Gameplay
BioShock Infinite is a first person shooter with role-playing game elements similar to the previous two games. As DeWitt, the player moves about the various structures of Columbia using a grappling hook, a series of railways connecting the buildings called the Skyline, and other transport means to search for Elizabeth. The player will gain weapons which can be used in numerous ways within the environment, including on the Skyline, to defeat enemies. DeWitt gains powers and abilities by using vigors and nostrums that are found through Columbia, the equivalent of BioShock's plasmids and tonics. Vigors grant activated powers such as telekinesis, electricity manipulation, or animal control (as seen by the manipulation of a flock of crows within the gameplay demo), while nostrums are passive abilities that can improve the player's strength or damage resistance. Unlike BioShock in which the player was able to use special Gene Banks to alter the loadout of plasmids and tonics they had, the choice to imbibe a certain vigor or nostrum is permanent and cannot be changed later in the game, placing emphasis on the consequences of the player's choices throughout the game. Infinite does not use EVE, the equivalent of magic points, for powering abilities gained by vigors or nostrums. Each container of vigor has a limited number of charges in it, and while more can be found around the game's environment, the player can only carry a limited number of vigors into battle, with more powerful vigors containing fewer charges. Nostrums are permanent changes to the character and cannot be removed once used. These come in two types, stable and unstable varieties, the latter referred to as "potlucks". Stable nostrums are more expensive, but the player knows exactly what effect applying the nostrum will gain them. Unstable nostrums are cheaper or can be found lying around the environment, but upon use, require the player to select one of four random effects to alter their character, an idea inspired by Heroes of Might and Magic according to Levine.
Once reunited with Elizabeth, who also has a set of such powers, the player must work together with her to escape Columbia. For example, Elizabeth can create a localized rainstorm on foes, which the player, as DeWitt, can then fire upon with an electricity-based attack, electrocuting the foes. The player will not be directly in control of Elizabeth, but instead she will react to the player and the current situation in a manner similar to the AI Director in Left 4 Dead, according to Levine. However, using Elizabeth's powers also harms her, an action compared to the choice of killing or saving the Little Sisters from the previous games.Elizabeth also has the ability to interact with the tears in the fabric of space-time, pulling objects from the other side to use within Columbia, escaping from battle through these, or repairing them. The player will need to protect Elizabeth, but will not need "to babysit and hand-hold" her through the game. Levine has stated that working with Elizabeth in the game is "in no way, shape, or form is this an escort mission", identifying that players reacted negatively to a late-game stage in the original BioShock in which they were tasked to protect a Little Sister.
Several different forces are at work opposed to the player's progress within the city. Furthermore, the player and Elizabeth are chased by both Songbird (sometimes simply referred to as "Him"), who is attempting to snatch Elizabeth from the player, and the Handymen (originally named Alpha), robotic-like monsters housing a human heart and head and with the ability to heal weaker units.
The Skyline is a rail-based system (originally designed for moving cargo around Columbia but later used for personnel transport) similar to the concept found in the Ratchet & Clank games and described by Levine as "a roller coaster, over another roller coaster, over another roller coaster"; players activate a wrist-mounted tool that DeWitt and other enemies wear to jump and hang onto the self-powered tracks. Players can jump onto, off of, and between Skyline tracks at any time, and may face enemies that use the system to attack; the player can use weapons in DeWitt's free hand to defend the character. The freedom of movement along the Skyline allows for several varieties of combat, including flanking, cover, and area-of-effect attacks through creative uses of the system.
Irrational Games has stated that the game's set pieces are not heavily scripted; this statement was made in response to reaction to a gameplay preview video released during the week of September 21, 2010, which, within ten minutes, demonstrated numerous elements of the game. The development team called the game's pacing "like BioShock 1", and that while there will be some scripted set pieces, the developers want the player to be able to explore Columbia at their own pace. Unlike Jack or Delta, the silent protagonists of BioShock and BioShock 2 respectively, and who are guided by radio commands from a third party, DeWitt will be a vocal character, with dialogue designed to aid the player in leading DeWitt to complete his mission.
At the present time, Irrational Games has not committed to including a multiplayer element within the game. While the team will experiment with concepts for a multiplayer component, Levine has stated that they would only proceed forward if it had elements not otherwise found in multiplayer games like Halo or Call of Duty.
During Sony's E3 press conference on Monday, June 06, 2011 creative director Ken Levine announced on-stage that BioShock Infinite will support the PlayStation Move.
