2D positional attenuation: turns a listener facing plus listener/source positions into a Voice (Volume and Pan set, Pitch 1). This is the portable alternative to the MonoGame-only 3D audio surface — raylib has no listener model, so the Core contract only promises flat 2D attenuation.

Linear fade interpolation shared by both backend services — the single definition of how a volume moves from a start value to a target over a duration, so raylib and MonoGame fades behave identically.

The backend-neutral audio service. Every windowed host registers one under this interface before user init runs; resolve it with GameContext.getService<IAudio> ctx (the MVU Cmd helpers and the adaptive intent helpers do this for you and no-op when it is absent).

Constructors for Voice values.

Per-play knobs for a sound effect: volume, pan, and pitch.