246 Personal Content Experience: Managing Digital Life in the Mobile Age previous values of the input fi eld (history), and user preferences. Another way is to show whether the fi eld is mandatory or optional; in the case of an optional fi eld, the user may skip it. To save screen space, additional information related to an object may be hidden until the user explicitly requests it. A popular method is known as a tooltip, which provides textual, and sometimes graphical, information for an object as a textbox superimposed over the object. The tooltip is displayed after a certain period of time when the user highlights the object, or the user hovers the pointer over it. 6.4.1.6 Create Aesthetically Pleasing Designs Even though it is essential to design for effi cient, fl exible, fast, and error-free UI, it is also important to create elegant, stylish, and aestheti- cal designs. This often leads to a situation where the designer must make a decision between enjoyable visual design and effi ciency. For example, selecting a stylish colour palette can easily result in reduced legibility of the text due to poor contrast, or using graphical dividers between screen sections overcrowds the screen and slows visual searching. What is considered beautiful is subjective and culturally dependant. Therefore, the UI should be customizable and personalizable. For example, the user can change to a more familiar set of icons, and change the order of objects. Minimal visual style is often considered benefi cial as the information that is rarely needed or irrelevant to the task is hidden. Also, because the UI contains little perceivable information, the user’s attention is guided towards parts that are the most important. 6.4.2 The UI Design Process and Methods Now we are ready to illustrate our approach to designing mobile user 13 interfaces. A mobile UI is an aggregate of many factors that should be taken into account in the design. For example, Lindholm et al. (2003) characterize user interface style as: “A combination of the user interaction conventions, audio-visual and tactile appearance, and user interface hardware.” The design of the system involves many concurrent activities. UI should be considered in the early phase of the design, when analyzing 13 Our UI design process is infl uenced by the OMT++ method (for further information, see Jaaksi (1995)). We do not claim that our process and method is the one and only – instead we wish to illustrate the phases of the user interface design.