⇐ Fairy Chess Classification Project

Glossary of Fairy Chess Elements: Text Layout

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  • Fairy Classification
    • 1. Stipulations
      The stipulation of a problem is the statement printed below the diagram that tells a solver what needs to be done in order to solve the problem. Many fairy problems have orthodox stipulations, and many of the stipulations described are either regarded as orthodox or are disputed territory. This classification makes no attempt to distinguish between orthodox and fairy stipulations. Note that special ‘one-off’ stipulations may be used in individual problems, e.g. “Mate in 3 without moving the knight” or “Where was wPc2 captured?” or “Minimum number of wK moves?”. Retro problems frequently use stipulations of this type. A stipulation consists of two components, the Goal (the aim of a problem) and the Play (the way in which that aim is to be achieved); these two are listed below as separate groups. Where symbols for particular goals or play are given, these would generally be accepted by solving programs. Note that most stipulations require a goal to be reached in ‘n’ or fewer moves, unless the stipulation specifies ‘Exact’. In some cases, a stipulation may have another stipulation as a goal. For example, the HelpSelfmate has Selfmate in 1 as the goal and Help Play as the way.
      • 1.1. Goals
        There is some disagreement about whether some goals are actually conditions. An alternate definition considers a goal to be a condition if it results in the rules of the game being changed. If not then it is a valid goal. Typical examples of this anomaly are Series movers and Reflexmates. A series mover changes the rules of “alternating play by both sides”. A Reflexmate adds the Reflex condition. However, due to these two being considered as stipulations for a long time in published sources, literature, the WFCC codex, Solving software, the FIDE Albums and other competitions, it would be difficult to change their category. We also follow the existing practice in these and other similar cases, while acknowledging the alternate interpretation. The following goals involve forward play, but are also applicable to retractors.
        • 1.1.1. Forward play goals involving mate or stalemate
          i.e. where achieving the goal ends play.
          • Mate (#):
            As normally understood, i.e. the side to play is checked, and cannot move to relieve its King from check. Unless otherwise stated, a fairy problem requires a Fairy Mate, i.e. one where the fairy conditions remain in force up to the envisaged capture of the king. For instance, in an Ultra Maximummer a king is not in check if the threatened capture of the king is not the longest possible move, but in an ordinary Maximummer, checks are normal, meaning that the threatened king capture is not subject to the maximummer condition.
          • Completely Unavoidable Mate (###):
            A position where mate by one side is inevitable although the mate may not be reached for several moves.
          • Stalemate (=):
            As normally understood, i.e. the side to play is not checked but has no legal moves.
          • Auto-stalemate (!=):
            The side that has just played has no more legal moves. This is only a significant goal in a series- mover where only one side plays. However, it could be applied where there is play by both sides; the solving program Jacobi indicates when this goal is reached in normal play.
          • Double stalemate (==):
            The side to play cannot move, nor could the other side, were it to have the move.
          • Stalematemate:
            The side to play is mated, and the mating side would be stalemated were it to have the move and be prohibited from capturing the opposing king.
          • Doublemate (##):
            Both sides are simultaneously mated. This involves a move normally illegal by the last side to move, thus implying an undefined condition to the effect that a side may leave or place its own King in check when giving mate. Jorg Kuhlmann has defined three types of doublemate, as follows: Gegenmatt: A side that is in mate or stalemate makes a move (which may be a king move leaving the two Kings in contact) that leaves both Kings mated. Beidmatt: A side that is not in mate or stalemate makes a move (which may be a king move putting the two Kings into contact) that leaves both Kings mated. Doppelmatt: A side that is not in mate or stalemate makes a move that leaves both Kings mated. However, this final move must not be a king move putting the two Kings into contact, but must completely parry any existing check to the side’s own King and replace it with a new mating check.
          • Monomate, Supermate and Groupmate.:
            These operate when the Rex Multiplex condition (q.v.) is in force. See 3.1.1
          • Provisional mate and Final mate.:
            These operate when the ‘Play after mate’ conditions #R and #C (q.v.) are in force; See 3.1.3.(Besides theses two, there could also be ‘one-off’ goals requiring several mates by one or both sides; with #C there is also Perpetual mate.) Note: these last three goals could be put into a separate sub-group of ‘Conditional Goals’ that require particular fairy conditions to be in force.
        • 1.1.2. Other Forward Play Goals
          • Win and Draw:
            These are as normally understood, though a composition with one of these goals would be regarded as an endgame study rather than a problem. These goals would be determined by the nature of the pieces and conditions involved. Endgame studies can also have fairy elements.
          • Capture (x):
            The side playing last has made a capture..
          • Check (+) and Double Check (++):
            The side playing last has given check or double check.
          • Target Square (Zxy):
            The side playing last has made a move to a specified square.
          • CapZug (xzNN):
            A position is reached in which the side to play must have one or more legal captures, no legal non-capturing moves, and not be in check. The number of legal captures available may be specified. See JF problem 474 (2013) and others.
          • Echo:
            A position is reached that exactly echoes the diagram position in a specified way (but does not repeat it on the same squares).
          • Symmetry:
            A position is reached that shows symmetry of a specified type.
      • 1.2. Play
        Note that most of the elements listed under Play are given in the form of a complete stipulation ending in the goal Mate. All of these may be varied to make the goal Stalemate (or one of the other listed goals). In general, all types of play could be considered as consisting of White and Black playing either in opposition or cooperation.
        • 1.2.1. Opposition play
          White plays to achieve the goal, Black to oppose it. Included here are 4 types of Defensive Retractor, in which White and Black retract moves. White starts and aims to reach a position where in forward play some goal may be reached, usually #1 or S#1. Black tries to retract moves to thwart this aim. In a –n & #1, White must play the forward mating move immediately after retracting the nth move, or after an earlier retraction. All retractions of both sides must be to legal positions that could have been reached in a game played under whatever fairy conditions are in operation. The rules for uncaptures depend on the individual type.
          • Direct Mate (#n):
            White to play and mate in the given number (n) moves or fewer, whatever Black plays.
          • Selfmate (S#n):
            White to play and force Black to mate White in n moves or fewer.
          • Reciprocal (Grazer) Selfmate (Reci-S#n):
            White and Black play in opposition to reach a position where W can both #1 and S#1. See article about reciprocal stipulations in JF (https://juliasfairies.com/wp-content/uploads/Reciprocal-Stipulations.pdf).
          • Reflexmate (R#n):
            White to play and force Black to mate White in n moves or fewer, under the rule that either side must give mate on the move if possible. Could also be considered as a Selfmate with a condition “Reflex Chess”. See 3.1.1 (and also 1.1).
          • Semi-Reflexmate (Semi-R#n):
            White to play and force Black to mate White in n moves or fewer, under the rule that Black (but not White) must give mate on the move if possible.
          • Reciprocal SemiReflexmate (Reci-Semi-R#n):
            White and Black play in opposition to reach a position where White can both #1 and Semi-R#1.
          • Proca Retractor:
            (–n & #1, –n & S#1 (e.g.)): A Defensive Retractor (see above) in which the side retracting chooses what unit (if any) should be uncaptured on any retraction.
          • Hoeg Retractor:
            (–n & #1, –n & S#1 (e.g.)): A Defensive Retractor (see above) in which the opposite side to that retracting chooses what unit (if any) should be uncaptured on any retraction.
          • Klan Retractor:
            (–n & #1, –n & S#1 (e.g.)): A Defensive Retractor (see above) in which White always chooses what unit (if any) should be uncaptured on any retraction.
          • Pacific Retractor:
            (–n & #1, –n & S#1 (e.g.)): A Defensive Retractor (see above) in which no retractions may be uncaptures.
        • 1.2.2. Help Play
          White and Black cooperate in achieving the goal.
          • Helpmate (H#n):
            Black starts and helps White to deliver mate on White’s nth move. If n is a half-integer, White starts.
          • Helpselfmate (HS#n):
            White starts and Black helps to reach a position where White has a S#1, i.e. Black is forced to mate on Black’s nth move. If n is a half-integer, Black starts.
          • Reciprocal (Grazer) Helpmate (Reci-H#n):
            Black starts and helps White to a position where either Black can mate White on Black’s nth move, or play another move and allow White to mate on its nth move (as in a H#n). If n is a half-integer, White starts.
          • Reciprocal HelpSelfmate (Reci-HS#n):
            White and Black play in cooperation to reach a position where W can both #1 and S#1.
          • Help Retractor (H# -n & 1):
            White and Black retract moves (White starting), together aiming to reach a position where in forward play some goal may be reached, usually #1 or H#1. The forward play must follow the nth move retraction or an earlier retraction. All retractions of both sides must be to legal positions that could have been reached in a game played under whatever fairy conditions are in operation.
          • Help Free Play:
            A series of moves, of a length equal to the indicated number of moves, some played by White, some by Black, is made in order that after the last move, the aim is reached by White.
        • 1.2.3. Series Play
          This involves several consecutive moves played by the same side. There will generally be more to the play than just the series of consecutive moves, so that the first three members of the group are parts of elements rather than complete elements. Series play could also be considered as a condition, by stating that one side simply passes while the other side moves. See also under 1.1: Goals.
          • Series (Ser-):
            Several consecutive moves played by the same side (i.e. simple series play). During the series the side moving may not expose its King to check. The other side’s King may also not be checked, except possibly on the last move of the series before play transfers back to the that side.
          • Parry Series (pSer-):
            Several consecutive moves played by one side, except that the other side’s king may be checked and the series punctuated by that side moving out of check. This may happen as often as desired, but the length of the series does not include these check parrying moves.
          • Introductory Series Play:
            A series move stipulation is preceded by a move or series of moves by the other side. For instance, 2->Ser-H#3 means: White plays a series of 2 moves, following which Black plays a series of 3 moves, following which White mates.
          • Series Retractor:
            Several moves are retracted by one side to leave a legal position from which forward play leading to a set goal (e.g. H#) will result.
          • Series Mate (Ser-#n):
            White plays a series of n moves concluding in mate to Black.
          • Series Helpmate (Ser-H#n):
            Black plays a series of n moves after which White mates in 1 move.
          • Series Selfmate (Ser-S#n):
            White plays a series of n moves following which Black is compelled to mate White in 1 move.
          • Series Reflexmate (Ser-R#n):
            White plays a series of n moves following which Black is compelled to mate White in 1 move, under the rule that either side must give mate on the move if possible. (White must avoid being under that compulsion whilst playing the series, except possibly after the last move).
          • Series Helpselfmate (Ser-HS#n):
            Black plays a series of n-1 moves, after which White has a S#1, i.e. after White's single move Black is compelled to mate on move n of Black.
          • Double Series Helpmate (Double-Ser-H#n):
            Black plays a series of n moves, following which White plays a series of n moves culminating in mate. The same as n->Ser-#n.
        • 1.2.4. Retro Play
          This group includes stipulations involving the process of retroanalysis, together with concepts related to the legality of a position. In contrast to Retractors, the play in them actually leads forward play to a diagram position rather than backward from it.
          • Proof Game (PG n):
            The diagram position is to be reached from the normal game array in n double moves. If n contains a half-integer, White moved last, e.g. ‘PG 8.5’ means a game to the position after White’s 9th move. Could also be considered as a form of help play.
          • a=>b Proof Game (a=>b n):
            The diagram position marked ‘B’ is to be reached from the diagram position marked ‘A’ in n double moves. Could also be considered as a form of help play.
          • Shortest Proof Game (SPG):
            The diagram position is to be reached from the normal game array in the minimum number of half-moves. Could also be considered as a form of help play.
          • One-sided Proof Game :
            The diagram position is to be reached from the normal game array (or possibly from some other position) in n single moves played by one side only. This can also be considered as a form of series play.
          • Last Move(s):
            The last move(s) leading to the diagram position from the normal game array must be determined. This may be generalized by an instruction such as ‘Reach the position’ or ‘Release the position’, which involves starting retro play from a position which is clearly legal. Alternatively, a ‘one-off’ stipulation such as “Where was wPc2 captured?” or “Minimum number of wK moves made?” may be made. (The solutions to problems with these stipulations are often given as if the moves were retractions, but this is purely a convention used for convenience to avoid having to give a legal position to start forward play from.)
          • Illegal Cluster:
            An illegal position (one which cannot have arisen in play from the game array) which becomes legal if any one of the units present (except Kings) are removed. The stipulation to a problem could require the cluster to be produced by modifying the diagram position is a specified way.
          • Legal Cluster:
            A legal position which becomes illegal if any one of the units present is removed. The stipulation to a problem could require the cluster to be produced by modifying the diagram position is a specified way.
        • 1.2.5. Hidden Play
          Some aspects of the pieces present in a diagram position and/or the moves played from that position are not disclosed to the solver, and must be identified in order that the problem may be solved. Problems with hidden play are very varied, and may have very different goals involving either forward play (e.g. helpmates) or retro play (e.g. proof games or the construction of legal positions). They may thus be grouped under different headings (and in a further revision of this classification are likely to be treated quite differently). The undisclosed aspects of the pieces initially present (which may in some cases be neutral as well as black or white) are also very varied; the types listed are merely the main ones that have been named. With the partial exception of the special case Kriegspiel, the different types of ‘hidden piece’ differ only in the amount and nature of the information initially provided, and forward play problems using them may be tackled in the same general way, as follows: First, the hidden pieces are provisionally identified to give a legal position from which a solution of the problem would be possible. Next, the moves of this solution are chosen to try to ensure that they would only be playable if all the provisional identities were correct, these two steps being repeated until a full solution had been obtained. In recording each move of this solution, any piece definitely identified could be treated as a normal piece; otherwise, only the details actually determined (i.e. initial or final square, and whether the move is a capture or check) should be given, and the move should be followed by a statement of the identification(s) made as a result of the move being playable.
          • Kriegspiel:
            In a Kriegspiel game the rules for play are orthodox, but each player’s moves are hidden from the opponent, though monitored by a Referee who provides limited about each move played. In an opposition play Kriegspiel problem Black's moves are hidden, and the number and positions of some of Black's pieces in the diagram position may also be hidden. To solve the problem, White must provide responses to all Black’s possible defences without knowing directly which defence has actually been played. Thus to solve a #2 problem, White would play the proposed key-move followed by all mating moves that would be required for the solution (though not necessarily all possible moves that would give mate), ensuring that each such move attempted would either give mate or be declared illegal. The information provided by the hypothetical Referee of a problem is as follows: (i) if a move played by Black is a capture (in which case the capture square would be stated), (ii) if a move played by Black gives check (in which case it would be stated whether the check was on a rank, file, short diagonal, long diagonal, or by a knight), (iii) when asked by White, if Black’s last move allowed White to make a pawn capture (in which case White must attempt such a capture, i.e. move a pawn diagonally forward to a square not occupied by another White unit), (iv) if a move attempted by White was legally playable (in which case it must stand). Note that Kriegspiel problems always involve opposition play, since with Help or Series Play everything is orthodox. For more information see M McDowell: Book Review of Are there any? by G F Anderson, pp466-7, The Problemist July 2006; And the thread on the MatPlus forum: http://www.matplus.net/start.php?px=1570818322&app=forum&act=posts&fid=gen&tid=603
          • Unidentified Pieces (Rebus):
            Pieces whose locations are shown in the diagram position, their colours and types being indicated either by the use of different letters or symbols for pieces of each colour and type or by a general statement of the numbers of different coloured pieces of each type.
          • Variables:
            Pieces whose locations and colours are shown in the diagram position, but with no indication of the type of any piece. Invented by Tadashi Wakashima, 1992. See the article in http://quartz.chessproblems.ca/pdf/50/Quartz50.pdf
          • Undefined Pieces:
            Pieces whose locations are shown in the diagram position, but with no indication of the colour or type of any piece.
          • Invisibles:
            Pieces whose locations are not shown in the diagram position, and whose identities are indicated only by a general statement of the total numbers of Invisibles of each colour. Invented by Japanese composers, 2009. See JF problem 675 (2014) https://juliasfairies.com/problems/no-675/ and JF problem 1463 (2019) https://juliasfairies.com/problems/no-1463/. Also the article in http://quartz.chessproblems.ca/pdf/50/Quartz50.pdf
          • Total Invisibles:
            Pieces whose locations are not shown in the diagram position, and whose identities are indicated only by a general statement of their total number. Invented by Japanese composers, 2018. See the article in http://quartz.chessproblems.ca/pdf/50/Quartz50.pdf
          • Add Pieces:
            Pieces about which no information concerning their location, number, colour or identity is given in the statement of a problem (except perhaps that their minimum number is required). The ultimate type of ‘hidden piece’.
      • 1.3. Other retro and mathematical elements
        This is a Group, to be possibly developed later, that will include such things as Chessboard Dissections, Knight’s Tours, and Construction Tasks. (These are not strictly chess problems, in the sense that they do not need to be solved in order to uncover their content.)
        • 1.3.1. [ ]
          no elements for now
          • :
            [...]
    • 2. Fairy Pieces
      These include the orthodox pieces for completeness. Note that the 1- or 2-letter symbols for named pieces generally agree with those used by the solving program Popeye for English input (as listed in the file py-engl.txt). In the descriptions (m,n): indicates m ranks and n files, or vice versa. For instance, a Knight can be said to take steps of (1,2) indicating it can reach squares either 1 rank and 2 files away in any direction, or 1 file and 2 ranks. Similarly, a King can take steps of (0,1) (1 step away on the same rank or file) or (1,1) (one square diagonally in any direction, i.e. 1 rank and 1 file). Unless otherwise indicated, the pieces described here move and capture in the same way.
      • 2.1. Pawns
        • 2.1.1. Pawns
          A Fairy pawn (like an orthodox pawn) typically moves and captures by different single steps in one general direction (so that its moves cannot be reversed). From its game array square (normally on its 2nd rank), it may optionally move by a double step if not impeded, but is then subject to an immediate en passant (e.p.) capture by an opposite-colour pawn on the square passed. On reaching its final rank (which under some conditions may be by other means than a move of that pawn), a pawn immediately promotes by becoming any orthodox piece or any fairy piece present in the diagram position. (Various conditions allow the possibility of a pawn on its back rank; the rules applicable vary between conditions.) See also Chinese Pawn (2.5.1) and Prawn (or Marine Pawn) (2.5.4). WinChloe has an extensive and modifiable definition system for promotions with various fairy pieces and conditions.
          • Pawn P:
            Moves one square directly forward (or two squares from its 2nd rank), and captures one square diagonally forward. Orthodox unit.
          • Medieval Pawn:
            As Pawn, but without the double-step initial move. Promotes only to a Fers (1,1 leaper).
          • Berolina Pawn BP:
            As Pawn, but moves one square diagonally forwards (or two squares from its 2nd rank) and captures one square directly forwards. May capture e.p. immediately after a double step by another Berolina Pawn.
          • Complete Pawn:
            As Pawn, but moves and captures either directly forwards or diagonally forwards [i.e. combined Pawn+Berolina Pawn].
          • Reverse Pawn PP:
            As Pawn, but moves and captures in a backwards rather than a forwards direction.
          • Reversible Pawn:
            As Pawn, but (unlike other pawns) may move and capture in either a forwards or a backwards direction. Promotes on its 8th rank as normal, but may not move to its 1st rank and may not make a backward double-step from its 7th rank.
          • Superpawn SP:
            As Pawn, but moves any number of squares directly forwards and captures any number of squares diagonally forwards. Promotes on its 8th rank as normal. May not capture or be captured e.p.
          • Berolina Superpawn BS:
            As Pawn, but moves any number of squares diagonally forwards and captures any number of squares directly forwards. Promotes on its 8th rank as normal. May not capture or be captured e.p.
      • 2.2. Leapers
        Pieces which move and capture directly from one square to another, even when there are other units on the straight line between the starting and ending squares of the move. WinChloe has an option for user defined pieces in which a regular leaper can be restricted to only some of its possible squares. For example a Knight on d5 can be restricted to moving only to f6 by defining it as a “Bondisseur Simple” with m = 2 and n = 1. In this way, we could have a “Right Knight” which moves/captures only to its right by having the components m = 1, n = 2; m = 1, n = -2; m = 2, n = 1 and m = 2, n = -1.
        • 2.2.1. Simple Leapers
          The following (m,n)-leapers can move to (or capture on) any of the squares a single step of (m,n) away.
          • Zero:
            (0,0)-leaper; can only make null moves.
          • Wazir WE:
            (0,1)-leaper
          • Fers FE:
            (1,1)-leaper.
          • Dabbaba DA:
            (0,2)-leaper.
          • Knight S:
            (1,2)-leaper. Orthodox piece.
          • Alfil AL:
            (2,2)-leaper.
          • Camel CA:
            (1,3)-leaper.
          • Zebra Z:
            (2,3)-leaper.
          • Giraffe GI:
            (1,4)-leaper.
          • Antelope AN:
            (3,4)-leaper.
          • Ibis:
            (1,5)-leaper.
          • Corsair:
            (2,5)-leaper.
          • Flamingo:
            (1,6)-leaper.
        • 2.2.2. Compound Leapers
          These may make more than one type of leap. Many can be regarded as ‘combined pieces’ which can move or capture like any one of their constituent units; these are shown below as X+Y(+Z...), where X, Y etc. are the constituents. WinChloe has an option wherein the user can create up to 8 new compound pieces by combining one or more defined pieces, along with rules on promotions and captures. Definitions of such "user-defined pieces" are saved and these new pieces can be used in problems for solving. With this option, the number of compound pieces that can be defined is practically limitless.
          • King K:
            (0,1)+(1,1)-leaper [i.e. Wazir+Fers] with royal powers and additional move of castling. Orthodox piece.
          • Erlking EK:
            (0,1)+(1,1)-leaper [i.e. Wazir+Fers]; a non-royal K unable to castle.
          • Alibaba:
            (0,2)+(2,2)-leaper [i.e. Alfil+Dabbaba].
          • Squirrel SQ:
            (0,2)+(1,2)+(2,2)-leaper [i.e.Dabbaba+Knight+Alfil].
          • Gnu GN:
            (1,2)+(1,3)-leaper [i.e. Knight+Camel].
          • Okapi OK:
            (1,2)+(2,3)-leaper [i.e. Knight+Zebra].
          • Impala:
            (1,2)+(3,4)-leaper [i.e. Knight+Antelope].
          • Bison BI:
            (1,3)+(2,3)-leaper [i.e. Camel+Zebra].
          • Zebu ZE:
            (1,3)+(1,4)-leaper [i.e. Camel+Giraffe].
          • 5-Leaper BU (Root-25-leaper, Bucephale):
            (3,4)+(0,5)-leaper. The two leaps are of equal length.
          • Root-50-Leaper RF:
            (5,5)+(1,7)-leaper. The two leaps are of equal length.
          • Equileaper:
            Combination of all possible (m,n) leapers where m and n are both even. This piece can leap to any square that is a multiple of 2 squares distant both vertically and horizontally.
          • Leafhopper:
            Leaps in any direction on queen lines a distance equal to its distance from some other unit standing on one of these lines (but may not capture that other unit). [See JF problem 346 (2013)]
          • Greater Leafhopper GF:
            Leaps in any direction a distance equal to its distance from some other unit standing anywhere on the board (but may not capture that other unit).
      • 2.3. Riders
        Pieces which move or capture through a series of one or more squares to reach their destination. All intermediate squares (if any) must be vacant. Riders may thus take part in pins and in attacks by discovery; in most cases they will have a choice of moves to vacant squares in a particular direction. See also note about WinChloe under Leapers (2.2) which is also applicable here.
        • 2.3.1. Simple Riders
          The following (m,n)-riders make moves consisting of one or more  (m,n)-steps that are either linear or angled in the same direction.
          • Rook R:
            (0,1)-rider. Orthodox piece.
          • Wazirrider WR:
            (0,1)-rider. Moves as Rook (but cannot take part in castling) As a fairy piece, will have a different Circe rebirth square from a Rook.
          • Bishop B:
            (1,1)-rider. Orthodox piece.
          • Fersrider FR:
            (1,1)-rider. Moves as Bishop, but as a fairy piece, will have a different Circe rebirth square from a Bishop.
          • Nightrider N:
            (1,2)-rider, i.e. a piece whose moves consist of a number of knight steps in the same direction. The archetypal fairy rider; should logically have been named ‘Knightrider’!
          • Rose RO:
            A (1,2)-rider moving on octagonal paths made up of knight steps changing direction by approximately 45°, e.g. d1-f2-g4-f6-d7-b6... From some squares it may make a complete circuit amounting to a null move, e.g. d1-d1. (Included in this sub-group partly because several hopper families include pieces based on it.)
          • Camelrider CR:
            (1,3)-rider.
          • Zebrarider ZR:
            (2,3)-rider.
        • 2.3.2. Compound Riders
          This sub-group includes combinations of Riders with Leapers or Pawns as well as with other Riders. Note that pawn combinations do not promote, nor move from the back rank as pawns. They may make a double step from squares where a pawn may do so; but are not subject to e.p. capture (though they may capture Pawns e.p.). See also note about WinChloe under Compound Leapers (2.2.2) which is also applicable here.
          • Queen Q:
            Combined Rook+Bishop. Orthodox piece.
          • Empress EM:
            Combined Rook+Knight.
          • Princess PR:
            Combined Bishop+Knight.
          • Amazon AM:
            Combined Queen+Knight [or Rook+Bishop+Knight].
          • Ship SH:
            Combined Rook+Pawn.
          • Gryphon (Griffin):
            Combined Bishop+Pawn.
          • Dragon DR:
            Combined Knight+Pawn.
          • Waran WA:
            (0,1)+(1,2)-rider [i.e. combined Rook+Nightrider].
          • Elephant ET:
            (0,1)+(1,1)+(1,2)-rider [i.e. combined Queen+Nightrider].
          • Gnurider GR:
            (1,2)+(1,3)-rider [i.e. combined Nightrider+Camelrider].
          • Alibaba Rider:
            (0,2)+(2,2)-rider [i.e. rider derived from combined Alfil+Dabbaba].
        • 2.3.3. Limited Riders
          A miscellaneous sub-group of pieces for which the rider moves are limited in some way.
          • Rankrider:
            Rook confined to a single rank.
          • Filerider:
            Rook confined to a single file.
          • Mao MA:
            Has a fixed 2-step move consisting of a (0,1) step followed by a (1.1) step to reach a square a knight’s move away (e.g. a1-b1-c2); the intermediate square must be vacant. Also classified as a Chinese piece (see 2.5.3).
          • Moa MO:
            Has a fixed 2-step move consisting of a (1,1) step followed by a (0.1) step to reach a square a knight’s move away (e.g. a1-b2-c2); the intermediate square must be vacant.
          • Maorider AO:
            Moves in a series of alternating pairs of (0,1) and (1,1) steps to reach a square a number of knight’s moves away (e.g. a1-b1-c2-d2-e3 or a1-b1-c2-d2-e3-f3-g4); all intermediate squares must be vacant.
          • Moarider OA:
            Moves in a series of alternating pairs of (1,1) and (0,1) steps to reach a square a number of knight’s moves away (e.g. a1-b2-c2-d3-e3 or a1-b2-c2-d3-e3-f4-g4); all intermediate squares must be vacant.
          • Jaguar:
            Moves as a Queen, but only towards another unit of either colour standing on the same line, thus capturing only if there is another unit of either colour behind the unit to be captured.
          • Edgehog EH:
            Moves as a Queen, but all moves must start or end (but not both) on an edge square.
        • 2.3.4. Zigzag Riders
          These pieces make complex moves consisting of steps in different directions. The angles given are those of the changes of direction along the path of the move.
          • Girlscout GT:
            Moves on a zigzag path in a series of  (0,1) steps angled at 90°, e.g. a3-a4-b4-b5-c5..., thus making progress along two parallel bishop lines.
          • Boyscout BT:
            Moves on a zigzag path in a series of (1,1) steps angled at 90°, e.g. a3-b4-c3-d4-e3..., thus making progress along two parallel rook lines.
          • Serpent:
            Moves on a zigzag path in a series of alternating (1,1) and (0,1) steps angled at 45°, e.g. a1-b2- c2-d3-e3-f4…, thus making progress along two parallel knight’s move lines,
          • (1,1)-Zigzag Nightrider S1:
            Moves on a zigzag path in a series of (1,2) knight steps angled at 37°, e.g. b1-a3-c2-b4-d3..., thus making progress along two parallel bishop lines.
          • (0,2)-Zigzag Nightrider S2:
            Moves on a zigzag path in a series of (1,2) knight steps angled at 53°, e.g. b1-d2-b3-d4-b5..., thus making progress in (0,2) steps along two parallel rook lines.
          • (3,3)-Zigzag Nightrider S3:
            Moves on a zigzag path in a series of (1,2) knight steps angled at 143°, e.g. b1-c3-e4-f6- h7…, thus making progress in (3,3) steps along two parallel bishop lines.
          • (0,4)-Zigzag Nightrider S4:
            Moves on a zigzag path in a series of (1,2) knight steps angled at 127°, e.g. b1-c3-b5-c7..., thus making progress in (0,4) steps along two parallel rook lines.
          • Quintessence QN:
            Moves on a zigzag path in a series of (1,2) knight steps angled at 90°, e.g. b1-a3-c4-b6-d7…, thus making progress along two parallel (1,3)-lines.
          • SpiralSpringer SS:
            Combined (0,2)+(0,4) Zigzag Nightrider; moves on zigzag paths in a series of (1,2) knight steps angled at 53° or 127°, e.g. b1-c3-d1-e3-f1... or b1-c3-b5-c7...
          • Diagonal SpiralSpringer DS:
            Combined (1,1)+(3,3) Zigzag Nightrider; moves on zigzag paths in a series of (1,2) knight steps angled at 37° or 143°, e.g. b1-a3-c2-b4-d3... or b1-c3-e4-f6-h7…
        • 2.3.5. Bouncing Riders
          These are riders whose moves can be extended by interacting with the edge of the board.
          • Archbishop AR:
            A Bishop which can extend its move by a single bounce off a board-edge rank or file, in the process staying on the same colour squares, e.g. c6-d7-e8-f7-g6....
          • Reflecting Bishop RB:
            A Bishop which can extend its move by bouncing any number of times off a board-edge rank or file, in the process always staying on the same colour squares, e.g. c6-d7-e8-f7-g6-h5- h3…. In this way it may make a complete circuit, resulting in a null move.
          • Cardinal C:
            A Bishop which can extend its move by a single bounce off the actual board-edge, in this way changing the colour of its squares, e.g. c6-d7-e8-f8-g7....
      • 2.4. Hoppers
        A hopper is a piece which moves or captures by ‘hopping’ over another unit (or possibly more than one unit) of either colour, called a hurdle, which is unaffected by the move. For a leaperhopper, the path followed is that of two steps (one up to the hurdle and one beyond it) of a named leaper. For a riderhopper, the path followed is that of the complete move of a named rider.
        • 2.4.1. Leaperhoppers and Short Riderhoppers
          These are closely related pieces which move or capture by ‘hopping’ over a unit of either colour (called a hurdle, and which is unaffected by the move), making a single step beyond the hurdle. All other squares between the start and end squares must be vacant.
          • Grasshopper G:
            Moves on queen lines any distance to reach a hurdle and then a single step beyond it. The archetypal fairy hopper, which should logically have been named ‘Queenhopper’, could be described as a combined (0,1)+(1,1)-riderhopper.
          • Rookhopper RH:
            Moves on rook lines any distance to reach a hurdle and then a single step beyond it. Could be described as a (0,1)-riderhopper.
          • Bishophopper BH:
            Moves on bishop lines any distance to reach a hurdle and then a single step beyond it. Could be described as a (1,1)-riderhopper.
          • Nightriderhopper NH:
            Moves on straight lines consisting of a number of (1,2) knight steps [i.e. nightrider lines], making any number of steps to reach a hurdle and a single step beyond it. Could be described as a (1,2)-riderhopper.
          • Camelriderhopper CH:
            Moves on straight lines consisting of a number of (1,3) steps [i.e. camelrider lines], making any number of steps to reach a hurdle and a single step beyond it. Could be described as a (1,3)-riderhopper.
          • Rosehopper RP:
            Moves on octagonal paths consisting of a series of (1,2) knight steps changing direction by approximately 45°, e.g. d1-f2-g4-f6-d7-b6... [i.e. rose lines], making any number of steps to reach a hurdle and then a single step beyond it. The final step may complete a circuit.
          • Kinghopper KH:
            Makes a single (0,1) or (1,1) king step to reach a hurdle and a further king step beyond it in the same direction. Could be described as a combined (0,1)+(1,1)-leaperhopper.
          • Knighthopper KP:
            Makes a single (1,2) knight step to reach a hurdle and a further knight step beyond it in the same direction. Could be described as a (1,2)-leaperhopper.
          • Pawnhopper:
            When not capturing, moves by making a single forward (0,1) step (or two steps if starting on its 2nd rank) to reach a hurdle and another single forward (0,1) step beyond it. When capturing, makes a single diagonally forward (1,1) step to reach a hurdle and another forward (1,1) step to capture on this square. May promote only to other types of hopper – but details are unclear. Needs clarifying.
        • 2.4.2. Long Riderhoppers (Lion family)
          Pieces which move on rider paths that must hop over a unit of either colour (called a hurdle, and which is unaffected by the move), moving any distance to reach the hurdle and then any further distance beyond it. All other squares between the start and end squares must be vacant. The Lion (moving on queen lines) is the archetypal member of the sub-group, and all other members have names based on it.
          • Lion LI:
            Moves on queen lines any distance to reach a hurdle and then any further distance beyond it.
          • Rook Lion RL:
            Moves on rook lines any distance to reach a hurdle and then any further distance beyond it [i.e. as a Lion restricted to rook lines].
          • Bishop Lion BL:
            Moves on bishop lines any distance to reach a hurdle and then any further distance beyond it [i.e. as a Lion restricted to bishop lines].
          • Nightrider Lion NL:
            Moves on straight lines consisting of (1,2 knight steps, making any number of steps to reach a hurdle and any number of steps beyond it [i.e. as a Lion moving on Nightrider lines].
          • Rose Lion RN:
            Moves on octagonal paths consisting of (1,2 knight steps changing direction by approximately 45°, e.g. d1-f2-g4-f6-d7-b6..., making any number of steps to reach a hurdle and any number of steps beyond it [i.e. as a Lion moving on Rose lines]. The latter part of the move may complete a circuit and result in some squares being visited more than once.
        • 2.4.3. Other non-angled Hoppers
          A miscellaneous group of pieces, all moving in a way determined by the presence of a unit of either colour called a hurdle, which is unaffected by the move. Some have moves that are not based on those of leapers or riders; some do not actually hop over the hurdle. Unless otherwise indicated, all other squares between the start and end squares must be vacant.
          • Contra-Grasshopper CG:
            Moves on queen lines by a single step to reach a hurdle and then any distance beyond it [i.e. as a Grasshopper with the relative lengths of the parts of its move reversed.]
          • Contra-Bishophopper:
            Moves on bishop lines by a single step to reach a hurdle and then any distance beyond it [i.e. as a Bishophopper with the relative lengths of the parts of its move reversed.]
          • Contra-Rookhopper:
            Moves on rook lines by a single step to reach a hurdle and then any distance beyond it [i.e. as a Rookhopper with the relative lengths of the parts of its move reversed.]
          • Grasshopper-2 G2:
            Moves on queen lines any distance to reach a hurdle and then 2 steps beyond it [i.e. as a Grasshopper making 2 steps after the hurdle instead of 1].
          • Grasshopper-3 G3:
            Moves on queen lines any distance to reach a hurdle and then 3 steps beyond it [i.e. as a Grasshopper making 3 steps after the hurdle instead of 1].
          • Chopper (Andernach Grasshopper):
            Moves on queen lines any distance to reach a hurdle and then a single step beyond it [i.e. as a Grasshopper], but changing the colour of its hurdle (except a King) in the process.
          • Orix OR (Oryx):
            Moves on queen lines any distance to reach a hurdle and then an equal distance beyond it, to finish on the square diametrically opposite its starting point.
          • Nonstop Equihopper NE (French Equihopper):
            Moves (not necessarily on a rider line) any distance and in any direction to reach a hurdle and then an equal distance beyond it, to finish on the square diametrically opposite its starting point. It cannot be blocked by a unit on any intermediate square.
          • Equihopper EQ (English Equihopper):
            Moves (not necessarily on a rider line) any distance and in any direction to reach a hurdle and then an equal distance beyond it, to finish on the square diametrically opposite its starting point. However, its move will be blocked by a unit on an intermediate square.
          • French Equistopper QF:
            Moves (not necessarily on a rider line) towards a hurdle any even number of steps away in any direction, to finish halfway between the hurdle and its starting point, irrespective of any other units directly between it and the hurdle.
          • English Equistopper QE:
            Moves (not necessarily on a rider line) towards a hurdle any even number of steps away in any direction, to finish halfway between the hurdle and its starting point. It may capture on the halfway square, but will be blocked by a unit on any other square directly between it and the hurdle.
          • Hamster HA:
            Moves on queen lines any distance to reach a hurdle and then a single step in the reverse direction, to finish one step short of the hurdle. It can never capture under normal circumstances, but if starting on a square next to a hurdle may return to its original square to make a null move.
        • 2.4.4. Short Angled Hoppers
          A closely related group of pieces which move on rider paths but must hop over a unit of either colour (called a hurdle, and which is unaffected by the move), making any number of rider steps to reach the hurdle and then changing direction to make a single rider step beyond the hurdle. All other squares between the start and end squares must be vacant. The pieces moving on queen lines form the basis for the names of the other pieces.
          • Moose M:
            Moves on queen lines any distance to reach a hurdle and then a single step beyond it, changing direction by 45°. Invented by George Jelliss, who described it as a ‘Bifurcating Grasshopper’.
          • Rook Moose RM:
            Moves on rook lines any distance to reach a hurdle and then a single step beyond it, changing direction by 45° [i.e. as a Moose restricted to rook lines on the approach].
          • Bishop Moose BM:
            Moves on bishop lines any distance to reach a hurdle and then a single step beyond it, changing direction by 45° [i.e. as a Moose restricted to bishop lines on the approach].
          • Eagle EA:
            Moves on queen lines any distance to reach a hurdle and then a single step beyond it, changing direction by 90°.
          • Rook Eagle RE:
            Moves on rook lines any distance to reach a hurdle and then a single step beyond it, changing direction by 90° [i.e. as an Eagle restricted to rook lines on the approach].
          • Bishop Eagle BE:
            Moves on bishop lines any distance to reach a hurdle and then a single step beyond it, changing direction by 90° [i.e. as an Eagle restricted to bishop lines on the approach].
          • Sparrow SW:
            Moves on queen lines any distance to reach a hurdle and then a single step beyond it, changing direction by 135°.
          • Rook Sparrow RW:
            Moves on rook lines any distance to reach a hurdle and then a single step beyond it, changing direction by 135° [i.e. as a Sparrow restricted to rook lines on the approach].
          • Bishop Sparrow BW:
            Moves on bishop lines any distance to reach a hurdle and then a single step beyond it, changing direction by 135° [i.e. as a Sparrow restricted to bishop lines on the approach].
          • Scarabeus:
            Moves on queen lines any distance to reach a hurdle and then a single (1,2) knight step beyond it, changing direction by approximately 27°. [See JF problem 1173 (2016) by Sebastian Luce]
          • Marguerite MG:
            Moves on queen lines any distance to reach a hurdle and then a single step beyond it in any direction (including a complete reversal) [i.e. as a combined Grasshopper+Moose+Eagle+Sparrow+Hamster].
        • 2.4.5. Long Angled Hoppers
          A miscellaneous group of pieces, all moving in a way determined by the presence of a unit (which may be of either colour unless otherwise stated) called a ‘hurdle’ which is unaffected by the move, and changing direction on passing that hurdle. Unless otherwise stated, their path cannot be blocked by any other unit on it.
          • Moose Lion:
            Moves on queen lines any distance to reach a hurdle and then any distance beyond it, changing direction by 45° [i.e. moves as a Lion but changes direction like a Moose]. All other squares on its path must be vacant.
          • E90:
            Moves (not necessarily on a rider line) any distance and in any direction to reach a hurdle and then an equal distance beyond it, changing direction by 90°.
          • Radial Leaper RK:
            Moves (not necessarily on a rider line) any distance and in any direction to reach a hurdle (which must be a unit of the opposite colour) and then an equal distance beyond it in any direction.
          • Treehopper TH:
            Moves on queen lines any distance and in any direction to reach a hurdle and then an equal distance beyond it in any direction (but may not return to its starting square). [See JF problem 346 (2013)]
          • Greater Treehopper GE:
            Moves (not necessarily on a rider line) any distance and in any direction to reach a hurdle and then an equal distance beyond it in any direction (but may not return to its starting square).
        • 2.4.6. Multi-hoppers
          A miscellaneous group of pieces whose moves involve somehow making more than one ‘hop’ over one or more units of either colour (called hurdles), which are unaffected by the move. All other squares between any start and end squares must be vacant.
          • Kangaroo KA:
            Moves any distance on queen lines over a hurdle consisting of two units any distance apart on the same line, to finish on the first square beyond the second unit.
          • Bob BO:
            Moves any distance on queen lines over a hurdle consisting of four units any distance apart on the same line, to finish on the first square beyond the fourth unit.
          • Dolphin DO:
            Moves any distance on queen lines over a hurdle consisting either of a single unit or of two units any distance apart on the same line, to finish on the first square beyond the last unit. [i.e. a combined Grasshopper+Kangaroo].
          • Kangaroo Lion KL (Rabbit RT):
            Moves any distance on queen lines over a hurdle consisting of two units any distance apart on the same line, to finish on a square any distance beyond the second unit. [i.e. as Lion, but hurdles over any two units like a Kangaroo].
          • Double Grasshopper DG:
            Must make two consecutive moves as part of a single turn of play, in each one moving any distance on queen lines over a hurdle to finish on the first square beyond it, [i.e. making two consecutive Grasshopper moves]. The first such Grasshopper move must be to a vacant square; the second may be a capture, and may involve change of direction, including switchback.
          • Double Rookhopper DK:
            Must make two consecutive moves as part of a single turn of play, in each one moving any distance on rook lines over a hurdle to finish on the first square beyond it, [i.e. making two consecutive Rookhopper moves]. The first such Rookhopper move must be to a vacant square; the second may be a capture, and may involve change of direction, including switchback.
          • Double Bishophopper DB:
            Must make two consecutive moves as part of a single turn of play, in each one moving any distance on bishop lines over a hurdle to finish on the first square beyond it, [i.e. making two consecutive Bishophopper moves]. The first such Bishophopper move must be to a vacant square; the second may be a capture, and may involve change of direction, including switchback.
          • Grasshopper Bul:
            Moves any distance on queen lines over a hurdle to finish on the first square beyond it [i.e. makes a Grasshopper move], but as part of the same turn of play the unit that has acted as a hurdle must then make a similar Grasshopper move itself over some other hurdle. Invented by Petko Petkov; programmed in WinChloe 3.50 as a Sauterelle Bul. One of the Bul Pieces described in 2.7.2.
      • 2.5. Hybrid Pieces
        These are pieces that have similar powers of movement to leapers, riders and hoppers, but can either exercise these powers only in particular circumstances or else exercise different powers of movement in different circumstances.
        • 2.5.1. Hunter
          These pieces move and capture in one way when moving forwards and in another way when moving backwards (with purely sideways movement not allowed).
          • Bishop-Rook Hunter BR:
            Moves and captures like a Bishop when moving forwards and like a Rook when moving backwards, and may not move directly sideways.
          • Rook-Bishop Hunter RR:
            Moves and captures like a Rook when moving forwards and like a Bishop when moving backwards, and may not move directly sideways.
        • 2.5.2. Capturing Pieces
          These are essentially orthodox pieces (invented by J de A Almay, FCR 4/5/p.83) which move only to make normal captures.
          • Atlantosaurus:
            Royal piece; King which can move only to capture.
          • Dinosaurus:
            Queen which can move only to capture.
          • Mammoth:
            Rook which can move only to capture.
          • Brontosaurus:
            Bishop which can move only to capture.
          • Hippopotamus:
            Knight which can move only to capture.
        • 2.5.3. Chinese and associated Pieces
          These typically move as simple riders but capture as long riderhoppers (members of the Lion family), hopping over a unit of either colour (called a hurdle, and which is unaffected by the move) and moving any distance to reach the hurdle and then any further distance beyond it. All other squares between the start and end squares must be vacant. The term ‘Chinese pieces’ as normally used, refers to the Pao, Vao, Leo – and also Mao (Chinese Knight).
          • Pao PA (Chinese Rook):
            (0,1)-Chinese rider or ‘Chinese Rook’; moves and captures on rook lines, but when capturing moves any distance to reach a hurdle and then any further distance beyond it.
          • Vao VA (Chinese Bishop):
            (1,1)-Chinese rider or ‘Chinese Bishop’; moves and captures on bishop lines, but when capturing moves any distance to reach a hurdle and then any further distance beyond it.
          • Leo LE (Chinese Queen):
            The ‘Chinese Queen’, equivalent to combined Pao+Vao; moves and captures on queen lines, but when capturing moves any distance to reach a hurdle and then any further distance beyond it.
          • Nao NA (Chinese Nightrider):
            (1,2)-Chinese rider or ‘Chinese Nightrider’; moves on straight lines made up of (1,2) knight steps [i.e. nightrider lines], but when capturing moves any distance to reach a hurdle and then any further distance beyond it.
          • Rao RA (Chinese Rose):
            Chinese rider on Rose lines; moves on octagonal paths consisting of a series of knight steps changing direction by approximately 45°, e.g. d1-f2-g4-f6-d7-b6... [i.e. rose lines], but when capturing moves any distance to reach a hurdle and then any further distance beyond it.
          • Chinese Pawn CP:
            In its own half of the board, moves and captures one square straight forwards. In the further half of the board, moves and captures one square directly forwards or sideways. Does not promote.
        • 2.5.4. Argentinian Pieces
          These typically make capturing moves as simple riders, and non-capturing moves as long riderhoppers (members of the Lion family), hopping over a unit of either colour (called a hurdle, and which is unaffected by the move) and moving any distance to reach the hurdle and then any further distance beyond it. All other squares between the start and end squares must be vacant. (Contrast Chinese Pieces; the name was chosen because Argentina is directly opposite to China on the globe!). The Argentinian condition uses only Argentinian pieces.
          • Faro FA (Argentinian Rook):
            (0,1)-Argentinian rider or ‘Argentinian Rook’; moves and captures on rook lines, but when not capturing moves any distance to reach a hurdle and then any further distance beyond it.
          • Loco LO (Argentinian Bishop):
            (1,1)-Argentinian rider or ‘Argentinian Bishop’; moves and captures on bishop lines, but when not capturing moves any distance to reach a hurdle and then any further distance beyond it.
          • Senora SE (Argentinian Queen):
            ‘Argentinian Queen’, equivalent to Faro+Loco; moves and captures on queen lines, but when not capturing moves any distance to reach a hurdle and then any further distance beyond it.
          • Saltador SA (Argentinian Knight):
            The ‘Argentinian Knight’, and a very different type of piece, effectively making a (1,2)-step knight move by passing through either the (0,1) square or the (1,1) square. It can move without capturing to the same squares as a knight whenever either of the intermediate squares is occupied, and can capture on the same squares as a knight whenever either of the intermediate squares is empty.
        • 2.5.5. Hop-capturing Pieces (Locust family)
          Pieces derived from hoppers, which cannot make non-capturing moves, and which capture not by landing on the captured unit but by moving across it to land on the vacant square one step beyond. All other squares between the start and end squares must be vacant.
          • Rook Locust LR:
            (0,1)-locust; moves on rook lines to a vacant square, but only to pass over and capture a unit of opposite colour standing at any point on the line.
          • Bishop Locust LB:
            (1,1)-locust; moves on bishop lines to a vacant square, but only to pass over and capture a unit of opposite colour standing at any point on the line.
          • Locust L:
            ‘Queen Locust’ or combined Rook Locust+Bishop Locust; moves on queen lines to a vacant square, but only to pass over and capture a unit of opposite colour standing at any point on the line.
          • Nightrider Locust LN:
            (1,2)-locust; moves on straight lines made up of (1,2) knight steps [i.e. nightrider lines] only to capture, doing this by landing on the vacant square one step beyond the captured unit.
          • Rose Locust LS:
            Moves on octagonal paths consisting of a series of knight steps changing direction by approximately 45°, e.g. d1-f2-g4-f6-d7-b6... [i.e. rose lines] only to capture, doing this by landing on the vacant square one step beyond the captured unit.
          • Mantis:
            Combined Locust+Knight; either moves or captures normally as a knight, or else moves on queen lines to a vacant square, but only to pass over and capture a unit of opposite colour standing at any point on the line.
        • 2.5.6. Marine Pieces
          Pieces which typically make normal non-capturing moves, but which capture not by landing on the captured unit but by moving across it to land on the vacant square one step beyond [i.e. like a locust]. All other squares between the start and end squares must be vacant.
          • Triton TR (Marine Rook):
            (0,1)-marine rider; moves on rook lines, either by a normal non-capturing move or by a capture in which it lands on the vacant square one step beyond the captured unit.
          • Nereid ND (Marine Bishop, Nymph):
            (1,1)-marine rider; moves on bishop lines, either by a normal non-capturing move or by a capture in which it lands on the vacant square one step beyond the captured unit.
          • Siren SI (Marine Queen):
            Combined Triton+Nereid’; moves on queen lines, either by a normal non-capturing move or by a capture in which it lands on the vacant square one step beyond the captured unit.
          • Poseidon PO (Marine King):
            Makes non-capturing moves as a King, and captures an adjacent opposite-colour unit by moving across it to a vacant square immediately beyond.
          • Squid MS (Marine Knight):
            Makes non-capturing moves as a Knight, and captures an opposite-colour unit a (1,2) step away by moving across it to a vacant square a further (1,2) step away.
          • Prawn MP (Marine Pawn):
            Makes non-capturing moves like a Pawn, and captures diagonally forwards, landing on a vacant square one square beyond the captured unit in the same direction. Promotes to any of the Marine Pieces above that correspond to orthodox pieces.
          • Scylla SK (Skylla, Marine Mao):
            A rather different piece. It moves to a vacant square a knight’s move away by making a (0,1) step and then a (1,1), step, capturing an opposite-colour unit on the (0,1) square but being blocked by a same-colour unit on that square. [See JF problem 346 (2013)]
          • Charybdis CY (Marine Moa):
            Another rather different piece. It moves to a vacant square a knight’s move away by making a (1,1) step and then a (0,1), step, capturing an opposite-colour unit on the (1,1) square but being blocked by a same-colour unit on that square.
      • 2.6. Other pieces
        Pieces that do not fall into any of the previous categories.
        • 2.6.1. Miscellaneous Pieces
          A varied set of pieces, including some that only operate on boards other than the normal one or which could be classed as something other than pieces.
          • Orphan O:
            Takes the powers of any opposite-colour unit which observes it, including any opposite colour orphan which is similarly empowered. An orphan observed by a Pawn moves like a Pawn of its own side. Cannot promote, capture or be captured e.p., or take part in castling.
          • Friend F:
            Takes the powers of any same-colour unit which observes it, including any same-colour Friend which is similarly empowered. Cannot promote, capture or be captured e.p., or take part in castling.
          • Joker:
            Takes the power(s) of the unit(s) moved in the preceding opposite-colour move.
          • Querquisite QQ (Odysseus):
            Takes the power of the piece whose home-square is on the file that it currently occupies. See WinChloe database problem (No. 41815) by J E H Creed, FCR 1947.
          • Dummy DU:
            Does not move, capture, nor check.
          • Dummy King:
            A King which cannot move or capture (i.e. a royal Dummy).
          • Imitator:
            Non-capturing and uncapturable piece without colour, which does not move by itself but makes a parallel move along with each moving unit. The Imitator’s path must be free for moves and checks to be legal. Castling is carried out with the K moving before the Rook for the purposes of the Imitator move. When multiple Imitators are present, they all move simultaneously in parallel with the moving unit. (Sometimes considered as a fairy condition rather than a piece.). In Popeye, it has to be entered as a condition, with a list of squares added if more than one is present. The condition noip (No Promotion to Imitator allowed) may also be added.
          • Prism 90°:
            May move to any empty square but cannot capture. It can be captured normally, but will also allow a line-piece (rider, hopper, etc.) of either colour moving towards it to continue its move beyond it on a line deflected by 90° in either direction.
          • Prism 45°:
            May move to any empty square but cannot capture. It can be captured normally, but will also allow a line-piece (rider, hopper, etc.) of either colour moving towards it to continue its move beyond it on a line deflected by 45° in either direction.
          • Prism 135°:
            May move to any empty square but cannot capture. It can be captured normally, but will also allow a line-piece (rider, hopper, etc.) of either colour moving towards it to continue its move beyond it on a line deflected by 135° in either direction.
          • Pyramid:
            Has no colour and does not move; cannot be captured or passed over by a moving unit and so is effectively a hole in the board. Listed under Conditions as ‘Holes’.
          • Soucie:
            A leaper on Queen lines, whose move length is determined by the number of all units (including the Soucie itself) on that particular file, rank or diagonal. In the position WKf1, WSOa1; BKh1,BPc3, the W Soucie on a1 can move to a2, d1 or capture on c3.
          • Unicorn:
            (1,1,1)-rider; a piece only operating on boards of 3 or more dimensions. Higher analogue of a Bishop. See Boards section 4.3.
          • Balloon:
            (1,1,1,1)-rider; a piece only operating on boards of 4 or more dimensions. Higher analogue of a Bishop. See Boards section 4.3.
      • 2.7. Piece Attributes
        These may affect any property of a pawn or piece in addition to its power of movement. Generally, the property is preserved through the play, and when a piece transforms or a pawn promotes, the property is retained. These piece attributes can be applied to most of the pieces listed above. In some cases, the attribute can be applied to all pieces on the board to produce a Fairy Condition.
        • 2.7.1. Simple Attributes
          These modify the powers of their own or other units in a permanent way. Unless otherwise indicated, they may apply to any type of piece, including a King.
          • Royal unit:
            Subject to check, in the same manner as the King in normal chess. (Typically, there will be only one royal piece on each side, so if a side has one, it will not have a King). As is the case for kings, if a royal unit is checked, the check must be annulled immediately, and if this is not possible, the side to which the royal unit belongs is mated. A royal pawn promote to a royal piece.
          • Neutral unit:
            May be regarded as belonging to either side at any turn, and may be moved or captured by either side. A neutral pawn moves only in the direction of the side playing it, but promotes to a neutral piece. A Neutral King would be the only King on the board; it may be checked or mated by either side, but may not be placed in check by an opposite-colour unit or by another neutral unit.
          • Kamikaze unit:
            When capturing, is removed from the board along with the captured unit. Also a Condition.
          • X-Ray unit:
            Any unit able to move more than one step in the same direction, that moves normally but may also move through other units.
          • Transparent unit:
            Moves normally, but allows other units to move through it.
          • Uncapturable unit:
            A unit which cannot be captured.
          • Non-capturing unit:
            Unable to capture.
          • Siamese Units:
            This is made up of two or more identical units of the same type and colour placed on different squares that behave as a single piece. When one moves, the other(s) moves the same distance in the same direction (both moves having to be legal according to the conditions in force). When one is captured, the other(s) disappears also; if they are Pawns and one promotes, the other(s) promotes identically (even though it(they) may not have reached its(their) last rank).
        • 2.7.2. Change-producing Attributes
          These modify the powers of their own or other units in a way that changes during the play. Unless otherwise indicated, they may apply to any type of piece, including a King.
          • Half-neutral unit:
            This exists in one of three phases: white, black or neutral. In the white phase, White may play it, after which it enters the neutral phase. In the black phase, Black may play it, after which it enters the neutral phase. In the neutral phase, either side may play it, after which it enters the phase of that side. It may be captured when in the opposite phase to the side making the capture, or by either side when in the neutral phase.
          • Volage unit:
            Any unit except a King, that changes colour the first time it moves from light to dark squares or vice versa.
          • Functionary unit:
            A unit which may only move, capture or check when observed by any opposite-colour unit.
          • Magic unit:
            This does not itself change, but may change the colour of other units. At the end of each move, any unit (except a King) newly attacked or observed by a magic unit (or by an odd number of magic units) changes colour. If the unit is newly attacked by an even number of magic units there will be no colour change.
          • Magic Wandering unit (MWU):
            Changes colour on moving or capturing. If captured by anything except a king, the capturing piece changes colour and becomes a MWU in turn. There can only be one MWU unit on the board. [There are various other rules, including two types for AntiCirce, described in JF problem 1223 (2019)].
          • Anda unit:
            Changes colour on giving a direct check. If black or white it becomes neutral; if neutral, it takes the colour of the moving side.
          • Chameleon unit:
            This may be any unit except a King. After each of its moves, a chameleon piece transforms into another piece in the sequence Knight > Bishop > Rook > Queen > Knight>… A chameleon pawn does not transform, but promotes to a chameleon piece in any phase. In the presence of chameleon units, normal pawns may promote to either normal or chameleon pieces. Also a condition; see under 3.3.2.
          • Chameleon Hopper:
            This must be one of four short rider-hoppers described in 2.4.1. After each of its moves, it transforms into another piece in the sequence Nightriderhopper > Bishophopper > Rookhopper > Grasshopper > Nightriderhopper>…
          • Protean unit:
            Optionally assumes the powers of any unit it captures. A Protean pawn moves in the direction of a pawn which it captures, and promotes when reaching the last rank in that direction.
          • Paralysing unit:
            Moves normally, but does not capture; instead, it paralyses any opposite-colour units it observes, which can then neither move, capture or check. A paralysed paralysing unit will still paralyse other units. A paralysing pawn promotes to a paralysing piece. When paralysing pieces are present, the rules for mate are altered so that it is only mate if the side being checked, though lacking a legal move annulling the check, has at least one possible move of any unit (i.e. not all are paralysed or blocked).
          • Hurdle colour-changing unit (Andernach hopper):
            A hopper of any type (see 2.4) which, when moving, changes the colour of whichever unit (except a King) that it uses as a hurdle. (A Grasshopper with this attribute is named a Chopper.)
          • Bul Piece:
            A hopper of any type (see 2.4) whose move involves two separate steps, the first of which may not be made unless a second step is possible. The first step takes the Bul piece over any unit of either colour acting as a ‘hurdle’; the second step (chosen by the side making the move) consists of the hurdle itself making a non-capturing step of the same type over a second hurdle. If the first hurdle is itself a Bul piece, there is no third step. If the first hurdle is a Pawn which ends up on its 1st rank, it may subsequently make a normal single-step pawn move or capture.
    • 3. Fairy Conditions
      These form the largest and most complex category of elements, and also the area in which new elements are most frequently introduced. No classification system is therefore likely to be permanent! In this new system, Conditions are grouped in the order of six recurrent concepts: Check and Mate, Rebirth, Transformation and Promotion, Transfer of Powers, Observation and Move Length, plus ‘Other Concepts’ as a sixth. Rebirth is divided (as before) into three sub-groups based on the rebirth square, plus a fourth with Rebirth plus Transformation. Some of the other larger groups are subdivided according to the three ‘aspects’ of Nature, Restrictions and Effects and/or into their applicability to either Captures (or distinctions between captures and non-captures) or All Moves. Note that most conditions apply to both colours, but some of these can also be used in ‘White only’ or ‘Black only’ forms. This possibility is not always noted, but where the single colour forms are the most common ones, both are listed separately. Note also that conditions may be applied singly or in combinations, though some combinations may be incompatible and/or give unexpected results when tested with solving programs. Conditions may also be applied consecutively or for only part of a solution, the program WinChloe being able to handle some of the simpler conditions put in force up to or from a particular half-move in a problem’s solution. This is with regard to the alternative definition of conditions mentioned under the Goals sub- group (1.1). Using new boards (instead of plane 8x8), new pieces (instead of KQRBSP), cooperation (instead of opposition) and new goals (instead of checkmate) could also be considered as "changes in the rules". Therefore, usage of new boards, pieces, goals and help play could also be interpreted as using new conditions. A helpmate would have to be called as #n with the condition "cooperation chess". We will not go down this rabbit hole!
      • 3.1. Check and Mate
        This wide-ranging group covers changes to the most fundamental aspects of Chess.
        • 3.1.1. Nature
          This sub-group covers the nature of checks and/or mates, and includes alternatives to mate in conditions without mates.
          • Losing:
            Each side must capture if able. Kings may be captured, but are not subject to check or mate. Pawns may promote to Kings. The equivalent to giving mate at Losing Chess is either losing all one’s pieces or being stalemated.
          • Extinction:
            Kings are not royal, but a threat to capture the last surviving member of any one of the other side’s different types of units counts as a check, and mate is achieved if such a threat cannot be prevented. Pawns may promote to Kings, and a check may be answered by promoting a Pawn to another unit of the type threatened.
          • Reflex:
            Each side plays to be mated and to avoid giving mate, but if a mate on the move exists at any stage it must be given. Invented by B G Laws in 1885. See ‘Reflexmate’ in 1.2.1. This is of use only with Selfmates. The current practice is to consider Reflexmates as a stipulation.
          • Republican:
            There are no Kings on the board, but if the side which has just played can put the other King on an empty square where it would be legally mated, this counts as mate. There is also a Type 2 form (the default in Popeye), in which such a mate can be immediately reversed by the apparently mated side putting the other King on a square on which it is mated.
          • Rex Multiplex:
            Several kings of the same colour may be present on the board at any one time. Three different types of mate are possible, so that this condition has its own special goals. The mates are: Monomate, where one King only is mated; Supermate, where all Kings are mated simultaneously; Groupmate, where no King is necessarily mated, but a multiple check would leave at least one King liable to capture on the next move. With Monomate or Supermate as the goal, a move producing one of the other mates would not be allowed. [These mates were named by George Jelliss.]
          • Royal Dynasty:
            Pawns of either side may promote to Kings. Multiple Kings of one side lose their royal power, but this is regained when a king-capture leaves the side with one King only.
          • MAFF (Mate with A Free Field):
            In the mating position, the mated King must have exactly one square to which it is free to move. A normal mating move, in which the King does not have any free flights, is not allowed. This condition is considered as a goal in WinChloe, though it is shown as a condition in most sources.
          • Royal Squares:
            These are designated squares in a diagram position that have royal properties for one side or the other. A Royal Square may be crossed or occupied by units of its own side, but a threat to occupy it by a capturing move of an opposite-colour unit counts as a check, this being mate if the threat cannot be parried. A side may not have more than one Royal Square, and may not also have a King or other royal piece.
          • SAT (Salai’s Mat):
            Kings are not subject to normal checks, but a side is in check if its King has a flight, and is mated if that flight cannot be prevented. The name derives from the inventor Ladislav Salai sr.
          • Anti-Kings:
            A side is in check if its King is not attacked, and mated if it has no move that exposes the King to attack. In the normal game-array position both Kings are simultaneously in check.
          • Vogtländer:
            Kings are not subject to normal checks, but a side is in check if one of its own units attacks the opposite-colour King (which may not be captured), and is mated if that attack cannot be removed.
          • Bicolores:
            A King is in check if it is observed by a unit of either colour, i.e. Kings are liable to check by units of their own side as well as by units of the opposing side. In the normal game-array position both Kings are simultaneously in check.
          • Brunner Chess:
            Checks are normal, except that a King is not in check if its capture would leave the opposite-colour King liable to capture.
          • Half-check:
            Checks are normal, but only become effective after the next move has been played (assuming that neither checking unit nor King has moved). Invented by Kostas Prentos for JF problem 218 (2013).
        • 3.1.2. Restrictions
          This sub-group covers cases where the possibility of checking and/or mating moves is restricted.
          • AMU (Attacked Mating Unit):
            A mating move must be given by a unit which, prior to the mating move, is attacked by exactly one opposite-colour unit.
          • OWU (One White Mating Unit):
            A position where Black is mated must have exactly one white unit in the black king’s field.
          • Exclusive:
            A mating move may only be played if it is the only mating move available.
          • Checkless:
            Neither side may give check unless the check is also mate.
          • Black Checks:
            Black checks if able but otherwise passes, allowing White to make two moves in succession.
          • Black Must Check:
            Black checks if able but otherwise makes another move.
          • Black Ultraschachzwang:
            Black must check if able but otherwise is stalemated.
          • White Ultraschachzwang:
            White must check if able but otherwise is stalemated.
        • 3.1.3. Effects
          This sub-group covers conditions where mate does not necessarily end play, or where possible responses to a check are changed in some way.
          • #Removal (#R):
            A game does not end with mate; instead, the mating piece (defined as the piece or pieces giving check in the mating position) is removed, and (unless illegal self-check results, in which case the mate is a ‘final’ one) play continues with the mated side moving next. Games may thus contain an indefinite number of mates in successions, and mating stipulations may require specified combinations of mates by White or both colours. The condition (together with two related conditions, #C and Kk) is supported by Jacobi, which uses ‘$’ instead of ‘#’ for all mates except final ones.
          • #Colour (#C):
            A game does not end with mate; instead, the colour of the mating piece (defined as the piece or pieces giving check in the mating position) is changed, and (unless illegal self-check results, in which case the mate is a ‘final’ one) play continues with the mated side moving next. See also #Removal (#R).
          • Vaulting Kings:
            When checked, a King may move either normally or like an English Equihopper (see 2.4.3) – or some other designated unit. In Popeye: vaul: whitevau: blackvau, followed if required by the symbol of the designated unit, and by the option trans to indicate that the King may not move normally, but only as the Equihopper or other designated unit.
          • Transmuting Kings:
            When checked, a King may move only like the unit or units giving check. A King checked by a Pawn moves in the direction of the Pawn of its own colour.
          • Reflecting King:
            When checked, a King may move either normally or like the unit or units giving check. A King on its 2nd rank checked by a Pawn may make a double-step pawn move forward.
          • Supertransmuting King (Pressburger King):
            When checked, a King must play as the unit or units giving check if possible, thereafter the King becomes an ordinary (non-royal) unit of this type permanently, and play continues without that side having a royal piece. If it is not possible to move as the checking unit, another piece may parry the check and the King does not change. If that is not possible, the King is mated.
          • Swapping Kings:
            After a checking move, the two Kings are interchanged; the checking move may not be played if self-check results.
          • Masand:
            When a unit gives a direct check, all units (except Kings) observed or attacked by it change colour.
          • Masand generalised:
            When a unit gives a direct or indirect check, all units (except Kings) observed or attacked by it change colour.
          • Anda:
            A non-neutral piece (except a King) that gives a direct check becomes neutral. A neutral piece (except a King) that gives a direct check takes the colour of the side that moved it.
          • Anda Inverse:
            A non-neutral unit (except a King) that makes a non-checking move becomes neutral. A neutral unit (except a King) that makes a non-checking move takes the colour of the side that moved it.
      • 3.2. Rebirth after Capture Effects
        In these Conditions, a capture may not result in the captured unit being simply removed from the board; instead, one of the two units involved will be ‘reborn’ by being placed on a clearly defined Rebirth Square. The two main types are Circe, in which the captured unit is reborn, and AntiCirce, in which the capturing unit is reborn. Kings are not normally subject to rebirth The division of this group into three sub-groups is arbitrary, determined mainly by the need to prevent any sub-groups from being inconveniently large.
        • 3.2.1. Rebirth on home square
          This sub-group contains conditions in which either a captured or a capturing unit is reborn either on its own home square, i.e. the square it occupies in the normal game array, or on the home square of some other piece. To resolve any choice of rebirth squares, a Rook, Bishop or Knight is reborn on the home square of the same colour as the capture square, a Pawn is reborn on the same file as the capture square, and a fairy piece is reborn on the promotion square of that file. A Rook or King reborn on its home square may subsequently castle before making another move. In a Circe condition where the captured unit is reborn, Kings are not subject to rebirth unless otherwise indicated. A capture may be made (and would be a normal capture) if the rebirth square is occupied or if the capture takes place on that square. In an AntiCirce condition where the capturing unit is reborn, Kings are included in the rebirth condition; this means that a King may make a capture if the capture square is attacked by an opposite-colour unit but not if the rebirth square is so attacked. A capture may not be made if the rebirth square is occupied, but a capture on the rebirth square may be made (and would be a normal capture) unless otherwise indicated.
          • Circe:
            The standard and archetypal form of Circe; a captured unit is reborn on its own home square.
          • Alsatian Circe:
            A captured unit is reborn on its own home square, as above, but only if the resulting position is one which would be legal in orthodox chess.
          • Circe Rex Inclusive:
            A captured unit is reborn on its own home square, as above, but the rebirth condition also applies to kings; this rebirth never actually happens, but its possibility means that a check is only effective if the rebirth square is occupied, so preventing rebirth.
          • Strict Circe:
            A captured unit is reborn on its own home square, but the capture may only be made if the rebirth square is empty so that rebirth can take place.
          • Volcanic Circe:
            A captured unit is reborn on its own home square, but if the rebirth square is occupied, the rebirth is delayed and only happens if and when the square is vacated.
          • AntiCirce Calvet:
            The archetypal form of AntiCirce; a capturing unit is reborn on its own home square.
          • AntiCirce Cheylan:
            A capturing unit is reborn on its own home square, but a capture on the rebirth square may not be made.
          • Circe Assassin:
            A captured unit is reborn on its own home square, replacing any other unit that may already occupy that square.
          • Diametral Circe:
            A captured unit is reborn on the square symmetrically related to its home square with respect to the centre of the board, e.g. c1>f8.
          • AntiCirce Assassin:
            A capturing unit is reborn on its home square, replacing any other unit that may already occupy that square.
          • Cuckoo Circe:
            A captured unit is reborn on the home square of the capturing unit. A pawn captured by a piece will be reborn on its 8th rank and will therefore promote immediately; with opposition play problems, the choice of promotion is made by the captured pawn’s side.  This condition is supported by WinChloe, but not by Popeye. Some problems exist where the composer has assumed that the capturing side decides the promotion and consequently the problems are unsound in WinChloe. These could possibly be made sound by changing the condition to Circe Couscous.
          • Couscous Circe:
            A captured unit is reborn on the home square of the capturing piece. A pawn captured by a piece will be reborn on its 8th rank and will therefore promote immediately; with opposition play problems, the choice of promotion is made by the capturing unit’s side. (With help-play problems, this condition is identical to Cuckoo Circe above.)
          • Couscous AntiCirce:
            A capturing unit is reborn on the home square of the captured unit. A capture on the rebirth square may not be made.
          • Circe Clone:
            A captured unit is reborn on the home square of a unit of its own colour and of the type that has made the capture.
          • AntiCirce Clone:
            A capturing unit is reborn on the home square of a unit of its own colour and of the type that has been captured.
          • Mirror Circe (Circe Malefique):
            A captured unit is reborn on the home square of an opposite- colour unit of its own type.
          • Mirror AntiCirce:
            A capturing unit is reborn on the home square of an opposite- colour unit of its own type.
        • 3.2.2. Rebirth determined by capture square
          This sub-group contains conditions in which either a captured or a capturing unit is reborn on a square that depends in some variously defined way on the capture square. A Rook or King reborn on its home square may subsequently castle before making another move. In a Circe condition where the captured unit is reborn, Kings are not subject to rebirth unless otherwise indicated. A capture may be made (and would be a normal capture) if the rebirth square is occupied or if the capture takes place on that square; In an AntiCirce condition where the capturing unit is reborn, Kings are included in the rebirth condition; this means that a King may make a capture if the capture square is attacked by an opposite-colour unit but not if the rebirth square is so attacked. A capture may not be made if the rebirth square is occupied, but a capture on the rebirth square may be made (and would be a normal capture) unless otherwise indicated.
          • File Circe:
            A captured unit is reborn on the file of capture, a Pawn on its 2nd rank, any other orthodox unit on its 1st rank, and any fairy piece on its 8th rank.
          • File AntiCirce:
            A capturing unit is reborn on the file of capture, a Pawn on its 2nd rank, any other orthodox unit on its 1st rank, and any fairy piece on its 8th rank.
          • Antipodean Circe (Circe Antipodes):
            A captured unit is reborn on the square 4 ranks and 4 files away from the capture square. (If the board were a torus, this would be the furthest away or ‘antipodean’ square.)
          • Antipodean AntiCirce:
            A capturing unit is reborn on the square 4 ranks and 4 files away from the capture square.
          • Symmetry Circe:
            A captured unit is reborn on a square symmetrically related to the capture square with respect to the centre of the board, e.g. a3>h6.
          • Symmetry AntiCirce:
            A capturing unit is reborn on a square symmetrically related to the capture square with respect to the centre of the board, e.g. a3>h6.
          • Horizontal Symmetry Circe:
            A captured unit is reborn on a square symmetrically related to the capture square with respect to a horizontal mirror across the centre of the board, e.g a3>a6.
          • Horizontal Symmetry AntiCirce:
            A capturing unit is reborn on a square symmetrically related to the capture square with respect to a horizontal mirror across the centre of the board, e.g a3>a6.
          • Vertical Symmetry Circe:
            A captured unit is reborn on a square symmetrically related to the capture square with respect to a vertical mirror across the centre of the board, e.g a3>h3.
          • Memory Circe:
            The captured unit disappears on capture, but is reborn on the capture square itself when the next capture by either side takes place. If by then the capture square is still occupied, the original capture is permanent. [From JF, apparently invented by Diyan Kostantinov for JF problem 184 (2012).
          • Frischauf Circe:
            The captured unit is only reborn if it can be proved by retro analysis to have been a promoted piece. In this case it is reborn on the promotion rank of the file of capture.
        • 3.2.3. Rebirth on other squares
          This sub-group contains conditions in which either a captured or a capturing unit is reborn on a square that varies considerably according to the individual condition. In a Circe condition where the captured unit is reborn, Kings are not subject to rebirth unless otherwise indicated. A capture may be made (and would be a normal capture) if the rebirth square is occupied or if the capture takes place on that square; In an AntiCirce condition where the capturing unit is reborn, Kings are included in the rebirth condition; this means that a King may make a capture if the capture square is attacked by an opposite-colour unit but not if the rebirth square is so attacked. A capture may not be made if the rebirth square is occupied, but a capture on the rebirth square may be made (and would be a normal capture) unless otherwise indicated.
          • Platzwechsel Circe (PWC):
            A captured unit is reborn on the departure square of the unit making the capture – so that the two units simply change places. A Pawn reborn on its 1st rank will subsequently be unable to move.
          • Diagram Circe:
            A captured unit is reborn on the square occupied by it in the diagram position of a problem.
          • Diagram Anticirce:
            A capturing unit is reborn on the square occupied by it in the diagram position of a problem.
          • Equipollents Circe:
            A captured unit is reborn on the square that continues the capture move an equal distance in the same direction. If that square is occupied or does not lie on the board, the captured unit disappears as normal.
          • Equipollents AntiCirce:
            A capturing unit is reborn on the square that continues the capture move an equal distance in the same direction. If that square is occupied or does not lie on the board, the capture may not be made.
          • Parrain Circe (Circe LastMove Equipollents):
            A captured unit is reborn, not immediately but on completion of the following move made by the other side. The rebirth square lies at the same distance from the capture square as the length of the above-mentioned following move and in the same direction as that move.  If the rebirth square is occupied or does not lie on the board, the captured unit is not reborn and the capture is permanent. A Pawn reborn on its 1st rank will subsequently be able to move 1 square directly forward or capture 1 square diagonally forward.
          • ContraParrain Circe (Circe LastMove Equipollents Mirror):
            A captured unit is reborn, not immediately but on completion of the following move made by the other side. The rebirth square lies at the same distance from the capture square as the length of the above-mentioned following move and in the diametrically opposite direction to that move. If the rebirth square is occupied or does not lie on the board, the captured unit is not reborn and the capture is permanent.
          • Cage Circe:
            A captured unit is reborn on any vacant square on the board (at the choice of the capturing side) from which it would have no non-capturing legal moves (including responses to a check on the capture move), and thus would be reborn in a ‘cage’. A Pawn reborn on its first rank has a single-step move.
          • Super Circe:
            A captured unit is reborn on any vacant square on the board (at the choice of the capturing side in opposition play).
          • Super AntiCirce:
            A capturing unit is reborn on any vacant square on the board (at the choice of the capturing side in opposition play).
        • 3.2.4. Rebirth combined with Transformation
          This small and assorted sub-group contains conditions in which a captured unit (not a king) changes its colour while being reborn on some clearly defined square, which may be the home square of some unit. To resolve any choice of home square rebirth, a Rook, Bishop or Knight is reborn on the home square of the same colour as the capture square, a Pawn is reborn on the same file as the capture square, and a fairy piece is reborn on the promotion square of that file.
          • Circe Turncoats:
            A captured unit is reborn on its home square, but with its colour reversed. See N Shankar Ram, 187 Die Schwalbe 1989.
          • Circe Double Agents (Circe Turncoat Mirror):
            The colour of a captured unit is reversed, and the unit is then reborn on the home square appropriate to its new colour. See N Shankar Ram, 187 Die Schwalbe 1989.
          • Conversion Captures:
            The colour of a captured unit is reversed, and this unit moves according its own power to the departure square of the capture move and is reborn on that square; if it cannot make such a move, the capture is a normal one. Invented by A.J.Karwatkar, 1975.
      • 3.3. Transformation and Promotion.
        This group covers a varied set of conditions where units change their colour and/or nature, either permanently or temporarily, during the play.
        • 3.3.1. Captures
          This sub-group covers conditions where transformations or promotions depend on whether or not captures are involved.
          • KoBul (KoBul Kings):
            After a piece (not a pawn) is captured, the King of the same side retains its royal nature but adopts the powers of movement of the captured piece and no longer moves as a King. After a pawn of that side is captured, the King reverts to its normal movement.
          • Andernach:
            Non-capturing moves are normal, but a unit (except a King) changes its colour after capturing. A Rook on its home square after a colour change may subsequently castle under the normal castling rules.
          • Anti-Andernach:
            Captures are normal, but a unit (except a King) changes its colour after a non-capturing move. A Rook will not change colour after castling, but a Rook on its home square after a colour change may subsequently castle under the normal castling rules.
          • Einstein:
            After a capture, the capturing unit is transformed according to the sequence Pawn > Knight > Bishop > Rook > Queen > Queen. After a non-capturing move the moving unit is transformed according to the reverse sequence Queen > Rook > Bishop > Knight > Pawn > Pawn. Castling (which is also possible with a newly-transformed Rook) results in the Rook transforming to Bishop. A Pawn on its 1st rank may move 1, 2 or 3 steps and is subject to e.p. capture if moving more than 1 step. There is no normal promotion on the 8th rank.
          • Anti-Einstein:
            Captures are normal, but after a non-capturing move the moving unit is transformed according to the sequence Queen > Rook > Bishop > Knight > Pawn > Pawn. Castling (which is also possible with a newly-transformed Rook) results in the Rook transforming to Bishop. A Pawn on its 1st rank may move 1, 2 or 3 steps and is subject to e.p. capture if moving more than 1 step. There is no normal promotion on the 8th rank.
          • Reversal Einstein:
            After a capture, the capturing unit is transformed according to the sequence Queen > Rook > Bishop > Knight > Pawn > Pawn. After a non-capturing move the moving unit is transformed according to the sequence Pawn > Knight > Bishop > Rook > Queen > Queen. Castling (which is also possible with a newly-transformed Rook) results in the Rook transforming to Bishop. A Pawn on its 1st rank may move 1, 2 or 3 steps and is subject to e.p. capture if moving more than 1 step. There is no normal promotion on the 8th rank.
          • Protean (Frankfurt):
            When a unit captures, it retains its colour but takes the nature of the captured unit. A King capturing retains its royal power as a royal piece.
          • Tibet:
            When a black unit (King excepted) captures a white unit of a different type, it changes colour.
          • Double Tibet:
            When a unit (Kings excepted) captures an opposite-colour unit of a different type, it changes colour.
          • SneK:
            The capture of a Queen/Rook/Bishop/Knight results in any available Rook/Bishop/Knight/King of the same colour being transformed into a piece of the same type as the one captured, without its royal or non-royal status being affected, and any choice of transformed piece being made by the capturing side, while the capture of a Pawn results in any royal Knight of that colour being transformed into a normal King. Invented by Diyan Kostadinov, and named after his wife Snejina; see JF problem 432 (2013) and a later one for more details.
          • SneK Circle:
            The capture of a Queen/Rook/Bishop/Knight results in any available Rook/Bishop/Knight/Queen of the same colour being transformed into a piece of the same type as the one captured, without its royal or non-royal status being affected, and any choice of transformed piece being made by the capturing side. Captures of Pawns are normal.
          • SneK Adverse:
            The capture of a Queen/Rook/Bishop/Knight results in any available Rook/Bishop/Knight/King of the opposite colour being transformed into a piece of the same type as the one captured, without its colour or its royal or non-royal status being affected, and any choice of transformed piece being made by the capturing side, while the capture of a Pawn results in any royal Knight of the opposite colour being transformed into a normal King. Invented by Diyan Kostadinov, and named after his wife Snejina.
        • 3.3.2. All moves
          This sub-group covers conditions where transformations or promotions do not depend on whether captures are involved.
          • Super Andernach:
            A unit (King excepted) changes colour after all moves and captures.
          • Volage:
            Any unit (King excepted) changes colour the first time it moves from a light to a dark square or vice versa.
          • Hypervolage:
            Any unit (King excepted) changes colour whenever it moves from a light to a dark square or vice versa.
          • Relegation:
            A piece moving to its 2nd rank changes to a pawn.
          • Changeants:
            On moving to any game-array square, a unit (King excepted) is transformed into a unit of the type and colour associated with that square; if more than one king results, Rex Multiplex rules apply; (see under 3.1.1: Nature.) [A generalisation of Relegation Chess.]
          • Oscillating Kings:
            After any move the two Kings change places. (In the ‘Black/White only’ form of the condition this only happens after a Black/White move.
          • Chameleon:
            After each move by that piece, a Knight, Bishop, Rook or Queen will transform into another in the sequence Knight > Bishop > Rook > Queen > Knight >… A Pawn does not transform, but promotes to a chameleon piece in any phase. Kings are orthodox. (See also Chameleon pieces described in 2.7.2.)
          • Glasgow:
            Pawns promote on their 7th ranks instead of their 8th ranks.
          • Single Box:
            Pawns promote normally only when the promoted piece would be one of a normal set of chess pieces containing one Queen and two each of Rooks, Bishops and Knights. There are two types. Type 1: the Pawn which cannot promote may not move to its 8th rank. Type 2: The Pawn may move to its 8th rank, remaining there as an immobile Pawn; it will immediately promote when a piece capture make promotion possible.
          • Variable (Wandelschach):
            Any piece (King excepted) playing to any square in the game array will immediately change colour and nature to that of the piece (including a King) associated with that square. (Not to be confused with the Variables described under ‘Hidden Play’ in 1.2.5.)
          • Norsk:
            After moving, a Rook changes to a Bishop and vice versa, and a Queen changes to a Knight and vice versa. Also, a unit may only capture opposite colour units of the same type, though checks are normal.
          • Pandemic:
            When a black unit moves, all white units adjacent to its arrival square change colour. A white unit (King excepted) can only move to a square not adjacent to any black unit. Invented by Alexandre Leroux, 2020.
          • Magic Squares:
            In the diagram position, the board contains one or more squares marked as ‘Magic Squares’, each of which would cause any unit (except a King) landing on it to change colour. This condition could also be considered as an attribute of the board.
      • 3.4. Transfer of Powers
        This group covers the possibility that pieces may move under the power of other pieces.
        • 3.4.1. Captures
          This sub-group covers conditions where the transfer of powers depends on whether on not captures are involved. (It includes a few related conditions where there is no actual transfer of powers.)
          • Take & Make:
            After a capture, the capturing unit (King included) must make a further non-capturing step in the manner of the captured unit as part of the same move; such a step must be possible, otherwise the capture may not be made. A pawn can only promote if it captures and is conveyed to the promotion rank by such a step, but a capturing pawn may not be conveyed to its 1st rank by such a step. Checks are normal.
          • Anti Take & Make (Circe Take&Make):
            After a capture, the captured unit must make a non-capturing step as part of the same move; such a step must be possible, otherwise the capture may not be made. Checks are normal.
          • Make & Take:
            A capturing unit must first make a non-capturing step in the manner of the unit to be captured unit before capturing normally as part of the same move. Checks are normal. (There may also be additional castling possibilities, but details are unclear.)
          • Bolero:
            A piece (not the King or a Pawn) makes capturing moves normally, but makes non-capturing moves according to the power of the piece whose home square is on that file. (Pieces moving as Kings do not become royal.)
          • Inverse Bolero:
            A piece (not the King or a Pawn) makes non-capturing moves normally, but makes capturing moves according to the power of the piece whose home square is on that file. (Pieces moving as Kings do not become royal.)
        • 3.4.2. All moves
          This sub-group covers conditions where the transfer of powers does not depend on whether captures are involved.
          • Annan:
            A unit (including a King), when standing one square directly in front of another unit of its own side, moves as that other unit. Pawns may move to the first rank but cannot subsequently move; however, a piece standing directly in front of a pawn on the first rank moves one or two squares forward or captures diagonally as a pawn.
          • Point Reflection:
            Two units standing on squares symmetric with respect to the centre of the board (e.g. c2 and f7, one square being the ‘reflection’ of the other) exchange their powers of movement. Only a non-reflected King and Rook can castle, and only non-reflected pawns can capture e.p..
          • Nanna:
            A unit (including a King), when standing one square directly behind another unit of its own side, moves as that other unit. A pawn on its back rank is immobile unless moving as its front piece. A piece moving with the power of a pawn may capture e.p.; a King and Rook may only castle if moving with their own power.
          • Back-to-back:
            Two opposite-colour units (Kings included) exchange their powers of movement if they stand with the white unit one square directly above the black unit.
          • Face-to-face:
            Two opposite-colour units (Kings included) exchange their powers of movement if they stand with the white unit one square directly the black unit.
          • Cheek-to-cheek:
            Two opposite-colour units (Kings included) exchange their powers of movement if they stand directly beside one another on the same rank. A unit standing between two opposite-colour units gets the powers of both the adjacent units.
          • Circe Power Transfer:
            A unit (except a king) moves as the unit occupying its home square at the time (if such a unit is present).
          • Transmission Menace:
            In addition to its normal moves, a unit may also move as any opposite-colour unit that observes it.
      • 3.5. Observation - Restrictions on moves
        • 3.5.1. Observation - Restrictions on moves
          These conditions all relate to situations where pieces guard other pieces of the same colour or attack pieces of the opposite colour – the term observe being used in both cases. Pinned units also observe. Some of these conditions have opposites, but these are named not by the use of ‘anti’ but by reversing the letters of a condition’s name. Some relate specifically to captures.
          • Madrasi:
            A unit (except a King) is paralysed if it and any opposite-colour unit observe one another; it can then neither move, capture or check, but retains the power to paralyse other units.
          • Madrasi Rex Inclusive:
            A unit (including a King) is paralysed if it and any opposite-colour unit observe one another; it can then neither move, capture or check, but retains the power to paralyse other units.
          • Isardam:
            A move or capture may not be made if it leaves two opposite-colour units observing one another. This applies to checks also, so that a check is not effective if the threatened king capture would leave two opposite-colour units observing one another.
          • Eiffel:
            A unit is paralysed if observed by an opposite-colour unit according to the sequence Pawn > Knight > Bishop > Rook > Queen > Pawn, e.g. a Knight will be paralysed if observed by an opposite-colour Pawn. A paralysed unit cannot move, capture or check, but retains the power to paralyse other units.
          • Leffie:
            A move may not be made if it leaves any unit observed by an opposite-colour unit according to the sequence Pawn > Knight > Bishop > Rook > Queen > Pawn, e.g. if it leaves a Knight observed by an opposite-colour Pawn.
          • Partial Paralysis:
            If a unit stands observed by an opposite-colour unit, the observed unit may not move or capture in the manner of the observing unit, e.g. a Queen observed by an opposite-colour Rook may not make orthogonal moves but only diagonal moves.
          • Provocation:
            Units move normally, but a unit (including a King) may only capture when observed by any opposite-colour unit.
          • Functionary (Beamtenschach):
            A unit (including a King) may only move, capture or check when observed by any opposite-colour unit.
          • Black Functionary:
            A Black unit (including a King) may only move, capture or check when observed by any White unit.
          • White Functionary:
            A White unit (including a King) may only move, capture or check when observed by any Black unit.
          • Manager:
            A unit (including a King) may only move, capture or check when observing any opposite-colour unit.
          • Black Manager:
            A Black unit (including a King) may only move, capture or check when observing any White unit.
          • White Manager:
            A White unit (including a King) may only move, capture or check when observing any Black unit.
          • Superguards:
            Any unit observed by another unit of the same colour cannot be captured, and a King observed by another unit of the same colour cannot be put in check.
          • Patrol:
            Units move normally, but a unit (including a King) may only capture or check when observed by another unit of the same colour.
          • Ultrapatrol:
            A unit (including a King) may only move, capture or check when observed by another unit of the same colour.
          • Lortap:
            A unit (including a King) may only move, capture or check when not observed by another unit of the same colour.
          • Devresbo:
            A move may only be made if the moving piece stands observed by another unit of either colour at the end of the move.
          • Central:
            Kings move and capture normally, but any other unit may only move or capture if observed by its own King or by another unit of its own side that is observed directly or indirectly by its King.
          • Woozles:
            Two units of either colour which observe one another may not capture or check.
          • Mono-Woozles:
            Two units of the same colour which observe one another may not capture or check.
          • Bi-Woozles:
            Two units of opposite colour which observe one another may not capture or check.
          • Heffalumps:
            Two units of either colour which observe one another may not capture or check along their common line of action.
          • Mono-Heffalumps:
            Two units of the same colour which observe one another may not capture or check along their common line of action.
          • Bi-Heffalumps:
            Two units of opposite colour which observe one another may not capture or check along their common line of action.
      • 3.6. Move Length - Restrictions on moves
        • 3.6.1. Move Length - Restrictions on moves
          These conditions all relate to situations where pieces guard other pieces of the same colour or attack pieces of the opposite colour – the term observe being used in both cases. Pinned units also observe. Some of these conditions have opposites, but these are named not by the use of ‘anti’ but by reversing the letters of a condition’s name. Some relate specifically to captures. These restrictions all apply to both moves and captures. They involve the geometrical length of moves, which is the distance measured between the centres of the departure and arrival squares of the moving pieces. Thus if a1-a2 is 1 unit, then a1-b2 is approximately 1.41 units, the knight step is approximately 2.24 units. O-O is 4 units and O-O-O 5 units. Maximummers or Minimummers with colour unstated are Black by default, though in a duplex problem, the condition applies to the defending side.
          • Maximummer (Black Maximummer):
            Black must play the geometrically longest legal move available, choosing freely from among equal longest legal moves. Checks are normal.
          • White Maximummer:
            White must play the geometrically longest legal move available, choosing freely from among equal longest legal moves. Checks are normal.
          • Double Maximummer:
            Each side must play the geometrically longest legal move available, choosing freely from among equal longest legal moves. Checks are normal.
          • Ultra (Black) Maximummer:
            Black must play the geometrically longest legal move available, choosing freely from among equal longest legal moves. Attacks on a King are only checks if the king capture would be one of the longest legal moves available.
          • (Black) Minimummer:
            Black must play the geometrically shortest legal move available, choosing freely from among equal shortest legal moves. Checks are normal.
          • White Minimummer:
            White must play the geometrically shortest legal move available, choosing freely from among equal shortest legal moves. Checks are normal.
          • Double Minimummer:
            Each side must play the geometrically shortest legal move available, choosing freely from among equal shortest legal moves. Checks are normal.
          • (Black) Equimover:
            If possible, Black must play a move equal in length to the previous White move. If this is not possible, any move may be made.
          • Shrinking Men:
            No unit can make a longer move than it made on its previous move.
          • Growing Men:
            No unit can make a shorter move than it made on its previous move.
      • 3.7. Other Concepts.
        A large group covering general concepts other than those listed above. It is subdivided according to whether the nature, restrictions on or consequences of particular moves being played is involved, and also whether or not these particular moves involve captures.
        • 3.7.1. Nature of Captures
          This sub-group covers conditions where the actual nature of a capture (or of a specifically non- capturing move) is involved.
          • Mars Circe:
            Units move normally when not capturing, but in order to capture a unit (King included) must first be replaced on the home square of the capturing unit and then make the capture from there, all as one move. If this home square is occupied, the capture may not be made. (The home square of a Rook, Bishop or Knight is of the same colour as the capture square, that of a Pawn is on the same file as the capture square, and that of a fairy piece is the promotion square of that file.)
          • Mars Mirror Circe:
            Units move normally when not capturing, but in order to capture a unit (King included) must first be replaced on the home square of an opposite-colour unit of the same type as the capturing unit and then make the capture, all as one move. If this home square is occupied, the capture may not be made. (The home square of a Rook, Bishop or Knight is of the same colour as the capture square, that of a Pawn is on the same file as the capture square, and that of a fairy piece is the promotion square of that file.)
          • AntiMars Circe:
            Units capture normally, but in order to make a non-capturing move a unit (King included) must first be replaced on its home square and then make the capture from there, all as one move. If the home square is occupied, the move may not be made. (The home square of a Rook, Bishop or Knight is of the same colour as the capture square, that of a Pawn is on the same file as the capture square, and that of a fairy piece is the promotion square of that file.) See No 513082 in WinChloe database, Erich Bartel, Problemkiste 2010.
          • Dynamo:
            No normal captures are made. Instead, units may push or pull opposite-colour units any number of squares along their lines of action; either or both units may move or be moved off the board. [See JF problem 954 (2015)]
          • Mated Units:
            This condition extends the idea of ‘mate’ to other units. Normal captures and checks may be made, but in addition, if an opposite-colour unit (other than the King) is threatened with capture after a move, and no opposite-colour move is available which would prevent this capture, the unit is ‘mated’ and is removed at that point (unless an illegal self-check position would result). More than one unit may be removed in one move. Once mated units are removed no further evaluation is done to see if other units are mated. Example: in a position with bPs h6, h7, wRh1, wBh3; if White plays 1.B~ the bPh6 is mated and removed but not now the Ph7. If 1.Bf5, however, both Ps are mated and removed. The example alongside solves by 1.Sg4 b6+(-e4) 2.Rc6 bxc7(-c6)#. Note the bB does not disappear immediately after 1.Sg4 but only following the white move. As a further example, there is a fool’s mate from the normal game array, 1.e3(4) g5 2.Qh5(-f7, -g5)#.
        • 3.7.2. Restrictions on Captures
          This sub-group covers conditions where the possibility of either capturing or non-capturing moves is restricted in some way.
          • Black must capture:
            Black captures if able but otherwise makes another move.
          • White must capture:
            White captures if able but otherwise makes another move.
          • No captures:
            Neither side may make a capture, but checks are normal.
          • No Black captures:
            Black may not make a capture, but checks are normal.
          • No White captures:
            White may not make a capture, but checks are normal.
          • Immune:
            Moves, captures and checks are as normal, but a capture may only be made if the home square of the captured unit is vacant. A unit (Kings excepted unless a Rex Inclusive option is applied) is thus immune to capture if its home square is occupied. (The home square of a Rook, Bishop or Knight is of the same colour as the capture square, that of a Pawn is on the same file as the capture square, and that of a fairy piece is the promotion square of that file.)
          • Geneva:
            Moves, captures and checks are as normal, but a capture may only be made if the home square of the capturing unit is vacant. A unit (Kings excepted unless a Rex Inclusive option is applied) is thus immune to capture by any opposite-colour unit whose home square is occupied. (The home square of a Rook, Bishop or Knight is of the same colour as the capture square, that of a Pawn is on the same file as the capture square, and that of a fairy piece is the promotion square of that file.).
          • CAST (Capture after Sole Threat):
            A unit may capture only if it could make no other capture.
          • CAST (Capture after Sole Threat) Inverse:
            A unit may capture only if it could make more than one capture.
          • Multicaptures:
            A unit may be captured only if it is directly attacked in at least two ways.
          • Blockade:
            A unit may give check normally, but may only capture an opposite-colour unit of the same type.
          • Madcap Zigzag:
            White does not capture, check, or ever have his King in check. Black moves only to capture and does so whenever he can. (If he has no capture, he does not move; if he has two or more captures in succession he makes them all before White moves again). It is implied (but not implicitly stated) that only one Black man makes the captures and that a White man may not remain en prise in the mate.
        • 3.7.3. Effects of Captures
          This small sub-group covers conditions where the consequences of a capture is changed.
          • Ghost:
            A captured unit disappears at first, but re-appears on its capture square as an uncapturable ‘ghost’ of itself as soon as the capturing unit moves away.
          • Breton:
            When a unit is captured, one other unit of the same type as the capturing unit (if any are present) is removed at the same time. If more than one such unit is present, the choice of which is to be removed is made by the capturer.
          • Breton Adverse:
            When a unit is captured, one other unit of its type (if any are present) is removed at the same time. If more than one such unit is present, the choice of which is to be removed is made by the capturer.
        • 3.7.4. Nature of all moves
          This sub-group covers conditions where the general nature of moves is changed, or where something other than normal moves may be played.
          • Black Passes if Stuck:
            Black passes when unable to make a legal move, allowing White to make two moves in succession.
          • Alice:
            Positions consist of units on two separate boards, normally referred to as ‘A’ (the game array board) and ‘B’, with no square being occupied on both boards. (A position is often represented on one board by the ‘B’ pieces being shown in a different state.) After each move, which must be legal on the board on which it is played, the moving unit is transferred to the same square on the other board, which must have been empty.
          • All-in:
            The side making a move may move a unit of either colour, Kings included, with Pawns always moving in the correct direction for their colour, but no move may cancel out the last move played. A side may move an opposite-colour King into check, and may cancel a check to its own King by moving the checking unit away.
          • All-in type 2:
            The side making a move may move a unit or either colour, Kings included, with Pawns always moving in the correct direction for their colour, but no move may cancel out the last move played. However, a side may not move an opposite-colour King into check, and may not cancel a check to its own King by moving the checking unit away. (This condition may be used in ‘White only’ or ‘Black only’ forms.)
          • Phantom:
            Units may move and capture normally; alternatively, a unit may be replaced on its home square (if empty) and move or capture from there. (The home square of a Rook, Bishop or Knight is of the same colour as the capture square, that of a Pawn is on the same file as the capture square, and that of a fairy piece is the promotion square of that file.)
          • Plus:
            Units may move and capture normally, but a unit standing on one of the four central squares de45 may move, capture or check as if it were standing on any unoccupied central square.
          • Messigny:
            Normal moves may be played, but instead of a normal move a side may exchange the position of any one of its units with that of a similar unit of the opposite colour. No unit may be part of an exchange in two consecutive moves.
          • Castling:
            A King, even if it has already moved, may castle with any unit of either colour standing anywhere three or more squares away on the same orthogonal or diagonal, moving two squares in the process. This is subject to the normal rules about not castling over occupied squares, out of check or through check.
          • Rokagogo:
            A king and rook may castle from any positions three squares apart on any rank or file, subject to the normal rules about not castling over occupied squares, out of check or through check.
          • Chinese:
            This uses the Chinese Queen, Rook, Bishop, Knight and Pawn described in 2.5.1 in place of orthodox pieces. Kings are orthodox.
          • Argentinian:
            This uses the Argentinian Queen, Rook, Bishop and Knight described in 2.5.2 in place of orthodox pieces. Kings are orthodox; Pawns are also orthodox, but promote to Argentinian pieces.
          • Marine:
            This uses the Marine King Queen, Rook, Bishop, Knight and Pawn described in 2.5.4 in place of orthodox pieces.
          • Cavalier Majeur:
            This uses the Nightriders described in 2.3.1 in place of orthodox Knights.
        • 3.7.5. Restrictions on all moves
          This sub-group covers conditions where there are general restrictions on the moves that may be played.
          • Grid:
            The board is envisaged as being covered by a set of grid-lines, the only legal moves by any units (including Kings) being those that cross one or more of the grid-lines. In the standard form the grid-lines cut the board into 16 2x2 squares, but other patterns of grid-lines are possible. This is really an attribute of the board as well as being a condition. See the Popeye file py-engl.txt for details of entering other patterns of grids.
          • Contact Grid:
            The board is envisaged as being covered by a set of grid-lines, the only legal moves by any units (including Kings) being those that cross one or more of the grid-lines. In addition all moves must finish with the moving unit adjacent to an occupied square; an attacked King will only be in check if it stands adjacent to an occupied square. In the standard form the grid-lines cut the board into 16 2x2 squares, but other patterns of grid-lines are possible. This is thus a combination of the Grid and Koeko conditions.
          • Monochrome:
            All moves must be made from light squares to light squares or from dark squares to dark squares. It follows that a King cannot be checked by a unit on an opposite-colour square, and that queen-side castling and all knight moves are impossible.
          • Bichrome:
            All moves must be made from light squares to dark squares or from dark squares to light squares. It follows that a King cannot be checked by a unit on a same-colour square, and that all castling or bishop moves are impossible.
          • Black Edgemover:
            All Black moves must end on a square on the edge of the board, and Black is mated if no such move is possible.
          • White Edgemover:
            All White moves must end on a square on the edge of the board, and White is mated if no such move is possible.
          • Edgemover:
            All Black/White moves must end on a square on the edge of the board, and Black/White is mated if no such move is possible.
          • Black Follow my Leader:
            Black must when possible play to the square vacated on White’s last move. Checks and mates are normal.
          • White Follow my Leader:
            White must when possible play to the square vacated on Black’s last move. Checks and mates are normal.
          • Follow my Leader:
            Black/White must when possible play to the square vacated on White’s/Black’s last move. Checks and mates are normal.
          • Forced (Obligatory) Square:
            These are squares in a diagram position designated Black or White, that the designated side must play to where possible. Checks and mates are normal.
          • Ultra (Consequent) Forced (Obligatory) Square:
            These are squares in a diagram position designated Black or White, that the designated side must play to where possible, this compulsion being extended to cover checks and mates.
          • Back-home:
            On any move, if a unit (including a promoted pawn) can move to the square it occupied in the diagram position, it must do so (with a free choice between alternatives). Checks are included in the condition, so that an attacked King will only be in check if the king-capture would take the capturing unit back to its diagram position, or if no move by a unit back to its diagram position is available as well as the king-capture. [Invented by Nicholas Dupont, used in JF problems 332-3 (2013)].
          • Alphabetic:
            Each side must play with one of its units that stands on the square which is earliest in alphabetical sequence (a1,a2,...,a8, b1,...,h8) and which has a legal move. Checks and mates are normal.
          • Single Combat (Duellist):
            The last moved unit of each side must continue to play all subsequent moves for that side until it has no legal moves left, after which a new unit can be chosen freely to make the next move.
          • Koeko (Köko):
            All moves must finish with the moving unit adjacent to an occupied square; an attacked King will only be in check if it stands adjacent to an occupied square.
          • Anti-Koeko (Anti-Köko):
            No move may finish with the moving unit adjacent to an occupied square; an attacked King will not be in check if it stands adjacent to an occupied square.
          • New Koeko (New Köko):
            Any unit standing adjacent to an occupied square may only move to finish adjacent to an occupied square, and any unit not standing adjacent to an occupied square may not move to finish adjacent to an occupied square. An attacked King will only be in check if its capture would be allowed under those conditions.
          • Anti-New Koeko (Anti-New Köko):
            Any unit standing adjacent to an occupied square may not move to finish adjacent to an occupied square, and any unit not standing adjacent to an occupied square may onlyt move to finish adjacent to an occupied square. An attacked King will only be in check if its capture would be allowed under those conditions.
          • Disparate:
            After a unit has moved, the other side may not reply with a move (including a reply to check or the notional capture of a checked King) by a unit of the same type. See: https://juliasfairies.com/articles/disparate-part-i-pap/
          • Fuddled Men:
            No unit can make two moves consecutively, and so cannot give a direct check when moving.
          • Active:
            No null moves may be made. (This condition only applies when it is combined with some other fairy condition and/or when fairy pieces are used, e.g a Rose that could otherwise complete a circuit.)
          • No Promotion:
            Pawn-promotion by one or both sides is not allowed.
          • Alsatian:
            Every position arising during the solution to a problem must be legal in orthodox chess. (This condition only applies when it is combined with some other fairy condition.)
          • Holes:
            In the diagram position, the board contains one or more squares marked as ‘holes’ which no unit may occupy or pass through. This condition could also be considered as an attribute of the board – or a special case of ‘non-rectangular boards’. (An individual hole is listed under Pieces as a ‘Pyramid’.)
        • 3.7.6. Effects of all moves.
          This sub-group covers conditions where moves are followed by a variety of special effects.
          • Sentinels:
            A piece (not a pawn) moving away from a square not on the 1st or 8th ranks leaves behind a pawn of the same colour, provided there are not already 8 pawns of that colour present. Neutral pieces moved by White and Black leave white and black pawns respectively.
          • Neutral Sentinels:
            A piece (not a pawn) moving away from a square not on the 1st or 8th ranks leaves behind a pawn of the same colour, provided there are not already 8 pawns of that colour present. Neutral pieces moved always leave neutral pawns. Also known as (Sentinels Pion Neutre).
          • Sentinels m/n:
            A piece (not a pawn) moving away from a square not on the 1st or 8th ranks leaves behind a pawn of the same colour, provided there are not already m white pawns or n black pawns present. Neutral pieces moved by White and Black leave white and black pawns respectively.
          • Enemy Sentinels:
            A piece (not a pawn) moving away from a square not on the 1st or 8th ranks leaves behind a pawn of the opposite colour, provided there are not already 8 pawns of that colour present. Neutral pieces moved by White and Black leave black and white pawns respectively. Also known as (Sentinels Pion Adverse).
          • Actuated Revolving Centre:
            The group of four central squares (de45) rotates 90° clockwise after any move into, within, or away from it. Invented by W.H.Rawlings and A.E.Farebrother Fairy Chess Review 1937. This condition could also be considered as an attribute of the board.
          • Actuated Revolving Board:
            The whole board rotates 90° clockwise after each move. Pawns moved to their first or last rank by this rotation are immobile and do not promote. This condition could also be considered as an attribute of the board.
          • Haaner:
            After each move, the departure square of the moving unit becomes a ‘hole’ which no unit may be occupy or pass through again.
          • Haanover:
            After each move, the departure square of the moving piece and all squares passed over by the move become ‘holes’ which no unit may occupy or pass through again.
          • Wormholes:
            In the diagram position, the board contains two or more squares marked as ‘wormholes’, which have invisible pathways between them. A unit (including a King) which plays to a wormhole immediately passes to any other wormhole as part of the same move. A capture can be made on the entrance wormhole but the exit wormhole must be empty. This condition could also be considered as an attribute of the board.
    • 4. Boards
      The board is perhaps the most basic and fundamental element of a chess problem, being the framework on which the different pieces are placed in a diagram position and on which they move according to their various powers and the condition in force. The effect of changing the nature of the board on the movement of the pieces may be negligible or may be very large.
      • 4.1. Simple Square-Lattice Boards
        These boards are essentially simple modifications of the normal board and change only the scale or possible complexity of play rather than its nature.
        • 4.1.1. Simple Square-Lattice Boards
          • 1D Boards:
            These consist of a single rank or file only. Possibilities seem small, with Bishops and Knights immobile, Pawns able (at best) to move but not capture, and Queens equivalent to Rooks. Nevertheless, problems are possible, the WinChloe database currently containing 38. An example: Eugene Albert, Frankfurter Notizen, 1965: WKa1, BKa5, BPa6. h=2.5*. Set Play: 2.Ka4 Ka2 3.Ka5 Ka3=; 1...Ka2 2.Ka4 Ka1 3.a5 Ka2=. This shows ideal chameleon echo stalemates.
          • Rectangular Boards:
            As normal boards, but of dimensions other than 8x8. Play on these boards would be as normal, except that there might be special rules for castling and for the initial moves of Pawns. These might be used as ‘one-off’ boards to show individual problem effects; a large board might show complex interactions between line-moving pieces impossible on the normal board, while smaller boards would allow an economical presentation of a simpler idea without the need for blocking units. However, some sizes have been used fairly frequently; according to the WinChloe database (2020) the most popular sizes (with numbers of examples) are 7x8 (212), 4x4 (141), 10x10 (78), 4x8 (51), 3x3 (50), 9x9 (49) and 7x7 (47).
          • Irregularly shaped Boards:
            Rectangular boards with squares missing to form an irregular shape, possibly with gaps or holes. These could be ‘one-off’ boards, an example being the ‘Revolver Practice’ problem by T R Dawson, 1911 (P 29, A Guide to Fairy Chess). However, the WinChloe database contains several problems with ‘H’ shaped boards.
          • Infinity Plain:
            A rectangular board considered as extending indefinitely in one or more directions. In a problem by T R Dawson (P 31, Caissa’s Fairy Tales 1947, this board is used for an extension of a normal board problem.
      • 4.2. Modified Square-Lattice Boards
        These are boards where the square lattice is modified in some way to extend the possible moves of pieces, perhaps by removing the limitations associated with a board’s edge, thus introducing complications into the play without essentially changing its nature. Those included in this ‘Version 0’ form a closely related group of rectangular boards (assumed here to be 8x8, but could be of other sizes) where the pieces move as if one or both pairs of opposite edges were joined. They are named according to the shape produced if this joining was done physically with a flexible board, but it is not necessary to visualise this shape in order to determine the movement of pieces. These boards have no discontinuities, and may be validly presented with the ‘join’ in any position, e.g. down the centre, so that moves of pieces across ‘edges’ may be clarified by re-drawing diagrams in this way. However, the often complex paths of unobstructed rooks and bishops on these boards are indicated below. Individual boards are named according to the shape produced if this joining was done physically with a flexible board, but it is not necessary (and indeed sometimes impossible) to visualise this shape in order to determine the movement of pieces.
        • 4.2.1. Modified Square-Lattice Boards
          • Vertical Cylinder:
            Pieces move as if the board was a cylinder, with h1-h8 joined to a1-a8. On it, a Rook could move c4-b4-a4-h4-g4…, and could return to c4 to complete a circuit, while a Bishop could move c4-b5-a6-h7-g8 (but no further). This is the simplest of these boards, with no real complications. The term ‘vertical’ indicates the edges of the board that are considered to be joined, but it is the horizontal movement of pieces that is actually affected.
          • Horizontal Cylinder:
            Pieces move as if the board was a cylinder, with a8-h8 joined to a1-h1. On it, a Rook could move c4-c3-c2-c1-c8-c7…, and could return to c4 to complete a circuit, while a Bishop could move c4-d3-e2-f1-g8-h7 (but no further). The term ‘horizontal’ indicates the edges of the board that are considered to be joined, but it is the vertical movement of pieces that is actually affected. Pawns have no clear promotion rank, and may move indefinitely rather than promoting, though their starting and promotion ranks may be defined. In the normal game-array position both Kings are simultaneously in check.
          • Vertical Moebius:
            Pieces move as if the board was a Moebius strip, with h1-h8 joined to a8-a1. On it, a Rook could move c4-b4-a4-h5-g5…-a5-h4…, and could eventually return to c4 to complete a circuit, while a Bishop could move c4-b5-a6-h2-g1 (but no further). This joining will bring same-coloured squares together, resulting in the colour of squares losing all meaning. The term ‘vertical’ indicates the edges of the board that are considered to be joined, but it is the horizontal movement of pieces that is mainly affected. However, there is an inconsistency (which could perhaps be ignored in a problem) about the direction in which Pawns move – as may be seen by considering two white Pawns on a7 and h2, which are obviously on different ranks but through the join stand next to each other on the same rank.
          • Horizontal Moebius:
            Pieces move as if the board was a Moebius strip, with a8-h8 joined to h1-a1. On it, a Rook could move c4-c3-c2-c1-f8-f7…-f1-c8…, and could eventually return to c4 to complete a circuit, while a Bishop could move c4-d3-e2-f1-b8-a7 (but no further). This joining will bring same-coloured squares together, resulting in the colour of squares losing all meaning. The term ‘horizontal’ indicates the edges of the board that are considered to be joined, but it is the vertical movement of pieces that is actually affected. Pawns have no clear promotion rank, and may move indefinitely rather than promoting, though their starting and promotion ranks may be defined. In the normal game-array position both Kings are simultaneously in check.
          • Torus (Anchor Ring):
            Pieces move as if the board was a torus, with h1-h8 joined to a1-a8 and a8-h8 joined to a1-h1. On it, a Rook could complete a circuit by moving c4-b4-a4-h4-g4…-c4 or c4-c3-c2-c1-c8-c7…-c4, and a Bishop could complete a circuit by moving c4-b5-a6-h7-g8-f1…-c4 or c4-b3-a2-h1-g8…-c4. Pawns have no clear promotion rank, and may move indefinitely rather than promoting, though their starting and promotion ranks may be defined. In the normal game-array position both Kings are simultaneously in check.
          • Vertical Cylinder + Horizontal Moebius (Klein’s Bottle):
            Pieces move as if h1-h8 was joined to a1-a8 and a8-h8 joined to h1-a1. On it, a Rook could complete a circuit by moving c4-b4-a4-h4-g4…-c4 or the longer c4-c3-c2-c1-f8…-f1-c8-c7…-c4, and a Bishop could complete a circuit by moving c4-b5-a6-h7-g8-c1…-h6-a7-b8-f1…-c4 or c4-b3-a2-h1-b8…-h2-a1-g8…-c4. This joining will bring same-coloured squares together, resulting in the colour of squares losing all meaning. Pawns have no clear promotion rank, and may move indefinitely rather than promoting, though their starting and promotion ranks may be defined. In the normal game-array position both Kings are simultaneously in check.
          • Vertical Moebius + Horizontal Cylinder:
            Pieces move as if h1-h8 was joined to a8-a1 and a8-h8 joined to a1-h1. On it, a Rook could complete a circuit by moving c4-b4-a4-h5…-a5-h4-g4…-c4 or the shorter c4-c3-c2-c1-c8-c7…-c4, and a Bishop could complete a circuit by moving c4-b5-a6-h2-g1-f8…-a3-h7-g8…-c4 or c4-b3-a2-h8-g1…-a7-h1-g8…-c4. This joining will bring same-coloured squares together, resulting in the colour of squares losing all meaning. Pawns have no clear promotion rank, and may move indefinitely rather than promoting, though their starting and promotion ranks may be defined. However, there is an inconsistency (which could perhaps be ignored in a problem) about their direction of movement – as may be seen by considering two white Pawns on a7 and h2, which are obviously on different ranks but through the join stand next to each other on the same rank. In the normal game-array position both Kings are simultaneously in check.
          • Vertical Moebius + Horizontal Moebius:
            Pieces move as if h1-h8 was joined to a8-a1 and a8-h8 joined to h1-a1. On it, a Rook could complete a circuit by moving c4-b4-a4-h5…-a5-h4-g4…-c4 or c4-c3-c2-c1-c8-c7…-c4 or c4-c3-c2-c1-f8…-f1-c8-c7…-c4, and a Bishop could complete a circuit by moving c4-b5-a6-h2-g1-c8…-h3-a7-b8-f1…-c4 or c4-b3-a2-h8-b1…-h7-a1-g8…-c4. This joining will bring same-coloured squares together, resulting in the colour of squares losing all meaning. Pawns have no clear promotion rank, and may move indefinitely rather than promoting, though their starting and promotion ranks may be defined. However, there is an inconsistency (which could perhaps be ignored in a problem) about their direction of movement – as may be seen by considering two white Pawns on a7 and h2, which are obviously on different ranks but through the join stand next to each other on the same rank. In the normal game-array position both Kings are simultaneously in check.
      • 4.3. Other Boards
        These are boards on which possible moves are modified to such an extent that even orthodox pieces need to have their powers of movement redefined; they must therefore be considered not in isolation but in combination with their pieces. In the present ‘Version 0’ of the database, the boards in this group are either multi-dimensional but based on a square lattice or else 2-dimensional but based on a hexagonal lattice. In both cases they are made up of something other than squares, but the incorrect term ‘square’ will still be used for convenience.
        • 4.3.1. Other Boards
          • Stereo-Schach Board:
            Invented in 1975 by Gerhard W. Jensch. This is a composite 2D+3D square-lattice board with a 4x4x4 cube sitting over a normal 8x8 board and aligned with the squares c3-c6-f6-f3 on that board. Positions are shown on an 8x8 diagram plus four 4x4 diagrams, and squares on the central block are indicated by prefixing the normal coordinate with A, B, C or D (going upward); the A and C diagrams have the normal square-colouring reversed. The pieces are the orthodox set with the normal game-array; they move according to normal rules, but on the central block can move in the forward-upward or sideways-upward dimensions as well as in the normal forward-sideways dimension. A Pawn makes non-capturing moves 1 square directly forward or upwards, capturing moves 1 square diagonally forward and sideways, forward and upward or sideways and upward, and (for a white Pawn) promotes on a8-h8 or on Dc6-Df6. Initial pawn double-step moves, e.p. captures and castling are as normal. For more information see https://www.chessvariants.com/3d.dir/stereo.html
          • 3D Space (Raumschach) Board:
            Invented in 1907 by Dr Ernst Maack and used in what is called the ‘Normal Form’ of Space Chess. It is a 5x5x5 purely 3D board based on a square lattice and made up of 125 ‘squares’. Positions can be visualised in three dimensions, but are shown on five 5x5 diagrams labelled A-E, these letters being used as upward coordinates when identifying squares; thus the central square would be ‘Cc3’. The A, C and E diagrams have dark squares in the corners, the others having light squares. The pieces used on this board are those of the orthodox set, but with 10 Pawns plus two new pieces, these being Unicorns or [1,1,1]- riders. Moves are as normal but adapted to the three dimensions (which can be described as ‘forward’, ‘sideways’ and ‘upward’). Thus a Rook can move in any one of the three dimensions, a Bishop or Knight move across any two of them, while a King (which has no castling move) or Queen can move in either of these ways. The Unicorn is the only piece that moves simultaneously across all three dimensions (alternating its square colour on every step. White Pawns start off on the A2 and B2 ranks with no initial double-step, making non-capturing moves 1 square forwards or upwards, capturing moves 1 square diagonally forward and sideways, forward and upward or sideways and upward; they promote on the E5 rank. Black Pawns similarly start off on the E4 and D4 ranks, promoting on the A1 rank. For more details see A Guide to Fairy Chess pp 16-18; And https://www.chessvariants.com/3d.dir/3d5.html
          • 4-Dimensional Board:
            This is a 4x4x4x4 board of 256 ‘squares’ developed by T R Dawson to extend the ‘space’ concept. Positions are shown on a 4x4 set of 4x4 diagrams with alternating square colouring (the bottom left diagram having the normal colouring); these diagrams are labelled A-D in rows and I-IV in columns. A square may thus be identified by four coordinates, the extreme top right square being IVDd4. The pieces used are the orthodox ones adapted for 4-dimensional movement (but without castling or double-step Pawn moves), plus the two new pieces Unicorn (a [1,1,1]-rider) and Balloon (a [1,1,1,1]-rider). It is not really possible to visualise moves in 4 dimensions, and the best way to think about them is as the ranks and files of any one of the 16 diagrams plus the rows and columns made up by the diagrams themselves. Thus a Rook move will be along any one of these four dimensions, a Bishop or Knight move across any two of them, and a King or Queen may move in either of these ways. A Unicorn moves in straight lines across any three of these dimensions, and a Balloon in straight lines across all four dimensions. A Pawn moves without capturing a single step in a direction that takes it towards its promotion rank (IVD4 for White and IA1 for Black), and captures by moving a single diagonal step across 2 dimensions that also takes it towards this rank. For more details see A Guide to Fairy Chess pp 18-19; And https://www.chessvariants.com/invention/4chess-four-dimensional-chess.
          • Hexagonal Plane Board:
            This is a hexagonal board composed of 91 ‘squares’ (that are actually hexagons) with 6 along each side. These ‘squares’ are in three colours (the actual colours apparently not being standardised), and form orthogonal and diagonal lines in three directions (though along the diagonals the squares are not in contact). The board is orientated so that one orthogonal is vertical (giving it files but not ranks, the file-length varying between 6 and 11); individual ‘squares’ are labelled in the normal way with the letters a-k for the files and a number for the position of a ‘square’ up from the bottom of the file. Two different sets of pieces may be used on this board, though the difference between them involves Pawns only. The main pieces consist essentially of the normal orthodox set adapted for the changed geometry (though the existence of 3 different sets of diagonals means that 3 bishops instead of 2 are needed to cover the whole board). The main changes to the moves bring an increase in possibilities; Rooks and Bishops have 6 possible lines of action instead of 4, and Queens 12 instead of 8, while Kings and Knights have 12 possible destination squares instead of 8 (though there is no castling). Pawns always make non-capturing moves 1 square directly forwards (or 2 squares initially, with the possibility of e.p. capture); they promote on reaching the final angled row a6-f11-k6. The McCooey version uses 7 pawns of each colour, the white ones initially on c1, d2, e3, f4, g3, h2, i1; these capture 1 square diagonally forwards. The Glinski version uses 9 pawns of each colour, the white ones initially on b1, c2, d3, e4, f5, g4, h3, i2, j1; these capture 1 square orthogonally forwards. (In this version, a capture from a starting square may bring a Pawn to another starting square, from which it may make an initial double-step move.) Note: An actual hexagonal board is needed to appreciate the play properly, but an approximation on a normal board can show the differences between moves. Mark the squares b1, b7, d4, f1, f7, h4 with one colour, b5, d2, d8, f5, h2, h8 with a second colour, and b3, d6, f3, h6 with a third colour, ignoring the other squares. Starting from b1, a wR can move to b3-b5-b7 or d2-f3-h4, a wB to d4-f7 or f1, the wK to b3 or d2 or d4 or f1, a wS to d6 or f5 or h2. Under McCooey rules, a wP could move to b3 (or to b5 if b1 was the starting square) and capture on d4; under Glinski rules, it could move to b3 (or to b5 if b1 was the starting square) and capture on d2. For more details on the Glinski version see https://www.chessvariants.com/hexagonal.dir/hexagonal.html For more details on the McCooey version see https://www.chessvariants.com/hexagonal.dir/hexchess2.html