A true offline installer is a single .exe file (or a split archive like .rar or .7z parts) that contains the entire game data — all campaigns, multiplayer assets, patches, and the engine — in a pre-compiled state. You double-click it, wait for the extraction, and play.
The core of the "patched" label is a modified SC2.exe or a DLL proxy (e.g., version.dll , wow64.dll ) that hooks Windows API calls. The patch does three specific things: starcraft 2 offline installer patched