyggyr
ryxxb
pprry
xxxbpg

Now we can take this chain by pushing the yellow petal at the top down.