The Lost Coast level was initially created for Half-Life 2, but was ultimately removed from the game. Lost Coast follows Half-Life protagonist Gordon Freeman as he travels up a coastal cliff to destroy a Combine headcrab artillery launcher in a monastery, which is firing on a nearby town, Saint Olga. Lost Coast was the first video game developed by Valve to allow developers to explain various elements of design as the player progresses through the level. The level was designed with a variety of appropriate environments to emphasize these effects. Lost Coast serves as a technology demonstration, specifically showcasing the high-dynamic-range rendering implemented in the Source engine.
Developed by Valve, it was released on October 27, 2005, through the Steam content delivery service as a free download to owners of the Windows version of Half-Life 2. Half-Life 2: Lost Coast is an additional level for the 2004 first-person shooter video game Half-Life 2.