An ambigram of a word is legible even when it is read from a different orientation, either when rotated upside down or when viewed in a mirror.
Popular examples of ambigrams are seen in the novel "Angels & Demons" by Dan Brown, notably the ambigram of the "Illuminati" cult and those of the 4 elements - 'Earth', 'Air', 'Fire' and 'Water'.
The Latin script wasn't designed to be legible when read upside-down, which makes the idea of designing an ambigram of a word seem really difficult...at first.
This 45-minute course shares a technique to make rotational ambigrams; which are legible even when read upside down. It will cover the following forms of rotational ambigrams: