only interacts with .txt files for simplicity

CARDPUTER CircuitPython/projects/README.md

 A mostly functional, but incredibly basic text editor.
 ### Features
 - Cursor-less text editing (remember how Minecraft book writing used to feel like? Yeah. That.)
-- Save file - You have to type in the filename and extension yourself. The good news is the "." key works on this screen.
+- Save file - You only have to type the filename; the ".txt" extension will be automatically added.
 - Open file - You can select from a list of files in the SD card. Still no line scrolling here, so only the first 7 files will be visible
 - If you open a file, the save menu conveniently fills in the filename for you, so you don't have to write it again to re-save.
 ### Dependencies
 - adafruit_display_text from the bundle
 ### Issues
 - No line scrolling. Once you exceed 7 lines, you're guessing, bud
-- No folder support. Selecting folders in the SD card folder will break it.
+- No folder support. It will only show text (.txt) files in the root /sd folder.
 - There are no confirmation or warning messages. Use with caution and be sure that you aren't using a repeat filename, or it will overwrite the file without warning. 

CARDPUTER CircuitPython/projects/text_editor.py

     index = 0
     for file in os.listdir("/sd"):
         filename = str(file)
-        if index == open_cursor:
-            filename = "> " + filename
-        files_text = files_text + filename+"\n"
-        index += 1
+        if ".txt" in filename:
+            if index == open_cursor:
+                filename = "> " + filename
+            files_text = files_text + filename+"\n"
+            index += 1
     files_group.text = files_text
 
 ## SD Card set up for saving text to SD card
 
         ## The save file menu - for typing the filename
         elif page == "save":
-            if key == "DOWN":
-                filename_text = filename_text + "."
-                filename_group.text = filename_text
-            elif key == "\n":
-                with open("/sd/"+filename_text, "w") as f:
+            if key == "\n":
+                with open("/sd/"+filename_text+".txt", "w") as f:
                     f.write(text)
                     f.close()
                 board.DISPLAY.root_group = intro_text_area
                 for line in lines:
                     text = text + line
                 text_area.text = text
-                filename_text = fn
+                filename_text = fn.split(".txt")[0]
                 filename_group.text=filename_text
                 page = "editor"
                 board.DISPLAY.root_group = intro_text_area