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.