ZeptoLab CTO Efim Voinov on how its million selling Cut the Rope was inspired by a yo-yo ninja

Plus the joy of feeding babies

ZeptoLab CTO Efim Voinov on how its million selling Cut the Rope was inspired by a yo-yo ninja
With only its second iPhone game already a million seller, ten days after launch, things are going very well at Russian studio ZeptoLab.

Probably a good time then to catch up with CTO Efim Voinov and find out the development process behind its addictive, casual physics puzzler Cut the Rope, and how it learnt from its debut game, the charming but tricky Parachute Ninja.

Pocket Gamer: What was the inspiration behind Cut the Rope?

Efim Voinov: ZeptoLab's first game Parachute Ninja was actually intended to be called Yo-Yo Ninja and feature the little ninja swinging on the rope. You can still see the rope bundle inside the ninja equipment chest which is presented in one of the game's cut scenes.

However, at a certain point in development, the team realised that the controls weren't working well, and decided to swap the rope with the tilt operated parachute. By that time, many hours had been spent creating and fine tuning the realistic rope physics, so when we started to think about the next project, we've decided to utilise that engine - and that was the starting point for the game design.

The success of Angry Birds also encouraged us to try the physics puzzle genre.

Some people also said Parachute Ninja was too difficult so how did that affect Cut the Rope?

Parachute Ninja had a combination of touch and tilt controls, which made it tricky to understand and operate for some players. In fact, we have even seen a few YouTube videos where players were reviewing the game without knowing that the parachute can be operated by the tilt.

Most of people just don't read tutorial messages no matter how short they are, and prefer to find out the controls themselves. If they are not able to do this, the game will lose a big part of an audience.

Also, some players felt that Parachute Ninja's gameplay was frustrating at times, so we've tried to minimise that feeling in Cut the Rope.

How difficult was it to get the physics working in a smooth way?

Rope physics are not as easy to get right as it might look. We've decided to go with our own engine instead of using an existing technology such as Box2D, partly because we wanted the rope looking as smooth as possible, and party because it looked like an interesting task.

One of the challenges we initially had was the game performance, but over time we were able to maintain quite a high framerate.

How difficult was it to get a good balance between an enjoyable game and a challenging game?

During the development, we've asked many of our friends to try the game, and while they were playing it, we were observing the process behind their backs. I think this is the best way of knowing if the difficulty curve is good or not, and if the game is moving in a right direction overall.

Also, the three star system is a great way to satisfy a wide range of players. Some people will just deliver the candy to the Om Nom's mouth, but some won't stop until they get all three stars in all of the game levels. So, the game difficulty is pretty much manageable by the players themselves.

Who came up with the idea of Om Nom?

We had a concept of some object being delivered from point A to point B from the very beginning of the project. After brainstorming several theme possibilities, we've got a monster feeding idea, since we believed that the casual audience likes interacting with the animated characters much more than with the blocks or geometric shapes.

In a way, we also wanted to exploit the parental instinct of the players, because feeding a little baby is one of the warmest experiences the parents get. So, we felt that the emotional motivation for the player to complete the level would work best, not to mention that chewing action itself has some weird power of emitting the cuteness.

Why did you publish the game with Chillingo?

Chillingo has showed many times its ability to deliver the games to the top of the charts, and also our game fits Chillingo's audience really well.

Working with Chillingo so far has been a great experience, and all the feedback and help its team is providing to us has definitely helped us making a better game.

Will Cut the Rope come to other mobile devices?

We are now looking into possibilities of porting Cut the Rope to other platforms, and most likely it will appear on many kinds of devices quite soon.

What's next for ZeptoLab?

We are positively surprised and very excited about all the love players are showing to Cut the Rope, and we are eager to pay the credit back with the new levels and other cool features coming with the updates.

Quite likely, we'll spent at least a few upcoming months doing the updates and possible ports of the game, but of course we don't want to stuck on just doing the updates, and will start developing the next game quite soon.

Thanks for the interview and stay tuned!

Thanks to Efim for his time.
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A Pocket Gamer co-founder, Jon is Contributing Editor at which means he acts like a slightly confused uncle who's forgotten where he's left his glasses. As well as letters and cameras, he likes imaginary numbers and legumes.