Prevent a key from turning keyboard backlight back on

I have a 2018 MacBook Pro running 10.15.3, and I'd like to be able to turn the keyboard backlight off (without simply turning it all the way down) when watching a full-screen video, but allow it to return if any key *other than the spacebar* is pressed. The ultimate goal is to make the keyboard backlight less intrusive when watching a video, and allow pausing and un-pausing of a video without activating the keyboard backlight. However, *if a key other than the spacebar is pressed*, this 'mode' would be cancelled, and everything returned to normal, until the user again chooses to (provisionally) deactivate the keyboard backlight. I can't find any ways to do this in the OS or with any third-party software, including Karabiner (which I don't use, but can't find references to backlight) or through any preference or extension to VLC. The "Turn keyboard backlight off after [...] seconds of activity" setting in Keyboard within System Preferences would need to remain unchecked.