Python GUI guizero: ListBox and Picture

# This Python code is a demo of the GUI guizero (with PushButton trigger)
# guizero works with tkinter but simpler with extra widgets eg. Slider
# https://lawsie.github.io/guizero/slider/
# guizero - Hero name generator
from guizero import App, Text, CheckBox, Combo, PushButton, TextBox, ListBox, Picture
app = App(title="Hero-o-matic", width=500, height=600)

# Function definitions for your events go here.
def make_hero_name(): # triggered by PushButton :'Make me a hero'
    adjective = bgp_adjective.value
    colour = txt_colour.value
    animal = cmb_animal.value
    title = listbox.value
    if (title == ""):
        title = "The"

    # is Super selected ?
    if (cbSuper.value <= 0): # not checked
        honour = ""
    else:
        honour = "Super "

    hero = title + " " + honour + adjective + " " + colour + " " + animal
    lbl_output.value = "You are... " + hero + "."

def set_dark_mode(): # if CheckBox selected, use white on black styling otherwise use colour !
    # is Dark selected ?
    if (cbDark.value <= 0): # not checked .. apply chosen colour styling
        # App ..
        app.bg = "#DDDD33"
        app.text_color = "#000000"

        h1.text_color="#CC3333" # main Heading

        # Make me a hero: PushButton
        btn_make_name.bg = "#CC3333"
        btn_make_name.text_color = "#FFFFFF"
    else: # Dark mode request
        app.bg = "#000000"
        app.text_color = "#FFFFFF"

# -- GUI widgets .. starting with a main heading Picture & Text ------------------------
picture = Picture(app, image="images/header_img001.png")
h1 = Text(app, text="Hero-o-matic name builder", size=26, font="Times New Roman")

cbDark  = CheckBox(app, text="DARK mode", command= set_dark_mode )
cbSuper = CheckBox(app, text="Super")
messageListBox = Text(app, text="Choose a title ..")
listbox = ListBox( app, height= 70, width= 120,items=["","Ms.","Miss","Mrs.","Mr.","Lord","Lady","Right Honourable"], scrollbar= True, selected= "")

message1 = Text(app, text="Choose an adjective")
bgp_adjective = Combo(app, options=["Amazing", "Bonny", "Charming", "Delightful", "Vundebar"], selected="Amazing", width=20)

message2 = Text(app, text="Enter a colour?")
txt_colour = TextBox(app)

message3 = Text(app, text="Pick an animal")
cmb_animal = Combo(app, options=["Aardvark", "Badger", "Cat", "Dog", "Dolphin", "Velociraptor"], selected="Aardvark", width=20)

btn_make_name = PushButton(app, text='Make me a hero', command= make_hero_name ) # event handler linked here
lbl_output = Text(app, text="A hero name will appear here")

# -- Set STYLING & other properties -------------------------------------------
# Sizes ..
btn_make_name.text_size = 16  # Make me a hero: PushButton

set_dark_mode() # initial colour styling

app.display()   # Show the GUI on the screen, start listening to events.