---
title: A Unity City Where Bad PLC Code Made Cars Crash
description: A REST-controlled traffic-light sim for a cybersecurity event. Bad PLC code showed up as car crashes, the most honest feedback loop I've shipped.
date: 2026-05-01
projectPeriod: 'July-August 2018'
thumbnail:
  src: ./_assets/city-simulation.jpg
  alt: Screenshot of a Unity traffic simulation.
tags: ['simulation', 'systems']
role: Simulation author
stack: ['Unity', 'C#', 'REST API', 'Blender']
outcome: Visible consequences for an otherwise abstract PLC challenge
audience: technical
links: []
---

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.