angleTo(target) {
		const a = this.getBounds();
		let ax;
		let ay;

		if (target instanceof Renderable) {
			const b = target.getBounds();
			ax = b.centerX - a.centerX;
			ay = b.centerY - a.centerY;
		} else {
			// vector object
			ax = target.x - a.centerX;
			ay = target.y - a.centerY;
		}

		return Math.atan2(ay, ax);
	}
return the angle to the specified target
@param {Renderable|Vector2d|Vector3d} target
@returns {number} angle in radians