User:OneWeirdDude/Nana shogi

Nana shogi (possibly "nano shogi", ナノ将棋 nano shōgi, dwarf-sized chess, since Japanese "nana" means "seven") is a modern variant of shogi (Japanese chess); however, it is not Japanese. It was invented in 1998–2001 by Georg Dunkel of Finland—who calls it the "World's Smallest Shogi Variant"—and it incorporates elements of Unashogi by starting with an empty board. A smaller variant, Gufuu Shogi (2×3), is also introduced by Georg Dunkel, but it incorporates rules considerably different from traditional shogi variants, particularly the concept of shared pieces and unusual rules for giving check and checkmate.

Objective
The objective of the game is to capture your opponent's king.

Game equipment
Two players, Black and White (or 先手 sente and 後手 gote), play on a board ruled into a grid of 3 ranks (rows) by 3 files (columns). The squares are undifferentiated by markings or color.

Each player has a set of 3 cube-shaped pieces, of generally the same size. They are:


 * 1 king
 * 1 orthogonal piece:
 * rook (hisha)
 * chariot (hensha)
 * swallow's wing (enu)
 * go-between (chuunin)
 * 1 diagonal piece:
 * bishop (kakugyou)
 * tile general (gashou)
 * cat's sword (myoujin)
 * dog (inu)

Some of the English names were chosen to correspond to rough equivalents in Western chess, rather than as translations of the Japanese names.

Each piece has the names of each of its states in the form of one kanji written on its faces, one state per face, so that a piece's next state is obtained by rolling it forward. The pieces of the two sides do not differ in color, but instead the top of each piece faces in the same direction as the owning player's king, and in the opposite direction to his opponent's king. This shows who controls the piece during play.

Table of pieces
Listed here are the pieces of the game with their Japanese representation:

Setup
The board, 3×3, starts out empty. The kings are dropped first, anywhere but the center of the board.

Gameplay
The players alternate making a move, with Black moving first. (The traditional terms 'black' and 'white' are used to differentiate the sides during discussion of the game, but are not literally descriptive.) A move consists of moving a single piece on the board and promoting that piece whenever applicable, displacing (capturing) an opposing piece or dropping a captured piece onto an empty square of the board. Each of these options is detailed below.

Movement and capture
An opposing piece is captured by displacement: That is, if a piece moves to a square occupied by an opposing piece, the opposing piece is displaced and removed from the board. A piece cannot move to a square occupied by a friendly piece (meaning another piece controlled by the moving player).

Each piece on the game moves in a characteristic pattern. Pieces move either orthogonally (that is, forward, backward, left, or right, in the direction of one of the arms of a plus sign, +), or diagonally (in the direction of one of the arms of a multiplication sign, ×).

Many pieces are capable of several kinds of movement, with the type of movement most often depending on the direction in which they move. The movement categories are:

Step movers
Most pieces move only one square at a time. (If a friendly piece occupies an adjacent square, the moving piece may not move in that direction; if an opposing piece is there, it may be displaced and captured.)

The step movers are the rook, swallow's wings, go-between, tile general, cat's sword, and dog.

Ranging pieces
The bishop and [reverse] chariot can move any number of empty squares along a straight line, limited only by the edge of the board. If an opposing piece intervenes, it may be captured by moving to that square and removing it from the board. A ranging piece must stop where it captures, and cannot bypass a piece that is in its way. If a friendly piece intervenes, the moving piece is limited to a distance that stops short of the intervening piece; if the friendly piece is adjacent, it cannot move in that direction at all.

Promotion
There is no promotion zone in Nana shogi. Every time a piece (other than a king) makes a move it changes its state in a specific manner. Promotion is effected by rolling the cube forward over after it moves, revealing the name of its new rank.

The promotion rules are reminiscent of Kyoto shogi and entirely different from standard shogi:


 * A king (K) cannot promote: 王, 玉
 * The orthogonal cube goes from rook (R) to chariot (C), to swallow's wings (SW), to go-between (GB), and back: 飛 → 反 → 羽 → 仲 → 飛 → ...
 * The diagonal cube goes from bishop (B) to tile general (TG), to cat sword (CS), to dog (D), and back: 角 → 瓦 → 猫 → 犬 → 角 → ...

Individual pieces
Below are diagrams indicating each piece's movement. Except for the kings, pieces are placed above what state they change to, with the one on the bottom changing to the one on the top. Betza's funny notation has been included in brackets for easier reference.

Drops
Like with other shogi variants, captured pieces are truly captured in nana shogi. They are retained "in hand", and can be brought back into play under the capturing player's control. On any turn, instead of moving a piece across the board, a player can take a piece he has previously captured and place it on any empty square, facing the opponent. The piece is now part of the forces controlled by that player. This is termed dropping the piece, or just a drop.

A drop cannot capture a piece; that requires an additional move.

A piece cannot be dropped in the middle square, 2b—nor can a piece be dropped to give check or checkmate.

Check and mate
When a player makes a move such that the opponent's general could be captured on the following move, the move is said to give check to the general; the general is said to be in check. If a player's general is in check and no legal move by that player will get the general out of check, the checking move is also a mate, and effectively wins the game.

Immediate mate may not be achieved by the drop of any piece, nor is mate permitted on any move, capturing or not, that begins with the mating player having one or more pieces in hand.

Game end
A player who captures the opponent's king wins the game. In practice this rarely happens, as a player will resign when checkmated or stalemated, as otherwise when loss is inevitable.

A player who makes an illegal move loses immediately. (This rule may be relaxed in casual games.)

Due to the small size of the board, stalemate is a lot more common than in other variants with drops, and counts as a win for the player who performed the stalemate, since his opponent has nowhere to move but into check.

Another possible (but fairly uncommon) way for a game to end is repetition (千日手 sennichite). If the same position occurs four times with the same player to play, then the game is no contest. For two positions to be considered the same, the pieces in hand must be the same, as well as the position on the board.

Variations
In the first variant of nana shogi developed by Dunkel, the rook had unlimited range and the swallow's wing moved as it does in wa shogi. However, Dunkel believed this to be much too powerful, and gave black a big advantage as he is first to drop this piece.

Game notation
The method used in English-language texts to express shogi moves was established by George Hodges in 1976. It is derived from the algebraic notation used for chess, but differs in several respects. It has been modified for use in nana shogi.

A typical example is B-2b=TG. The first letter(s) represents the piece moved: R = rook, C = reverse chariot, SW = swallow's wings, GB = go-between, B = bishop, TG = tile general, CS = cat's sword, D = dog. The designation of the piece is followed by a symbol indicating the type of move: - for an ordinary move, x for a capture, or * for a drop. Next is the designation for the square on which the piece lands. This consists of a number representing the file and a lowercase letter representing the rank, with 1a being the top right corner (as seen from Black's point of view) and 3c being the bottom left corner. (This method of designating squares is based on Japanese convention, which, however, uses Japanese numerals instead of letters. For example, the square 2c is denoted by 2三 in Japanese.)

If a piece other than a king moves, it changes state, and an = is added to the end, followed by the name of the new state, to signify that the state was changed. In the above example, the bishop moved to 2b and changed to a tile general.

In cases where the above notation would be ambiguous, the designation of the start square is added after the designation for the piece in order to make clear which piece is meant. For example, if there are two cat swords that can move to 2a, one at 1b and one at 3b, these are distinguished as CS1b-2a=D and CS3b-2a=D.

Moves are commonly numbered as in chess.