The git repo feels like German bureaucracy, one needs to dig around to find the info.... https://github.com/entropia/tip-toi-reveng/wiki/PEN-Optical-ID-and-cod

The git repo feels like German bureaucracy, one needs to dig around to find the info.... https://github.com/entropia/tip-toi-reveng/wiki/PEN-Optical-ID-and-codes https://github.com/entropia/tip-toi-reveng/wiki/PEN-Optical-... TL; DR: the tip of a pen has a sensor, the books have dot patterns overlaid on top of image areas, the patterns are decipherable into (hexa-)decimal code, and with a script file the codes do different actions (set a variable, play an audio file).