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# ECUMENICAL EURASIAN NINJACHESS

### Charles Gilman

Here is another entry to the 10-Chess contest inspired by, among others, Fergus Duniho's Eurasian Chess. Perhaps that variant should have a special award for inspiring new variants in the contest. The theme is of the sum 10=5+5, and the sequence of 10, 5, and 5 is a recurring one. This is a 3d variant - unusual for a contest, but there is the precedent of Mark Thompson's Tetrahedral Chess in the 84-square contest, although its cells are rhombic dodecahedra rather than squares! Ecumenical Eurasian Ninjachess uses a board of 10x5x5 cubic cells, so that 10 is both the long dimension (number of ranks) and the sum of the short ones (whose product, 25, is the number of files). The number of steppers is also 25. Of the remaining pieces 10 aside are purely radial, 10 aside purely oblique (including 3d ones with names from my article Punning By Numbers), and 20 aside mixtures which can be subdivided into 2 groups of 10 in 2 ways. There are 10 rules derived directly from 3 existing variants, 5 additional basic rules, and 5 rules deriving from the 10+5 making 10+5+5. It has much in common with my other entry in this contest, my 2d Wildeurasian Qi.

The variant differs from FIDE Chess in the following ways, derived from three existing variants on these pages:

From TUNNELCHESS:
(1) Each player's half of the board is a cube of cells. Files are lettered from White's left to right along the top row, then along the row below it, et cetera. The short dimensions make diagonal pieces and components less powerful.
(2) There is no castling as Kings are within two steps of every other non-Pawn.
(3) There is a mixture of Pawnlike pieces.

From ECUMENICAL CHESS:
(4) There are four groups of five pieces comprising two aside in each of a pair of dual directions and one aside of their compound. The long-range FIDE pieces form such a group.
(5) There are also compounds of every simple long-range radial piece with every simple oblique piece, two aside where both components are colourbound, one aside otherwise. I decided against compounds of a linepiece and a hopper, as there is too much overlap between their moves, or a 2d leaper and a 3d one, for consistency. A subset of Samurai, Merchant, Comerchant, and two Cosamurai must wait for a Cannonless 3d variant outside the remit of the contest.

From EURASIAN CHESS
(6) The board has 10 ranks. Whether ranks are numbered 1 to 10 or 0 to 9 is a matter of style, and has no bearing on how the game is played.
(7) A forward-only piece may, on moving to or within the three-rank enemy camp, be further promoted to a symmetric piece captured by the enemy, and cannot reach the end rank unless such promotion is possible.
(8) Pieces of the "Chinese family", in the style of the Xiang Qi Cannon, are included.
(9) Kings cannot stand a Rook or Bishop move apart without an intervening piece. They CAN stand a Unicorn's move apart as this direction does not exist in Eurasian Chess and is not used here.
(10) Kings cannot enter the enemy half of the board. Note that this applies ONLY to Kings as this variant is NOT influenced by my Anglis Qi.

Further differences are:
(A) There are oblique leapers with three nonzero coordinates, hereafter termed 3d leapers, and compounds thereof. The use of such pieces, and of the 3d board is denoted by the name of one of them, the Ninja, in the variant name. Note that there are no Unicorns, Viceroys, or compounds thereof as these do not fit in with the pairs of duals.
(B) The two kinds of Pawnlike pieces are different in number, start on different ranks, and do not fill their ranks.
(C) Hoppers, as pieces or components, are the mirror image across files KLMNO of the corresponding linepieces. Likewise 3d leapers, as pieces or components, are the mirror image across files CHMRW of the corresponding 2d leapers. This means that the exclusively radial-and-long-range group of 10 start on files CHMRW and the exclusively oblique group on files KLMNO.
(D) All pieces with a Rook or Cannon move are on the back rank with a piece directly in front and a Pawn in front of that. This is to prevent pieces from starting en prise to Cannons and their compounds. It could be argued that this is similar to the array in Pawnless Tunnelchess, where all pieces with a Rook move are on the back-rank, but it is not general to Tunnelchess.
(E) Because of the odd number of files, all pairs of colourbound pieces start adjacent, so that they are on opposite cell colours in a manner both symmetric and easy to relate to.

Combining these differences results in:
(F) Rules 1 and 6 mean that there are 5x5 files, with each rank a 5x5 square of cells.
(G) Rules 3 and 7 mean that Yeomen as well as Pawns are promotable to captured pieces.
(H) Rules 4 and 8 mean that each army has a Tank=Cannon+Arrow.
(I) Rules 4 and A mean that each army has a Nintu=Ninja+Nimel.
(J) Rules 5, 8, and A mean that there are 16 types of hybrid piece, with two aside of the four colourbound types and one aside of the rest, in four groups of 1+1+1+2. These groups can be paired into ten starting with Ma- or Ca- (2d oblique component) and ten starrting with Ni- (3d oblique component). Alternatively they can be paired into ten with Ecumenical Chess name endings (FIDE radial component) and ten ending with -hopper (hopping radial component). Members of this last group may be qualified as "Chinese-style" to specify the kind of hopping move.

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Here is the full piece list with their moves and recommended equipment. Five FIDE sets, or four Grand Chess sets, easily distinguishable by size may be used, with some pieces left over, especially Pawns. For ease of reference sets are numbered 1 to 5 in descending order, with set 3 3 omitted from the Grand Chess ones.

Steppers, 25 aside, 50 on board altogether:
PAWN: the familiar Occidental front-rank piece, surviving from Chaturanga right through to Ecumenical Chess and now to this combination. Moves one step forward at a time, on the stanadrd diagonal if capturing otherwise on the orthogonal. Pawns start on the third rank and may make an initial noncapturing double move. On reaching the enemy camp they may be promoted to captured pieces. FIDE or GC equipment: 4 and set 5 Pawns.
YEOMAN: the Pawn with its capturing and noncapturing moves swapped round. Yeomen serve here as a filler to ensure that nothing is en prise to a Cannon or compound thereof, and so start on the second rank between some orthogonal pieces and their Pawns, with no initial double move. FIDE equipment: set 3 Pawns; GC equipment: set 2 Pawns.
KING: the familiar Occidental ruling piece, surviving et cetera et cetera. Moves one step in any of the six orthogonal and twelve standard diagonal direction. Note that it CANNOT use the nonstandard diagonal (aka triagonal) as this has no dual and is therefore not used in the variant. This may be an advantage as Emperors (Kings that CAN also use that direction) are notoriously elusive. Must be kept out of check, with checkmate and stalemate as per FIDE Chess, plus the Eurasian Chess bare facing rule. Starts at the centre of the back rank, surrounded by the four compounds of duals. FIDE/GC equipment: set 1 King.

Linepieces, 5 aside, 10 on board altogether:
ROOK, BISHOP, QUEEN: the familiar FIDE long-range pieces, and in the familiar numbers. Note that the Queen cannot move like a Unicorn. Bishops are confined to cells the same colour as their starting ones. Rooks and Queens start on the back rank, Bishops on the second. FIDE or GC equipment: Queen from set 1 and the rest from set 4.

Hoppers, 5 aside, 10 on board altogether:
CANNON: added to Xiang Qi following the invention of gunpowder to strengthen the array. Moves exactly like a Rook, except that when capturing it must pass through exactly one occupied cell - plus any number of unoccupied ones including zero. The intervening piece is NOT itself captured, and can be friend or foe. A Cannon checks if it is an orthogonal line with the enemy King and separated by exactly one intervening piece. Note that a Cannon cannot capture or check an adjacent piece. 2 aside, starting on the back rank. FIDE or GC equipment: set 5 Rooks.
ARROW: first invented for fairy problems, but taking its place as a full-game piece courtesy of Fergus Duniho, who gave it this name and used it in Yang Qi and then in Eurasian Chess which was a development thereof. Moves like a Bishop, including confinement to cells of one colour each, but again must pass through an occupied cell as per the Cannon. 2 aside, starting on the second rank. FIDE or GC equipment: set 5 Bishops. The choice of image in this text is one widely used for diagonal pieces, including the Timur's Chess Picket which like this piece cannot capture or check an adjacent piece.
TANK: the compound of Cannon and Arrow. My choice of name is an attempt to follow Dr. Duniho's precedent of Arrow by conveying the sense of a powerful but mobile projectile launcher. Moves like a Queen, but again must pass through an occupied cell et cetera. 1 aside, starting on the back rank. FIDE or GC equipment: upturned set 1 Rook.

2d Leapers, 5 aside, 10 on board altogether:
KNIGHT: the familiar Occidental 2:1 leaper et cetera. Cannot be blocked by an intervening piece. 2 aside, starting on the second rank. FIDE or GC equipment: set 4 Knights.
CAMEL: the colourbound dual of the Knight. The Camel's 3:1 leap is equivalent to two Knight leaps at right angles. This piece too cannot be blocked by an intervening piece. 2 aside, starting on the second rank. FIDE or GC equipment: two set 1 Pawns. No other set 1 Pawns are used.
GNU: the compound of Knight and Camel. Cannot be blocked. 1 aside, starting aside, starting on the back rank. FIDE equipment: set 1 Knight; GC equipment: set 2 King.

3d Leapers, 5 aside, 10 on board altogether:
NINJA: the 2:2:1 leaper, named after a Japanese stealth warrior. Cannot be blocked by an intervening piece. 2 aside, starting on the second rank. FIDE or GC equipment: set 5 Knights.
NIMEL: the colourbound dual of the Ninja. The Nimel's 4:1:1 leap is equivalent to two Ninja leaps at right angles. This piece too cannot be blocked by an intervening piece. 2 aside, starting on the second rank. FIDE equipment: two set 2 Pawns, no others used; GC equipment: set 2 Rooks. The choice of image in this text is to combine a human head for the Ni- of Ninja with a beastly body for the -mel of Camel.
NINTU: the compound of Ninja and Nimel, named after a female deity of ancient Mesopotamia. Cannot be blocked. 1 aside, starting on the back rank. FIDE equipment: set 2 Knight; GC equipment: set 2 Queen. The choice of image in this text has the double symbolism of ziggurat (for Mesopotamian) and altar (for deity).

Compounds of linepiece and 2d leaper, 5 aside, 10 on board altogether:
MARSHAL: the compound of Rook and Knight, long established under various names in historic 10-file Italian and British Chess. 1 aside, starting on the back rank. FIDE equipment: set 4 Queen; GC equipment: set 1 Marshal.
CARDINAL: the compound of Bishop and Knight, long established under various names in historic 10-file Italian and British Chess. The name is perhaps more suited to such variants, where the bishop component dominates, than to this one, where with the narrow ranks the Knight component dominates. 1 aside, starting on the back rank. FIDE equipment: set 4 King; GC equipment: set 1 Cardinal.
CANVASSER: the compound of Rook and Camel, first grouped with the two compounds above in Ecumenical Chess. 1 aside, starting on the back rank. FIDE or GC equipment: set 1 Rook.
CALIPH: the compound of Bishop and Camel, also appearing in Ecumenical Chess. As this piece's components share a colourbinding, the piece itself has this binding and therefore there are 2 aside, starting on the same file on the back 2 ranks. FIDE or GC equipment: set 1 Bishops.

Compounds of linepiece and 3d leaper, 5 aside, 10 on board altogether:
NINSHAL: the compound of Rook and Ninja, a 3d extrapolation of the Marshal. 1 aside, starting on the back rank. FIDE equipment: set 2 Queen; GC equipment: set 2 Marshal.
NIRDINAL: the compound of Bishop and Ninja, a 3d extrapolation of the Cardinal. 1 aside, starting on the back rank. FIDE equipment: set 2 King; GC equipment: set 2 Cardinal.
NINVASSER: the compound of Rook and Nimel, a 3d extrapolation of the Canvasser. 1 aside, starting on the back rank. FIDE or GC equipment: set 2 Rook.
NILIPH: the compound of Bishop and Nimel, a 3d extrapolation of the Caliph. As this piece's components share a colourbinding, the piece itself has this binding and therefore there are 2 aside, starting on the same file on the back 2 ranks. FIDE or GC equipment: set 2 Bishops.

Compounds of hopper and 2d leaper, 5 aside, 10 on board altogether:
MARSHHOPPER: the compound of Cannon and Knight. 1 aside, starting on the back rank. FIDE equipment: set 3 Queen; GC equipment: set 4 Marshal.
CARDIHOPPER: the compound of Arrow and Knight. 1 aside, starting on the back rank. FIDE equipment: set 3 King; GC equipment: set 4 Cardinal.
CANVAHOPPER: the compound of Cannon and Camel. 1 aside, starting on the back rank. FIDE equipment: set 3 Rook; GC equipment: set 4 Queen.
CALIPHOPPER: the compound of Arrow and Camel. As this piece's components share a colourbinding, the piece itself has this binding and therefore there are 2 aside, starting on the same file on the back 2 ranks. FIDE equipment: set 3 Bishops; GC equipment: set 1 Knights.

Compounds of hopper and 3d leaper, 5 aside, 10 on board altogether:
NINSHHOPPER: the compound of Cannon and Ninja. 1 aside, starting on the back rank. FIDE equipment: set 5 Queen; GC equipment: set 5 Marshal.
NIRDIHOPPER: the compound of Arrow and Ninja. 1 aside, starting on the back rank. FIDE equipment: set 5 King; GC equipment: set 5 Cardinal.
NINVAHOPPER: the compound of Cannon and Nimel. 1 aside, starting on the back rank. FIDE equipment: upturned set 3 Rook; GC equipment: set 5 Queen.
NILIPHOPPER: the compound of Arrow and Nimel. As this piece's components share a colourbinding, the piece itself has this binding and therefore there are 2 aside, starting on the same file on the back 2 ranks. FIDE equipment: set 3 Bishops; GC equipment: set 2 Knights. ﻿