diff --git a/DemoPrograms/Demo_PNG_Viewer.py b/DemoPrograms/Demo_PNG_Viewer.py
index 3604ec6e..5edb8ba1 100644
--- a/DemoPrograms/Demo_PNG_Viewer.py
+++ b/DemoPrograms/Demo_PNG_Viewer.py
@@ -3,7 +3,11 @@ import PySimpleGUI as sg
 import os
 
 '''
-    Simple Image Browser based on PySimpleGUI
+    Simple Image Browser 
+    
+    This is an early demo program, so perhaps not quite as sophisticated as later ones.
+    
+    Copyright 2021 PySimpleGUI
 '''
 
 
@@ -16,8 +20,8 @@ def main():
         return
 
     # get list of PNG files in folder
-    png_files = [folder + '\\' + f for f in os.listdir(folder) if '.png' in f]
-    filenames_only = [f for f in os.listdir(folder) if '.png' in f]
+    png_files = [os.path.join(folder, f) for f in os.listdir(folder) if f.lower().endswith('.png')]
+    filenames_only = [f for f in os.listdir(folder) if f.lower().endswith('.png')]
 
     if len(png_files) == 0:
         sg.popup('No PNG images in folder')
@@ -27,39 +31,39 @@ def main():
     menu = [['File', ['Open Folder', 'Exit']], ['Help', ['About', ]]]
 
     # define layout, show and read the window
-    col = [[sg.Text(png_files[0], size=(80, 3), key='filename')],
-           [sg.Image(filename=png_files[0], key='image')],
+    col = [[sg.Text(png_files[0], size=(80, 3), key='-FILENAME-')],
+           [sg.Image(filename=png_files[0], key='-IMAGE-')],
            [sg.Button('Next', size=(8, 2)), sg.Button('Prev', size=(8, 2)),
-               sg.Text('File 1 of {}'.format(len(png_files)), size=(15, 1), key='filenum')]]
+               sg.Text('File 1 of {}'.format(len(png_files)), size=(15, 1), key='-FILENUM-')]]
+
+    col_files = [[sg.Listbox(values=filenames_only, size=(60, 30), key='-LISTBOX-', enable_events=True)],
+                 [sg.Text('Select a file.  Use scrollwheel or arrow keys on keyboard to scroll through files one by one.')]]
 
-    col_files = [[sg.Listbox(values=filenames_only, size=(60, 30), key='listbox')],
-                 [sg.Button('Read')]]
     layout = [[sg.Menu(menu)], [sg.Col(col_files), sg.Col(col)]]
-    window = sg.Window('Image Browser', layout,
-            return_keyboard_events=True,
-            location=(0, 0),
-            use_default_focus=False)
+
+    window = sg.Window('Image Browser', layout, return_keyboard_events=True, use_default_focus=False)
 
     # loop reading the user input and displaying image, filename
-    i = 0
+    filenum, filename = 0, png_files[0]
     while True:
 
         event, values = window.read()
         # --------------------- Button & Keyboard ---------------------
         if event == sg.WIN_CLOSED:
             break
-        elif event in ('Next', 'MouseWheel:Down', 'Down:40', 'Next:34') and i < len(png_files)-1:
-            i += 1
-        elif event in ('Prev', 'MouseWheel:Up', 'Up:38', 'Prior:33') and i > 0:
-            i -= 1
+        elif event in ('Next', 'MouseWheel:Down', 'Down:40', 'Next:34') and filenum < len(png_files)-1:
+            filenum += 1
+            filename = os.path.join(folder, filenames_only[filenum])
+            window['-LISTBOX-'].update(set_to_index=filenum, scroll_to_index=filenum)
+        elif event in ('Prev', 'MouseWheel:Up', 'Up:38', 'Prior:33') and filenum > 0:
+            filenum -= 1
+            filename = os.path.join(folder, filenames_only[filenum])
+            window['-LISTBOX-'].update(set_to_index=filenum, scroll_to_index=filenum)
         elif event == 'Exit':
             break
-
-        if event == 'Read':
-            filename = folder + '/' + values['listbox'][0]
-        else:
-            filename = png_files[i]
-
+        elif event == '-LISTBOX-':
+            filename = os.path.join(folder, values['-LISTBOX-'][0])
+            filenum = png_files.index(filename)
         # ----------------- Menu choices -----------------
         if event == 'Open Folder':
             newfolder = sg.popup_get_folder('New folder', no_window=True)
@@ -67,24 +71,23 @@ def main():
                 continue
 
             folder = newfolder
-            png_files = [folder + '/' +
-                         f for f in os.listdir(folder) if '.png' in f]
-            filenames_only = [f for f in os.listdir(folder) if '.png' in f]
+            png_files = [os.path.join(folder, f) for f in os.listdir(folder) if f.lower().endswith('.png')]
+            filenames_only = [f for f in os.listdir(folder) if f.lower().endswith('.png')]
 
-            window['listbox'].update(values=filenames_only)
+            window['-LISTBOX-'].update(values=filenames_only)
             window.refresh()
 
-            i = 0
+            filenum = 0
         elif event == 'About':
             sg.popup('Demo PNG Viewer Program',
                      'Please give PySimpleGUI a try!')
 
         # update window with new image
-        window['image'].update(filename=filename)
+        window['-IMAGE-'].update(filename=filename)
         # update window with filename
-        window['filename'].update(filename)
+        window['-FILENAME-'].update(filename)
         # update page display
-        window['filenum'].update('File {} of {}'.format(i+1, len(png_files)))
+        window['-FILENUM-'].update('File {} of {}'.format(filenum + 1, len(png_files)))
 
     window.close()