Touch-enabled +vs. touch-optimized

Rather than being +touch-enabled, certain applications can be touch-optimized, that is, designed +primarily for touch screen interaction. When developing applications for a +touch interface, it is important to consider interactions which benefit the +most from touch UI. While physical strokes and gestures allow for more natural +interaction with objects, the fact that one can apply them does not mean they +are appropriate for every situation.

Following are some useful tips +that can be used when designing applications for touch use:

It is imperative that design decisions are based on real-time touch +use cases.
Since touch functions require a fair amount of discovery from the user, +it is good if only very obvious functions are made touch-enabled.

Why to use touch

More flexible: Compared to fixed hardware keys, the interface +can change dynamically. This allows for more flexible configurations depending +on the functionality requirements, languages, and so on. Thus a very small +screen can change its buttons as required. Also, with indirect strokes and +gestures, there are numerous possibilities of flexibility. No use of physical +buttons is required.
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More intuitive: Manipulating objects directly by touching them +is natural and intuitive. Keyboards, mice, trackballs, and other input devices +are not able to convey as much subtlety as touch can. Direct manipulation +can deliver a lot more meaning to controlling a tool.
More fun: One can design a game in which users press a button +and an on-screen avatar swings a tennis racket. But it can be simply more +entertaining to mimic movements physically, and to see the action mirrored +on-screen. Strokes and gestures encourage play and exploration of a system +by providing a more hands-on experience.
More engaging: Through play, users start to engage with the +interface, first by trying it out to see how it works.

Limitations of touch

Heavy data input: A hardware keyboard is faster for most people +to use when entering a large amount of text or numbers, and applications which +involve heavy data input are not necessarily ideal for touch devices. Virtual +keyboards are adequate, for example, for messaging applications. Consider +utilizing adaptive methods - such as options and selections filtered according +to what is available on the screen or in a list - and pre-filled items, when +possible.
Reliance on the visual: While the Symbian platform provides +tactile feedback capability, some applications can rely heavily on visual +feedback to indicate actions. Allow for scalability, larger buttons and text +sizes, for example, for visually impaired users.
Reliance on the physical: Touch interface can be more demanding +on the physical context than mechanical keys. Tapping a touch screen button +can be difficult while wearing winter gloves, or with long fingernails. The +inverse is also true: the more subtle and small the movement, the less likely +it is that everyone will be able to do it. To overcome this, the most basic +use cases, such as answering an incoming phone call, must utilize large enough +elements and straightforward interaction.