Jared Sinclair:

Comfortable also means physical comfort, which is an aspect of mobile app design that designers often forget. Anyone with a new baby knows how convenient it is to be able to use an app with one hand. Some areas of the screen are hard to reach, especially on an iPhone 5 or later. Grip your phone in one hand observe the sweep of your thumb. It’s easy to reach objects in the center, but the navigation bar is too far away to reach without adjusting your grip. Although it’s tempting to jump to the conclusion that closer is always better, positioning an item too close to your hand can cause discomfort because of the way your thumb has to flex to reach it.

One of my favorite aspects of Unread. Check out Jared’s post for more details on his design process, as well as concepts he didn’t end up using.