The single-player game focuses heavily on team-based gameplay. The player can have a squad of up to several NPCs following them at any given time. Each NPC can be issued one of 4 orders: attack, defend, follow, or stop. NPCs ordered to attack can independently make their way from the beginning to the end of the level without any guidance from the player, although they will stop moving and wait for the player to catch up if they get too far ahead of the player. In the game's initial levels, the game ends if any NPC squadmate is killed, but squadmate health regenerates fairly quickly to prevent this aspect of gameplay from being too frustrating.