In a distracted environment, the best form of smartphone interaction is a high-speed, easy-to-use one. Luke calls the typical mobile usage a "one thumb, one eyeball" experience, since the highly distracted environment causes most mobile users to engage in one-handed use with short spans of partial attention.

Fitts's Law describes how long time it takes to click a target, based on the distance to the target and its size. Use this information to make buttons and links faster to click.