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Piececlopedia: A Taxonomy

This is a start at categorizing various chess variant pieces. John William Brown, in his book Meta-Chess, does a fine job both naming and categorizing chess pieces by extending and expanding on the normative moves from existing and historical chess games. He also introduces the idea of a novelty piece, that is, any piece with movement capabilities (or other abilities) which fall outside the Meta-Chess graphic conventions. There are many such pieces (perhaps an infinite number), and it is possible to categorize them to some extent. Below I have attempted to create categories that describe the various capabilities of such chess variant pieces. I've tried to keeps descriptions as general as possible, and provide specific examples where available.

This document is by no means complete or comprehensive. I would encourage an effort to build on this, so that a more complete resource would be available to Chess Variant designers or problemists.

Size

The size of a piece measures how many squares (or positions) the pieces occupies on the board.

The span of a piece represents the number of squares (or positions) the piece occupies. Ortho-Chess pieces all have a span of 1x1, or simply 1 square. The Wall from Ganymede Chess, is a multi-positional piece which is rectangular and has a span of 1x2, that is, it occupies a 1 square high, by 2 squares wide area. Pieces with a span of more than 1x1 typically can capture more than one piece on a turn, but are also more easily attacked since a displacement on any of their occupied squares results in their capture.

Another piece, the ooze (my own invention), is a multi-positional, continuous piece that moves like a king. However, it may also 'ooze' instead of moving. An ooze move is simply growing the piece by one adjacent position. oozing to a square occupied by an enemy piece captures that piece. The ooze is an example of a multi-positional piece which is of variable size.

Complexity

The Complexity of a piece describes how many ways the piece can move, and possibly how those different moves are combined. There are two basic categories here:
Simple A piece which has only one (primitive) type of move. Examples of this type of piece are the Bishop, Rook and Knight of orthodox chess.
Compound A piece which has a movement capability that is a combination of 2 or more Simple pieces. This term was coined in Meta-Chess. Here, however, I intend to expand on this term. There are two flavors of Compound pieces:

Exclusive: An Exclusive Compound piece has the option, on any one move, of moving as one and only one of it's component piece moves (eg. a Cardinal may move either as a Bishop or as a Knight).

Pieces which have a different way of capturing than they have of moving without capturing, we might call Divergent (after Divergent Chess, where such pieces are used exclusively.

Inclusive: An Inclusive Compound piece has the option, on any one move, of moving as one or more of its component piece moves. Such pieces tend to be extremely powerful and should be used with care.

eg. a Super Cardinal may move either as a Bishop or as a Knight, or may move first as a Bishop followed by a Knight move (in the same direction), or may move first as a Knight followed by a Bishop move (in the same direction).

Variability

The variability of a piece describes how the capabilities of a piece vary (or don't vary) over the course of a game. Generally, pieces are assigned a movement capability which they keep throughout the entire game. However there are many pieces which have movement capabilities which change throughout a game.
Static A piece that does not change it's movement capabilities during the course of a game (eg. Rook, Bishop, Knight and Queen from orthodox chess).
Dynamic A piece that changes its movement capabilities during the course of a game.

Mimic: A detailed discussion of Mimics can be found here. An example of a Mimic would be the Joker or Orphan.

Alternator: An Alternator has two (or more) movement capabilities, alternating between them according to some pattern (eg. Flip chess pieces or Chameleon used in Fairy Chess problems).

Adaptor: An Adaptor changes its movement capabilities based on where it is on the board. For examples of Adaptors, see Big Outer Chess.

Promoter: A Promotor becomes another piece (typically more powerful in some way) after meeting some predefined condition (eg. Pawn).

Singular: A singular piece has one special move that may be taken once per game (eg. a pawn's double square move or King's Castling).

Movement

Movement/Capture properties. Some of the following terms are taken from D. B. Pritchard's Encyclopedia of Chess Variants.
Rider Moves from its current square to a destination square given a specified path (typically in a straight line), which must be clear of pieces. We might call Riders that move in a straight line, Straight Riders, and other riders that do not, Curve Riders. An example of a Curve Rider is the Rose, or the Windmill. Straight Rider examples are: Rook, Bishop and Nightrider.
Leaper Moves from its current square to a destination square given a specified path. Pieces along the path do not necessarily block it.

eg. Knight, Camel

Leapers may be further subdivided into the following:

Generic Leapers: may leap over both friendly and hostile pieces.
Friendly Leapers: may leap over friendly pieces only.
Enemy Leapers: may leap over hostile pieces only.

Hopper Moves from its current square to a destination square given a specified path (typically in a straight line). There must be a certain number of intervening pieces between the source and destination squares.

eg. Cannon, Grasshopper

Directional A Directional piece is restricted based on which direction it is attempting to move. Such restrictions may apply to how far it may move, what type of move it may make, or even whether it may capture or not.

eg. the orthodox chess pawn, or the Spearman from Centennial Chess. Also take a look at the various "Spear" pieces used in Pick-the-team Chess.

Kinetics

Kinetic pieces are able to effect other pieces in some way other than capturing. The number and types of Kinetic pieces are only limited by the imagination, so the following classifications are not even close to covering all the possiblities.

Kinetics may be latent or active. A latent Kinetic piece may effect other pieces without having to take any action, whereas an active Kinetic requires the some sort of move to be made with the piece.
Restrictor Restricts the movement of pieces that are in a certain relative position. The Immobilizer from Ultima is an example of a Restrictor.
Mobilizer Changes the positions of other pieces. The Mobilizer may be further subdivided into:

Attractor: Pulls other pieces towards itself. For an example of an Attractor, see the game Magnetic Chess. In this game, practically all the pieces are Attractors (and Repulsers too).

Repulser: Pushes other pieces away from itself. For an example of a Repulser, see the Ox piece in Dragons, Archers & Oxen.

Spinner: Rotates other pieces around itself. For an example of a Spinner, see the Spider piece in Ben 39.

Transposer: Swaps places with another piece. For an example of such a piece, see the Humming Bird of Typhoon.

Transporter This is a piece which enables other pieces to move in ways they normally could not move. Transporters typically are able to cohabitate a position with another piece.

Teleporters are Transporters which work in coordination with other Transporters to allow other pieces to move between the positions of two or more of the Transporters.

For an example of a Teleporter type piece, take a look at the Transporter piece in Dragons, Archers & Oxen. Also see Ben 39 and its Wizard piece. For an example of a Transporter that is not a Teleporter, see the Disk in Vyrémorn Chess. Another interesting piece is the Dervish from Scirocco.

Capturing

Displacer A Displacer captures a piece by occupying the square that the captured piece occupies. All orthodox chess pieces are Displacers.

Displacers can further be broken down into Singular and Multiple. Multiple Displacers are able to capture more than one piece in a single turn (eg. the Typhoon piece from Typhoon).

Implicator An Implicator captures in some other way than moving onto the square of an enemy piece. Pieces from the game Ultima tend to fall into this category.

Detonator: Captures by "exploding". This results in one of more pieces in certain relative positions being captured. Typically the piece itself is also captured. (eg. the Bomb from Bomberman Chess).

Ranger: Captures at a distance (eg. the Bowman, or the Archer in Jester Chess).

Coordinator: captures by forming (in concert with other pieces) a pattern relative to the piece to be captured. (eg. the Pincer pawn or Coordinator from Ultima).

Overtaker: captures by leaping over an enemy piece in some way (eg. the Long Leaper from Ultima).

Relator: captures by changing its position relative to an enemy piece in a certain way (eg. Withdrawer from Ultima).

Converter: is able to convert an enemy piece to a friendly piece (eg. the Cuckoo from Typhoon).

Written by David Howe. Thanks to Ivan A Derzhanski for pointing out an error.
WWW page created: June 7, 1999. Last modified on: 24 Aug 2000.