Skipping Stone did very well for Gamevil, selling over 1 million copies.

Gamevil has been publishing games in South Korea since the year 2000, but has recently gained some fame for their one-button mobile title, Skipping Stone – the 2005 mobile game of the year across many publications.

Kyu C. Lee, president of Gamevil, delivered this talk, discussing the success of their own one-button games, and hinting at how developers could use this model to their own advantage. He was a bit nervous, and overly humble, but the message still came across – one-button games are big business.

All of their one-button games are timing-based, and very simple, so it's important to vary the gameplay a bit. “Gamevil has promoted one-button games as ‘games that your grandmother can play,'” as Lee put it.

He then gave three examples of their games that use only one-button. Skipping Stone is just based on timing – you're skipping a stone, and press the button when the stone hits the water, to keep it going. Items and perspective vary the gameplay a bit from time to time.

In Coinstack, coins are on a moving platform, and you have to drop them at just the right point so that the stack will stay straight. Again, items vary the gameplay.

	Nom is a very unique one button action game.

Nom was a much more interesting title, in which you play as a runner, jumping over obstacles, catching girls to kiss, and, apparently, making dogs follow you around. The gameplay is varied enough as it is, but the game also requires you to rotate the screen as you play on occasion, in a throwback to the Wonderswan. This game was actually a million-seller in Korea (not released in the US yet), and was released in 2003. Very quirky game, which just saw a sequel.

Another strategy is to take a number of minigames and put them together into a collection, as Korean firm Com2uS has done with its title Minigame Heaven, which that company has plans to publish in Europe or the US under the monikerMinigame Pack.

Game details aside, Lee says that one-button games have been very big in Korea , with a number of million sellers (four for Gamevil). “One of the reasons could be that it's easy to demo to other people. It's easier for word of mouth to spread. High-score functions also helped it to spread,” he said.

Most traditional games are two-handed, he says – even the N-Gage and much mobile content. Lee says that mobile handsets are much better suited to one-handed gameplay though, adding “I personally think that one-handed gameplay is really important for success of mobile games.”

He also mentioned that he checked the Wikipedia, and noticed that while cellphones are getting smaller and smaller, the human hand is getting bigger, due to advances in medical science. That elicited a bit of a chuckle from the audience.

So where do people play mobile games, he posed? They play on the subway, or on the go, or in school (each example was accompanied by a rather amusing graphic). These are all situations which are suited to one-handed gameplay.

There are three key points to the success of one-button mobile games. One is the ease of play. This makes them much more accessible to a wider audience. Gamevil created a game called Path of the Warrior, an action RPG which uses a bit of AI to make the game work with a single button. Enemies come from all sides, and the AI autofaces your character toward them, so you only need to hit the attack button to fight. He also mentioned that one-button aspects can easily be integrated into other types of game.

Another is that they're addictive. The simple nature of play makes it engaging, and a bit of difficulty makes the task at hand seem just out of reach. Lee quoted the designer of Skipping Stone as saying (slightly English fixed): “People have a strong tendency to fill things up. For example, people will try to fix things that are loose. Or if there's something that's empty, people will try to fill it up.” Essentially, simple play is often based on instinct.

The last point is productivity. Put simply, one-button games are easier to develop. Kyu Lee put out some statistics for their own game development. Skipping Stone took 6 months to develop, Skipping Stone 2 was 4 months, and other Gamevil games took 10 months on average. What's more, Lees says “you can get a return on your investment pretty quickly with these games.”

After the design document is finished, development is pretty smooth, he says. The timing aspect of the game is the most difficult, taking about half the total programming schedule. Timing is the critical element in these games, so it needs to be fine-tuned. “We spend more than a month deciding which timing is correct, and if it'll be too easy or too difficult.” The initial stage of design is also very critical. Even if you have a good concept, the game will be boring if not planned properly.

He then talked about one of the company's newest games, Nom 2. He added the rather cryptic statement that the company “signed a contract with NASA of Ukraine to send messages to outer space, and we picked the stars. It was a unique experience.” Apparently in Nom 2, “in one part you have to get on the boss's tongue so you can kick her in the nose. The designer of this game was a very unique person. Many people in Korea don't even understand it.”

	Minigochi is also a one-button game, a rather advanced Tamagochi clone.

After the talk, Lee fielded a few questions from the audience – the first of which addressed whether there were any game types other than timing-based for one-button games. Lee responded by saying “That's something we'll have to think about. I mentioned the combination of AI and one-button, and I don't think it has to be fully one-button, but I think it's important to keep it in mind. You should reduce the number of buttons you have to press. I don't really like to touch the numberpad at all. I prefer games that only use the d-pad.”

Another question mentioned that the revenue share is much larger, asking if the one-button games any cheaper than complicated games. Lee said that in Korea , it's pretty fixed. It used to be 2 dollars, when the industry really got going, but now it's up to about $3.50. With network games, it can go up to $10. The prices are pretty much the same though, making cheaper-to-develop one-button games even more appealing.

The final question asked whether there were any downsides to one-button games.

Lee finished up by saying that the risks are smaller, but it's harder to propose these types of games to consumers, and even tougher to spread word of mouth. They had a rough time popularizing Nom, but it wound up being a million seller eventually. By the time Nom 2 came out, their work was much easier.

Though the talk was light on actual development details, the fact remains that Nom 2 is one hell of a crazy game.