Sorry, but the fact that I'm a Japanese major forces me to comment here. XD; It's actually a mixture of hiragana, katakana, and kanji - a formula most Japanese sentences are comprised of. Particles and other what have you are typically kept in hiragana, foreign words or those meant to stand out are in katakana, and kanji are used on most nouns and verb stems to help assuage the meaning and quickness of reading.
Just thought you should know. ^^