Game Development Reference
In-Depth Information
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The level of activity of the cells is a good indicator for the complexity of the
behavior of the system. In a system that has only a very few active cells, interesting,
complex behavior is unlikely to emerge. In Wolfram's automaton, activity is under-
stood as changes to a cell's state: A cell is active when it changes from black to white
or from white to black.
Interestingly, some of these qualities can be ”read” from the rules that govern each
cell's behavior. The fact that each cell takes input from itself and two neighbors
indicates that there is a good chance at long-range communication: All the cells are
connected. In addition, four of the eight rules in Figure 3.2 cause the cell to change
its color, which indicates that there probably is going to be a fair amount of activity
in the system.
Cellular automata show us that the threshold for complexity is surprisingly low.
Relatively simple rules can give rise to complex behavior, as long as there are enough
parts, activity, and connections. Most games are built in a similar way. Games
consist of many different elements that are governed by fairly simple mechanics.
Usually there are many possible interactions between the individual game elements.
Obviously, the player is an important source of activity within the system, but as
cellular automata show, emergence can take place even without human input.
Tower defense games illustrate these properties well (
Figure 3.3
). Tower defense
games consist of a number of relatively simple parts. Enemies follow a predesigned
path toward the player's fortress. Each enemy has a particular speed, a number of
hit points, and perhaps a few attributes to make it more interesting. The player
places towers to defend his position. Each tower fires projectiles at enemies within
a certain range and at a certain rate. Some towers deal damage while others produce
other effects, such as slowing enemies down. Sometimes towers will boost the per-
formance of neighboring towers. In a tower defense game, there are many elements
defined by local mechanisms (enemies and towers). Like cellular automata, these
elements are active (enemies move, towers respond to enemies) and interconnected
(towers shoot at enemies, towers can boost each other's performance).
The level of activity and the number of connections between elements are good
indicators that can be used to distinguish games of emergence from games of pro-
gression. In a typical game of progression, all elements (puzzles, characters, and so
on) interact only with the player's avatar and not with each other, and they become
active only when they are on the screen. The elements not currently visible on the
screen in a game of progression are usually inactive. Similarly, the number of con-
nections among the elements is low. Game elements can interact only in a limited
number of predesigned ways. Obviously, this gives the designer a lot of control over
the events in a game of progression, but, as we have shown in the previous chapter,
it also results in more predictable games that cease to be fun when all the predesigned
options have been explored.
