Major streets and public venues in Hong Kong are dressed up to celebrate the 20th anniversary of Hong Kong's return to China. [Photo by Hong Shaokui/provided to China Daily]

He buys whatever he wants with a tap of his phone, and the goods arrive within a day.

"The mainland is leapfrogging," he says.

"Many things here skipped stages they underwent in Hong Kong and the West, and dashed straight into a new era."

He describes his work experiences as "fruitful".

Cheung was a software engineer in Hong Kong. He leads an engineering team in Beijing.

"I've surpassed my peers career-wise," he says.

"Even if I returned to Hong Kong tomorrow, becoming familiar with the mainland has been advantageous."