Interface - Designing Games - page 236

ContRol aRRangement
There are a huge variety of physical interfaces: buttons, joysticks, motion
sensors, touch pads, and more. In each case, we have to decide which con-
trol does what. We have to determine that the A button jumps while B
crouches, or a waving left arm casts a fireball while a pointing left arm
casts a flame stream.
There are two key principles that should guide us in arranging con-
trols to correspond to in-game actions: mapping and control exclusivity .
MAPPING is the relationship between physical interface elements and
the actions they control.
The goal of mapping is to create a similarity between a physical con-
trol and its in-game effect. Done well, this similarity serves as a built-in
mnemonic that helps players remember how to use the control. The classic
example of mapping is a stovetop that looks like this:
This stove doesn't need labels. The spatial mapping between the
knobs and the elements means people intuitively know how they corre-
spond with each other.
Games do the same thing. For example, in BioShock , the player char-
acter can fire spell-like plasmid effects from his left hand and weapons
from his right hand. These are controlled with the left and right trigger,
respectively. This creates a mapping between the player's physical hands
and the character's hands on-screen.
Mapping isn't limited to physical position. We can map through shape,
color, motion, or a hundred other kinds of signal. For example, in BioShock
the on-screen health indicator is red, as is the button used for healing. This