Simple question - how can I hide the main gui

In my use-case, I have an autoexec.py script that immediately starts a movie when kodi starts - and closes kodi as soon as the movie is stopped.
The only problem is that before the video starts and after the video ends - you can see kodi's main interface. I want to keep that hidden this entire user session.
I thought maybe there was a window that was all black that I could activate - or use a script to set the screensaver to blank and activate it - but so far the interface is still visible. 
To be clear - I still want the user able to interact with the video during playback - pause and stop and all the other features of kodi. It's only when the video is not playing that I want the interface to be hidden.

Open to any and all ideas and suggestions! Thanks!