private void kill()
 {
     this.gameObject.GetComponent <SpriteRenderer> ().sprite   = sprite_list [10];
     this.gameObject.GetComponent <Rigidbody2D> ().isKinematic = true;
     this.gameObject.GetComponent <BoxCollider2D> ().enabled   = false;
     this.gameObject.transform.rotation = Quaternion.Euler(0, 0, (float)Random.Range(-90, 90));
     this.alive_state = alive_state_enum.dead;
     this.transform.Translate(new Vector3(0, 0, 0.5f));
 }
 private void burn()
 {
     this.dying_time  = Time.time;
     this.alive_state = alive_state_enum.burning;
     this.gameObject.GetComponent <SpriteRenderer> ().sprite = sprite_list [9];
 }