public void set_ki_inactive()
 {
     for (int i = 0; i < pool.Count; i++)
     {
         if (pool[i].activeInHierarchy)
         {
             enemy_behavior e = pool[i].GetComponent <enemy_behavior>();
             e.ani.Play("ki_peace");
             StartCoroutine(e.die());
         }
     }
 }
    // TODO: provide direction of instantiated object
    void spawn_ki()
    {
        for (int i = 0; i < pool.Count; i++)
        {
            if (!pool[i].activeInHierarchy)
            {
                pool[i].SetActive(true);
                enemy_behavior e = pool[i].GetComponent <enemy_behavior>();


                int dir_multiplyer = dirs[Random.Range(0, 2)];
                e.transform.position = get_spawn_point_ki(dir_multiplyer);
                e.speed = speeds[wave];
                e.dir   = Vector3.right * -dir_multiplyer;
                break;
            }
        }
    }