Team Fortress Classic
The "Half-Life" software development kit served as the development base for many multiplayer mods, including the Valve-developed "Team Fortress Classic" and "Deathmatch Classic" (a remake of "Quake"s multiplayer deathmatch mode in the GoldSrc engine). Other mods such as "Counter-Strike" and "Day of Defeat" ("DOD") began life as the work of independent developers (self-termed "modders") who later received aid from Valve. Other multiplayer mods include "Action Half-Life", "Firearms", "Science and Industry", "The Specialists", "Pirates, Vikings and Knights", "Natural Selection" and "Sven Co-op".