BB-8 is shown going down stairs at least once in the film
on Takodana, following Rey into the basement, sort of clunking down step-by-step
but there are a few scenes that cut away right before the little guy would have to go up stairs
like right before entering Maz Kanata's castle.
Is there a canon explanation of how he goes up stairs?
I can't locate it right now, but I read a quote from one of the designers (in an answer about the droid's gender) that mentioned having to think about how BB-8 goes up and down stairs as an extension of defining gender, but didn't see a mention of how the droid accomplishes it.
Does it have to do with those cables he uses for steeper ascents?
to clarify: I'm looking for a canon explanation of how BB-8 ascends stairs, under the assumption that it likely differs from how he descends them.