Gift boxes of the Double 11 shopping spree. Photo: IC

The Double 11 shopping spree, the world's largest online shopping event during which billions are spent, got underway at the stroke of midnight Sunday with some netizens complaining about how difficult it was to get deep discounts this year.

E-commerce platforms have added many new rules and steps to obtain coupons this year. Some require shoppers to participate in a "building" game that asks players to construct virtual buildings, and those that build the highest building get the largest discounts.

 "I cannot understand the rules for getting the discount coupons," one Net user wrote. "It takes a lot of time to figure it out."

"Calculating these discounts is like winning a prize in an international mathematics contests," a Sina Weibo user sarcastically commented.

Some online shops also offered deeper discounts to shoppers who pay a larger deposit or perhaps pay upfront more quickly for the items.

Wang Minchao, an employee of a China's e-commerce platform, maintains the quizzes and the online games are not that complicated. "It only requires two steps: opening the website and finding the coupons in the shops," he said to the China News Service.