A pure functional Ruby implementation of the General Gameplay Notation (GGN) specification v1.0.0. Provides a movement possibility oracle for evaluating pseudo-legal moves in abstract strategy board games. Features include hierarchical move navigation (piece → source → destination → transitions), pre-condition evaluation (must/deny). Works with Chess, Shogi, Xiangqi, and custom variants.

LCN (Location Condition Notation) provides a rule-agnostic format for describing location conditions in abstract strategy board games. This gem implements the LCN Specification v1.0.0 with a modern Ruby interface featuring immutable condition objects and functional programming principles. LCN enables standardized representation of environmental constraints on board locations using reserved keywords ("empty", "enemy") and QPI piece identifiers with CELL coordinate system integration. Perfect for movement validation, pre-condition checking, constraint evaluation, and rule-agnostic game logic requiring precise location state requirements across multiple game types and traditions.

Parse and generate Portable Action Notation (PAN) strings for representing atomic actions in abstract strategy board games including chess, shogi, xiangqi, and others. PAN provides an intuitive operator-based syntax with six core operators: "-" (move to empty square), "+" (capture), "~" (special moves with side effects), "*" (drop to board), "." (drop with capture), and "=" (in-place transformation), plus "..." (pass turn). Supports coordinates via CELL specification and piece identifiers via EPIN specification. Handles transformations ("e7-e8=Q"), enhanced/diminished states ("+R", "-P"), and style derivation markers ("K'"). Provides comprehensive validation, immutable action objects, and functional API design. Examples: "e2-e4" (move), "d1+f3" (capture), "e1~g1" (castling), "P*e5" (drop), "e7-e8=Q" (promotion), "..." (pass), "+d4" (static capture), "e4=+P" (modify).

PMN (Portable Move Notation) provides a rule-agnostic, JSON-based format for describing the mechanical decomposition of moves in abstract strategy board games. This gem implements the PMN Specification v1.0.0 with a functional Ruby interface, breaking down complex movements into sequences of atomic actions while remaining completely independent of specific game rules. PMN reveals the underlying mechanics of any board game move through sequential action decomposition, supporting both explicit and inferred piece specifications. Built on CELL (coordinate encoding), HAND (reserve notation), and QPI (piece identification) specifications, it enables universal move representation across chess variants, shōgi, xiangqi, and any abstract strategy game. Perfect for game engines, move validators, and board game analysis tools.

STN (State Transition Notation) provides a rule-agnostic format for describing state transitions in abstract strategy board games. This gem implements the STN Specification v1.0.0 with a modern Ruby interface featuring immutable transition objects and functional programming principles. STN captures net changes between game positions by recording modifications in piece locations, hand/reserve contents, and active player status using standardized CELL coordinates and QPI piece identification. Perfect for game engines, position diff tracking, undo/redo systems, and network synchronization requiring efficient state delta representation across multiple game types and traditions.