Audio volume, screen brightness, and font size—these three attributes are all important features of a mobile operating system like the iPhone.
We often discuss ways to quickly let our user pick between two different choices. A or B, up or down, left or right, black or white, a mobile interface often relies heavily on limiting the choices in order to optimize usability. But what about scenarios that are a bit more gray?
For example, we don't want to give our user the option between either loud music or no music. Likewise, an extremely bright screen or very dim screen may not be preferable for user readability. There will be situations when the user wants a moderate music volume or medium level of brightness.