Game Development Reference
In-Depth Information
44 / 6.41 = 6.86 mm
This is optimal and the secure size of a minimal touch zone is provided by the man-
ufacturer. Of course, you can try to use interactive elements with lesser dimensions;
however, you should not forget Fitts's law, which in this case can be formulated
based on the fact that smaller targets need more effort and accuracy to be touched.
So the speed of the player's movements decreases, but the level of errors, on the
contrary, increases. The smaller the elements, the more dramatic is the situation.
The user can touch a very small button, but only on condition that there are no any
other buttons nearby. If the small buttons are tight, it is hard to aim properly, and the
chance to tap the wrong button is very high. Usually, such situations irritate people,
they get a little stressed and perceive the interface as an uncomfortable environ-
ment.
Overall, if the elements are small and stay tight, it is better to select dimensions not
less than 4 x 4 mm; the player will use the very tip of his finger to tap the target.
Something tiny can be used only with a low density of elements on the screen; for
instance, an adventure game can feature a secret tiny trigger, and in such cases its
dimension plays the role of a critical gameplay element.
Definitely, the most comfortable touch elements are those that have dimensions
closest to the finger size. They are noticeable and can be tapped without painstaking
aiming. Such elements can be successfully adapted for the tapping by thumbs.
Game accessibility guidelines (available at
http://gameaccessibilityguidelines.com/
)
say that 24 mm is the ideal size for touch screens of large devices and 9.6 mm is
recommended for phones.
Naturally, an index finger is used for more precise operations; it sets the direction of
a movement, marks the destination and aims, interacts with game elements, and so
on. So it is the basic tool of the gamer. The index finger tip usually helps to tap small
targets. If a UI element is big, the user prefers to tap with a finger pad, because it is
more comfortable. The thumb can participate in gaming too. It is not as accurate as
the index finger is, so it needs a large touch zone; in other words, it would be better
to use it for larger buttons.
