A gameplay modification for GZDoom https://github.com/coelckers/gzdoom
To use: Save the entire project zip (using the green "Clone or download" button on the top of the git project page) into your local folder and run it in GZDoom as you would any wad, pk3, etc. (including dragging the zip onto GZDoom.exe).
Make sure you have keys bound for speed, crouch, reload, zoom, and user1 through 4.
hd_manual.txt contains the full manual. hd.txt contains a draft of the relevant information for any future archival in /idgames.