Alex shared Factorio.v1.1.73.zip with Sam. Because it was a portable zip version, Sam didn't have to uninstall their current game. They simply: the zip to a new folder. Isolated the mods folder specifically for that version. Launched the .exe directly from the bin folder.
: Alex’s favorite "Industrial Revolution" mega-base was built on v1.1.73. Updating meant the save file would break, turning a 500-hour masterpiece into a graveyard of "Missing Entity" errors. Factorio.v1.1.73.zip
: Always keep a "frozen" copy of a working environment before a major update. Alex shared Factorio