OpenRA is an open source game engine reimplementation and remake of several Command & Conquer games, including Red Alert. It is built using OpenGL and SDL, has support for HiDPI, and is cross platform, supporting Windows, Linux, macOS, and FreeBSD. The engine has support for custom mods via an SDK. The games are remade for modern computers with updated gameplay, new campaigns, user-created and curated maps, and online play. Deviations from the originals included a choice between “right click” and classic “left click” control schemes, an overhauled sidebar interfaces for managing productions, support for game replays and an observer interface designed for video game live streaming. Fog of war that obscures the battlefield outside your units’ line of sight, civilian structures that can be captured to provide benefits and units gain experience as they fight and improve when they earn new ranks. The game supports handicapping players, Discord integration and community ladders. Experimental support for the remastered assets was published in 2023 as a binary compatible yet separate mod.

Coinciding with the release of Command & Conquer Remastered Collection in 2020, Electronic Arts released the original source code for both Tiberian Dawn and Red Alert through GitHub under the GNU General Public License in collaboration between EA and the Command & Conquer community to aid in the development of mods. The source release has also allowed community developers to produce source ports of the original PC version of the game which was released as freeware. This now includes unofficial ports to platforms such as the PlayStation Vita derived from an upstream project called Vanilla-Conquer.

via: https://en.wikipedia.org/wiki/Command_%26_Conquer:_Red_Alert#OpenRA