Well, this was supposed to be a weekend hack. Only it took a few months. In any case, it’s kind of working now! What is it? It’s a light printer that uses an array of UV LEDs mechanically scanned across phosphorescent paper, leaving a matrix of glowing dots that slowly fade. Hence “ghostmatrix.” I scavenged the linear motor from SRL discard pile, and used an Adafruit Mini POV3 with custom software as the light engine.