SanAndreasUnity
About
Grand Theft Auto: San Andreas is a 2004 Rockstar North action-adventure game in which Carl "CJ" Johnson returns to rebuild his declining gang while uncovering the truth behind his mother's murder, across the fictional state of San Andreas. SanAndreasUnity is an open-source reimplementation of the GTA San Andreas game engine built in Unity, focused on gameplay features, multiplayer, and moddability rather than a complete reimplementation; it runs on Windows, Linux, macOS, and Android, and requires the player's own copy of the original GTA San Andreas files to load assets from.
How it differs from the original
Unlike the original singleplayer-only release, this reimplementation supports full multiplayer as a dedicated server, host, or client, runs on additional platforms including Android, and is designed to be extended through C# plugin "game modes."
Getting started
Download a prebuilt Windows or Linux build (Android has its own separate setup) and run it; on first launch it asks for the path to your own GTA San Andreas installation, which is required to play.