import { Vector2D } from "../geometry";
import { AnyParticle } from "./AnyParticle";
import { SomeParticleForce } from "./SomeParticleForce";
/**
 * Applies a central attractive force pulling the particle toward
 * a fixed center (e.g., like a spring).
 */
export declare class CentralAttractionForce implements SomeParticleForce {
    /**
     * the point particles are attracted to, i.e. The point where the particles
     * will move towards to.
     *
     */
    center: Vector2D;
    /** Attraction constant (e.g., spring stiffness k) */
    strength: number;
    isActive: boolean;
    constructor(center: Vector2D, strength: number, isActive?: boolean);
    /**
     * Applies a force to the particle:
     * `F = -strength * (particle.position - center)`
     *
     * This simulates a harmonic potential pulling particles inward.
     *
     * @param particle The particle to apply the force to.
     */
    apply(particle: AnyParticle): void;
}
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