0 A.D. is a free and open-source real-time strategy video game under development by Wildfire Games. It is a historical war and economy game focusing on the years between 500 BC and 1 BC, with the years between 1 AD and 500 AD planned to be developed in the future. The game is cross-platform, playable on Windows, macOS, Linux, FreeBSD, and OpenBSD. It is composed entirely of free software and free media, using the GNU GPLv2 (or later) license for the game engine source code, and the CC BY-SA license for the game art and music.