Titles in the GTA series have traditionally been heavily mission based (fixed missions must be completed to progress through each game), but the freedom to explore and play outside of the set missions in GTA IV will now be more relevant to progress through the game, according to comments by a Rockstar spokesperson: "We're really trying to blur the line between on-[mission] and off-mission. So storyline, and what you do outside [it], and how those two things influence each other."