I just love this apps and after i got this site i am just writing everything upside down :D. Its so cool.
How does it works(Start reading from end): "˙ǝpoɔ ǝɔɹnos ןɯʇɥ s,ǝƃɐd sıɥʇ ƃuıʍǝıʌ ʎq ʇxǝʇ uʍop ǝpısdn ǝɥʇ sǝʇɐɹǝuǝƃ ʇɐɥʇ ƃuıddɐɯ ɹǝʇʇǝן ǝɥʇ uɹɐǝן uɐɔ noʎ ˙ʇxǝʇ pǝddıןɟ ǝɥʇ ʎɐןdsıp oʇ „sɯ ǝpoɔıun ןɐıɹɐ„ ʇuoɟ ǝɥʇ sǝsn ǝƃɐd sıɥʇ ˙ʎןuo sɹǝʇʇǝן ǝsɐɔɹǝʍoן sʇɹoddns ןooʇ sıɥʇ os 'sɹǝʇʇǝן ןɐʇıdɐɔ uʍop ǝpısdn ɥƃnouǝ ʇou puɐ sɹǝqɯnu uʍop ǝpısdn ou ǝɹɐ ǝɹǝɥʇ ʎןǝʇɐunʇɹoɟun ˙„ʇǝqɐɥdןɐ ɔıʇǝuoɥd ןɐuoıʇɐuɹǝʇuı„ puɐ „pǝpuǝʇxǝ uıʇɐן„ sʇǝs ɹǝʇɔɐɹɐɥɔ ǝɥʇ ɯoɹɟ ǝɯoɔ ɯǝɥʇ ɟo ʇsoɯ ˙ɹǝʇndɯoɔ ǝɥʇ uo ʇxǝʇ uʍop-ǝpısdn pǝʇɐǝɹɔ ǝʌ,noʎ ǝʞıן ʞooן ʇı ǝʞɐɯ oʇ 'pǝʇɹǝʌuı ʞooן ʇɐɥʇ sןoqɯʎs puɐ sɹǝʇɔɐɹɐɥɔ ǝpoɔıun oʇ sɹǝʇʇǝן ɥsıןƃuǝ sʇɹǝʌuoɔ ɯɐɹƃoɹd ʇdıɹɔsɐʌɐɾ ǝɥʇ ¿pɹɐʍʞɔɐq puɐ uʍop ǝpıs dn ʇxǝʇ dıןɟ ןooʇ sıɥʇ sǝop ʍoɥ" Link for the app:
http://www.sevenwires.com/play/UpsideDownLetters.html