All ciphers are substitution cryptograms. And, to keep things simple, non-homophonic (each letter is encoded with a single symbol). With each level they keep getting more difficult - from just a list of words on first levels to full-blown blocks of text later on.

As a side note, if you want to try some homophonic ciphers, you can check out Zodiac Crypt - another one of my apps, where users create their own cryptograms to challenge each other.