export declare class Spring {
    x: number;
    v: number;
    k: number;
    c: number;
    config(k: number, c: number): void;
    /** Starts (or restarts mid-flight) preserving velocity. */
    start(): void;
    /** Advances dt seconds. Returns true on settle (|1−x| < 0.001 ∧ |v| < 0.02). */
    step(dt: number): boolean;
}
/** Spring presets (ζ = c/(2√k)) with the API's public names. */
export declare const SPRING_PRESETS: {
    /** ζ = 1.00 — critically damped, no overshoot. */
    readonly smooth: {
        readonly k: 170;
        readonly c: 26;
    };
    /** ζ = 0.73 — fast, subtle overshoot. */
    readonly snappy: {
        readonly k: 420;
        readonly c: 30;
    };
    /** ζ = 0.40 — playful. */
    readonly bouncy: {
        readonly k: 300;
        readonly c: 14;
    };
};
export type SpringPreset = keyof typeof SPRING_PRESETS;