"Frankly, I don't want my young readers to come into contact with religion while reading my books," she says.

As a result, Chang spent two years researching in the "endless sea of Dunhuang studies", trying to find, among the papers from all over the world, the origins of the Buddhist stories in the frescos, "since many of them were adapted from folk tales in ancient India, Nepal, Dunhuang, or other parts of China".

Based on the original version of those stories, Chang created her own versions that cater to contemporary tastes and morality.

"Since people in ancient times could adapt those folk tales, so can I," she says.

However, it does not mean that she could fabricate everything. Her research included the details of the way of life at the time when the stories are set, because she needed to accurately describe customs, makeup, clothing, furnishings, transportation, decorations and architecture.

In Chang's version, the ugly princess did not turn into a beauty. As she found through her research, the folk tale came from ancient India under the caste system. Being of "low birth", King Prasenajit was looked down upon by people, although Kosala was really powerful under his reign. When Prasenajit offered to marry a princess from the neighboring country, he got a slave disguised as a princess instead. However, the couple lived happily. When their daughter was born, it was said she was astonishingly ugly.

"Perhaps she was not ugly at all. People just made up the story to mock the 'low birth' of the king and queen," she says.

As a result, in her story, the ugly princess escapes from the palace with the help of the heroine of the book, Luo Yiyi, a 13-year-old student from a middle school in Beijing. The book starts with Luo stumbling into the world of cave No 98 at Mogao Grottoes. Through Luo's eyes, the ugly princess is not as ugly as she was rumored to be. Bold and straightforward, the princess aspires to see the world outside the palace.