Mobile applications pose a different design challenge: how to make a great user experience on a far smaller screen when the main input device is a touch screen where your fingers may obscure content. The companies behind the major mobile operating systems (Apple, Google, and Microsoft) spent many years developing a visual language and standard interactions that provided a smooth flow through increasingly complicated applications. As previously with web applications, it was important that native mobile applications behave in a consistent manner for users to quickly learn and feel comfortable with these new platforms. iOS, Android, and Windows Phone provide standard APIs that developers can use to create applications that fit with the platform standards. Within each platform, there are enough customization options to support brand identity through use of color, icons, or the content of each screen within the app. While the specific design aesthetic of mobile platforms has changed over the years, it is clear that the carefully designed layout and workflow aspects remain consistent throughout. Users can comfortably pick up the latest iPhone, appreciate its new design, and still be completely familiar with how the applications will work:

There is clearly a lot more to designing an application GUI than designing a workflow and picking a color scheme. Will your application take inspiration from modern application UX, or is it aimed at users who are more familiar with the classic look of desktop applications established over many years? Will you be sticking to a single platform and its standard look and feel, or are you interested in launching your software across multiple operating systems? Before we look at the different toolkits available, take some time to consider these options and identify which is likely the right strategy for your application.