/**
 * Pure semi-implicit Euler spring stepper used as the single easing
 * source-of-truth for marker motion (stick endpoint + circle↔pill morph).
 *
 * The spring drives a scalar value (typically a `0..1` progress) toward a
 * target. Each `step` call advances the simulation by `dtMs` milliseconds and
 * returns the next state — no React, no DOM, no time source. Callers own time
 * and apply the result however they like (rAF loop, fake timers in tests).
 *
 * Defaults are tuned for a snappy, decelerating attack: fast initial movement
 * with a slight overshoot, settling in ~180–220 ms. Pair with an ease-out
 * curve on CSS-driven companions (see `MARKER_MORPH_EASING`) so the morph
 * reads as one decelerating motion across stick + pill rather than the
 * mushy symmetric ease-in-out it replaced.
 */
export type SpringConfig = Readonly<{
    /** Spring constant (higher = snappier). */
    stiffness: number;
    /** Damping coefficient (higher = less overshoot). */
    damping: number;
    /** Effective mass (higher = more inertia). */
    mass: number;
    /** Velocity below which the spring is considered at rest. */
    restVelocity: number;
    /** Distance to target below which the spring is considered at rest. */
    restDelta: number;
}>;
export type SpringState = Readonly<{
    value: number;
    velocity: number;
}>;
export declare const MARKER_SPRING_CONFIG: SpringConfig;
export declare const createSpringState: (initialValue: number) => SpringState;
export declare const isSpringAtRest: (state: SpringState, target: number, config: SpringConfig) => boolean;
/**
 * Advances the spring by `dtMs`. Long frames are clamped and split into
 * sub-steps to keep the integrator stable when the tab was throttled.
 */
export declare const stepSpring: (state: SpringState, target: number, dtMs: number, config: SpringConfig) => SpringState;
/**
 * Estimated settle time, in milliseconds, used to derive an equivalent CSS
 * transition duration for properties that cannot be ref-driven (e.g. label
 * grid track). Computed by simulating the spring from 0 to 1.
 */
export declare const estimateSpringSettleMs: (config: SpringConfig) => number;