Storytelling and Narrative - Fundamentals of Game Design - page 174

example involves 21 branch points and 35 different branches, each of which requires
its own story content: gameplay and narrative material. If none of the branches
merged again, there would be even more. This rapid growth in the number of
branches is called the combinatorial explosion. (Combinatorics is the field of math-
ematics that studies the number of possible combinations of a set of things—in this
case, a set of branch points in a branching story.)
As a result, most modern games don't actually include much branching, and they
often include long periods during which the player plays but doesn't change the
story. Wing Commander , a space combat simulator, contained a branching story,
but it branched only between missions, not during them. Eventually, the Wing
Commander series abandoned branching storylines entirely because they proved to
be too expensive.
Every critical event (those that affect the entire remainder of the plot) has to
branch into its own unique section of the tree. Suppose a character can live or
die at a particular branch point. If he dies, he must never be seen again, which
means none of the plot lines from his death onward can include him. His death
requires an entirely separate part of the tree that can never merge back into the
rest—otherwise, he might reappear after the player knows that he's dead. If this
happens with two characters, the game requires four separate versions of the story:
a version in which both live; a version in which both die; a version in which A lives
and B dies; and a version in which B lives and A dies. Again, the number of possible
combinations explodes.
The player must play the game repeatedly if he wants to see all the content.
If the storyline branches based on how well the player meets the game's challenges
and he's very successful, then the next time he plays he has to play badly on pur-
pose in order to learn the dramatic consequences of his failure! A lot of players
would consider this to be absurd. They paid a great deal of money for the content
in the game, and the only way to see it all is to play badly part of the time. This fac-
tor further contributed to the industry's abandoning stories that branch frequently.
If you want to make a branching story, you will have to plan out the structure in
the concept stage of design. You should not actually write the story at that point in
the design process, but you won't be able to plan a budget or schedule for your
game unless you know how much content it will require, and a branching story's
resource requirements expand very rapidly.
If you find that these drawbacks discourage you from using a branching structure,
you can choose the compromise that the game industry most often uses when it
creates nonlinear stories today: the foldback story.
Foldback Stories
Foldback stories represent a compromise between branching stories and linear ones.
In a foldback story, the plot branches a number of times but eventually folds back to