The iPhone fairy tale is becoming a familiar one for game developers: A small indie developer creates a hit, people love it, and it spreads like wildfire through the App Store. Tens of millions or hundreds of millions of downloads later, and the developers are rich and on their way to building a mobile gaming empire. Sometimes they even sell adorable plush toys based on their game characters.

It has happened with Rovio, maker of Angry Birds; Outfit7, maker of Talking Tom Cat; Lima Sky, maker of Doodle Jump; Halfbrick, maker of Fruit Ninja; Bolt Creative, maker of Pocket God; and Andreas Illiger, creator of Tiny Wings. So the question isn’t why were two Russian brothers so successful with their iPhone game, Cut the Rope, which has been downloaded more than 60 million times in just a year. It’s more, ‘Why not?’

Semyon (pictured above left) and Efim Voinov (above right), two twin brothers in Moscow in their 20s, have been making games since they were ten. They have put in their time, making dozens of games for the old feature phones and a handful for iPhones too. So it’s only right that, finally, one of their games has paid off with blockbuster results.

Efim got his first iPhone in 2008 and decided to work on games for the device. He created  ZeptoLab, a game development company where he serves as technical director and his brother Semyon works as creative director. Misha Lyalin (pictured middle) is the chairman of the company. With a team of just four people, they created a zany game called Parachute Ninja. The game, which stars a ninja with a ball-like body that bounces and floats, debuted in February 2010.

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Parachute Ninja was almost based on the rope mechanic that’s in Cut the Rope. Efim spent a lot of time getting the physics right by creating a custom engine that could simulate the behavior of the rope. There were other open-source physics engines available, but Efim liked the challenge of creating his own. He wanted to create a rope engine that worked well even on a device with a weak processing brain. To do so, he had to dust off his old physics books.

At the last minute, the developers decided to substitute a parachute for the rope. Parachute Ninja was downloaded 3 million times — a solid hit, but not as spectacular as some of the other mega-hit games on the iPhone.

“We found that there were no barriers for small developers,” said Efim Voinov, in an interview. “It is possible to be successful without a huge team on the iOS platform.”

The game gave the small team some good experience with its core development tools. After the first iPhone game shipped, the brothers decided to make use of their rope engine with another creation. They studied their first game and felt like the combination of touch and tilt controls made Parachute Ninja tricky to understand for players. Other games used rope physics.

“We experimented with different ideas,” Semyon Voinov said. “One of them was Cut the Rope.”

The concept phase was in the spring of 2010 and the prototyping took place in the summer. The team settled upon a mechanic where the player can draw a rope on the screen to solve various puzzles. Playing with a rope was pretty universal. The game play involved predicting the behavior of different objects in the rope environment.

It turned out that the visual element of how the rope looked wasn’t the key. The game play was the secret. It was an arcade-like experience that was simple to learn but players had to think and act fast.

The team also decided to create a funny character since casual gamers enjoy interacting with animated characters more than blocks or geometric shapes. They decided to use the rope to deliver food to Om Nom, the little green monster with a big appetite. Semyon thought that the monster should be cute, like a baby or a pet. That would tap into the feeding instincts of the players.

The 99-cent game came out on the iPhone on Oct. 5, published by Chillingo, which is now a part of Electronic Arts. Chillingo helped to get it off the ground and noticed with promotions and marketing. On its first day, the game shot into the top ten on the App Store. On its second day, it hit No. 1 on the App Store charts. Within 10 days, it crossed a million downloads. In June 2011, the game made its debut on Android. The game took off, Efim said, because it makes people smile.

“The monster is like a stress reliever,” Efim said. “They look at the animations and feel better.”

After the runaway success, the fairy tale has continued to play itself out. The team has done six or seven updates of the game, and Zeptolab has now grown to 20 employees in Moscow thanks to profits from Cut the Rope. Zeptolab has no plans to raise fuding, since it already has a lot of money coming in from game sales. The brothers are now mini-celebrities in the mobile game development world.

“I don’t have a lot of girls standing by my house yet,” Efim said. “But we are known in the industry. What we see as a great sign is that Om Nom is liked by people. We see a hunger for something more.”

And, of course, like Angry Birds before them, there are Om Nom plush toys. The toys hit the market in September and they’re selling well. On Nov. 18, they released a free holiday edition with new game content on iOS.

Efim and Semyon have some advice for small developers. “[If you] do what you like,” Semyon said. “You will not waste time doing things you don’t like.”

They suggest developers study games that have been successful and understand the features that made them successful. They also say developers should study games that were duds and understand what people didn’t like. Developers should create games that appeal to as many people as possible and to keep at it. Altogether, the brothers had worked on 30 mobile games before they had a major hit.

“We were mentally prepared to work on many titles, hoping one would be a hit,” Efim said. Semyon added, “It’s very important when you develop games to show it to others. Listen to them. Understand what they like. Show it to non-gamers.”

And what’s next, beyond the plush toys? They are working on a sequel to Cut the Robe that should be released in 2012. They want to keep fans happy with updates and they are working on a new intellectual property (an original title) that should come out next year as well. That’s where the 20 employees come in. The company now has the ability to work on multiple projects at once, including a new digital comic book.

“We want it all, basically” Efim said. “We want to expand the Cut the Rope brand. We plan to offer new titles that are similar. At the same time, as creative people, we have an urge to work on something different.”

The team will expand Cut the Rope to new platforms, but is aware that it can’t pursue all opportunities due to resource constraints. The company continues to hire, but only people who are perceived as the best at what they do. Facebook is intriguing, as is HTML5 for multi-platform games. The growth of the mobile game industry, which is now in the billions of downloads, is surprising them most of all.

“We started working on mobile games a long time ago, when the phones were not powerful and had tiny screens,” Efim said. “There was hype back then, and we expected it to become huge. I had some illusions. It didn’t happen then, but it surprisingly happened with the iPhone.”

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