/**
 * QuadTree - Spatial partitioning data structure for Barnes-Hut algorithm
 * Divides 2D space into quadrants for efficient force calculations
 */
export interface QuadTreeNode {
    x: number;
    y: number;
    mass: number;
    centerX: number;
    centerY: number;
}
export declare class QuadTree {
    private boundary;
    private capacity;
    private nodes;
    private divided;
    private northwest?;
    private northeast?;
    private southwest?;
    private southeast?;
    private totalMass;
    private centerOfMassX;
    private centerOfMassY;
    constructor(x: number, y: number, width: number, height: number);
    /**
     * Insert a node into the quadtree
     */
    insert(node: QuadTreeNode): boolean;
    /**
     * Subdivide this quadrant into four children
     */
    private subdivide;
    /**
     * Check if a point is within this quadrant's boundary
     */
    private contains;
    /**
     * Calculate force on a node using Barnes-Hut approximation
     * theta: determines accuracy vs speed tradeoff (typical: 0.5)
     */
    calculateForce(node: QuadTreeNode, theta?: number, repulsionStrength?: number): {
        fx: number;
        fy: number;
    };
    /**
     * Get all nodes in this quadtree (for debugging)
     */
    getAllNodes(): QuadTreeNode[];
    /**
     * Get center of mass (for debugging)
     */
    getCenterOfMass(): {
        x: number;
        y: number;
        mass: number;
    };
}