Annelids

[Note: Some of the finer details in these instructions are out of date. I will get around to modifying them eventually after I’ve convinced myself that the new rules actually make the game more fun.]

Annelids is my second abstract board game, invented in 2011 and played with two people.

Board

Annelids is played on a board with truncated square tiling that has 12 octagons on each side.

12x12

Objective

The objective of Annelids is to leave your opponent with no legal moves.

No draws are possible in Annelids.

Play

At the beginning of the game, each player has 8 annelid tails, arranged as shown below. Note that the tails are directional (click on the image for a better view).

starting positoins

Players move alternatingly, starting with Blue. On Blue’s first move, he or she must place four segments on the cell edges adjacently extending from the flat ends of the blue tails. Segments extend from annelid tails like chains, and can only extend from the farthest segment. For example, the following move is legal:

legal chain

However, the following move is illegal because it requires placing a segment from the tail after it has already been extended:

illegal chain

There is no distinction between segments placed by Blue and by Green. As many or as few body pieces may extend any particular annelid tail, as long as all moves are used in a turn.

An example of a legal first move is shown below.

first move

A collection of annelid tail and segments that forms a continuous chain is called an annelid.

After Blue has placed four segments, it becomes Green’s turn. For every following turn (including Green’s first), a player must place as many segments as he or she has surviving annelids at the beginning of the turn. For Green’s first turn, this will always be eight.

Players may only extend their own annelids.

Removing annelids

A player may remove an annelid by attempting to extend it into part of any annelid. For example, consider the following arrangement, where the chain of segments on the right is extending from some annelid tail elsewhere on the board:

annelid death setup

If it is Blue’s turn, then he or she may extend the blue annelid toward the right by one:

annelid death setup 2

[Note that when a snapshot like this is taken out of context, it cannot be determined which segments belong to which annelid, but in practice it is almost always clear. Players may use segment pieces with distinguishing characteristics if they are concerned about becoming confused.]

If Blue wishes to extend the annelid farther, he or she may deflect the chain downward, as shown:

annelid death setup 3

However, Blue may also extend the annelid into the other annelid. This causes the entire Blue annelid to be removed from the board, leaving the following configuration:

annelid death setup 4

It is sometimes strategically desirable for players to remove their own annelids, but in many cases there is no alternative. Removing an annelid counts toward a player’s allotted moves for that turn just as if he or she placed a segment.

When a player removes his or her last annelid, that player loses.

Reconnection

If two annelids pass by each other through a square in opposite directions, their heads and tails can be swapped as long as doing so brings them to a more intermediate length. For example, consider the following configuration:

reconnection 1

At any point during either player’s turn, the segments in the small square can be moved so that the following configuration occurs:

reconnection 2

This is called a reconnection. After a reconnection, each player’s control of the chains has switched. In the example above, now Green can only add segments to the lower chain and Blue can only add segments to the top chain.

Note that since a reconnection must bring the annelid lengths closer together, it cannot be immediately reversed. The easiest way to determine whether a reconnection is allowed is to count the number of segments belonging to Blue and to Green both before and after the reconnection junction. In this example, prior to reconnection, Blue has five segments before the junction and two segments after it. Green has two segments before the junction and one after it. A reconnection is allowed if and only if the annelid with a larger number of segments before the junction also has a larger number of segments after the junction. For example, a reconnection is illegal in the following situation:

reconnection illegal

Further, reconnections cannot be made when the annelids pass through the junction in the same direction. In other words, players may not attach annelid tails through a reconnection.

Reconnections are also allowed between two annelids of the same color, but may only be made by the player controlling the annelids during his or her turn.

Commentary

As with Inversion, I have not been able to play test Annelids as much as I would like. However, I think it’s pretty likely to hold up as a good game. It bears some spiritual resemblance to Amazons, insofar as you need to block your opponent’s pieces from escaping confined regions of the board. I strongly encourage players to end games through resignation, as is conventional in Go, since there is typically a clear winner long before a player is strictly forced to remove his or her last annelid. This might seem like a strange practice to some people, but you really don’t want to play a game out turn-by-turn when both players have a single remaining annelid and there are 168 positions on the board! (The situation is even worse in Go.)

One thought on “Annelids

Leave a Reply

Your email address will not be published.

To write LaTeX output, type $latex [input]$ with [input] replaced by LaTeX input.