These guys set out to make a 'Flappy Bird' clone, and instead created this crazy addicting game that's blowing up the app store

In the first weekend Mr Jump became available, more than 5 million people downloaded the game to see if they could make it past the first level.

Mr Jump, like the viral hit Flappy Bird last year, had managed to strike the sweet spot between difficult and addicting, and the charming platform game featuring polygon-based artwork reached 10 million downloads by the two-week mark.

The concept of Mr Jump was simple: Tap on the screen to cause Mr Jump to jump over the spikes and water, and survive long enough to make it to the end of each of the 12 levels.

"The reactions were similar to Flappy Bird - 'This is impossible, I can't beat level one' - and that makes people download the app," Thomas Castel, one of the three developers behind Mr Jump, told Business Insider.

"There was a lot of virality to the game, a lot of sharing on Twitter on Facebook and other social networks, so Mr Jump just rocketed to the top of the charts and it was top free app in the U.S. for more than a week which was great."

Castel and the two other developers behind the game, Jérémie Francone and Alexandre Konieczny, started making apps together in 2010 after graduating from the same engineering school. Mr Jump was their second big hit.

Their first big hit, Mr Flap, was a Flappy Bird clone.

"Last year, we had our first really big success, Mr Flap, during the Flappy Bird craze," Castel said. "We wanted to make a Flappy Bird clone, our take on the concept, and it did really great and after that we made more puzzle games. The most successful was Bicolor, a simple puzzle game based on two colors, which was promoted by Apple."

The success of Mr Flap and Bicolor ensured that the three friends could continue making apps full time, which wasn't always the case. While the three had been creating utility and social networking apps on the side since 2010, their first app only made them $18, and they didn't have enough money to start their company 1Button until three years later in 2013.

Castel, who worked at telecommunications company developing video-on-demand apps, was the first to quit his job in 2012, followed by his childhood friend Jérémie Francone, who dropped out of his PHD program in computer science after three years of study and creating glasses-free 3D display for the iPad. Alexandre Konieczny, who met Castel and Francone at engineering school, was the last to join the team full-time in 2014 after quiting his job developing software for the Airbus A350.

"We started by making puzzle games because it's simple and we loved them on game consoles, so we thought it was a good place to start because it is easy to do and doesn't require years of development," Francone said.

Fast iteration quickly became a core theme for the 1Button team, who could now afford to purchase a small office in the French Alps - complete with a TV and every Nintendo game console to serve as inspiration and a way to wind down at the end of the day.

"We mostly make small apps that take less than two or three months to develop, and we don't try to force the success of an app," Castel told Busines Insider. "If an app doesn't work and doesn't gain users or make money, we just give up and start a new app."

One of these experiments later evolved into Mr Jump, which originally started out as an endless runner-style game with one endless level.

"In November last year, we had an epiphany, we realized we should make finite levels instead of an endless runner," Castel said. "After that, we had the idea for the graphics, these kind of isometric graphics that Mr Jump has, and everything was perfect so we started to really develop the game and make the levels."

The rest is history, and the Mr Jump team is already busy putting the finishing touches on a big update to Mr Jump that will double the size of the game, adding an additional 12 levels and a new power - the jetpack.

To allow players who haven't beaten all of Mr Jump's original 12 levels a chance to play the new expansion, 1Button is dividing things into two sections: World A, with the original 12 levels, and World B, with 12 new levels and the jetpack.

The update is launching April 30th, but 1Button has shared a preview of the expansion with Business Insider, which you can see below.

Looking to the future, Castel says 1Button will set to work on a new game after the Mr Jump update goes live.

"We are going to continue making new games, and I can tell you that our next game will be a puzzle game - so we won't stop, it's really what we love."

You can download Mr Jump for free over at the App Store.