Upside down text generator

A generator does two things. It swaps each character for one that looks like it after a half turn, then reverses the whole line, because rotating text by 180 degrees puts the last letter first. Swap without reversing and you get upside down letters in the wrong order.

Eleven of the 26 lower-case letters need nothing special: b, d, n, p, q and u trade places with each other, and l, o, s, x and z stay as they are. Among the capitals, H, I, N, O, S, X and Z survive the turn, and M and W swap.

Unicode has no upside down alphabet, so flipped text is pieced together from whatever looks right. The lower-case letters come mostly from the International Phonetic Alphabet, which linguists use to write down speech sounds. Many of its symbols are ordinary letters set upside down, a trick that let printers make new symbols from type they already had, and ʌ, a turned v, is still the vowel of “cup” in many dictionaries.

The capitals are a patchwork. ∀ is the logic symbol meaning “for all”, ⊥ is a maths sign called up tack and ∩ means intersection. ꓘ and ꓤ are letters of Lisu, an alphabet used for the Lisu language in parts of China, Myanmar and Thailand. ᗺ and ᗡ come from Canadian Aboriginal syllabics, Λ is Greek, Ԁ is Cyrillic, and ſ, standing in for J, is the old long s. Even the digits travel: a flipped 2 is the Korean letter ᄅ, and a flipped 4 and 7 are ㄣ and ㄥ from Bopomofo, the phonetic script used in Taiwan to teach Mandarin.

That mix explains why flipped capitals look uneven, and why they're the first thing to break. Most of the phonetic letters have been in Unicode since version 1.1 in 1993, and almost every font has them. The Lisu letters only arrived in Unicode 5.2, in 2009.

On most phones the screen won't rotate into upside down portrait, so turning the phone over really does put flipped text the right way up. On a laptop you have to tilt your head or read it from across the desk. That small effort is the fun of it: the reader has to do something before the joke lands.

Tip: Some puzzle books print their answers upside down so nobody reads them by accident. A caption can do the same: ask the question in plain text and put the answer upside down underneath.

• A plot twist: “Week one at the new job” on top, and a flipped line underneath about how it really went.
• April Fools' Day posts, or a caption for a photo taken mid-handstand.
• A quiz or riddle with the answer flipped below it.
• One flipped word in a bio as a wink, beside plain text that says what you do.

It gets in the way just as fast. Screen readers see real phonetic letters and may read out nonsense or announce names such as “Latin small letter turned t”. Search won't connect a flipped word to the plain one. And a whole flipped caption is hard work for everyone, so keep anything people need to understand the right way up.