All operations must use simple gestures that need only a single touch. Gestures that need two fingers or complicated movements can be hard to operate for people with hand tremors or limited movement. Users with alternative input devices such as a mouth stick, sip-and-puff, or head mouse also benefit. Simple gestures are easier for someone with cognitive impairments to remember and use. If the site or application does use multi-touch gestures, be sure to also provide simple interfaces.
Make it easier for users to operate functionality through various inputs beyond keyboard; however, it is essential that functions emulate a keyboard and that a mechanism to undo or abort an action is provided.
This guideline helps people with tremors or mobility impairments who may touch or click on the wrong location by mistake. This mistake can cause an unintended action. This success criterion also benefits people with cognitive disabilities, who can become confused when something unexpected happens because they activated a control by accident.
Ensure that functions that are triggered by moving a device (for example, shaking or tilting) or by gesturing towards the device (so that sensors like a camera can pick up and interpret the gesturing), can also be operated by more conventional user interface components, unless the motion is essential for the function or not using motions or gestures would invalidate the activity.
Users who may be unable to perform particular motions (such as tilting, shaking, or gesturing) because the device may be mounted or users may be physically unable to perform the necessary movement, should still be able to operate all functionality by other means (e.g., touch or voice input).
Some users may accidentally activate sensors due to tremors or other motor impairments. The user must have the ability to turn off motion actuation to prevent accidental triggering of functions.