On November 16, 2004, Valve released "Half-Life 2". The game had a six-year development cycle, which saw several delays and the leak of the game's source code. "Half-Life 2" returns the player to the role of Gordon Freeman. Set twenty years after the original game, Earth has been occupied by the Combine, a transdimensional race that exploited the events of the first game to invade. The G-Man inserts Freeman into City 17 in Eastern Europe to combat the Combine occupation. "Half-Life 2" garnered near-unanimous positive reviews and received critical acclaim much like its predecessor, winning over 35 Game of the Year awards for 2004. Considered one of the greatest video games of all time, the game has been critically praised for its advances in computer animation, sound, narration, computer graphics, artificial intelligence, and physics. "Half-Life 2" was the first game to use Valve's Steam content delivery system, a system that eventually led to Valve falling out with publisher Sierra Entertainment.