Game Development Reference
In-Depth Information
the screen at a time—she has to wait for a shot to strike an enemy, or leave the back of the
screen, before she can fire another one. How does that affect the player's choices?
For one thing, a miss means that the player has to wait a while before she can fire again, but
a hit allows her to fire again more quickly. So she's given an incentive to pick her shots more
carefully. Shooting invaders who are closer—who are a more immediate threat—affords the
player a greater rate of fire than ones who are far away. There's some balance here: the player
has more ammunition to use against enemies who are more dangerous. A miss against a close
enemy means a longer interval before the player can shoot again—but nearer enemies are also
easier to aim at.
Verb Relationships
In fact, there are a few different verbs that are interacting in
Space Invaders
. How does the
player interact with the game other than shooting? She moves left and right. There's a relation-
ship between these verbs: when she presses the shoot button, the shot is fired from her current
position. Lining up shots with an invader means moving into the range of enemy fire. Dodging
enemy fire means moving behind an obstacle, where the player can't return fire. There's an
ongoing dialogue between moving left and right and firing shots, and the left/right verbs are
more developed as a result. You use them to aim your shots
and
to avoid being hit.
By establishing relationships between verbs, we give ourselves more opportunities to design
choices. The relationship between those verbs is also something that we can develop over the
course of the game, the same as with any two characters in a story.
At the heart of
Super Mario Bros.
is a strong relationship between Mario's ability to move
horizontally—to walk left or right—and his ability to move vertically—to jump. But notice that
that relationship becomes stronger over time. At the beginning of the game, the player isn't
expected to coordinate these verbs in a very complicated way.
The first jump the game requires is over an enemy that moves of its own volition. Mario is
safe if he lands on the enemy—he only has to avoid being touched by the side. This jump
doesn't even require horizontal motion: Mario can jump straight up while the monster walks
underneath him. The next jump the game requires is onto a stationary, solid obstacle from the
ground next to it. This requires a minimum of horizontal motion. It isn't until much later in the
game that the player is expected to perform really complicated jumps, with careful manage-
ment and coordination of both horizontal and vertical movement (see Figure 2.3). By that point,
the player understands how to use horizontal and vertical movement as a pair of verbs that
work together in harmony.
