def open_config_window(self):
        config_window = Toplevel(self)
        config_window.iconbitmap(r'data\app.ico')
        config_window.minsize(500, 350)

        config_frame = Labelframe(config_window)
        config_frame.config(text="App Configuration",
                            relief='groove',
                            borderwidth=5)
        config_frame.pack(expand=1, fill='both', padx=5, pady=5)

        offset_title = Label(config_frame)
        offset_title.config(text='Numbering offset (Default 0)')
        offset_title.pack(anchor='nw', padx=5, pady=5)

        offset_entry = Entry(config_frame)
        offset_entry.config(
            width=10,
            exportselection=0,
            validate='key',
            validatecommand=(offset_entry.register(validate_config_entry),
                             '%P'))
        offset_entry.pack(anchor='nw', padx=5, pady=5)

        battle_value_frame = Labelframe(config_frame)
        battle_value_frame.config(text='Battle weighting',
                                  relief='groove',
                                  borderwidth=5)
        battle_value_frame.pack(anchor='nw',
                                fill='both',
                                expand=1,
                                padx=5,
                                pady=5)

        descriptor_frame = Frame(battle_value_frame)
        descriptor_frame.pack(side='left', fill='both', expand=1)

        entry_frame = Frame(battle_value_frame)
        entry_frame.pack(side='left', fill='both', expand=1)

        skirmish_title = Label(descriptor_frame)
        skirmish_title.config(text='Skirmish weighting (Default = 1):')
        skirmish_title.pack(anchor='nw', padx=5, pady=7)

        skirmish_entry = Entry(entry_frame)
        skirmish_entry.config(
            width=10,
            exportselection=0,
            validate='key',
            validatecommand=(skirmish_entry.register(validate_config_entry),
                             '%P'))
        skirmish_entry.pack(anchor='nw', padx=5, pady=5)

        advance_title = Label(descriptor_frame)
        advance_title.config(text='Advance weighting (Default = 1):')
        advance_title.pack(anchor='nw', padx=5, pady=10)

        advance_entry = Entry(entry_frame)
        advance_entry.config(
            width=10,
            exportselection=0,
            validate='key',
            validatecommand=(advance_entry.register(validate_config_entry),
                             '%P'))
        advance_entry.pack(anchor='nw', padx=5, pady=5)

        clan_war_title = Label(descriptor_frame)
        clan_war_title.config(text='Clan War weighting (Default = 3):')
        clan_war_title.pack(anchor='nw', padx=5, pady=6)

        clan_war_entry = Entry(entry_frame)
        clan_war_entry.config(
            width=10,
            exportselection=0,
            validate='key',
            validatecommand=(clan_war_entry.register(validate_config_entry),
                             '%P'))
        clan_war_entry.pack(anchor='nw', padx=5, pady=5)

        buttons_frame = Frame(config_frame)
        buttons_frame.pack(anchor='sw', fill='both', expand=0)

        apply_button = Button(buttons_frame)
        apply_button.config(text='Apply',
                            command=partial(self.config_apply, offset_entry,
                                            skirmish_entry, advance_entry,
                                            clan_war_entry))
        apply_button.pack(side='right', padx=5, pady=5)

        cancel_button = Button(buttons_frame)
        cancel_button.config(text='Cancel',
                             command=lambda: config_window.destroy())
        cancel_button.pack(side='right', padx=5, pady=5)

        ok_button = Button(buttons_frame)
        ok_button.config(text='OK',
                         style='OK.TButton',
                         command=partial(self.config_ok, offset_entry,
                                         skirmish_entry, advance_entry,
                                         clan_war_entry, config_window))
        ok_button.pack(side='right', padx=5, pady=5)

        offset_entry.insert('end', self.offset)
        skirmish_entry.insert('end', self.skirmish_value)
        advance_entry.insert('end', self.advance_value)
        clan_war_entry.insert('end', self.clan_war_value)