Why is Candy Crush So Addictive?

Mobile game Candy Crush has generated billions of dollars (and perhaps as many hours of wasted time) since its release, in 2012. What's the secret of this procrastination juggernaut? "It's very easy to learn," says Jesper Juul, who has written a history of this simple and addictive genre of games, known as Match-3.

Candy Crush, like other Match-3 games, uses a grid of tiles in various colors and shapes. Players swap those tiles to make matching stripes of three (or more) tiles, which then vanish with a satisfying whoosh. But Juul says it gets surprisingly hard, level by level, to clear each board of tiles. A group of computer scientists in Rome proved last year that the course a Match-3 game will take is exceedingly difficult to predict.

If the game were too hard, players would just give up, so Match-3 games lure users with lots of tiny victories. You can’t make a move without getting a match and clearing tiles, so every turn delivers a jolt of positive feedback. Another factor, says Juul, is the lack of time pressure, which allows users to play distractedly, on their own time.

Candy Crush is not the first game to cash in on these qualities. Match-3s first gained popularity in 2001, with the release of Bejeweled, which uses gems in place of candy. The makers probably got the idea from the simple Russian game Shariki, released in 1994. If you follow the lineage all the way back to the 1980s, you'll arrive at what Juul calls the "primordial" matching tile game: Tetris.

The addictiveness of Match-3 games might not be inherent to their design, though. It's likely more about trends. Juul points out that the genre's popularity fluctuates in tandem with complex games like World of Warcraft. "It's popular because it's popular," says Juul. "It becomes a cultural moment … that would have been impossible to predict."

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This article was originally published in the July 2015 issue of Popular Science.