Wang Baorong (left), 71, travels several hours every day to dance at Taoranting Park with other middle-aged and elderly people.

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Popular video websites, including Baidu.com and Tangdou.com, have special sections teaching square-dance moves and offering free music downloads.

Zhou Yehong, a 44-year-old office worker at a bank in Luohe city, Henan province, started dancing in 2006 and put her choreography online. One of her videos has been viewed nearly 100 million times.

"In the beginning, I just danced with my colleagues because sitting in the office for a long time caused lots of physical problems, such as back pain and putting on weight," says Zhou, who is also known as Mei Jiu, meaning lasting beauty.

"Within a short period of time, we had more than 200 people joining us, and I realized dancing is a good way to stay healthy and entertain ourselves."

However, square dancing by retirees is not without controversy. Residents in nearby buildings say that the noise is annoying and some complain that it disturbs their children's studies.

Residents in Wuhan, Hubei province, have thrown water and eggs on dancers. In 2013, a Beijinger fired a shotgun into the air and sent three Tibetan mastiffs into a dancing crowd because he "couldn't bear the dance music any more". The man was jailed six months for illegal possession of a firearm.

"Are old people supposed to sit around and wait for death? No. We still have our beautiful days," says Wang.