A classic and influential first-person shooter science fictionvideo game series developed by Valve Software and first released in 1998, with sequels made from 2004 to 2007.
Famous for being one of few mainstream, western made FPS game series that was popular in Japan. It is notable because it introduced gameplay mechanics and immersive and realistic video game world design that has become the norm for most 3D FPS games up to this day.
