Emergence and progression - Game Mechanics: Advanced Game Design - page 38

integrate constantly increasing challenges into an overarching story line. The over-
all experience is much easier to design in a game of progression than it is in a game
of emergence.

The shape of the probability space generated by typical mechanics of emergence and
mechanics of progression is quite different. Games of emergence have a probability
space that is large and wide, because the game presents players with many options,
and the game's direction is often subject to factors outside the player's direct control
(such as die-rolling). In contrast, the probability space of games of progression tends
to be small but deep. For a designer, it is easier to create a sequence of many game-
play choices—but with fewer options at each decision point—and still have a good
idea of, and control over, the possible outcomes. This is why games of progression
are usually longer than games of emergence and can deliver coherent stories. Games
of emergence, such as checkers, tend to be shorter. In a long game of emergence,
you run the risk that the player will make a small mistake early on that makes the
game unwinnable hours later—a design flaw. X-COM: UFO Defense, although an
excellent game in many respects, exhibited this property.

The mechanics of emergence are efficient at creating a large probability space. The
mechanics that control progression do the opposite, restricting the probability space
by limiting the number of options that players have at any one time—they cannot
proceed until a particular problem is solved. As a designer, the mechanics of progres-
sion allow you to carefully structure the player's experience and deliver a well-told
story. They also enable you to control the difficulty of the game so that players do
not encounter challenges for which they are not yet prepared. Table 2.1 summarizes
these differences.

TAble 2.1
structural differences
Between mechanics
of emergence
and mechanics of
Progression

STRuCTuRE EMERGENCE PROGRESSION

number of rules Low high

number of game elements high Low-high

interactions among elements high Low

Probability space Large, wide small, deep

replay value high Low

designer control of game sequence Low high

Length of game Tends to be short

( Civilization is a rare exception)

Tends to be long

Learning curve Tends to be steep Tends to be gentle