There are a couple of factors coming together here that require some explanation in order for the individual parts to make sense. Everything he writes appears

There are a couple of factors coming together here that require some explanation in order for the individual parts to make sense. Everything he writes appears backwards because he's facing us as he writes. Hence, someone standing in the room would see everything in reverse. This isn't a problem because he uses flip teaching, where students view a video of the lecture at home. This only becomes clear if you read the details. The camera he uses to record his lecture does so through a mirror, so the image is reversed by the mirror, not by software. Also, overlays need not be reversed, because they aren't projected anywhere. They're composited in to the video stream by a switcher. All of this becomes clear if you read the creator's write up on how to build one. I'd highly recommend it: https://sites.google.com/site/northwesternlightboard/home https://sites.google.com/site/northwesternlightboard/home