Once effectively banned, Chinese sci-fi has exploded into the mainstream, embraced by Beijing and public alike - inviting scrutiny of a genre that has become known for its expanding diversity and relative freedom.

Its new status was epitomized by Worldcon, the world's oldest and most influential sci-fi gathering, which closed Sunday after taking place in China in a first.

Held in Chengdu Science Fiction Museum, the star was Liu Cixin, author of the Three-Body series and inspiration for the domestic blockbuster Wandering Earth.

The wider sci-fi fandom has become a rare space where diverse voices have flourished and a vast array of issues - environmental, social, even political - can be raised.

"By nature, part of sci-fi is about the present," award-winning author Chen Qiufan said. "It has the advantage of talking about space, or being set in different times, but reflects the human condition right now."

Chen's own novel The Waste Tide is set in a dystopian future China, where migrant e-waste workers toil in hazardous conditions, exploited by corrupt conglomerates.

He grew up near Guiyu, once one of the largest e-waste dumps in the world.

Ecological destruction, urbanization, social inequality, gender, corruption, to name a few - "these issues are intersectional and intertwined with each other", said Xi'an Jiaotong-Liverpool University's Liu Xi.

Together, they "allow everyone to understand Chinese writers' exploration of Chinese society," she said.

Sci-fi has had a turbulent relationship with Beijing - it effectively disappeared during the Cultural Revolution and then was banned as "spiritual pollution" in the 1980s.

Though it returned, it remains obscure.

For writer Regina Kanyu Wang, it was only at university that she met other fans and formed one of the smaller clubs there.

That sci-fi was seen as for children and young adults, Chen said, had its advantages.

"There was a lot of freedom because nobody was reading sci-fi, [authors] could just do whatever they wanted," the University of Zurich's Jessica Imbach said.

The global success of the Three-Body series changed everything, catapulting its epic themes of tech prowess and the fate of humanity into the public consciousness.

"Whether you like sci-fi or not, the social reality we are facing is becoming more and more like sci-fi," said Yu Xuying from Hong Kong Metropolitan University. The pace of digital change in China, already fast, was accelerated by Covid-19.

The international interest spike in Chinese sci-fi is also related to real-world concerns, Chen believes.

"I think there are different layers of reasons for the phenomenon," he said. "But a major one is the rising economic and technological power of China."

Beijing has been happy to capitalize on all this.

"At a national level, sci-fi is a good vehicle for conveying the country's discourse on its science and technology strength," said Yu.

It can also help "highlight the relationship between the Chinese dream (a Xi-era aspirational slogan) and science," she said.

Authorities have put their money where their mouth is.

The nebula-shaped Chengdu Science Fiction Museum, designed by Zaha Hadid Architects, was built at lightspeed in just a year to coincide with Worldcon.

The event, historically fan-led and funded, was a "capitalistic initiative, coming top-down from the Chinese government" this year, said Chen.

"They want sci-fi to be the namecard of the city, showing China's openness and inclusiveness to the world," he said.

Government attention comes with potential risk.

In English,The Three-Body Problem begins with a violent Cultural Revolution scene. In Chinese, it was buried halfway through the book, translator Ken Liu was told.

Liu said in 2019 that increasingly, "it's gotten much harder for me to talk about the work of Chinese authors without causing them trouble".

"If you're very marginal, if you have low print numbers in China, then it's OK, you have more leeway. If you're doing a mega big-budget movie... it's much more complicated," said Imbach.

"That's what's now also happening with science fiction," she said.

"As it's becoming more mainstream, there is increased scrutiny."

Increased scrutiny looms as Chinese sci-fi booms