Description A baboon has escaped from the zoo. It seems to be following Oona and causing havoc in her life. How will Oona get rid of the baboon? The phoneme /oo/ is featured in this title. In Level 4 - Blue books, children build on the letter-sound combinations learned in levels 1 and 2. They learn consonant digraphs (sounds made up of two letters together such as 'ch' or "ll") and long vowel sounds (such as 'igh' or 'ai').