unicode - How does u?op-?p?sdn text work?

Question

Here's a website I found that will produce upside down versions of any English text.

how does it work? does unicode have upside down chars? Or what?

How can I write my own text flipping function?

Answer 1

how does it work? does unicode have upside down chars?

Unicode does have upside-down characters. They have "TURNED" in their name:

? U+018D LATIN SMALL LETTER TURNED DELTA
? U+019C LATIN CAPITAL LETTER TURNED M
? U+01DD LATIN SMALL LETTER TURNED E
? U+0245 LATIN CAPITAL LETTER TURNED V
? U+0250 LATIN SMALL LETTER TURNED A
? U+0252 LATIN SMALL LETTER TURNED ALPHA
? U+0265 LATIN SMALL LETTER TURNED H
? U+026F LATIN SMALL LETTER TURNED M
? U+0270 LATIN SMALL LETTER TURNED M WITH LONG LEG
? U+0279 LATIN SMALL LETTER TURNED R
? U+027A LATIN SMALL LETTER TURNED R WITH LONG LEG
? U+027B LATIN SMALL LETTER TURNED R WITH HOOK
? U+0287 LATIN SMALL LETTER TURNED T
? U+028C LATIN SMALL LETTER TURNED V
? U+028D LATIN SMALL LETTER TURNED W
? U+028E LATIN SMALL LETTER TURNED Y
? U+029E LATIN SMALL LETTER TURNED K
? U+02AE LATIN SMALL LETTER TURNED H WITH FISHHOOK
? U+02AF LATIN SMALL LETTER TURNED H WITH FISHHOOK AND TAIL
? U+02B4 MODIFIER LETTER SMALL TURNED R
? U+02B5 MODIFIER LETTER SMALL TURNED R WITH HOOK
? U+02BB MODIFIER LETTER TURNED COMMA
? U+0312 COMBINING TURNED COMMA ABOVE
? U+10F9 GEORGIAN LETTER TURNED GAN
? U+1D02 LATIN SMALL LETTER TURNED AE
? U+1D08 LATIN SMALL LETTER TURNED OPEN E
? U+1D09 LATIN SMALL LETTER TURNED I
? U+1D14 LATIN SMALL LETTER TURNED OE
? U+1D1A LATIN LETTER SMALL CAPITAL TURNED R
? U+1D1F LATIN SMALL LETTER SIDEWAYS TURNED M
? U+1D44 MODIFIER LETTER SMALL TURNED A
? U+1D46 MODIFIER LETTER SMALL TURNED AE
? U+1D4C MODIFIER LETTER SMALL TURNED OPEN E
? U+1D4E MODIFIER LETTER SMALL TURNED I
? U+1D5A MODIFIER LETTER SMALL TURNED M
? U+1D77 LATIN SMALL LETTER TURNED G
? U+1D9B MODIFIER LETTER SMALL TURNED ALPHA
? U+1DA3 MODIFIER LETTER SMALL TURNED H
? U+1DAD MODIFIER LETTER SMALL TURNED M WITH LONG LEG
? U+1DBA MODIFIER LETTER SMALL TURNED V
? U+2129 TURNED GREEK SMALL LETTER IOTA
? U+2132 TURNED CAPITAL F
? U+2141 TURNED SANS-SERIF CAPITAL G
? U+2142 TURNED SANS-SERIF CAPITAL L
? U+2144 TURNED SANS-SERIF CAPITAL Y
? U+214B TURNED AMPERSAND
? U+214E TURNED SMALL F
? U+2319 TURNED NOT SIGN
? U+275B HEAVY SINGLE TURNED COMMA QUOTATION MARK ORNAMENT
? U+275D HEAVY DOUBLE TURNED COMMA QUOTATION MARK ORNAMENT
? U+29A2 TURNED ANGLE
? U+2C6F LATIN CAPITAL LETTER TURNED A
? U+2C79 LATIN SMALL LETTER TURNED R WITH TAIL
? U+2C7B LATIN LETTER SMALL CAPITAL TURNED E
? U+A77E LATIN CAPITAL LETTER TURNED INSULAR G
? U+A77F LATIN SMALL LETTER TURNED INSULAR G
? U+A780 LATIN CAPITAL LETTER TURNED L
? U+A781 LATIN SMALL LETTER TURNED L

However, it's far from a complete set. Most upside-down text works by choosing characters that happen to have a close-enough resemblance to upside-down letters. It's the equivalent of typing 0.7734 on your calculator to spell "hELLO".