@bendonahue It looks like he’s using the MMM-OnScreenMenu module. I don’t know how he’s using it, but he’s probably hiding/showing Home Assistant as some sort of embedded module or webpage.
Possibly his Home Assistant page is inside an iFrame using the MMM-iFrame module and he’s using a toggle to show/hide the iFrame (as per the show/hide clock example in the MMM-OnScreenMenu module). This might explain the white ‘border’ that appears on the right & bottom of his HA controls page.
There will be some HA dashboard cards don’t like being inside an iFrame so may not work correctly.