var detector : GroupCollisionDetector = new GroupCollisionDetector( A, B, C, D );
  

  detector.alphaThreshold = 0.5;       // areas with an alpha >= 0.5 will create a collision.
  detector.excludeColor( 0xffff0000 );     // The 32-bit color to exclude from collisions.
  detector.returnAngleType = CollisionAngle.RADIAN;  // would return the collision angle as radian in the Collision instance
  

  private function collisionHandler( e : CollisionEvent ) : void {
    var list = e.collisions; // a TypedArray containing one or more Collision instances.
    for ( var i : int = 0; i < list.length; i++) {
     var collision : Collision = list[i] as Collision;
     trace("Collision detected: " + collision.object1 + " & " + collision.object2 + " (angle: " + collision.angle + ", overlap: " + collision.overlap + ")");
    }
  }
  detector.addEventListener( CollisionEvent.COLLISION, collisionHandler );
  detector.startMonitor();