PNN (Piece Name Notation) provides a rule-agnostic, scalable naming system for identifying abstract strategy board game pieces. This gem implements the PNN Specification v1.0.0 with a modern Ruby interface featuring immutable piece name objects and functional programming principles. PNN uses canonical ASCII names with optional state modifiers and optional terminal markers (e.g., "KING", "queen", "+ROOK", "-pawn", "KING^", "+GENERAL^") to unambiguously refer to game pieces across variants and traditions. Ideal for engines, protocols, and tools that need clear and extensible piece identifiers.