Half-Life: Dreamcast is a PC port of the unreleased Sega Dreamcast console version of Half-Life.
This review may contain spoilers
Half-Life was released on several platforms during it's life time:It was originally on the PC but later came to Mac and Playstation 2. Also there was an Dreamcast port underway with an early form of Blue shift known as Guard Duty and a "HD Pack"
Sadly, This was not to be and the port later saw interest after being leaked but this mod:Recreating the dreamcast port feels like the actual thing.
The Difference between Valve's hyped HD pack and the Dreamcast Pack was to a whim:Models looked much different then on pc and it also was the basis for the Playstation 2 HD pack.
Some of the maps and levels had been reworked to resemble what they looked like in the Dreamcast version (from either advertisements or screenshots)