General Recommendations
Metaphors
Metaphors provide users with a familiar environment on the screen. This allows users to transfer prior real-world knowlegde to an application: they learn new applications faster and relearn rarely used applications easier.
So, metaphors might just be THE solution for touchscreens where users are often untrained. However, there are also some caveats:
- Metaphors make break and thus confuse users, because they require interaction that does not make sense to the users, or they make the application behave unexpectedly.
- Often applications are abstract, and there is no suitable real-world metaphor available.
- Metaphors may waste precious screen space, because the graphical elements that maintain the metaphor (e.g. a room) need room to be realistic enough.
- The graphics for the metaphor may be too detailed to allow fast orientation and operation.
topSource: Interaction Design Guide for Touchscreen Applications