Valve was disappointed with the lack of innovation in the FPS genre, and aimed to create an immersive world rather than a "shooting gallery". Unlike other games at the time, the player has almost uninterrupted control of the player character; the story is mostly experienced through scripted sequences rather than cutscenes. Valve developed the game using GoldSrc, a heavily-modified version of the Quake engine, licensed from id Software. The science fiction novelist Marc Laidlaw was hired to craft the plot and assist with design.