BioShock Infinite's 1999 Mode isn't a parody of a Prince song, but was inspired by Irrational Games' classic PC title System Shock 2, which was released in -- wait for it -- 1999. After conducting a survey of BioShock-player preferences, Irrational decided 1999 Mode would add a layer of difficulty drawn from the hardcore structure of System Shock 2, particularly its permanent-upgrade mechanics.
For example, if you decide to upgrade a shotgun in BioShock Infinite's 1999 Mode, you're committing to a close-range play style for the rest of the game, Irrational Games Design Director Bill Gardner told Joystiq. "The second you pick up a sniper rifle, because you haven't been specializing in long-range weapons, you're going to be pretty gimped," Gardner said.
1999 Mode won't add any new abilities to enemies, but re-tunes the game with scarce resources, health and accuracy adjustments, and the ability-permanence handicap. Nostrums -- equivalent to gene tonics of previous BioShocks -- will be permanent in the normal game modes and in 1999, but the effect on overall fighting style is what puts the hardcore in 1999.
1999 Mode doesn't follow a separate narrative or setting, Gardner said, although he hinted there may be some surprises still to come. "All I can say right now is that 1999 is the year we released System Shock 2, our first game, so that's at least part of it," Gardner said, laughing