The eleventh and twelfth books in the series, Puffin Cliffs and Traffic Jam, use only decodable regular words made up from the first six groups of letter sounds:
s, a, t, i, p, n
c k, e, h, r, m, d
g, o, u, l, f, b
ai, j, oa, ie, ee, or
z, w, ng, v, little oo, long oo
y, x, ch, sh, voiced th, unvoiced th
Tips and guidance for teachers and parents are provided at the end of each book. Light type is used as a guide for those few letters that should not be sounded out, such as the /b/ in ‘lamb’.