Reminds me of when I was watching William Gibson (Vancouver, early 90s(?)) recite a piece talking about "the glow of light pens [on some device]"... being of a

Reminds me of when I was watching William Gibson (Vancouver, early 90s(?)) recite a piece talking about "the glow of light pens [on some device]"... being of a generation that grew up w/ a Commodore 64, my understanding was that light pens read light (and raster position), they don't emit light. I let Mr. Gibson go on in peace, though...