Plattraum

Then I wondered what would happen if, alongside the Forerook and Hindrook, I were to use a long-range piece along the hex diagonals as another basic long-range piece, with an oblique short-range piece? That would be bringing aboard more characteristics of Glinski and McCooey, but the presence of three kinds of basic piece reminded of a quite different game: Raumschach, an early form of 3d Chess. The fact that the "third" long-range piece would be one whose shortest-steps had a length of root-3 emphasised this connection. In fact they can be seen as the same piece, thanks to the geometry used in Tetrahedral Chess. As a compromise between the AltOrth/Glinski Migrants and the McCooey Brokers, I use the Corporal of Chevron Ranks.

This similarity inspired the name. I rejected Plattschach as simply meaning "flat chess" - which is effectively what all forms of 2d Chess are. The oxymoron of "flat space" had a pleasing ring to it, and so I chose the German for that.

I devised various versions of the game. The first has the strongest Raumschach resonance, with the compound only of all three basic long-range pieces. Others use additional compounds, of just two basic pieces, including in some cases the short-range piece. I considered a Shogi-like variant, but decided against it because of the complexities of promotions.

Setup

Plattraum
with single compound:___
________________ ___/ . \___ ________________
____________ ___/ . \___/ . \___ ____________
________ ___/Sn3\___/ . \___/Sn2\___ ________
____ ___/Fr3\___/ . \___/ . \___/Fr2\___ ____
 ___/Ds3\___/Cp3\___/ . \___/Cp2\___/Gd2\___
/Un3\___/Hr3\___/ . \___/ . \___/Hr2\___/Un2\
\___/Un3\___/Cp3\___/ . \___/Cp2\___/Un2\___/
/Gd3\___/Un3\___/ . \___/ . \___/Un2\___/Ds2\
\___/Hr3\___/Cp3\___/ . \___/Cp2\___/Hr2\___/
/Fr3\___/Cp3\___/ . \___/ . \___/Cp2\___/Fr2\
\___/Cp3\___/ . \___/ . \___/ . \___/Cp2\___/
/Sn3\___/ . \___/ . \___/ . \___/ . \___/Sn2\
\___/ . \___/ . \___/ . \___/ . \___/ . \___/
/ . \___/ . \___/ . \___/ . \___/ . \___/ . \
\___/ . \___/ . \___/Cp1\___/ . \___/ . \___/
/ . \___/ . \___/Cp1\___/Cp1\___/ . \___/ . \
\___/ . \___/Cp1\___/Un1\___/Cp1\___/ . \___/
____\___/Sn1\___/Hr1\___/Hr1\___/Sn1\___/____
________\___/Fr1\___/Un1\___/Fr1\___/________
____________\___/Ds1\___/Gd1\___/____________
________________\___/Un1\___/________________
____________________\___/____________________

Plattraum with
multiple compounds : ___
________________ ___/Gd2\___ ________________
____________ ___/Rk2\___/Rk2\___ ____________
________ ___/Hd2\___/Un2\___/Hd2\___ ________
____ ___/Fr2\___/Fd2\___/Fd2\___/Fr2\___ ____
 ___/Cp2\___/Sn2\___/Un2\___/Sn2\___/Cp2\___
/ . \___/Cp2\___/Hr2\___/Hr2\___/Cp2\___/ . \
\___/ . \___/Cp2\___/Un2\___/Cp2\___/ . \___/
/ . \___/ . \___/Cp2\___/Cp2\___/ . \___/ . \
\___/ . \___/ . \___/Cp2\___/ . \___/ . \___/
/ . \___/ . \___/ . \___/ . \___/ . \___/ . \
\___/ . \___/ . \___/ . \___/ . \___/ . \___/
/ . \___/ . \___/ . \___/ . \___/ . \___/ . \
\___/ . \___/ . \___/Cp1\___/ . \___/ . \___/
/ . \___/ . \___/Cp1\___/Cp1\___/ . \___/ . \
\___/ . \___/Cp1\___/Un1\___/Cp1\___/ . \___/
/ . \___/Cp1\___/Hr1\___/Hr1\___/Cp1\___/ . \
\___/Cp1\___/Sn1\___/Un1\___/Sn1\___/Cp1\___/
____\___/Fr1\___/Fd1\___/Fd1\___/Fr1\___/____
________\___/Hd1\___/Un1\___/Hd1\___/________
____________\___/Rk1\___/Rk1\___/____________
________________\___/Gd1\___/________________
____________________\___/____________________

Plattraum Knighted : ___
________________ ___/Un2\___ ________________
____________ ___/Sp2\___/Gd2\___ ____________
________ ___/Fs2\___/Un2\___/Hs2\___ ________
____ ___/Fr2\___/Hd2\___/Fd2\___/Fr2\___ ____
 ___/Cp2\___/Sn2\___/Un2\___/Sn2\___/Cp2\___
/ . \___/Cp2\___/Hr2\___/Hr2\___/Cp2\___/ . \
\___/ . \___/Cp2\___/Rk2\___/Cp2\___/ . \___/
/ . \___/ . \___/Cp2\___/Cp2\___/ . \___/ . \
\___/ . \___/ . \___/Cp2\___/ . \___/ . \___/
/ . \___/ . \___/ . \___/ . \___/ . \___/ . \
\___/ . \___/ . \___/ . \___/ . \___/ . \___/
/ . \___/ . \___/ . \___/ . \___/ . \___/ . \
\___/ . \___/ . \___/Cp1\___/ . \___/ . \___/
/ . \___/ . \___/Cp1\___/Cp1\___/ . \___/ . \
\___/ . \___/Cp1\___/Rk1\___/Cp1\___/ . \___/
/ . \___/Cp1\___/Hr1\___/Hr1\___/Cp1\___/ . \
\___/Cp1\___/Sn1\___/Un1\___/Sn1\___/Cp1\___/
____\___/Fr1\___/Hd1\___/Fd1\___/Fr1\___/____
________\___/Fs1\___/Un1\___/Hs1\___/________
____________\___/Sp1\___/Gd1\___/____________
________________\___/Un1\___/________________
____________________\___/____________________

Plattraum Liu Yang : ___
________________ ___/Gd2\___ ________________
____________ ___/Sg2\___/Sg2\___ ____________
________ ___/Fc2\___/Hc2\___/Fc2\___ ________
____ ___/Fr2\___/Un2\___/Un2\___/Fr2\___ ____
 ___/Cp2\___/Sn2\___/Hc2\___/Sn2\___/Cp2\___
/ . \___/Cp2\___/Hr2\___/Hr2\___/Cp2\___/ . \
\___/ . \___/Cp2\___/ . \___/Cp2\___/ . \___/
/ . \___/ . \___/Cp2\___/Cp2\___/ . \___/ . \
\___/ . \___/ . \___/Cp2\___/ . \___/ . \___/
/ . \___/ . \___/ . \___/ . \___/ . \___/ . \
\___/ . \___/ . \___/ . \___/ . \___/ . \___/
/ . \___/ . \___/ . \___/ . \___/ . \___/ . \
\___/ . \___/ . \___/Cp1\___/ . \___/ . \___/
/ . \___/ . \___/Cp1\___/Cp1\___/ . \___/ . \
\___/ . \___/Cp1\___/ . \___/Cp1\___/ . \___/
/ . \___/Cp1\___/Hr1\___/Hr1\___/Cp1\___/ . \
\___/Cp1\___/Sn1\___/Hc1\___/Sn1\___/Cp1\___/
____\___/Fr1\___/Un1\___/Un1\___/Fr1\___/____
________\___/Fc1\___/Hc1\___/Fc1\___/________
____________\___/Sg1\___/Sg1\___/____________
________________\___/Gd1\___/________________
____________________\___/____________________

Pieces

AltOrth pieces:
The FOREROOK (Fr) moves like the Rook but only in the straight forward and both half backward directions. It is this page's analogue to the cubic Rook.
The HINDROOK (Hr) moves like the Rook but only in the straight backward and both half forward directions. It is this page's Bishop analogue, but is not colourbound.

Chevron-rank pieces:
The CORPORAL (Cp), Chevron analogue to Pawn, moves one steps forward. It does so along the straight-forward orthogonal except when capturing, which it does along the inward forward hex diagonal (like a Broker inward and outward) and the outward half-forward orthogonal (like a Migrant inward and outward).

Additional pieces:
The FOREDUCHESS (Fd) moves like a Forerook or a Unicorn. It is this page's analogue to the cubic Duchess.
The HINDDUCHESS (Hd) moves like a Hindrook or a Unicorn. It is this page's analogue to the cubic Governor.
The FORESEASEHOLDER (Fs) moves like a Forerook or a Sennight. It is this page's Marshal analogue.
The HINDSEASEHOLDER (Hs) moves like a Hindrook or a Sennight. It is this page's Cardinal analogue.
The SEPRECHAUN (Sp) moves like a Unicorn or a Sennight. It is this page's Cavalcade analogue.
The FORECANNON (Fc) differs from the Forerook in requiring exactly one intervening piece when capturing. It is this page's analogue to the square-board Cannon.
The HINDCANNON (Hc) differs from the Hindrook in requiring exactly one intervening piece when capturing. It is this page's Arrow analogue, but is not colourbound.
The SLING (Sg) differs from the Unicorn in requiring exactly one intervening piece when capturing. It is this page's analogue to the cubic piece of the same name.

Rules

Corporals reaching the far edges must be promoted to other capturable array pieces. In the case of Plattraum Liu Yang these must be pieces captured by the enemy, and if there is nothing to promote them to they cannot make the final move to the far edge.

Subvariants can be derived substituting promotion rules - and adding return-from-capture ones - based on Bishogi or Frontofhouse. In the first case all pieces are promotable in the enemy camp to Duchess but return in their unpromoted form. In the second case Corporals are promotable in the enemy camp to the Batman of Chevron ranks and return as Corporals, while symetric pieces return with only their forward moves (Forerook as Wing, Hindrook as Wingreservist, Unicorn as Horn, Sennight as Senhelm) which can be promoted in the enemy camp back to their original symmetric form.

There is no Castling. Plattraum Liu Yang has a Grandduke Swap to allow complete coverage by colourbound pieces. This means that in place of a normal move, the Grandduke may swap places with any adjacent long-range piece or Viceroy of the same army, if neither piece is threatened.

In 2-player subvariants Check, Checkmate, and Stalemate are as usual. In 3-player ones a player is Checkmated when their General is threatened by the player about to move. That player's pieces are removed from the game and the remaining players then alternate moves starting with the Checkmating one. The last player not Checkmated wins. A player can also win by getting a Migrant to the far corner while having a full complement of non-Migrants, in all subvariants and even if both 3-player enemies are uncheckmated.

Notes

When playing with return from capture, two distinguishable Shogi sets are more suitable. Simiilar substitutions can be made, but the small Bishop will need to be used alongside two small pieces of another Shogi type for Unicorns. In the Knighted case you will also need to use small Goldgenerals for one kind of piece unpromoted, and subsdtitute large ones for the promoted vbersion, swapping with a neutral reserve rather than either of the players' ones.