I did just remember one detail. It's to do with Cybernetics.

Cybernetics were invented just before the catastrophe and continue to be used in the City. In the Upper city cybernetics are state of the art and streamlined. Some people in the Upper City get Cybernetics to make their lives easier or for their jobs. While in the Undercity Cybernetics are ugly, cobbled together things built by unlicenced black market engineers and people only get them to compensate for injuries, so that they can keep on working.

I also remember the last time I did this roleplay, one player was a complete cyborg. A robotic body with an AI brain, but I'm not sure if I should have that in this one or not.