What goes into making a hit iPhone game?

Apple's App Store recently celebrated its second birthday, and a library of 250,000 apps. Most of these titles are games, which run the gamut from simple "hello world" touchscreen experiments to full-featured titles that took months or even years of development--and sometimes take just as long to play through.

Beyond all the development work is the cost of getting these items out there--something buyers rarely think about when hitting the green purchase button for titles that are often priced just below a dollar. In order to get an idea of what it takes to bring a game to market, CNET talked to a handful of successful developers, as well as with a company that helps people without the technical know-how to build a title connect with developers who can.

The short answer? It's expensive. And as with any other software project, as the list of things you want your software to do grows, so does the time--and money--it will take to finish the project.

But there's one bit of good news: The payoff can be big. "I could do nothing for a living, and live off it indefinitely," developer David Whatley told CNET. Whatley, who began his one-man development house, Critical Thought Games, as a side project to his main business, Simultronics, has three iPhone apps under his belt: Geodefense, Geodefense Swarm, and Geospark. The first two are simple tower defense games, while the last is a survival game that has players trying to match up moving pieces without letting them touch anything else.

"When I first got started doing this, everyone was saying that everyone who is going to make money has already made money. And then every year after that, someone would say it again," Whatley mused. "I would say, don't listen to that. It's an infinite shelf space. I still sell an amazing amount of software."

Part of the reason for that, Whatley explained, is that he's been featured by Apple several times, which in the world of app development is like getting your site on the front page of Digg or Reddit--but for an entire week. "During the last App Store anniversary [Apple] picked Geodefense as one of the apps they featured. It just constantly kept getting picked up again and again," he said. As a result, Geodefense Swarm (the sequel to Whatley's first Geodefense title), hit number one on Apple's top games chart last September, which in turn drove sales of the original game.

So how much time had Whatley sunk into building that app in the first place? "The original Geodefense--took six months to develop," Whatley said. "That was not full time, just nights and weekends--but not every night and not every weekend, just whatever I could give up." As for Swarm, which follows many of the same game mechanics as the first, Whatley explained that he was able to get it out the door much faster, since he could use some of the same code.

While Whatley went solo on his coding efforts, he did get a little help from others, including an outsider to pitch in on level design and strategy, as well as a PR company to manage press and promotion. "I don't like public relations, or I should say I'm not very good at it. I also farm out some of the ancillary art stuff." Whatley also collaborated with another developer, Imangi Studios for his third title, Geospark, which has yet to break into Apple's top 100.

Collaboration was, in fact, the name of the game for all of the developers we talked to. The number one thing that was outsourced? Music and sound. Both Backflip Studios, the makers of the popular Ragdoll Physics series and the hit game Paper Toss, as well as Venan Entertainment, which makes Space Miner: Space Ore Bust and Ninjatown: Trees of Doom, told us that the job of creating the music and sound effects was always given to outside contractors.

But what about going beyond that, and having outsiders create the entire game? For those that don't have a background in game development, or even in basic app creation, freelancers are effectively a magic bullet. There are places like Elance and Craigslist, and then there are companies like CenApp, which runs a ring of sites for the iPhone, the iPad, and Google's Android that all act as the middleman--connecting people with ideas for an app with developers who can do the dirty work. So far the company has helped create about 3,000 connections.

CenApp's promise, beyond being a job finder for freelancers, is to help weed out the good developers from the bad ones. Developers in its network have to be based in the U.S. and must already have an app on the app store. They also need a Web site with a portfolio and contact information.

One of the company's sites, called iPhone App Quotes, specializes in both iPhone apps and games. People who want to make an app first run the idea by CenApp, which goes through its directory of developers to find a good match. In turn, CenApp gets paid by the developers who end up taking the job. "What we said to the developers was that you don't have to be a certain size. There were people who were more appropriate for the freelancer, and more appropriate for the company with the graphics department, and can do an all system formats launch at the same time," CenApp CEO Mark Stetler explained to CNET in a phone call last week. "We have both in our system now--individuals and companies."

Besides figuring out the matches, CenApp's consultants will figure out the ballpark cost for an app before it even pitches the idea to developers in its network. Apps are split up into three tiers of pricing: $2,500 to $5,000; $5,000 to $10,000; and $10,000 and up. These estimates are derived by what your app does. Stetler explained that simple things like a calculator or RSS feed of an existing data source are the easiest, and fall into that first category. The second tier is made up of simple 2D games, GPS apps, and apps that tap into a proprietary database. The third, and most expensive tier, Stetler said, is typically reserved for 3D games, database development projects, and social-networking applications.

"Our top category...is $10,000 and above," Stetler said. "If you are a social-networking app, you're automatically going to be put into that category. That doesn't mean you're going to pay that, but for purposes of allocating the level of sophistication of projects, we assign it to one of those categories."

Stetler explained that the company does not actually keep track of what is spent after it pairs up an idea maker with a developer or development group. It does, however, send out a survey a few months later to ask if the customer was satisfied.

And speaking of follow-ups, there is one pesky detail about game development, and app development at large, that's worth mentioning: updates. Like any modern day software project, code is often updated. Sometimes it's for show stopping bugs, but more often than not it's to introduce new features, or changes that accommodate new Apple hardware, such as a sharper screen or additional motion sensors--two things that came with Apple's most recent iPhone hardware iteration.

In the App Store, the watchdog group for these updates is the customers, who can leave rated reviews of an app. If a developer abandons making changes, users will often go in to give it a low rating, which if done enough can affect sales and get a developer's attention. But there's another side to this. Some companies, like Lima Sky and Bolt Creative, have actually created a business around selling games at low cost, to a high volume of users, with the promise of frequent updates.

Bolt Creative's hit title Pocket God was first released in January of last year, and has since been updated 32 times, each time adding an additional piece of content at no cost. The same has been done with Lima Sky's Doodle Jump, which as of last month had sold more than 5 million copies at 99 cents a pop. "For somebody like Lima Sky, it's a big part of their strategy. If we had an app that was up there at the top of the charts, we would do the same thing." explained Venan's president and CEO Brandon Curiel. "In the case of Lima Sky it gives them lots of fans, but if you're hanging out on the bottom of the charts, it's not worth the resources."

Curiel said that part of the development process has to be letting go of something and moving forward, which in his company's case means focusing less on adding to old titles, and more on making new ones. "It really depends on the dynamics of the app store," Curiel said. "Things happen a lot more quickly, and you can use that to your advantage."

While no developers could give us specifics on the cost of getting one of their games out, or what was spent after release on marketing and updating budgets, they were frank about development times, which ranged anywhere from two to nine months. In some cases, these projects were just one or two people, and in others entire teams working full bore, which, if you do the math, very quickly gets these titles into the top tier of CenApp's development estimates. In other words, if you want to make a hit game, be prepared to invest.