Bioshock is a first-person hybrid (involving elements of a shooter and role-playing) set in an alternate 1960-era where people have become dependent on a substance, called "Adam," that enhances people genetically. The game takes place in an under-water ruined Utopian city called Rapture following a genetic arms race and war. The game begins with the character in the ocean near Rapture after a plane crash. The player will encounter genetically and mechanically modified opponents as he explores Rapture.
The game features "emergent gameplay" that involves "unprecedented" interactivity with many features from the System Shock games. The AI features "AI ecology," meaning it will explore opportunities in the environment and situation to carry out its goals rather than run scripted actions. The player can manipulate this to cause enemies to attack each other or NPCs to help the player. The player can upgrade the character with new abilities and weapons by collecting Adam (the currency in the game). These abilities can be used to manipulate enemies, such as confusing them into thinking you are one of them. The gameplay involves player decision making in moral situations that will impact events in the game.