void Start()
 {
     labyrinth = GameObject.FindGameObjectWithTag("Labyrinth").GetComponent<LabyrinthController>();
     // create droid
     var free = labyrinth.GetRandomFreePosition();
     droid = Instantiate(droidPrefab);
     droid.transform.parent = transform;
     droid.transform.position = new Vector3(free.x + 0.5f, 1, free.z + 0.5f);
     droid.layer = 8; // Player
     droid.GetComponent<DroidSound>().PlayScream();
     // create target
     do
     {
         free = labyrinth.GetRandomFreePosition();
     } while (free == droid.transform.position);
     target = Instantiate(targetPrefab);
     target.transform.parent = transform;
     target.transform.position = new Vector3(free.x, 0f, free.z);
 }