The online verification procedure to buy railway tickets has turned the process into an intellectual challenge, meaning that customers must be Internet savvy with fast-clicking fingers, sharp eyes and a quick mind.

The only website in the country allowed to sell train tickets, 12306.cn, has received numerous complaints about the verification code test that users must pass to buy tickets online.

The test is a multiple-choice question: "Click all the XXXs from the pictures below," requiring customers to match images to descriptions of things such as recorders, electric generators, fans and humidifiers.