> And it unlocked wondrous hacks, like using the IrDA transceiver on the RCX as a psuedo-lidar so that your robot could stop short of walls, it could even estimate distance.

Ha, I did that as well with Mindstorms RCX in like 11th grade or so! Later, in university, Mindstorms NXT was used: Our first assignment was to follow a track on the ground and the team I was the only one had two programs, one for recording the track with the sensors and another for following the previously recorded track in high speed without using sensors at all.