// Start is called before the first frame update
 void Start()
 {
     // set game object references
     highlightFrame = transform.Find("HighlightFrame").gameObject;
     shadowOverlay  = transform.Find("ShadowOverlay").gameObject;
     waterOverlay   = transform.Find("WaterOverlay").gameObject;
     heatOverlay    = transform.Find("HeatOverlay").gameObject;
     // set script references
     eSpriteList = EnvironmentSpriteList.instance;
     goRegistry  = GameObjectRegistry.instance;
 }
 /// <summary>
 /// Awake is called when the script instance is being loaded.
 /// </summary>
 void Awake()
 {
     // singleton pattern
     if (instance == null)
     {
         instance = this;
         // DontDestroyOnLoad(gameObject);
     }
     else
     {
         Destroy(gameObject);
     }
     Init();
 }