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, the first question you should ask is: which interactions +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.

There are +a few good tips when designing applications for touch use. First, it is imperative +that design decisions are based on real, considered touch use cases. Secondly, +as 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 needs, languages, and so on. Thus a very small screen +can change its buttons as needed. Also, with indirect strokes and gestures, +there are numerous possibilities. 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 onscreen 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 OS 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 +while wearing winter gloves, or with long fingernails can be difficult, for +instance. 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.