A Unity City Where Bad PLC Code Made Cars Crash

Most security challenges punish wrong answers with a red “incorrect.” This one punished them with car wrecks, and people learned faster. A PLC cybersecurity event in the summer of 2018 needed something visceral; I built a small Unity city where the traffic lights were driven by a REST API and contestants wrote the control logic.

All decisions ran on the server and got broadcast to clients. The harder problem wasn’t the simulation; it was making the broadcast fault-tolerant on conference Wi-Fi without flooding it. I built it solo, including the models and animations in Blender. Not a flex, just context for why everything’s a little janky.

There was also a HUD overlay for tweets. It felt clever at the time and dated horribly. Skip that part.