setWorldBorderSize(<size>, [seconds]). seconds is the time in seconds in which the border grows or shrinks from the previous size to that being set.
setWorldBorderCeneter(center(location)) -> Sets the new border center.
setWorldBorderDamage(damage(number)) -> Sets the amount of damage a player takes when outside the border plus the border buffer.
setWorldBorderBuffer(blocks(number)) -> Sets the amount of blocks a player may safely be outside the border before taking damage.
setWorldBorderWarningDistance(distance(number, default is 5 blocks)) -> Sets the warning distance that causes the screen to be tinted red when the player is within the specified number of blocks from the border.
setWorldBorderWarningTime(time(number, default is 15 seconds)) -> Sets the warning time that causes the screen to be tinted red when a contracting border will reach the player within the specified time.
resetWorldBorder -> Resets the border to default values.
setGameState(reason, value) -> (Deprecated) see resource page for more info.