Chapter 6: User Interfaces for Mobile Media 217 Mobility affects the device’s physical shape and dimensions, which are together referred to as the form factor. Furthermore, industrial design sets requirements and constraints for the form factor as the device should fi t on the palm, and should immediately reveal whether the orientation of the device is correct when grasping it. Furthermore, industrial design is affected by ergonomics aiming at maximizing per- formance, safety, and comfort of use. Ergonomics affect the location and the layout of the physical interface components, such as the display element and the arrow keys, even though the available surface space is often at premium, thus providing few options. Due to mobile use situations, industrial design should also try to reinforce so-called blind (eyes-free) use by carefully studying the place- ment, shape, and styling of the input devices. At the same time, the design should prevent unintentional key presses when placing the device in a bag or pocket. As a consequence, various key guard (or key lock) mechanisms (such as hardware switches, button press com- binations, and automatic key locks) have been developed. The most common form factors are monoblock, clamshell (or fl ip), swivel, and slide (Figure 6-3). Each form factor provides some benefi ts. In clamshell, the display and keyboard are protected when the device is closed; swivel form factor lets the user view the whole screen even though the keypad is hidden; slide mechanics enable the user to see the screen as well as some input devices; and monoblock does not contain mechanics that could be prone to mechanical failures in rough handling. Compared to desktop computing, where the display, keyboard, and mouse dominates the interaction hardware, the mobile devices are more heterogeneous. Before discussing how to use the various hard- ware components for interaction, let us review them quickly. Figure 6-3. Illustrations of mobile device form factors. From left to right: Monoblock, fl ip (clamshell), swivel, and slide.