The burgeoning popularity of Sudoku in China is not only improving youngsters' logical thinking, but fueling success at international competitions, Xing Wen reports.

It's Friday, and 500 primary school and junior high school students sit in a hall in Xianghe county, North China's Hebei province, each using a pencil to fill in the empty squares of a grid that is divided into nine blocks of nine squares each.

These young finalists have been selected from the preliminary contests of this year's national junior Sudoku competition which were held in Beijing, Shanghai, Hangzhou and 15 other cities across the country. Some of them are hoping to gain entry into the 2018 China Sudoku Championship on Saturday, where they will fight for the opportunity to represent the country at this year's World Sudoku Championship in Prague, the capital of the Czech Republic.

The numerical puzzle, first created by a Swiss mathematician in the 1780s, is now gripping China.

The country boasts 20 million Sudoku lovers and, according to Xu Yan, deputy secretary general of the Beijing Sudoku Association, the craze can be traced back to 2007 when a Chinese squad debuted in the World Sudoku Championship after China was granted membership of World Puzzle Federation-the organizer of the competition.

Xu, being among the first group of Chinese participants in the WSC, says her experience at the international event gave her great confidence for the development of Sudoku in China, which she believes has a promising future.

"The intellectual pursuit was introduced relatively late in China," says Xu. "I hope that, with a few years of systematic training, we can continue to send excellent players to compete on the global stage."

In the years following the foundation of the Beijing Sudoku Association in 2012, Xu and other Sudoku lovers spared no effort in promoting the puzzle, delivering speeches in communities and schools, organizing events for various age groups and even designing Sudoku teaching materials and courses for different levels.