‘ How’s this for an exciting new game: Players spin a wheel and land on a category like history or sports. They spin again if they get a multiple-choice question right within 25 seconds and lose their turn if they’re wrong. Whoever answers the most questions correctly across six categories first wins.

Its not exactly groundbreaking, but that game—an app called Trivia Crack—has millions of Americans addicted. Trivia Crack has raced past giant apps such as Facebook Messenger, Candy Crush Saga, and Instagram to claim the No. 1 spot for free apps in the U.S. and has held it for more than a month. User reviews of the app, and an embarrassing amount of personal experience (1,202 questions answered correctly), suggest the app creates the kind of dependency its name implies. As one player tweeted recently, “I seriously wonder how many people #TriviaCrack [have] gotten fired since it became such a fad #triviacrackprobs.” ‘  By Suzanne Woolley