Game Development Reference
In-Depth Information
The rock-paper-scissors (or RPS) mechanism is a classic design technique for avoid-
ing dominant strategies and forms the basis for balancing player strategies in many
games. Designer David Sirlin pointed out in his article “Rock, Paper and Scissors in
Strategy Games” that
Virtua Fighter 3
includes RPS relationships among general
types of moves available to the player: Attacking moves beat throwing moves,
throwing moves beat blocking moves, and blocking moves beat attacking moves
(Sirlin, 2000).
The Ancient Art of War
, an early example of a video game that
includes an RPS relationship, offers players three unit types: knights, archers, and
barbarians. Knights have an advantage over barbarians, barbarians over archers,
and archers over knights.
As Chapter 14, “Strategy Games,” explains further, a direct implementation of the
RPS model without any modifications fails to meet the needs of modern war games
due to its simplicity. It doesn't offer any interesting choices—there's no reason to
choose any one unit or strategy over any of the others. However, as Sirlin points
out, you can adjust the system to produce different benefits. If you give the player
different amounts of money for winning with rock, paper, or scissors, players have
to think not only about which object their opponent might choose but which
choice earns the most money.
Now imagine a system in which instead of just allowing each choice to beat
another in all circumstances, as in rock-paper-scissors, one choice is marginally
better than others in some circumstances but not in others. You can make this
adjustment in the core mechanics of your game, and it need not be a war game. For
example, suppose you set up a race between a lizard, a frog, and a mouse. The liz-
ard does best on rocky ground; the frog does best in swamps; and the mouse does
best on grassy ground. If you design the mechanics such that these advantages
remain slight rather than overwhelming, it will take a while for the players to learn
about the system of advantages. Make the race course a complex mixture of rocks,
grassland, and swamps, and give players partial but not total freedom over the
routes they take. Add some shadow costs: The frog is generally slower than the oth-
ers overall; the mouse has to stop for air every 15 seconds while swimming; and the
lizard slows down sharply at transitions between types of ground. If you set these
values carefully, your game remains balanced, and players will have some interest-
ing decisions to make about which creature they would rather play with.
ORTHOGONAL UNIT DIFFERENTIATION
In his lecture at the 2003 Game Developers' Conference, “Orthogonal Unit
Differentiation,” game designer Harvey Smith argued that each type of unit a
player can control in a game (a car, a soldier, an RPG character, or anything else the
player can command) should be orthogonally different from all the others (Smith,
2003). By orthogonal, he meant that each kind of unit should be unlike the others
in a different dimension, not simply more or less powerful when measuring in one
dimension. The example of the Ford, Dodge, and Chevy in the preceding section
