1- This is not a professional program at all, it pretty much just replaces each word with its nāwatl counterpart.
2- Nāwatl has various ways to be written, like the classical spanish transcription (Náhuatl), or the phonetic transcription (na'uɑtɬ). The one on this site, I made it up.
3- The art used as background isn't mine, I found it on google images and thought it looked cool.
4- The 'x' is pronounced like 'sh'.
5- Don't be surprised if a word doesn't get translated, I'm typing each word manually and there are a lot of words in english.
6- Don't trust the verbs. Because this site is english-based it doesn't allow any kind of conjugation.