Making a wuxia film is usually tough because of the action scenes, but in Hou Hsiao-hsien's The Assassin, it was the language that posed a challenge to the actors.
In the drama set during the Tang dynasty, Shu Qi plays the titular assassin, Nie Yinniang, who has been sent to take down her cousin Tian Ji'an, a powerful lord played by Taiwanese actor Chang Chen.
And they all had to speak in classical Mandarin.
While acknowledging that there was a "certain degree of difficulty", Chang, 38, took it in stride and simply memorised his lines.
Speaking over the telephone from Taipei, he adds: "It was more important to think about the emotions of the characters: What was he feeling when he was saying those words? Where do I put the emotional stresses?"
The Assassin opens in cinemas here on Thursday.
Hou, who won Best Director at the Cannes Film Festival for the film in May, is feted as a leading figure in Taiwan's New Wave cinema and hailed for his lyrically minimalist works such as A City Of Sadness (1989).
And he had a distinctive approach to making a wuxia movie. All the elements had to be in place naturally before shooting would take place, recalls Chang.
"Sometimes, we would be waiting for the sunlight or for the leaves to be moving constantly as the wind blew."
The insistence on realism and naturalism was in keeping with his conversations with the director before filming.
Chang says: "We chatted about movies and what he thought about the genre. I think he's more interested in what's closer to the truth and reality, so his movie is less likely to have scenes of fei yan zou bi (leaping onto roofs and vaulting over walls)."
Such stunts were a feature of Lee Ang's highly successful Crouching Tiger, Hidden Dragon (2000), which Chang also starred in. He says: "Every director is different because they have different personalities and want to express different things."
While Ang's film featured "elegant fight scenes", The Assassin was "more romantic and more realistic".
Since his debut in Edward Yang's acclaimed drama A Brighter Summer Day (1991), Chang has built a reputation as a versatile actor with a charismatic screen presence. He has also worked with auteurs such as Wong Kar Wai, Kim Ki Duk and John Woo.
The way he picks his projects is quite straightforward. "I'll look at the script and decide if I like it after the first read."
However, he may be slowing down after marriage and fatherhood. His wife, Ann Zhuang, gave birth to a girl in March.
He says: "I do think about taking on fewer projects as I can't bear to be away. As a new father, there's plenty to learn. While work can't be neglected, I want to spend more time with family."
He does not rule out taking on, say, explicit roles in the future.
"It's a process of deciding what to accept or reject. However, doing this work alone and with a family is different. There might be some changes in the decision-making process."
• The Assassin opens on Thursday.