Half-Life - often abbreviated as HL or HL1 - is a sci-fi first-person shooter computer game developed by Valve Software, first released by Sierra Studios on November 19, 1998. Designed for PCs running Microsoft Windows,[1] the game uses a heavily modified version of the Quake engine, called GoldSrc.[3] In Half-Life, players assume the role of Dr. Gordon Freeman, a recently graduated theoretical physicist who must fight his way out of an underground research facility whose teleportation experimentations have gone terribly wrong. On its release, critics hailed its overall presentation and numerous scripted sequences,[4] and it won over 50 Game of the Year awards in 1998-99.[5] Its gameplay influenced first-person shooters for years to come, and has since been regarded as one of the greatest games of all time.[6] With over eight million copies sold since, Half-Life is the best-selling PC first-person shooter to date.[7] The Half-Life franchise has seen over 15 million sales.[8] The game was also released for the PlayStation 2 on November 15, 2001.[2] A Sega Dreamcast port was made, but was cancelled just 2 weeks before release. The fully-playable Dreamcast version has since been leaked onto the Internet.[9] The titles of Half-Life and its expansion packs are all named after scientific terms. Half-Life itself is a reference to the half-life of a quantity (such as a radioactive material), the amount of time required for the quantity to decay to half of its initial value. The Greek letter lambda, which features prominently on the game\\\'s packaging, represents the related decay constant, as well as the Lambda Complex featured in the game. Opposing Force, while it could be named because the player assumes the role of one of the enemies in the original game, is also a reference to Newton\\\'s third law of motion, while Blue Shift refers to the blue shifting of the frequency of radiation caused by the Doppler effect, in a similar parallel reference to the blue color of the security uniforms