About
Return to Castle Wolfenstein is a 2001 first-person shooter developed by Gray Matter Studios and published by Activision, serving as a reboot of the Wolfenstein series; id Software, the original Wolfenstein 3D developer, oversaw its development as executive producer. iortcw is a baseline engine for playing Return to Castle Wolfenstein and its mods, modernizing the original engine with an SDL backend, OpenAL sound, native x86_64 support, Mumble-based VoIP, HTTP/FTP download redirection via cURL, PNG texture support, and many bug fixes, while running on Windows, Linux, and macOS. Development appears to have halted, though the engine remains playable.
How it differs from the original
Playing it still requires owning the original Return to Castle Wolfenstein game data, since specific original files need to be copied from an existing installation into iortcw's folder for single-player and multiplayer to work; iortcw also doesn't include the original map editor and tools, recommending a modern GtkRadiant build instead.
Getting started
After installing the original game, download the matching iortcw release for your OS along with its data patch, then copy the original installation's game files into the new folder before launching either the single-player or multiplayer build — a 64-bit version is provided for supported systems.