TerraGov Marine Corps (TGMC) is an open source multiplayer game built on the BYOND engine, forked from the Space Station 13 (SS13) codebase. It is a tactical, role-playing game that pits groups of human marines against alien forces in large-scale, cooperative and competitive scenarios. The project focuses heavily on teamwork, coordination, and immersive gameplay, providing players with different roles such as engineers, medics, or combat marines to ensure strategic variety. TGMC offers a persistent, evolving experience where community contributions shape mechanics, balance, and lore. The codebase serves as both a live game server foundation and a development platform for contributors who want to expand gameplay features, design new mechanics, or refine existing systems. With its mixture of roleplay, tactical combat, and science fiction setting, TGMC provides a distinctive twist on the SS13 lineage.