This level of freedom requires that levels, characters, and puzzles be designed with significant redundancy, as a single play-through of the game will miss large sections of dialogue, areas, and other content. In some missions, the player is encouraged to avoid using deadly force, and specific aspects of the story may change depending on how violent or non-violent the player chooses to be. The game is also unusual in that two of its boss villains can be killed off early in the game, or left alive to be defeated later, and this too affects how other characters interact with the player.