Half-Life 2 is a science fiction first-person shooter computer game and the sequel to the highly acclaimed Half-Life. It was developed by Valve Corporation and was released on November 16, 2004, following a protracted five-year,  $40 million  development cycle during which the game’s source code was leaked to the Internet. The game uses the Source game engine, which includes a heavily modified version of the Havok physics engine and was also the first video game to require online product activation. Originally available only for Windows-based personal computers, the game has since been ported to the Xbox, and was a part of The Orange Box compilation for Xbox 360  and PlayStation 3 video game consoles.