Game-Shogi
==========

Shogi, which is Japanese chess: a nine by nine board, twenty pieces a side, and
a captured piece that changes sides. It goes into its captor's hand and may be
dropped back onto the board as the captor's own, so material is never lost and
a game rarely runs down into an empty endgame.

The rules, the move generator and the search are in C behind a versioned
function table. There is no pure-Perl board.

    use Game::Shogi;
    use Game::Shogi::Bot;

    my $game = Game::Shogi->new;                    # an even game; Black moves first
    my $give = Game::Shogi->new(handicap => 'rook');

    $game->play('7g7f');            # 0, or a Game::Shogi::Error; it never dies
    if (my $no = $game->play('P*5e')) {  # a drop, written as USI
        print $no->message, "\n";        # refused: no pawn in hand yet
    }
    print $_->usi, "\n" for $game->legal;
    my $r = $game->result;          # mate, resign, sennichite, impasse_declared, cap

    my $move = Game::Shogi::Bot->choose($game, $game->turn, seed => 'mine');

Or play it in a terminal:

    shogi                   # the pieces in kanji, Black red and White blue
    shogi --ascii           # SFEN letters, for a terminal with no CJK font
    shogi --handicap rook   # the bot gives a rook
    shogi --usi             # speak USI to a shogi GUI instead


THE RULES THIS DISTRIBUTION CHOSE

Where the sources leave a choice, the choice made here:

- An illegal move is refused, not lost. The board only accepts legal moves.
- Perpetual check loses for the side that checks on the fourth repetition.
  Any other fourfold repetition (sennichite) is a draw, with no replay.
- The impasse is the 27-point declaration: the king in the enemy camp, ten
  other pieces there, not in check, and 28 points for Black or 27 for White,
  counting the pieces in the camp and in hand. A correct declaration wins.
- A game that nobody ends is drawn at 500 moves, the JSA's rule.


INSTALLATION

A C compiler is needed. Then:

    perl Makefile.PL
    make
    make test
    make install

Term::ReadKey is recommended, so the terminal game can take the arrow keys.
Without it a move is typed.


SUPPORT AND DOCUMENTATION

    perldoc Game::Shogi
    perldoc shogi

    https://metacpan.org/release/Game-Shogi


LICENSE AND COPYRIGHT

This software is Copyright (c) 2026 by LNATION <email@lnation.org>.

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)