declare class Point { x: number; y: number; timeStamp: number; constructor(x: number, y: number); } export declare class VelocityTracker { pointsLen: number; points: Point[]; constructor(len?: number); clear(): void; addMovement({ x, y }: { x: number; y: number; }): void; getYAcceleration(lastPointCount?: number): number; } export {};