Smartphones are full of this. Even if you've been using computers for decades, when you pick one up for the first time there's nothing to suggest, for example,

Smartphones are full of this. Even if you've been using computers for decades, when you pick one up for the first time there's nothing to suggest, for example, that "swipe" is a verb, or what it does, or whether the direction matters and if so how. I find it mind-boggling that more than a decade into the smartphone revolution there are a zillion fart apps and (AFAICT) zero tutorial apps teaching a user what the verbs and affordances and conventions are.