Metal Gear Solid 2: Sons of Liberty is the sequel to the espionage action game Metal Gear Solid. Much of the gameplay remains the same, as the game's protagonist has to sneak past guards, outsmart them using various gadgets and defeat the tricky boss enemies. The game expanded its predecessor's cover mechanic, with Solid Snake or Raiden able to take cover behind walls or objects and pop out to shoot at enemies, while the improved enemy AI allowed enemies to also take cover from the player. Metal Gear Solid 2 is considered to be one of the greatest video games of all time, as well as a leading example of artistic expression in video games.