The same basic design principles apply whether you are designing for small or large screens. On small devices, however, these principles take on added importance related to the unique characteristics of small-screen devices: They are always on, they often use indirect manipulation, and they are operated under variable light conditions and with a high potential for task interruption. These conditions are quite different from the typically relaxed, seated, mouse-in-hand, big-screen experience on a desktop computer. It is therefore important to take full advantage of design principles to ensure that your application’s functionality is quickly and clearly conveyed at every step of the user interaction.