Zero Tolerance is a first-person shooter developed by Technopop, the first independent studio to develop for the Sega Genesis, and published by Accolade exclusively for the console in 1994. It runs on a pseudo-3D, sprite-scaling ray-casting engine built entirely on stock Genesis hardware, letting players control Captain S. Ishii or fellow soldier Cyber-Cop, two of the earliest playable female and robotic protagonists in the FPS genre, as they fight off an alien invasion aboard a space station. Zero Tolerance also stood out for supporting two-player split-screen co-op through its full campaign via a system link cable, an unusually ambitious feature for the console at the time. It went on to sell more than 215,000 copies in the United States alone, making it a genuine commercial success and, for years, the only worldwide-released first-person shooter on the Genesis.