void CreateDatabase()
 {
     db = CreateInstance <WordDatabase>();
     AssetDatabase.CreateAsset(db, "Assets/" + WordDatabase.db_path);
     AssetDatabase.SaveAssets();
     AssetDatabase.Refresh();
 }
 void LoadDatabase()
 {
     db = AssetDatabase.LoadAssetAtPath <WordDatabase>("Assets/" + WordDatabase.db_path);
     if (db == null)
     {
         CreateDatabase();
     }
 }