Game Development Reference
In-Depth Information
Minimum screen areas
It is always important to determine the minimum size of an active element for your
game. The comfort of playing directly depends on this factor. The average width of an
adult human male finger varies from 15 to 20 mm, the average index finger width is
20 mm or 0.75 inch. In ancient times, this size was used as a measurement of length
called finger or digit (in Latin digitus means finger). Let's convert finger into pixels, all
we need for this is simple math; the digital length of the screen in pixels should be
divided into the physical length of the screen in millimeters its size in pixels, so we will
get the number of pixels in one millimeter. The conversion is shown as follows:
• iPhone: 480 px/75 mm is approximately 6.41 pixels per mm (163 ppi)
• iPhone (Retina): 960 px/75 mm is approximately 12.83 pixels per mm (326
ppi)
• iPad: 1024 px/197 mm is approximately 5.20 pixels per mm (132 ppi)
• iPad mini: 1024 px/160 mm is approximately 6.41 pixels per mm (163 ppi)
• iPad mini (Retina): 2048 px/160 mm is approximately 12.8 pixels per mm (326
ppi)
• iPad (Retina): 2048 px/197 mm is is approximately 10.40 pixels per mm (264
ppi)
As you can see, there is a wide range of pixel density on iOS devices, so a pixel in the
role of a measurement element is not very reliable. Wonderful examples are the first
generations of an iPad and an iPad Mini; they both have an equal resolution in pixels,
but physically, in millimeters, they are different. A more precise way is to operate with
physical measurements of length; nevertheless, our fingers are not made of pixels.
To determine the optimal minimum touch zone, we can recall the recommendation
from Apple that 44 x 44 points the comfortable minimum size of a tappable element
written in the Layout section of iOS Human Interface Guidelines. One point is equal
to one pixel on low-resolution devices, and equal to two on high-resolution screens.
Thereby, the minimum physical size of the touchable zone can be calculated in the
following manner:
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