Developer Q&A: Behind the Koi Pond Craze

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For many weeks after Apple's App Store opened its virtual doors, the most popular application in the place turned out to be nothing more than koi swimming lazily in a pond. And yet, if you were to glance at the Top Paid Apps listing at the App Store any time in recent weeks, you'd usually see Koi Pond holding down the top spot. Even now, with heavy hitters like Spore Origins and Star Wars: The Force Unleashed to contend with, Koi Pond remains a mainstay on the App Store's popularity charts.

Just how many downloads does it take to dominate the iPhone bestselling paid app spot for four weeks running? The Blimp Pilots, the five-person team behind App Store phenom Koi Pond, isn't telling. But there is a lot to learn from Koi Pond's journey from idea to actuality, and designer Bill Trost and engineer Brandon Bogle were more than happy to share with Macworld some helpful advice for aspiring iPhone developers.

What prompted you to make the leap from designing entire gaming worlds like Everquest to working on apps for the iPhone in your spare time?

Trost: When Apple announced their developer plan for iPhone 2.0, we just thought it seemed like a great idea. None of us had any real Mac experience before, but we thought we'd give it a shot. So we went out and bought Macs just to take part in iPhone development. We did it as a hobby, mostly for fun, thinking that after developing a few apps maybe we'd be able to pay for our computers.

Was making the jump from game development to Objective C and the Cocoa application environment difficult?

Bogle: It was challenging at first, of course. None of us had any prior experience with modern Mac development. I had done some professional game development back in the System 7 days, but none of that helped now. Objective-C was not very difficult to learn however, and being a strict superset of C, we were already very comfortable with the core language.

I was pretty impressed with the Cocoa framework. You get so much functionality, and consistency in look-and-feel, with surprisingly little work. Interface Builder is a very powerful tool, and it really helped me understand how things all fit together. There was a point where all of a sudden I just "got it", and really started to understand the power and flexibility of the Cocoa / Objective-C combination.

How did the idea for Koi pond come about?

Trost: I had come up with the idea of doing a water simulation because Brandon Bogle had done something like that in the past for one of our games. So I brought the idea to him of basically turning the iPhone into a surface of water that you could interact with using your finger.

Did you know from day one that your app would sell for 99 cents?

Trost: We pretty much decided on that early on. That was part of the reason why once we saw the water we started adding the fish--to make it feel like it was at least worth 99 cents [laughs]. We never really wanted price to be a barrier.

Did you have any inkling that Koi Pond would become such a big hit?

Trost: We had no clue. We're very happy that so many people are enjoying it. From the moment we saw the first prototype running, we knew it was definitely going to be something that, as soon as people saw it, they would want to show their friends.

How long did it take to bring Koi Pond from concept to App Store star?

Trost: It took about a month. Because we were experienced developers, we were hoping to get in early into Apple's development program. But it wasn't until they opened the floodgates with [the 2.0 release] that we actually got in. Brandon had done some experiments in the iPhone simulator, but our application was so tailored to the device that we couldn't really test the interactivity of the water until the release of 2.0, when we could actually run it on a device and make sure that it felt right.

Did working with the iPhone application store present any unique challenges?

Bogle: The process of submitting our app was pretty straightforward. Apple provides plenty of documentation to guide you through the entire process, and the tools for managing your application once it is on the store are very thorough.

What changes to the app submission and approval process would you suggest that might benefit developers?

Bogle: It would be helpful if Apple provided a detailed submission "checklist" covering precise requirements for engineering, art, legal, etc., which must be met as a prerequisite for approval. This would give developers more confidence when submitting their apps for the first time, and would presumably make the review process easier for Apple as well.

What sort of response have you gotten from Koi Pod users?

Trost: It's been really surprising. We've gotten a lot of good feedback on our Web site from people who have used it to entertain their children. We got one e-mail from a therapist who works with Alzheimer's patients who said she was using it with her patients. We didn't really anticipate that it would strike that kind of chord with people.

What's next? Can you tell us about any new Blimp Pilots iPhone apps in development?

Trost: I'm not really ready to talk about our next projects, but we have several in the works. Like I said, this is our hobby so we're taking our time with them and releasing them when we feel confident with them.

What advice would you give iPhone developers looking to follow in you footsteps?

Trost: The biggest advice I could give is to think about the device. A lot of applications are making the mistake of considering device-specific functions almost secondary. It's a really unique platform that offers all sorts of new ways for people to interact with it, and a lot of developers are selling short the power that that has. Think about why people bought an iPhone as opposed to other phones. If your application takes advantage of those things, I think you have a much better shot at being successful.

[Tim Haddock is a writer and corporate communications professional living in Vermont. He remains hopeful that someday soon AT&T coverage will come to the Green Mountain State and all the illicit iPhone users can finally come out of hiding.]

This story, "Developer Q&A: Behind the Koi Pond Craze" was originally published by Macworld.

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