The beep coming from your PDA is not a reminder for a meeting. It's a trull trying to communicate. Shouting, it looks at you from the screen. The only thing to do is to scribble some runes to make it quiet. Then run to the next holy place.

This is a perfectly real scenario, and has been since the release of The Visby Game,-an adventure computer game set not in the usual fantasy world but in the town of Visby, Sweden. The trull is a character in the game, and together you visit mystical places both in the physical world and the game world.

The choice of Visby for the game setting is no coincidence. This small, medieval town is the home of Zero-Game Studio, an applied research lab specializing in games. A dozen leading computer games researchers from all over the world have settled at this two-year-old lab to investigate what a game really is-and what it could be. Zero-Game is part of a company called the Interactive Institute, which is owned by a Swedish research foundation that is itself controlled and financed by the Swedish government.

The Visby Game is one of Zero-Game Studio's first projects-and one of the first games in the world to take advantage of mobile technology for multi-user gaming. Apart from investigating what can be done with portable gaming, it is also being used to gather knowledge about how location-based games can augment the tourism experience.  Being both portable and played by several participants at the same time, The Visby Game is hooked on the two trends right now.

"Mobile games and massively multiplayer games are the latest significant changes in the basic model of what a game is", says Craig Lindley, research manager at Zero-Game Studio and visiting professor at the Department of Engineering, Art and New Media at Sweden's University of Gotland. Lindley's research background is in the areas of knowledge base systems, artificial intelligence, and autonomous agents, but a chance to work in a group specializing in the new field of games research brought him to Visby, situated on an island in the middle of the Baltic Sea.

From the other side of the Baltic, in Finland, comes further evidence that portable and multi-user gaming are hot: telecom company Nokia's new N-Gage device is a combination of a high-end mobile phone and a game deck with fast graphics and color screen. N-Gage also incorporates Bluetooth wireless technology to make possible multiplayer games among people in the same vicinity as one another. Game Boy needs an adapter to get this kind of wireless gaming. Play Station Portable, Sony's long awaited answer to Nintendo's Game Boy, expected to debut next year, is said to use Wi-Fi.

The early reviews have called N-Gage clumsy and expensive, dismissing it as just another mobile phone with some game-play capabilities. But the publishers of computer games seem thrilled. They believe they are seeing a chance to expand through new channels and to new consumers. This fall should bring the release of several high-quality games for the N-Gage, including Tomb Raider, Tony Hawk's Pro Skater, and Sega Rally Championship.