<i>&gt; If a user can&#x27;t figure out how to navigate through an app in a reasonable amount of time without a great deal of existing knowledge</i><p>Having watched kids, teens, and 20-somethings, I&#x27;ve concluded that &quot;a reasonable amount of time&quot; to them is something on the order of 5 seconds on the outside. On a PC, they might look around and thoughtfully click on things. On a tablet or phone app, they just mash their fingers for about 3 seconds, then if they haven&#x27;t seen something, move on.<p>This even extends to 20-somethings and game controllers. I&#x27;ve seen 20-somethings walk up to an 80&#x27;s emulated arcade game, waggle the sticks on a controller for 2 seconds, not understand why the screen was shaking, then walk away.