USS Darkstar is a Half-Life mod created by Neil Manke and his team, largely based in Canada. The mod follows Gordon Freeman and several other scientists on board USS Darkstar, a large exploratory starship that resembles the Nostromo from the movie Alien. Very early in the game, a security guard is injured on an away mission to a nearby planet and is taken into the sickbay. USS Darkstar was selected by Valve Software for presentation at the first Half-Life Mod Expo at San Francisco in 1999.