Game Development Reference
In-Depth Information
if they should spring upon anyone, banks collect and pay interest, and so on.
When you specify one-shot
events
rather than continuous processes, the events
will often occur as a direct or indirect consequence of player actions or because
some process detects a special condition, such as when a runner crosses the finish
line in a race. (The later section “Mechanics” discusses events and processes in
greater detail.)
In a turn-based game with no artificial opponents, the core mechanics don't do
anything at all until a player takes his turn. Once he has done so, the core mechan-
ics can compute the effects of his actions on the game world. Then the mechanics
remain idle while the next player takes her turn, and so on. In some games, all the
players enter their intended actions simultaneously while the mechanics remain
idle; once the players finish for that turn, the core mechanics compute the effect of
all players' actions.
In a turn-based game, then, your design for the mechanics will read like a specifica-
tion for a sequence of events rather than a set of processes that operate all the time.
You will state the effects of each possible action and what other computations take
place as a consequence. Although you may design processes for a turn-based game,
you must realize that processes do not really operate continuously; they only run
between player turns. Your design for a process in a turn-based game must include
points at which the process may safely be interrupted for the next player's turn.
In a turn-based game that does have artificial opponents or NPCs, the mechanics
don't remain entirely idle between turns because they must compute the behavior
of these characters. However, the artificial characters still act in turns, just as the
player does.
Core Mechanics and Level Design
Most video games for consoles and personal computers present gameplay in sepa-
rate levels (also called chapters, missions, or scenarios, depending on the genre),
each with its own set of initial conditions, challenges, and termination conditions.
Level designers plan, construct, and test these levels, as Chapter 12, “General
Principles of Level Design,” discusses.
Ordinarily, the level design specifies the type, timing, and sequence of challenges
that appear during play, whereas the core mechanics specify how different chal-
lenges actually work. When a level starts up, the core mechanics read the level
design data from a file, which includes: the initial state of the game world for each
level; the challenges, actions, and NPCs for each level; and the victory conditions
for the levels (see
Figure 10.1
). If the game consists of only one level or creates ran-
domized levels, the core mechanics must also include mechanics for setting up the
level before the game first enters a gameplay mode.
Therefore, your design for the core mechanics should specify
how
challenges work
in general but not exactly
which
challenges each level will contain. As you design
the core mechanics, concentrate on those features of the game that will be needed
