An ambigram is a calligraphic composition of glyphs that can yield different meanings depending on the orientation of observation. Most ambigrams are visual palindromes that rely on some kind of symme
Sator square (word square and palindrome) with the letters S and N in mirror writing.
Rotational ambigram Puzzle / The end by Peter Newell designed in 1893.
Mirror ambigram ΝΙΨΟΝ ΑΝΟΜΗΜΑΤΑ ΜΗ ΜΟΝΑΝ ΟΨΙΝ (Wash your sins, not only your face, in Ancient Greek) in the monastery Panagia Malevi [el].
Ambigrams published in The Strand Magazine, June 1908.
Douglas Richard Hofstadter is an American cognitive and computer scientist whose research includes concepts such as the sense of self in relation to the external world, consciousness, analogy-making,
Ambigram
…that rely on some kind of symmetry, and they can often be interpreted as visual puns. Although the concept is older, the term "ambigram" was coined by Douglas Hofstadter in 1983–1984. Most often, ambigrams appear as visually symmetrical words. When flipped, they remain unchanged, or they mutate to reveal another meaning…
Musings on the Rainbow Ambigram, Douglas Hofstadter's mirror design featuring the names of the seven rainbow colors, followed by a perceptual shift ambigram "2006" / "Doug", fusion of the date and his signature.
Hofstadter in Bologna, Italy, in 2002