Game Development Reference
In-Depth Information
differentiates between them in the same dimension—speed—so they are not
orthogonally different.
To make the player's choice of units more interesting and to offer her a larger vari-
ety of strategies, Smith suggests that units should not only differ in the magnitude
of their power at performing one task, as the Fords and Dodges did, but also should
display entirely different qualities. Ideally, every type of unit should possess capa-
bilities that no other unit has, and this gives each type a distinct role to play in the
game. Otherwise, there's little point in including a weaker unit in the game except
as part of an upgrade path to a stronger one.
The more diverse the types of challenges in your game, the easier you will find it
to create orthogonally differentiated unit types. In a realistic car racing game, all
the cars face the same challenge and must be constructed to similar standards,
which makes racing games a poor field for examples of orthogonal differentiation.
Player success depends more on driving skill than on the attributes of their cars,
which is appropriate for a racing game. In a war game, however, opportunities to
create orthogonally differentiated units abound. Some units may fly or travel on
water, whereas others may not; some may transport other units; some may possess
ranged weapons and others only hand-to-hand weapons; and so on. You cannot
directly compare the advantages of a unit that wields hand-to-hand weapons with
the advantages of one that heals the wounded: These qualities make the player's
choices more interesting, and success in the game consists of deploying the appro-
priate combination of units to defeat the enemy's forces.
Orthogonally differentiated units also help to prevent dominant strategies from
arising if you define the victory condition in such a way that the player must use a
variety of different units in order to win the game. Many inexperienced chess play-
ers rely on using the queen aggressively, wrongly believing this a dominant strategy
because she is the most powerful piece on the board. In fact, however, each type of
chess piece plays a role and they work cooperatively. The queen cannot control the
board alone; she needs the help of the other pieces. The types of pieces exhibit
enough diversity to keep games interesting and prevent dominant strategies.
Dominant Strategies in PvE Games
As Chapter 9 explained, most games offer a large number of different types of chal-
lenges but a somewhat smaller number of actions with which to overcome them.
One action may overcome several different types of challenges. This encourages
players to experiment to find the right action or combination of actions to sur-
mount each type of challenge, whereas only offering one unique action for each
type of challenge makes for a dull game.
Implementing fewer actions does introduce a potential problem, however. By creat-
ing actions that can overcome several different kinds of challenges, you risk
accidentally creating
exploits
, actions so powerful because of a weakness in the
design that the player becomes unstoppable. This occasionally happens
