(defun approach-angle (x y)
    "calculates angle ship should reach to enter orbiting circle around fortress using worldsurf coordinates"
    (let ((distance (sqrt (+ (expt (- x 355) 2) (expt (- y 313) 2))))
          (angle-to-tan (asin (/ 140 (sqrt (+ (expt (- x 355) 2) (expt (- y 313) 2))))))
          (angle-from-x (atan (- 313 y) (- 355 x))))
        (if (< distance 140)
            (- 120 (* angle-from-x 57.2957795))
            (* 57.2957795 (- angle-to-tan angle-from-x)))))