Game Development Reference
In-Depth Information
CHEATING AI AND SECRET ASYMMETRY
In a single-player PvP game, the player takes on an artificial opponent and tries to
defeat it in exactly the same way she would a human player. Sometimes the single-player
competition mode in a PvP game is just an added feature in an otherwise multiplayer
PvP game. When a game is designed this way, the player naturally tends to assume that
the artificial opponent plays by the same rules that a human player would play by in
its place.
Unfortunately, the AI in many games isn't good enough to beat a human opponent on
equal terms. AI can beat most human players in games such as chess and checkers but
has a harder time with
Go
and a very hard time with complex war games. To help the AI,
designers occasionally let it cheat. Some classic cheats include allowing the AI to see
units that should be hidden by the fog of war; making the AI-controlled units tougher
than the player's units, while claiming that they are identical; or giving the artificial
opponent a faster production rate for valuable resources than the player gets for the
same resources. In effect, what the player thinks is a symmetric game is secretly asym-
metric; the artificial opponent plays by different rules.
You should only use this approach as a last resort. Although it can produce a well-
balanced single-player PvP game, players hate it when they discover that the AI is
cheating against them (and with enough effort, they will discover it eventually). A better
solution is to be open about the artificial opponent's advantages and build them into a
set of different difficulty levels for the player to choose from. This allows the player to
decide for himself how tough an opponent he wants to face, and the game doesn't have
to pretend to be symmetric.
THE POINT ASSIGNMENT SYSTEM
You can balance a more complex asy mmetric game than Fox and Geese by giving
the players identical quantities of raw materials at the beginning of the game and
then letting them choose what units to build using the raw materials. The Macintosh
game
Spectre
allows players to design a tank by assigning points to three attributes:
speed, armor (defensive strength), and shot power (offensive strength). Each player
gets the same number of points, so none has a built-in advantage, but each can
construct a tank that matches his own preferred style of play.
The point distribution system, while generally fair, doesn't absolutely guarantee
that no dominant strategy will emerge. The risk always exists that one particular
combination of features may be superior to any other combination. To help prevent
this, the attributes to which the player can assign points should be orthogonally
related. One attribute should not affect the domain of another attribute. Having
two closely related attributes, such as health and armor, undermines the point sys-
tem. The player should not be able to gain the same effect by pumping points into
one attribute as she can by pumping the points into another.
