private void Update()
    {
        if (PlayerCount == 1)
        {
            // automatic change when one of the character die.
            if (IsIceCharacter)
            {
                if (IceCharacterObject.GetCurrentHP() <= 0)
                {
                    ChangeCharacter();
                }
            }
            else
            {
                if (FireCharacterObject.GetCurrentHP() <= 0)
                {
                    ChangeCharacter();
                }
            }
            // change the character manually
            if (InputManager.GetButtonDown("Player1ChangeCharacter"))
            {
                ChangeCharacter();
            }
        }

        if (IceCharacterObject == null)
        {
            return;
        }

        if (IceCharacterObject.GetCurrentHP() <= 0)
        {
            IceCharacterObject.gameObject.SetActive(false);
        }

        if (FireCharacterObject.GetCurrentHP() <= 0)
        {
            FireCharacterObject.gameObject.SetActive(false);
            SoundManager.instance.StopSound("Flamethrower");
        }

        if ((IceCharacterObject.GetCurrentHP() <= 0 && FireCharacterObject.GetCurrentHP() <= 0) || stone.GetCurrentHP() <= 0)
        {
            SoundManager.instance.StopAllSound(SoundType.GAME);
            // Game End;
            EndGame(false);
        }
    }
 // Update is called once per frame
 void Update()
 {
     hpSlider.value = stone.GetCurrentHP() / stone.MaxHP;
 }