I was referring to what takes but a second to learn and makes perfect natural sense thereafter (not to be confused with learning painful rote/ugly process). Interface should be obvious in context - but that doesn't mean the user has ever encountered that context before, and initially doesn't understand it enough to know what constitutes "obvious". If you've never encountered gravity before, walking (i.e.: stand, then fall forward, then stop yourself with a foot, repeat) is not something you'd think of doing, but is obvious once you see it done.