What is Thumbability?

The Thumbability criteria is measured on how easy the application is to use with only one hand, specifically one thumb.  
  • Thumbs up
    The application can be comfortably used with one thumb.
  • It's a stretch
    Tasks may be accomplished with one thumb but requires considerable effort and focus on the task.
  • Two Fingers Required
    Many tasks may be thumbable, but two fingers are required to perform most tasks.  Activities such as typing, or pinch zoom.