Detecting edge of screen, and then turning around.

I am simply testing the water here, as have always used Clamp to maintain enemies, and players to window. However, with the window size being able to change, I'd need a more fluid system.

Ideally, what I'd want to do is attach this script to an enemy, whom would walk off, and when hitting the screen edge, turn around.

Here's what I thought would work...

 function Update () {    
 
     transform.Translate(0, Time.deltaTime*2, 0);    
 
     var pos : Vector3 = camera.WorldToScreenPoint (transform.position);
     
     if(pos.x < 0.0){
     transform.eulerAngles = Vector3(0,180,0);
     }
     
     if(1.0 < pos.x){
        transform.eulerAngles = Vector3(0,180,0);
     }
     
     if(pos.y < 0.0){ 
      transform.eulerAngles = Vector3(0,180,0);
     }
     
     if(1.0 < pos.y){
      transform.eulerAngles = Vector3(0,180,0);
     }
     
 }

Any ideas are welcome.

Thank you