/**
 * spring.ts - rAF-based damped harmonic oscillator
 *
 * Drop-in replacement for svelte/motion Spring in framework-agnostic code.
 * Same physics: stiffness controls return force, damping controls friction.
 * Snaps to target when velocity is negligible.
 */
export interface SpringOptions {
    /** Spring stiffness (default 300). Higher = snappier. */
    stiffness?: number;
    /** Damping coefficient (default 15). Higher = less bounce. */
    damping?: number;
}
export interface Spring {
    /** Current interpolated value. */
    readonly current: number;
    /** Set to animate toward a new value. */
    target: number;
    /** Register a callback fired every animation frame. */
    onUpdate(fn: (value: number) => void): void;
    /** Stop animation and remove listeners. */
    destroy(): void;
}
export declare function createSpring(initial: number, opts?: SpringOptions): Spring;
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