OpenRA is a project that recreates and modernizes the classic Command & Conquer real time strategy games. We have developed a flexible open source game engine (the OpenRA engine) that provides a common platform for rebuilding and reimagining classic 2D and 2.5D RTS games (the OpenRA mods). This means that OpenRA is not restricted by the technical limitations of the original closed-source games: it includes native support for modern operating systems and screen resolutions (including Windows 10, macOS, and most Linux distros) without relying on emulation or binary hacks, and features integrated online multiplayer.