sashite-ggn

https://github.com/sashite/ggn.rb

A Ruby implementation of the General Gameplay Notation (GGN) specification. GGN is a rule-agnostic, JSON-based format for describing pseudo-legal board-to-board transformations in abstract strategy board games. This library provides parsing, validation, and evaluation capabilities for GGN documents, focusing exclusively on piece movements, captures, and transformations on the game board. Features flexible validation system for both safety and performance. Supports Chess, Shogi, Xiangqi, and custom variants without hand management or piece drops.