private void upgradeShipyard()
    {
        App    app    = UnityEngine.Object.FindObjectOfType <App>();
        Nation player = State.getNations()[app.GetHumanIndex()];

        PlayerPayer.payShipyYardUpgrade(player);

        AP.text = player.getAP().ToString();
        TextMeshPro _shipyardLevel = shipyardLevelText.GetComponent <TextMeshPro>();

        _shipyardLevel.SetText("Shipyard Level: " + player.GetShipyardLevel().ToString());
        upgradeShipyardButton.interactable = false;
    }