Candy Crush rules, driving massive growth

Nearly 540 million people estimated to regularly play video games in some form

Staring silently and entirely focused on her game of Candy Crush 20-year-old Lingyi Tong, with a flick of her fingers, triggers a symphony of explosions on her iPad screen. Despite the bravura display, she fails to solve the level's challenge of matching fruit and destroying jellies with her two final moves - falling short by only a single jelly.

"I was so close," said Tong, groaning in exasperation.