As far as design requirements go, the primary input is Google Maps data, specifically the Google Maps Timeline and the estimated/accurate paths it maps. I would liken the experience inside to watching window-washers at work while inside a building, however these are leaving a mess on those windows instead of cleaning them, but the experience is still similar. While I can't speak for everyone, I enjoy those experiences. It becomes all the more relevant if the maps on both bridges aren't necessarily oriented the same way or show the same scale, improving the likelihood that the robot will be seen from a given floor on the bridge. If the audience chooses, they can engage with the robots, changing the color of the line drawn, and that would be a more detailed experience on the inside of the bridge, as from there you could actually see the marker quickly retract and redeploy, and some of the other inner working pressed against the glass. If someone wouldn't want to interact with it, they don't have to, they can just keep walking. However, it might also be interesting to take a few minutes to mess with the colors or even just watch the robots at work, like fish in an aquarium. At the end of the day, the bridge will have a mural of movement on each side, visible as colorful noise and lines from those below, and as crisper, colorful linework inside.