What the demo shows
A modder called Dryxio has stitched three Grand Theft Auto games into a single running process with working portals between them. San Andreas, Vice City, and GTA III all load at once, share a single Direct3D device, and let players walk through glowing windows from one era of the franchise straight into another.
The footage starts with CJ on Grove Street in San Andreas, opens fire on The Strip from a distance, and then steps through a pink portal to land in Vice City as Tommy Vercetti. After a few minutes of chaos, Tommy walks back through the same portal and returns to Grove Street, then repeats the trick into a third portal anchored in Liberty City.
The most striking moment is when CJ and Tommy stand in different games and shoot into each other's worlds. Bullets, NPCs, and physics appear to cross the portal boundary in real time, with each title's AI, traffic, save system, and missions running untouched in the background.
How it works
Dryxio reverse engineered all three games using the open source reimplementations re3 and reVC, which decompile the original code into readable C++. The proprietary RenderWare engine that powered the originals cannot render multiple spatial scenes at once, so the modder pulled in librw, a community reimplementation of RenderWare, and compiled all three games into one unified process.
Each portal is a live GPU texture, not a video capture. When the player walks through, the engine swaps to the destination game's renderer while the others keep running silently behind it. There is no loading screen, and the games retain their own saves, settings, and mission progress.
What is, and is not, public
The mod is not yet available. GTA modders have a long history of ambitious single-author projects, and this one is already being called the most technically complex in the series, mostly because it requires no special hardware to appreciate the trick. The open question is whether Take-Two Interactive or Rockstar treats the project as a fan tribute or as a copyright problem worth a takedown.
For now, the multiverse lives in a single demo video, and every GTA fan with a desktop PC is waiting to see whether it ever escapes the lab.