Bridging the Physical and Digital in Pervasive Gaming

Pervasive games extend the gaming experience out into the real world—be it on city streets, in the remote wilderness, or a living room. Players with mobile computing devices move through the world. Sensors capture information about their current context, including their location, and this is used to deliver a gaming experience that changes according to where they are, what they are doing, and even how they are feeling. The game player becomes unchained from the console and experiences a game that is interwoven with the real world and is potentially available at any place and any time.

This is an exciting idea, both from a commercial viewpoint where pervasive games extend current wireless games toward more connectivity and including real locations and activities, and where they may deliver much needed content for 3G mobile telephony. From a research perspective, pervasive games open up new technical and human challenges.

There are already various forms of pervasive games. One approach is to reinterpret classic computer games, mapping them onto real-world settings so that players must literally run about in order to control their avatars, as demonstrated by Human Pacman [4] and ARQuake [7]. Other examples focus strongly on social interaction, for example, Pirates!, a fantasy game about trading and fighting at sea [3], or the STARS platform for augmented tabletop games that preserve the rich social interaction found in traditional board and tabletop games [6] (see the sidebar “Computer-Augmented Tabletop Games“). Touring artistic games have mixed players on a city street with online players in a parallel virtual city, requiring them to exchange perspectives as in the chase game Can You See Now? [5], or exploring the theme of trust in strangers as in Uncle Roy All Around You [2] (see the sidebar “Mixing Street and Online Players“).

Pervasive games also have educational potential by encouraging learning through highly physical role play as shown by Savannah, a game in which groups of children hunt as lions on a school playing field [1]. Finally, early commercial offerings include BotFighters! from Its Alive, a multiplayer shooter for mobile phones, and Majestic from Electronic Arts, a seminal experiment aimed to interweave a fictional conspiracy with players’ daily lives.

These kinds of pervasive games build upon three core technologies:

• Displays that can make digital content available to players as they move through the physical world, including mobile phones, hand-held computers, earphones, wearable computers, and also interactive projections and tangible interfaces embedded into the surrounding environment;
• Wireless communications that enable players to communicate with remote servers and other players, including cellular telephony (3G, GPRS, and GSM) and Bluetooth; and
• Sensing technologies that capture players’ contexts including GPS positioning, cameras, microphones, and potentially even physiological sensors.

This blend of technologies, combined with the location-based and often public nature of game play, gives pervasive games their distinctive identity. At the same time, it also poses significant new challenges, five of which we now briefly discuss.

Dealing with uncertainty. Our first challenge arises from the considerable uncertainties associated with sensing and wireless communications. Both are constrained by limited coverage, especially in congested urban areas, so that players may often be unable to obtain a fix on their position or communicate with others. Sensing technologies are also associated with further uncertainties such as error and jitter, which can vary with both location and time. Previous research has proposed different approaches to dealing with uncertainty [5]: removing it, for example, by carefully choosing game locations and times; revealing it, so that players are able to understand; adapting to it; and even exploiting it by deliberately incorporating uncertainty into the structure of a game, for example, enabling players to “hide in the shadows” by moving out of network coverage.

Hybrid architectures. Our second challenge involves reconciling client-server and peer-to-peer architectures. Whereas client-server architectures enable players to share a consistent game experience, peer-to-peer architectures support highly localized and ad-hoc game play during encounters on the streets. The challenge here is to integrate these two approaches. For example, can we design games in which publicly visible and legitimate actions take place at central servers, but where there is the exciting possibility of more secret or private interactions occurring in peer-to-peer mode; for example, “pickpocketing” other players or black-market trading without revealing sources?

Hefting domains. Game elements in computer games are mostly tied to the virtual world, while traditional games reside in the real, physical world. Since pervasive games take elements from both the real and the virtual worlds, their design requires careful consideration of which elements to represent virtually, physically, or as a blend of both.

Configuration. A pervasive game may need to be configured to work at many different locations. For a game intimately tied with its local setting, the challenge is to quickly integrate rich local information—maps, plans, images, and sounds—into the game content. Pervasive games that are less integrated with a local setting; for example, Savannah, which takes place on an empty playing field [1], may still require considerable configuration of network and sensing technologies.

Orchestration. Our final challenge concerns orchestration, the real-time management of a live game from behind the scenes—an important issue when game providers assume responsibility for the safety of players who are on the streets of a city. Successful orchestration requires tools for managing the status of players; for example, knowing their connection status and last known location, and also for subtly intervening without disrupting the game; for example, by improvising game messages.

Pervasive games are therefore both an exciting and commercially promising new form of computer game that build on a combination of hybrid interfaces, wireless networking, and context-sensing technologies. However, while recent projects hint at a wide variety of potential gaming experiences, they also reveal some of the research challenges that must be addressed if pervasive games are to move forward, including designing for uncertainty, exploiting hybrid architectures, and support for configuration and orchestration. These challenges are being addressed in a number of new projects worldwide, including the U.K.’s Equator project (www.equator.ac.uk) and the new Integrated Project on Pervasive Gaming (www.pervasive-gaming.org) that draws together industry and academic partners from across Europe.

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Figure 1. Can You See Me Now? Runner on the street (left) and online view (right).

Figure 2. Uncle Roy All Around You: Street player (left) and online view (right).

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Figure. Playing computer-augmented tabletop games with the STARS platform.