228 Personal Content Experience: Managing Digital Life in the Mobile Age The system may provide shortcuts, accelerator keys, to speed up navigation. For example, in a Series 60-equipped smart phone, a three-by-four grid is used to display the installed applications. Each grid contains an icon that either launches an application or opens a sub- folder, in a three-by-four grid format. In addition to selecting the desired icon with the cursor keys and a selection key, each grid item is also mapped to a respective key in the ITU-T alpha keypad (for instance, pressing the key labelled “4” opens the fi rst item on the second row). This accelerates navigation, since the user does not have to fi rst highlight the desired item and then select it. ZoneZoom application takes the idea of using the keypad further by generalizing the method for 2D view navigation (Robbins et al. 2004). Each view is divided into nine segments that can be accessed with the keys from “1” to “9”, respectively. As the user selects and zooms in on the segment, they can re-segment it with the hash key (“#”) or zoom back to the previous view with the star key (“*”). If navigation in the hierarchical structure is problematic, how can it be supported? Most mobile computing platforms provide navigation aids, such as highlighting the item that has the input focus, providing a scroll bar for indicating current position in the list, labelling the view, and displaying the index number of the current menu item. For instance, 4-3-2 denotes that the user has selected the fourth item on the main level, the third from the next level, and now the focus is on the second item of the current view. Another option is to divide navigation into two: navigation between states, and navigation inside a state. For instance, Space Manager mobile document management system provides different views to navigating between folders (navigation level) and inside a folder (folder level) (Hakala et al. 2005a). Space Manager attempts to maximize the amount of visible folder structure while avoiding the need to pan and scroll. The navigation level (Figure 6-10) shows the folder structure as a tree on a tilted plane. Tilting adds to the sense of depth, thus making use of strong human spatial memory. At the navigation level, the highlight can be moved to any neigh- bouring folder by using the fi ve-way joystick. Moving up highlights the closest folder on the next level and moving down returns to the pre- vious level. Moving left or right navigates between folders on the same level. If all folders do not fi t on the screen at once, the view is automatically panned as the user moves near to any edge of the screen. Selecting the highlighted folder opens it and initiates animated transition that emphasizes the navigation step to the folder level (Figure 6-11).