I think you got it, it works fine. However the angle returned is always
relative to the world (absolute), but maybe this is what you want? You could
get relative offset angle in 0-360 from the "my" easily just by now subtracting
the my.pan, but I am sure you know this.

Code:

---

 
  vec_diff(temp, you.x, my.x);
  vec_to_angle(angle, temp);
  angle = (angle - my.pan)%360;

---

Josiah, you're absoultely right! but I haven't notice that. Actually,
In my flightsim game, I want to figure out what is the bearing and heading
of the enemy plane relative to the player. With my previous code, if the
enemy is infront of the player (0 degree), then I turn it 180 away from
the enemy and it still read 0 degree not 180. Yeah, this is what I'm
really looking for, thank you very much!

Glad to see you are still working on the flight sim, Last I remember it was
looking really good. Hope you can get a demo out sometime.

Well, I think you mean the F16, it just my first try, not seriously.
Recently, I'm gonna make a playable one, currently writing enemy and
wingman AI. I don't know when will it finish, cos I'm just do it in my
spare time.