Shogi

https://en.wikipedia.org/wiki/Shogi

Unmet requirements:
* #40 - specifically, promoted pieces, e.g. +P is a promoted pawn, +N is a promoted knight, although both these pieces are gold generals in practice.
* Complex drop rules:
* P, L, N can't be dropped on last rank. N can't be dropped on second last. The reasoning is "you can't drop pieces in places where they would have no legal moves" - so maybe that could be defined (though it would be less efficient unless compiled).
* _A pawn may not be dropped onto a file containing another unpromoted pawn of the same player (promoted pawns do not count)._ (ugh)
* _A pawn may not be dropped to give an immediate checkmate. (This rule only applies specifically to pawns, drops and checkmates − to clarify, a player may deliver an immediate checkmate by dropping a non-pawn piece, a player may checkmate a king with a pawn that is already on the board, and a pawn may be dropped to give an immediate check as long as it does not also result in checkmate.)_ - this might have to be left out until attacks/checks are refactored, otherwise it's going to be pretty slow. If that's going to take a long time we **could** build a specific action for Shogi
* Impasse rule - when both kings enter their respective promotion zones, the game ends with a piece count (usually a draw, but could be a win).
* Perpetual checks (4 is a loss).