Half-Life is a first-person shooter video game developed by Valve and published by Sierra Studios for Microsoft Windows in 1998. It was ported to the PlayStation 2 in 2001, along with another expansion Half-Life: Decay. It was Valve's debut product and the first game in the Half-Life series. Players assume the role of Gordon Freeman, a scientist who must escape the Black Mesa Research Facility after it is invaded by aliens. The core gameplay consists of fighting alien and human enemies with a variety of weapons and solving puzzles.