Is there a name for text that reads the same upside-down? [duplicate]
That is called an ambigram. It is a typographical design that can be read in more than one direction.
ambigram noun
A typographical design consisting of text modified in such a way that it can be read in multiple orientations, as in mirror image, inverted, or when rotated.
(ODO)
Famously (?) used in Dan Brown's Angels and Demons.