One day while on summer vacation, Ah Mai and Ah Si have a play-date to play the game of "Monster Breakthrough" at Ah Si's house. The two little monsters have a lot of fun. At lunchtime, Mrs. Ace carefully prepares pizza, chocolate muffins and orange slices for the two little monsters. But, wait! These foods seem to have some common characteristics… By telling the story of the little monster Ah Mai and Ah Si meeting to drink afternoon tea and taste delicious snacks, this book introduces the relevant knowledge of circular problems, combines teaching with fun, so that children can learn mathematics knowledge and cultivate Mathematical Olympiad thinking in the process of reading the story. After the book, there are also expanded reading and small exercises. The combination of learning and practice can expand children's mathematical vision and consolidate children's mastery of knowledge.