The fourth game in the Grand Theft Auto series, released in 2008. Known for its physics engine, Euphoria (that being protagonist Niko Bellic flying through the windshield of a car or a swing set flinging cars in high speeds towards the sky). Would see two expansions released for it, The Lost and Damned and The Ballad of Gay Tony, following two different sets of protagonists, which would later be sold together as Episodes from Liberty City.
It also marks the debut of the HD Universe, a separate timeline from its predecessors being the 3D Universe. The game is set in Liberty City but most of its islands, streets and areas names are changed along with a few map layout changes.
Niko Bellic moved in Liberty City to start a new life from his past war and experience the American Dream along with his cousin, Roman Bellic. Along his journey to get to the dream, he has made friends and enemies alike.
Grand Theft Auto IV is regarded as the darkest installment due to it's cynicism and critical views of America along with endings in a bittersweet or tragic end for Niko Bellic.