title: Rotate an object to face an opposite direction
body: <p>I have an object A and B. When I click on object B, A rotates to object B (A faces B). B doesn't face A. What I need to do is following :
  When A faces B, I need A to face opposite direction. I have code for A rotating to look at B. How to rotate  to face opposite direction after that?</p>
  
  <pre class="lang-cs prettyprint-override"><code>Vector3 targetDirection = target - transform.position;
  float step = speed * Time.deltaTime;
  Vector3 newDirection = Vector3.RotateTowards (turretDome.transform.forward, targetDirection, step, 0.0F);
  turretDome.transform.rotation = Quaternion.LookRotation (newDirection);
  </code></pre>