"The reason Flappy Bird is so popular is that it happens to be something different from mobile games today, and is a really good game to compete against each other," Nguyen told The Verge. "People in the same classroom can play and compete easily because [Flappy Bird] is simple to learn, but you need skill to get a high score."

And as users play over and over again, the Flappy Bird game displays banner ads at the top and bottom of the screen. With so many users now playing the game, all those ads are bringing in $US50,000 every day on average, Nguyen said.

That's a big accomplishment for the app, which was launched in May 2013 but didn't start to gain a following until November.

Often, mobile games give users the option to pay a small fee to remove ads, but Nguyen said he has no plans to remove ads or update the game in any way – no matter how distracting the ads may be for some gamers.

"Flappy Bird has reached a state where anything added to the game will ruin it somehow, so I'd like to leave it as is," he told The Verge. "I will think about a sequel, but I'm not sure about the time line."