GB2417694A

GB2417694A - Real-world interactive game

Info

Publication number: GB2417694A
Application number: GB0419520A
Authority: GB
Inventors: Sara Elizabeth Revell; Andrew John Radburn; Guy Bradley Heathcote
Original assignee: SEC DEP ACTING THROUGH ORDNANC; UK Secretary of State of
Current assignee: SEC DEP ACTING THROUGH ORDNANC; UK Secretary of State of
Priority date: 2004-09-02
Filing date: 2004-09-02
Publication date: 2006-03-08
Also published as: WO2006024866A1; GB0419520D0

Abstract

A plurality of mobile client devices can be used to implement a real-world interactive game played by users of those client devices. Each client device includes a positioning device such as global positioning system (GPS) device for determining a real-world position of the client device. The client device can display a graphical representation of a real-world geographical area in the vicinity of the client device and also can indicate the real-world position of the client device and of any other client devices participating in the game as determined by their respective positioning devices. The client device can also determine game events and transmit and receive data describing game events via a communications interface. A server can also be provided for coordinating the game. The server can arbitrate and prioritise between game events. One of the client devices participating in the game can assume the role of the server.

Description

REAL-WORLD INTERACTIVE GAME APPARATUS

BACKGROUND OF THE INVENTION

This invention relates to an apparatus and method for implementing a realworld interactive game.

Computer games which involve a game character that interacts with a fictional game environment are well known in the art. For example, in some known games, a fictional character moves through and interacts with a fictional 3-D environment that resides entirely in the memory of the computer upon which the game is being played.

In some games, the fictional environment is based upon a known real-world location.

Nevertheless, even in these games the 3-D environment in which the fictional character moves and interacts still resides entirely in the memory of the computer on which the game is being played, albeit that the fictional environment resembles a known location.

Real-world games involving a number of participants who play the game at a real- world location are also known. One example of such a game is paintballing. In games such as these, it is often difficult to arbitrate events that occur in the game (such as the capturing of a flag) or to confirm the movements of the participants of a game in the case of a dispute. Also, known real-world games can be limited by the fact that the game participants may not receive feedback on the progress of the game or on the status of their opponents.

This invention aims to provide an apparatus and method for implementing a real-world interactive game in which participants can receive information regarding game events and thereby, for instance, receive feedback in real time regarding the progress of the game and the status of their fellow participants in the game.

SUMMARY OF THE INVENTION

Aspects of the invention are defined in the accompanying independent and dependent claims.

An aspect of the invention provides a mobile device for implementing a real-world interactive game, the device comprising a processor, output means and a positioning device for determining a real-world position of the device, wherein the processor is operable to respond to the determination of a game event associated with the real world position of the device by outputting an indication of a game event using the output means. The mobile device can provide information in respect of a game event based on its determined real-world position.

For example, the mobile device can be operable to output an indication of at least one determined target distance, wherein each determined target distance is determined by: determining a distance between the real-world position of the device and a real-world position of a target. The mobile device can thus be operable, for example, to inform a user in real time of a distance from at least one target based on its determined real- world position, and this information, which can change as the client device moves in the real world, can then be used by the user to locate the target. In one example of the invention, the mobile device is operable to determine a distance associated with the real-world position of the device and a target position.

According to another aspect of the invention, there is provided a mobile client device for implementing a real-world interactive game. The mobile client device includes a processor, memory, output means including a display, a positioning device for determining a real-world position of the client device and a communications interface.

The processor is operable to determine a real-world position of the client device using the positioning device. The processor is also operable to display a graphical representation of a real-world geographical area in the vicinity of the client device on the display and indicate on the graphical representation the real world position of the client device determined by the positioning device. The processor is further operable to

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determine a game event associated with the real-world position of the client device determined by the positioning device. The processor is also operable to transmit game event data describing the game event via the communications interface. The processor is further operable to receive game event data in respect of game events associated with the real-world position of another client device via the communications interface.

The processor is also operable to output an indication of a game event using the output means.

Such a mobile client device can determine game events based on its realworld position and can notify other participants in the game and, for example, via a central, co-ordinating server of such events. The client device can also receive information relating to game events associated with other game participants and a user of the client device can thereby be notified of those events.

The client device can monitor the real-world position of the client device using the positioning device and update the display accordingly. Data describing the real-world position of the client device can be transmitted via the communications interface on a periodic basis, on a continual basis or in response to a game event.

Data describing the real world position of another client device can be received via the communications interface and the real-world position of the other client device can be indicated and updated on the graphical representation of the real-world geographical area displayed on the display.

Game events can include a target event in which the real-world position of a client device comes within a predetermined minimum distance of a target position allocated to that client device, and an opponent target event in which the real-world position of a client device comes within a predetermined minimum distance of a target position allocated to another client device The positioning device can, for example, comprise a global positioning device.

Alternatively, the positioning device can be based on a local positioning system, for example based on a terrestrial grid detection system, wireless triangulation system or proximity detection system, for example. The communications interface can have an interface for connecting to a remote server via a telecommunications or other network and/or an interface for connecting directly and wirelessly to a server or another mobile client device. The client device can, for example, be a personal digital assistant, a mobile telephone, a GPS navigation device, a special purpose gaming device, etc. According to another aspect of the invention there is provided a server for implementing a real-world interactive game played between users of a plurality of mobile client devices. The server includes a processor and memory storing data associated with each mobile client device, the data including an identifier for each mobile client device and data describing conditions for the triggering of at least one game event for each mobile client device, wherein each game event is associated with a real-world position of the mobile client device. The server also includes a communications interface operable to connect to the mobile client devices. The processor is operable to transmit and receive data describing game events to and from the mobile client devices via the communications interface.

Accordingly, the server can form a central store for game data and can relay data describing game events between participating mobile client devices.

The server can be a mobile communications device. In some embodiments, one of the mobile client devices can take on the role of the server.

The medium via which the client devices communicate with the server can be can be a large-scale communications network such as a mobile telephony network.

Alternatively, it could use a small-scale wireless communications system using wireless technology such as Wi-Fi or Bluetooth.

According to a further aspect of the invention there is provided a system comprising a plurality of mobile client devices as described above and a server as described above.

According to another aspect of the invention there is provided a method that includes determining a real-world position of a client device using a positioning device of the client device. The method also includes displaying a graphical representation of a real- world geographical area in the vicinity of the client device on a display of the client device, wherein the display is comprised in output means of the client device. The method further includes indicating on the graphical representation the real-world position of the client device determined by the positioning device. The method also includes determining a game event associated with the real-world position of the client device determined by the positioning device. The method further includes transmitting game event data describing the game event via a communications interface of the client device. The method also includes receiving game event data describing game events associated with other client devices via the communications interface. The method further includes outputting an indication of a game event using the output means of the client device.

According to a further aspect of the invention there is provided a method for implementing a real-world interactive game played between users of a plurality of mobile client devices. The method includes a server storing data associated with each mobile client device, the data including: an identifier for each mobile client device, and data describing conditions for the triggering of at least one game event for each mobile client device, wherein each game event is associated with a real-world position of the mobile client device. The method also includes transmitting and receiving data describing game events to and from the mobile client devices via a communications interface of the server.

According to another aspect of the invention there is provided a computer program product comprising program instructions executable by a processor to implement one of the methods described above.

A computer program product for implementing the invention can be in the form of a computer program, for example, on a carrier medium. The carrier medium could be a storage medium, such as a solid state, magnetic, optical, magneto-optical or other storage medium. The carrier medium could be a transmission medium such as broadcast, telephonic, computer network, wired, wireless, electrical, electromagnetic, optical or indeed any other transmission medium.

Further aspects and advantages of the invention will become apparent from the

following description of particular embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described hereinafter by way of example, with reference to the accompanying drawings in which like reference signs relate to like elements and in which: Figure I shows an overview of a network, a server and a number of mobile client devices in accordance with an example of this invention; Figure 2 shows an example of a mobile client device; Figure 3 shows a functional block diagram of parts of a mobile client device such as that shown in Figure 2; Figure 4 is a schematic of the memory space of a mobile client device such as that shown in Figures 2 and 3; Figure 5 is a schematic of a server in accordance with an example of this invention; Figure 6 is a schematic of the memory space of a server such as that shown in Figure 5; Figure 7 illustrates a real-world geographical location at which are situated a number of real-world objects (such as trees, buildings, etc.); Figure 8 illustrates the calculation of a distance between a target zone and a mobile client device; Figure 9 shows an example of the layout of a game screen which can be displayed on a display of a mobile client device during the playing of a real-world interactive game; Figure 10 shows a flow diagram that illustrates initial phases of a real-world interactive game that can be performed by a mobile client device; Figure 11 shows a flow diagram that illustrates a procedure for implementing a real world interactive game that can be performed by a mobile client device; Figure 12 shows a flow diagram which illustrates a procedure for co-ordinating a real world interactive game played between users of a plurality of mobile client devices; and Figure 13 shows a flow diagram illustrating another procedure for implementing a real-world interactive game that can be performed by a mobile client device.

While the invention is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the scope of the claimed invention.

DESCRIPTION OF PARTICULAR EMBODIMENTS

Embodiments and examples are described hereafter by way of example only in the following with reference to the accompanying drawings. s

Figure I is a schematic overview of a system that includes a number of mobile client devices 14, 16 and 18. In some embodiments, the mobile client devices can be configured to communicate directly with each other via, for example, a wireless link 8 using wireless technology such as WiFi or Bluetooth. The mobile client devices in this example are a Personal Digital Assistant 14, a mobile telephone 16 and a portable computer 18, such as a laptop computer.

Each mobile client device can also be operable to communicate with a server 12 via a network 10 using, for example, a General Packet Radio Service (GPRS) link. The network can be made up of a radio telephony network (for example, a cellular telephone network) and can incorporate elements of the public service telephone network (PSTN).

Each of the mobile client devices shown in this example include a communications interface which can allow the mobile client device to communicate directly with other mobile client devices using wireless communications as described above, or indirectly via the network 10 and server 12.

Figure 2 shows one of the mobile client devices shown in Figure 1 (the mobile telephone 16) in more detail. The mobile telephone 16 includes output means including a display 22. The mobile telephone 16 can also include an aerial 20 and a user input device such as a keypad 24. Similar components can be provided in other kinds of mobile client device (for example, PDA, laptop).

Figure 3 is a schematic overview of the functional components of a mobile client device such as one of those represented in Figure 1. As described in relation to Figure 2, these components can include a display 22, a user input device including, for example, a keypad 24 and an aerial 20. In this example, the mobile client device includes a communications interface 32 for communicating with a server. In other examples, the mobile client device may, as an alternative or in addition, communicate directly with one or more other mobile client devices. Accordingly, the communications interface 32 can have one or more aerials 20a, 20b according to the required communications. For example more than one aerial can be provided where wireless communications via a communications network to a server and also directly with other mobile client devices occur at different frequencies and/or use different communications protocols. The provision of more than one aerial can also allow these two modes of communication to occur in parallel. Alternatively, a single aerial may be provided for multiple modes of communication.

In this example of a mobile client device a processor 28 is operable to co-operate with a display driver 26 for controlling the display 22. A memory 30 is also provided for storing program instructions and data. The functional components also include a positioning device 25 for determining a real-world position of the mobile client device.

In some examples, the positioning device 25 is a Global Positioning System (GPS) device. In other examples, alternative andlor additional position devices may be provided. For example position devices based on a terrestrial grid detection system (based on signal emitted from a grid of wires embedded in the ground) and/or a terrestrial triangulation system (based, for example on radio, light or ultrasound signals) and/or a proximity detection system (such as a radio frequency identification (RFID) system) may be provided. The processor 28, display driver 26, memory 30 and communications interface 32 can be provided by one or more integrated circuits represented generally at 34. At least a portion of a positioning device 25 can be included in the circuitry 34.

The example of the mobile client device illustrated in Figure 3 is based on, for example, a portable digital assistant, a smart phone, a programmable position device or a programmable gaming device, or the like, that can be programmed to provide the functionality to be described below. To this end, program code and data can be held in the memory 30 for controlling the operation of the processor 28. However, in other examples of the invention, the functionality to be described in the following can be implemented using a special purpose device incorporating one or more special purpose integrated circuits, for example configured as one or more Application Specific Integrated Circuits (ASICs) for implementing the desired functionality. Such special purpose devices can then be mass-produced at low cost to meet specific applications of the invention.

Figure 4 shows a schematic of the memory space 36 of the example of the mobile client device represented in Figure 3. Operating System 38 occupies a section of the memory space 36 as do one or more software applications 40. Also present in the memory space 36 are one or more portions 42 that can be allocated to store data relating to game events and/or other information relating to the progress and status of a real- world interactive game.

Figure 5 shows a schematic overview of the functional components of an example of a server 12 in the form of a computer system. These functional components include a processor 52 and memory 54 for storing program instructions and other data. Storage 62 can also be provided for storing larger quantities of information. Storage 62 can, for example, include a hard disc drive, CD-ROM and/or other mass storage devices.

One or more peripheral devices such as a keyboard and monitor 64 can be provided.

The server 12 also includes a communications interface 56. The communications interface can have a link 58 to a communications network such as that described in relation to Figure 1 for communicating with a plurality of mobile client devices as described above.

Figure 6 shows a schematic of the memory space 66 of the memory 54 of the server 12. Operating System 68 occupies a section of the memory space 66 as do one or more software applications 70. Also present in the memory space 66 are one or more portions 72 which can be used to store data describing game events and/or other information relating to the progress/status of a game.

The technical functionality implemented by devices such as those described above allow a real-world interactive game to be played by a plurality of participants. Each participant carries a mobile client device as described herein. The mobile client device outputs information on a display thereof which relates to the progress of the game.

The mobile client device includes a positioning device that is used to determine a real- world position of the mobile client device (and thereby determine the real-world position of the user who is holding the mobile client device). Information relating to the real-world position of the user and of other users holding other mobile client devices can be displayed on the display of the mobile client device. The mobile client device can also display a graphical representation of a real-world geographical area in the vicinity of the mobile client device. Each mobile client device can determine game events associated with the real-world position of that mobile client device, as determined by its positioning device. Game event data describing the game event can be transmitted and/or received via a communications interface of each mobile client device, whereby game events triggered by one mobile client device can be notified to the other mobile client devices participating in the game. Each mobile client device can output an indication of a game event (for example, a game event triggered by that mobile client device, or a game event triggered by another mobile client device and about which a notification has been received). The notification can be outputted on the display and/or can be output as an audible or mechanical (vibrating) alert.

As used herein, the term game event refers to an event is associated with the real- world position of a device such as a mobile client device, as determined by a positioning device of the device. In one example, a game event is an event which is triggered by the mobile client device coming within a predetermined distance of a target location, which has been allocated to one of the mobile client devices participating in the game. The target location can be a target that has been allocated to that mobile client device when, for example, the game is initiated. Alternatively, the target location can be a target location that is allocated to another mobile client device.

The targets are real world locations, for example locations associated with an object in the real world, or locations not associated with any object in the real world.

Figure 7 illustrates an aerial view of a real-world geographical location 80. The real- world geographical location 80 can be relatively small (for example, the location may be a park or small woodland). Alternatively, the location 80 may be relatively large and encompass, for example, an entire city, region or country, etc. Accordingly, there is a large range of location types that are compatible with this invention. It will be understood that the location 80 shown in Figure 7 may extend far beyond the dashed line 82.

The real-world location 80 includes a number of real-world features. In this example, these features include a road 98, a number of buildings 90, a wall or fence 96 which includes a gate or opening 97, a footpath 94, a stream 92, a bridge 94 running over the stream 92, and a number of trees 88.

In accordance with an example of the invention, a portion of the realworld location 80 can be chosen as a real-world game area 84. The real world game area 84 can be bounded by a notional boundary 86. The real world interactive game takes place within the portion of the geographical location 80 that lies within the game area 84.

Areas which are known to be inaccessible to mobile communications and/or GPS signals and which lie within the notional boundary 86 can be excluded from the game area 84.

If the real world data used for defining the game area is based on OS (Ordnance Survey) MasterMap database, then areas that are inaccessible to mobile communications and/or position determination can readily be modelled. For example reception can be difficult and/or position determination can be inaccurate in the vicinity of tall buildings. The OS MasterMap database includes a topography layer that is a large-scale digital database that includes surface features such as roads, buildings and rivers. More information regarding OS MasterMap can be found at http://www.ordnancesurvey.co.uk.

In accordance with an example of the real-world interactive game described herein, game participants can move within the game area 84 while holding a mobile client device. As will be explained hereinafter, targets can be defined within this game area.

Participants navigate around the game area. Participants who step outside the game area 84 as defined by the notional boundary 86 can re-enter the game area, but the game may not display the actual position of the participant and/or a representation of the real world location.

In one example of a game that can be implemented by the apparatus and procedures described herein, each participant is allocated one or more targets to be located by that participant. Each target can be a real world location within the game area 84 determined by the game apparatus. The target can correspond to some object at a location in the real world, or it could merely be a location in the real world within the game area that is not associated with any object. Each target can be defined by co ordinate values for a real-world location. In order to "locate" the target, a participant to which a given target has been allocated can carry his mobile client device to within a given distance of that target. The given distance can be a predetermined distance and can be varied to alter the difficulty of the game. An example of this is shown in Figure 8.

In Figure 8, a mobile client device and participant 140 is shown to be at a position that is some distance away from a target 134. By comparing the real-world position of the mobile client device and participant 140 with the known position of the target, certain distances which are relevant to game play can be calculated. As described above, to "locate" a target for triggering a game event, a participant can carry his mobile client device to within a predetermined minimum distance of that target. This predetermined minimum distance 136 is indicated in Figure 8 for the target 134. Accordingly, to "locate" the target 134 in the present example of the invention, the participant 140 enter a region 132 represented by a notional circle which surrounds the target 134 and which has a radius defined by the distance 136. A distance between the participant and the region 132 can be calculated as the distance between the mobile client device held by the participant 140 as determined by a positioning device of the mobile client device and the position of the target 134, less the predetermined minimum distance 136. With knowledge of the real-world position of the mobile client device and of the location of a target, a processor of the mobile client device can calculate the distance 138. When it is determined that the distance 138 has a zero value or a negative value, it can be concluded that the mobile client device, and therefore the participant 140, has entered the region 132. This can trigger a game event that can correspond to the user having "located" the target. Information relating to this game event can be transmitted by the mobile client device via a communications interface thereof so as to notify other participants using their mobile client devices, for example by communicating via a central co-ordinating server, that a game event has been triggered, namely that the target has been located.

In some embodiments, a game event can also be triggered by a participant locating a target that has been allocated to an opponent. The consequences of this can be defined according to the chosen rules of the game. For example, the participant whose target has been located by another participant can be allocated a replacement target. The apparatus and methods described herein can implement this by generating a new target and by notifying each mobile client device of the position of the new target via the communications interfaces of the mobile client devices.

Figure 9 shows an example of a game screen which can be displayed on a display 22 of a mobile client device as described herein so as to provide a participant holding the mobile client device with information and feedback regarding the progress of the game. On the display 22 is displayed a graphical representation 100 of a real-world geographical area in the vicinity of the mobile client device. The geographical area in the vicinity of the mobile client device can be defined as a real- world geographical area that lies within a certain distance of the mobile clientdevice. In this example, the geographical area comprises a portion of the game area 84 near to the buildings 90 in the bottom left-hand corner of the game area 84. The geographical representation 100 of the real-world geographical area in the vicinity of the mobile client device can represent real-world features lying within the geographical area. For example, in the geographical representation 100 shown in Figure 9, the buildings 90, the footpath 94, the stream 92 and the bridge 95 are all represented. The geographical representation can be generated using map data and by calculating the appropriate geographical area which is to be represented according to the real world position of the mobile client device. The map data can either be held at the mobile client device or can be supplied to the mobile client device by a remote server in accordance with requests for map data issued by the mobile client device. As the mobile client device moves in the real world, the geographical area in the vicinity of the mobile client device changes. The movement of the mobile client device can be determined by the processor of the mobile client device using data received from the positioning device of the mobile client device, and the graphical representation 100 displayed on the display 22 can be updated accordingly.

The map data for generating the graphical representation 100 can be derived from a geographical database. As indicated above, an example of such a database suitable for generating the necessary data is the OS MasterMap database. The OS MasterMap database has a topography layer that is a large-scale digital database that includes surface features such as roads, buildings and rivers. The information contained in the OS MasterMap database can be used to select an appropriate game area 84 and generate the necessary graphical representations of geographical areas within the game area 84.

Other information can also be displayed on the display 22.

In the example described in relation to Figure 9, it is assumed that there are four participants in the real-world interactive game. These participants can be assigned character names - in this example, the characters are Mona, Piers, Reece and Rex. The names of the participants can be indicated on the display 22. In this example, the names are indicated at the bottom left-hand corner of the display 22 at 110. Each participant can be assigned a graphical indicator (or colour) 102, 104, 106 and 108.

These graphical indicators can be used to indicate the position of the real-world position of the participants on the graphical representation 100. For example, in the graphical representation 100 shown in Figure 9, Mona is shown to be positioned on the footpath 94, while Rex is shown to be positioned near to the footpath 94 and between two of the buildings 90. The real-world positions of each participant can be determined by the positioning device of the mobile client device held by that participant. The real-world position of each participant can be notified to the other participants by the transmission of data between the mobile client devices either directly or via a remote server as described above.

As described above, each participant can be assigned one or more targets. The positions of these targets are not displayed on the graphical representation 100, but the participant can be provided with clues regarding the target's position. At the bottom right-hand corner of the display 22 target information 1 14 can be displayed. The target information in this example includes three bars. The top bar and the middle bar in this example indicate to the user the distance of the user from two of the targets that have been allocated to the user. The two targets that are chosen for information display can, for example, be the two targets that are currently closest to the participant.

Accordingly, in this example, target I labelled "Tl" is indicated to lie 41 metres away from the participant as calculated by a processor of the mobile client device using information received from the positioning device of the mobile client device.

Similarly, target 5 labelled "T5" is indicated to lie 215 metres away from the participant. The display of the distance of two targets can enhance the appreciation of the user of a strategy for locating the targets. These distances correspond to the distance 138 described in Figure 8. Information regarding targets allocated to an opponent can also be displayed. For example, in Figure 9 the target information 114 includes a bottom bar that indicates a distance to the nearest target that is allocated to an opponent (in the present example the nearest opponent target is allocated to Rex).

Providing information based solely on the distance from one or more targets, presents a challenge to a user to locate the targets.

In one example of the game, each participant can be allocate a predetermined number of target (say six) of which at least a subset thereof (say any four thereof) have to be located. Once four targets have been located by a participant, the distance to a final target, which can, for example, be common to all participants, can be indicated to a user. Having a final common target can lead, for example, to all participants who have already found four of their allocated targets, converging on the final target.

Prior to the start of the game, one or more of the mobile client devices can request a participant to select a game area in which the game is to be played. Typically, the game area can be chosen from one or more predefined game areas, each of which corresponds to a portion of a real world location as described above in relation to Figure 7. Examples of game areas suitable for playing the game are a park, a town, woodland, or even a larger region such as an entire city, region, country, continent, the world, etc. The game area can be selected using user input such as a keypad of one of the mobile client devices. The mobile client device can transmit data indicating the selection either directly to the other mobile client devices in the game or to a remote server via a telecommunications network that can then relay this information to the other mobile client devices. Each participant that wishes to participate in the game can indicate this using the user input of their mobile client device. Each mobile client device can then transmit a signal requesting participation. Again, this information can be transmitted directly to other mobile client devices, or can be relayed via a remote server. Once the game area and the number of participants have been determined and this information has been received at each mobile client device, the game can begin.

Figure 10 is a flow diagram illustrating examples of initial phases of operation.

At 142, in a start phase, a user can start the application for the game on the mobile client device 14. The mobile client device 14 can then initiate an exchange of information with the server 12 to identify available games currently in operation. The information supplied by the server can include currently active games including information about the current participants and also games that could be started by the user. This information can then be displayed to the user on the display of the client device.

At 144, the user can then make a selection from among the currently active games or create a new game, and the results of the user selections are then transmitted to the server.

At 146, the server can register the user's client device with the selected game.

At 148, the server can transmit indications to the other participants in that game that the user has joined the game and can send the data necessary for initialising the game to the user's client device. This can include data defining the game area (possibly including map or other data representing the game area to be displayed), the positions of the opponents and the position of the targets for the user and the opponents.

Figure 11 shows a flow chart of a procedure which can be followed by a mobile client device for implementing information flow between the mobile client devices participating in the game for providing each participant with feedback as to the progress of the game, and in particular to notify each participant of game events associated with the real-world positions of the mobile client devices participating in the game.

The procedure starts at 150.

At 152 the mobile client device determines its real-world geographical position using its positioning device. The real-world geographical position can be represented either in two or three dimensions and accordingly can include x and y, or x. y and z co- ordinates.

At 154, the mobile client device displays a graphical representation 100 of the real- world geographical area in the vicinity of the mobile client device on the display 22.

The graphical representation 100 can, as described, be derived from two dimensional map data and can include representations of real-world features lying within the geographical area. The real world position of the mobile client device as determined by the positioning device 25 can be used to determine the appropriate portion of the game area that is to be displayed. For example, referring to Figure 9, the position of the mobile client device is assumed to lie at the centre of the graphical representation (in this example the mobile client device is held by the participant named Mona).

While the participant moves within the real world, the graphical representation 100 can be updated accordingly, given that the position of the mobile client device shown on the graphical representation is fixed to the centre of that graphical representation.

Accordingly, the graphical representation can scroll back and forth to represent different real-world features as the geographical area in the vicinity of the mobile client device changes.

Thus, at 156 the mobile client device indicates the position of the user holding the mobile client device. This can include displaying the position on the geographical representation 100, an example of which has been described in relation to Figure 9.

The mobile client device can also indicate the positions of the other participants in the game as determined by the positioning devices of the mobile client devices held by those other participants. This is also shown in Figure 9. The mobile client device can receive data describing the position of the other participants via the communications interface. The mobile client device can similarly transmit data describing its own real world geographical position (e.g., via the server) so that other mobile client devices can indicate its position to the other participants.

At 158, the mobile client device determines whether a game event has occurred. A game event can include a target event that occurs when the mobile client device comes within a predetermined distance of a target that has been allocated to that mobile client device. As described above, another type of game event is an opponent target event.

An opponent target event occurs when the mobile client device comes within a predetermined distance of a target that has been allocated to another participant. If no game event is determined to have occurred at 158, the process loops back to 152 where the position of the mobile client device is again determined and updated to account for movement of the mobile client device in the real-world game area. Accordingly, the mobile client device will continue to determine its position, display that position and possibly the positions of other participating mobile client devices on the display 22 until it is determined that a game event such as a target event or an opponent target event has occurred.

Where, at 158 it is determined that a game event has occurred, the procedure moves to 160. At 160, the mobile client device transmits data describing the game event via the communications interface. This allows other mobile client devices participating in the game to be notified of the game event. As described above, the data can be transmitted directly to the other mobile client devices or can be relayed to the other mobile client devices via a remote server. At 164, the mobile client device then outputs an indication of the game event. The indication can, for example, be displayed on the display and/or comprise an audible indication. Referring once more to Figure 9, the indication can, for example, include the addition of a further indication 112 to indicate that a further target allocated to the mobile client device has been "located".

In another example, where it is a target which has been allocated to another participant that has been located and where, subsequently, a replacement target is allocated to that other participant, the indication of the game event on the display 22 can include the changing of the target information 114. For example, the replacement target may no longer be the nearest opponent's target to the mobile client device.

In Figure 11, in parallel to steps 152 to 160 described above, the mobile client device can also monitor the communications interface for the receipt of information describing a game event triggered by another mobile client device. For example, another mobile client device may have "located" a target. It will be understood that the located target may have been allocated to the other mobile client device, in which case the other mobile client device has triggered a target event. Alternatively, the target located by the other mobile client device could be a target that was not allocated to the other mobile client device, in which the other mobile client device has triggered an opponent target event. At 164, the mobile client device can output an indication of the game event triggered by the other mobile client device in a manner similar to that described above. Where the mobile client device is to be allocated a replacement target, this replacement target can either be determined (for example, randomly generated) by the mobile client device and notified to other mobile client devices and/or a remote server or the remote server can itself determine and allocate the replacement target and notify each mobile client device in the game. $

After the game event has been indicated at 164, the process loops back to the start lSO and the mobile client device re-enters the phase of determining its position and displaying the appropriate graphical representation and positional indicators until a new game event is determined at 158. s

As indicated above, a central server, that can be remote from the mobile client devices, can co-ordinate the game.

Figure 12 shows a flow chart of a procedure that can be followed by the server.

The procedure starts at 170.

At 172, the server receives game event data from one of the mobile client devices participating in the game. As described above, the game event data can relate to, for example, a target event or an opponent target event triggered by one of the mobile client devices coming within a predetermined distance of a target which has been allocated to that mobile client device or to another mobile client device.

In some examples, the server can act to relay the game event data to the other mobile client devices participating in the game, thereby allowing the participants using those mobile client devices to be provided with real-time feedback as to the progress of the game and the status of the other participants in the game (for example, the number of targets remaining for each participant, and the number of targets located by each participant).

The server can also act as a referee or arbitrator. At 174 in the procedure shown in Figure 12, the server receives game event data describing a second game event.

Depending upon the particular rules of the game being played, the server may arbitrate between the data regarding the first game event and the second game event. In particular, the server can act to determine a priority between the first game event and the second game event. While in Figure 11 step 172 comes before step 174 in the procedure, it will be understood that these two steps are in fact interchangeable and that the game event data regarding the second game event may in fact have been received before the game event data regarding the first game event.

In one example, the priority is determined by the server according to the order in which the game event data is received. For example, priority can be assigned to the game event about which data was received first.

In one example, the data regarding the first game event received from a first mobile client device describes a target event in which that mobile client device or a participating user of the game holding that mobile client device has "located" a target allocated to that participant. The second game event about which data is received from a second mobile client device describes an opponent target event in which the target which was "located" by the first mobile client device was also "located" by the second mobile client device. This represents a situation in which the priority of the two game events is important, because if the target was first located by the second mobile client device, then that target can be regarded as having been "stolen", or "nobbled" by the second mobile client device. In particular, in embodiments where the first mobile client device is to be allocated a replacement target, the first mobile client device, should be notified that although it has come within a predetermined distance of a target allocated to it, the target was first located by another mobile client device and a replacement target has been allocated to it. In that case, the first mobile client device can update game data held in its memory to reflect these game events and can output appropriate indications on the display 22.

Accordingly, at 178 in the procedure shown in Figure 12, the server determines whether the first game event has priority. If it does, then the server transmits data describing the first game event to the second mobile client device (as well as to any further mobile client devices participating in the game) at 180. The server can also transmit at 182 a confirmation to the first mobile client device that the game event triggered by the first mobile client device is indeed valid and that the first mobile client device should update the game data in its memory and output the appropriate indications on its display 22.

Alternatively, if at 178 it is determined that it is the second game event which has priority, then the server can transmit data describing the second game event to the first mobile client device (and to any other mobile client devices participating in the game) S at 184. At 186, the server can also transmit a confirmation to the second mobile client device that the game event triggered by the second mobile client device is valid and that the game data stored in its memory should be updated accordingly and the appropriate indications should be displayed on its display.

In some examples, the confirmation, which is sent to the mobile client device which has triggered a valid game event, can comprise the notification message which is sent to the other participating mobile client devices so that no special, separate message need be composed and sent.

In the example described above, the priority between the first and second game events can be determined on a temporal basis. This can be operated simply on a first come first served basis. Alternatively, time stamps could be used. In such a case, it would be advantageous for the server to send a signal to set a clock in each of the client devices, which clock is then responsible for setting the time stamps for that device. In such a case, messages including notifications of game events sent by the mobile client devices can include time stamps that can be used for event arbitration.

Figure 13 shows a flow chart of a procedure that can be implemented by a mobile client device for checking whether the game events that it triggers are valid game events. The procedure starts at 190. At 192 a game event is determined as described above. For example, the game event can be a target event or an opponent target event.

At 194, the mobile client device transmits data describing the game event via its communication interface. At 196, the mobile client device determines whether confirmation that the game event is a valid game event (i.e., has been given priority) has been received. If confirmation has been received via the communications interface, at 198 the mobile client device updates the game data 42 in its memory 30 and outputs the appropriate indications of the game event on the display 22 as described above.

If, at 196, it is determined that no confirmation of the validity of the game event has been received, then at 200, the mobile client device determines whether other game event data has been received. The other game data may, for example, indicate that another game event has been given priority over the game event triggered by the mobile client device and accordingly if this is the case, at 202 the mobile client device updates the game data 42 held in its memory 30 to reflect the game event and also outputs the appropriate indications on its display 22.

If, on the other hand, no other game event data has been received at 200, then the procedure loops back to 196 where it is again determined whether confirmation that the game event triggered by the mobile client device is valid has been received.

IS Accordingly, once a game event has been triggered by the mobile client device, the mobile client device transmits data describing the game event and then waits until either a confirmation message or notification of an overriding game event has been received before updating the game data 42 held in its memory 30 and outputting indications of the game event which has been given priority.

In one example of the invention, each of the mobile client devices and the server keep a record of all players names, positions, colours and target information. In order that this information is held in a coherent manner in the various devices, messages are sent between the devices. In this example of the invention, the messages are transmitted in XML format.

Table 1 illustrates an example of a message that is sent periodically from a client device to the server. This message includes an identification of the client device (e.g., the player name), the position of the client device and the location and status (available or acquired) of the targets allocated to that client device.

TABLE 1

<player> <name>Rex</name> <position> <x>414010</x> <y>114020/y> <[position> <color> 1 <[color> <targeV <name>tl </name> <position> <x>414011</x> <y>414020</y> </position> <status>2</status> </targeV <targeV <name>t2</name> <position> <x>414039</x> <y>114054</y> </position> <status> 1 </status> </targeP <targeV <name>t3</name> <position> <x>414088</x> <y>114005</y> </position> <status>1 </status> </target> <targeV <name>t4</name> <position> <x>414094</x> <y>114099</y> </position> <status> 1 </status> </target> <target> <name>t5</name> <position> <x>414322</x> <y>114908</y> </position> <status> 1 </status> </target> <target> <narne>t6</name> <position> <x>414236</x> <y>114193</y> </position> <status> 1 </status> </target> <targeV <name>t7</name> <position> <x>414207</x> <y>114154</y> </position> <status> 1 </status> </target> </player> Where: Color: RED_PLAYER = 1 GREEN_PLAYER = 2 BLUE_PLAYER = 3 YELLOW_PLAYER = 4 Target Status: TARGET_AVAILABLE= 1 TARGET_ACQUIRED = 2 Position: Ordnance Survey British National Grid co-ordinates On receipt of the message indicated in table 1, the server can be operable to carry out certain tasks.

These can include: checking if any targets have been acquired by the incoming player and alter target status if hit; checking if any opponents' targets have been hit, if so move them and update their positions; checking if the game has been won; and sending updated player information back to incoming player.

Accordingly, on receipt of the client device message, the server can update its records of the status of the client device that sent the message and the forward a message to all client devices. An example of such a message is set out in Table 2 below.

TABLE 2

player> <name>Mona</name> 10.....

</player> <player> <n am e> Re x </n arn e> 15.....

</player> <player> <name>Reece</name> 20.....

</player> <player> <name>B ill </name> 25.....

/player> The information for each player corresponds to that as set out in Table 1. In other words, where there are four players, the message sent in table 2 includes four respective sets of data, a respective set for each player. As all of this information is sent to each of the client devices, each of the client devices has a full set of the current game data. This current game data can then be used by each client device to process the game operation.

The tasks that can be performed by a client device of one example of the invention can include: periodically send a position status update message as indicated above to the server, wherein each message has a reference to which board is being played and the game number; waiting for reply from server; checking the returned player statuses; if any of the targets allocated to the user owning the client device have been moved, displaying an appropriate message; if any opponents targets have been moved, displaying an appropriate message; if the user or an opponents has won the game, displaying an appropriate message; updating the screen display with our current position In order to minimise processing at the server and at the client devices, the player data can be held in local storage in each client device and in the server in a data structure having effectively the same format as that in which it is transmitted. This means that the data to be transmitted in a message can be transmitted as it read from storage and can be stored as it is received, without further processing. However, if transmission bandwidth requirements dictate that compression is employed, then the data to be transmitted can be compressed and/or only changed data can be transmitted, with a consequential increase in the processing requirements at the server and at the client devices.

Accordingly, various embodiments of the invention have been described. However, it will be appreciated that modifications to the described embodiments are possible within the scope of the claimed invention. For example, although in the described embodiments a map of a game area 84 is displayed to the user, in other examples an aerial view, for example formed from or derived from aerial photographs, may be displayed instead or as an alternative. Moreover, although in the present example a visual representation of the game area is displayed, in other examples this may be dispensed with. For example, in an embodiment in which the client device is to be as inexpensive as possible, only the identifications of the distances to one or more targets, possibly with an identification of the opponents may be displayed. For example, if the game is to be played within an amusement park, where the boundaries are well defined, the display of the game area may not be needed.

Also, as described in relation to Figure 1, in some embodiments the mobile client devices participating in the game can be operable to connect wirelessly and directly to each other without needing to relay information via a remote server. In some examples, where wireless links 8 using, for example, Wi-Fi or Bluetooth are used, one of the mobile client devices can assume the role of the remote server as described above. The functionality of the remote server can be carried out by one of the mobile client devices without the knowledge of the user. The mobile client device that assumes the role of the server does not need to transmit game data for determining whether a game event associated with that game data is validand has priority. Time stamps can be used to account for this apparent advantage.

Claims

1. A mobile device for implementing a real-world interactive game, the device comprising: a processor; output means; a positioning device for determining a real-world position of the device; and wherein the processor is operable to: respond to the determination of a game event associated with the real-world position of the device by outputting an indication of a game event using the output means.

2. The device of Claim I comprising a communications interface.

3. The device of Claim I or Claim 2, wherein the processor is operable to determine the game event.

4. The device of Claim 2, wherein the processor is operable to transmit data describing the real-world position of the device via communications interface.

5. The device of Claim 4, wherein the processor is operable to receive data describing the game event via the communications interface.

6. The device of any preceding claim comprising a display and operable to display a graphical representation of a real-world geographical area in the vicinity of the device on the display and indicate on the graphical representation the real-world position of the client device determined by the positioning device.

7. The device of Claim 6, wherein the processor is operable to receive data describing the real world position of another device via the communications interface and to indicate the real-world position of the other device on the graphical representation of the real-world geographical area displayed on the display.

8. The device of any preceding claim, operable to output an indication of a determined target distance for at least one target, wherein determining each determined target distance includes: determining a distance between the real-world position of the device and a real-world position of the target.

9. The device of Claim 8, wherein the target position is a target position which has been allocated to the mobile device and wherein a game event comprises a target event comprising the real-world position of the device falling within the predetermined minimum distance from the target position.

10. The device of Claim 8, wherein the target position is a target position which has been allocated to another mobile device and wherein a game event comprises an opponent target event comprising the real-world position of the device falling within the predetermined minimum distance from the target position.

11. The device of Claim 9 or Claim 10 when dependent on Claim 2, operable to transmit data describing the game event via the communications interface.

12. The device of any preceding claim, wherein the positioning device comprises a global positioning device.

13. The device of Claim 2, wherein the communications interface has at least one of: an interface for connecting to a remote server via a telecommunications network; and an interface for connecting directly and wirelessly to another mobile device.

14. The device of any preceding claim comprising one of a personal digital assistant, a mobile telephone, a GPS navigation device, and a special purpose gaming device.

IS. The device of any preceding claim, comprising a memory storing program instructions for implementing the real-world interactive game.

16. A mobile client device for implementing a real-world interactive game, the client device comprising: a processor; output means including a display; a positioning device for determining a real-world position of the client device; and a communications interface, wherein the processor is operable to: determine a real-world position of the client device using the positioning device; display a graphical representation of a real-world geographical area in the vicinity of the client device on the display and indicate on the graphical representation the real-world position of the client device determined by the positioning device; determine a game event associated with the real-world position of the client device determined by the positioning device; transmit game event data describing the game event via the communications interface; receive game event data describing game events associated with the real-world position of another client device via the communications interface, and output an indication of a game event using the output means.

17. The client device of Claim 16, wherein the processor is operable to monitor the real-world position of the client device using the positioning device and update the indication of the real-world position of the client device on the graphical representation of the real-world geographical area displayed on the display.

18. The client device of Claim 16 or Claim 17, wherein the processor is operable to transmit the data describing the real-world position of the client device via the communications interface.

l 9. The client device of Claim 18, wherein the processor is operable to transmit the data describing the real-world position of the client device via the communications interface in response to a game event.

20. The client device of any of claims 16 to 19, wherein the processor is operable to receive data describing the real world position of another client device via the communications interface and to indicate the realworld position of the other client device on the graphical representation of the real-world geographical area displayed on the display.

21. The client device of any of claims 16 to 20, wherein the processor is operable to calculate at least one target distance and display each calculated target distance on the display, wherein each calculated target distance is calculated by: determining a distance between the real-world position of the client device and a real world target position; deducting a predetermined minimum distance from the distance between the real-world position of the client device and the real world target position.

22. The client device of Claim 21, wherein the target position is a target position which has been allocated to the mobile client device and wherein a game event comprises a target event comprising the real-world position of the client device falling within the predetermined minimum distance from the target position, and wherein the processor is operable to transmit data describing the target event via the communications interface.

23. The client device of Claim 21, wherein the target position is a target position which has been allocated to another mobile client device and wherein a game event comprises an opponent target event comprising the real-world position of the client device falling within the predetermined minimum distance from the target position, and wherein the processor is operable to transmit data describing the target event via the communications interface.

24. The client device of any of Claims 16 to 23, wherein the positioning device comprises a global positioning device.

25. The client device of any of claims 16 to 24, wherein the communications interface has at least one of: an interface for connecting to a remote server via a telecommunications network; and an interface for connecting directly and wirelessly to another mobile client device.

26. The client device of any of Claims 16 to 25 comprising one of a personal digital assistant, a mobile telephone, a GPS navigation device, and a special purpose gaming device.

27. The client device of any of Claims 16 to 26, comprising a memory storing program instructions for implementing the real-world interactive game.

28. A mobile device for implementing a real-world interactive game, the device comprising: a processor; output means; and a positioning device for determining a real-world position of the device; wherein the device is operable to: determine a distance associated with the real-world position of the device and a target position; and output an indication of the determined distance.

29. The device of Claim 28, wherein the output means comprise a display, wherein the device is operable to display a graphical representation of a real-world geographical area in the vicinity of the device on the display and indicate on the graphical representation the real-world position of the device.

30. The device of Claim 28 or Claim 29 comprising a communications interface for transmitting data describing the real world position of the device.

31. The device of Claim 30 when dependent upon Claim 29, operable to receive data describing the real position of another device and to indicate on the graphical representation the real-world position of the other device.

32. The device of any of Claims 28 to 31, wherein the distance associated with the real-world position of the device and a target position is determined by: determining a distance between the real-world position of the device and the real-world target position; deducting a predetermined minimum distance from the distance between the real-world position of the client device and the real world target position.

33. The device of Claim 32 responsive to an event comprising the determined distance having a negative value to output an indication of the event.

34. The device of any of Claims 28 to 33, wherein the positioning device comprises a global positioning device. (

35. The device of any of Claims 28 to 34 comprising one of a personal digital assistant, a mobile telephone, a GPS navigation device, and a special purpose gaming device.

36. A server for implementing a real-world interactive game played between users of a plurality of mobile client devices, the server comprising: a processor; memory storing data associated with each mobile client device, the data 1 0 including: an identifier for each mobile client device; and data describing conditions for the triggering of at least one game event for each mobile client device, wherein each game event is associated with a real-world position of the mobile client device; and a communications interface operable to connect to the mobile client devices, wherein the processor is operable to transmit and receive data describing game events to and from the mobile client devices via the communications interface.

37. The server of Claim 36, wherein the processor is operable to receive data describing the real-world position of a mobile client device via the communications interface.

38. The server of Claim 37, wherein the processor is operable to transmit data describing the real-world position of a mobile client device to other mobile client devices via the communications interface.

39. The server of Claim 37 or Claim 38, wherein the processor is operable to use the data describing the real-world position of a mobile client device and the data describing the conditions for the triggering of game events for that mobile client device to determine whether a game event has been triggered, and where a game event has been triggered, to transmit data describing the determined game event to the mobile client devices via the communications interface.

40. The server of Claim 39, wherein the game event is a target event triggered by the real-world position of a mobile client device coming within a predetermined minimum distance from a target position allocated to that mobile client device.

41. The server of Claim 39, wherein the game event is an opponent target event triggered by the real-world position of a mobile client device coming within a predetermined minimum distance from a target position allocated to another mobile client device.

42. A system comprising a plurality of mobile client devices according to any of Claims I to 35 and the server of any of Claims 36 to 41.

43. A method for implementing a real-world interactive game, the method comprising: a positioning device of a mobile device determining a realworld position of the mobile device; and responding to the determination of a game event associated with the real-world position of the mobile device by outputting an indication of a game event using the output means of the mobile device.

44. The method of Claim 43 comprising the mobile device determining the game event.

45. The method of Claim 43 or Claim 44 comprising transmitting data describing the real-world position of the mobile device via a communications interface of the mobile device.

46. The method of Claim 45 comprising receiving data describing the game event via the communications interface.

47. The method of any of Claims 43 to 46 comprising displaying a graphical representation of a real-world geographical area in the vicinity of the mobile device on a display of the mobile device and indicating on the graphical representation the real-world position of the mobile device.

48. The method of Claim 47 comprising receiving data describing the real world l O position of another device via a communications interface of the mobile device and indicating the real-world position of the other device on the graphical representation of the real-world geographical area displayed on the display.

49. The method of any of Claims 43 to 48 comprising determining at least one target distance and outputting an indication of each determined target distance, wherein each determined target distance is determined by: determining a distance between the real-world position of the device and a real-world target position; deducting a predetermined minimum distance from the distance between the real-world position of the device and the real-world target position.

SO. The method of Claim 49, wherein the target position is a target position which has been allocated to the mobile device and wherein a game event comprises a target event comprising the real-world position of the device falling within the predetermined minimum distance from the target position.

51. The method of Claim 49, wherein the target position is a target position which has been allocated to another mobile device and wherein a game event comprises an opponent target event comprising the real-world position of the device falling within the predetermined minimum distance from the target position.

52. The method of Claim 50 or Claim 51 comprising transmitting data describing the game event via a communications interface of the mobile device.

53. A method comprising: determining a real-world position of a client device using a positioning device of the client device; displaying a graphical representation of a real-world geographical area in the vicinity of the client device on a display of the client device, wherein the display is comprised in output means of the client device; indicating on the graphical representation the real-world position of the client device determined by the positioning device; determining a game event associated with the real-world position of the client device determined by the positioning device; transmitting game event data describing the game event via a communications interface of the client device; receiving game event data describing game events associated with other client devices via the communications interface, and outputting an indication of a game event using the output means of the client device.

54. The method of Claim 53, comprising monitoring the real-world position of the client device using the positioning device and updating the indication of the real-world position of the client device on the graphical representation of the real-world geographical area displayed on the display.

55. The method of Claim 53 or Claim 54, comprising transmitting the data describing the real-world position of the client device via the communications interface.

56. The method of Claim 55, comprising transmitting the data describing the real- world position of the client device via the communications interface in response to a game event.

57. The method of any of Claims 53 to 56, comprising receiving data describing the real world position of another client device via the communications interface and indicating the real-world position of the other client device on the graphical representation of the real-world geographical area displayed on the display.

58. The method of any of Claims 53 to 57, comprising calculating at least one target distance and displaying each calculated target distance on the display, wherein each calculated target distance is calculated by: determining a distance between the real-world position of the client device and a real world target position; deducting a predetermined minimum distance from the distance between the real-world position of the client device and the real world target position.

59. The method of Claim 58, wherein the target position is a target position which has been allocated to the mobile client device and wherein a game event comprises a target event comprising the real-world position of the client device falling within the predetermined minimum distance from the target position, and wherein the method further comprises transmitting data describing the target event via the communications interface.

60. The method of Claim 58, wherein the target position is a target position which has been allocated to another mobile client device and wherein a game event comprises an opponent target event comprising the real-world position of the client device falling within the predetermined minimum distance from the target position, and wherein the method further comprises transmitting data describing the target event via the communications interface.

61. The method of any of Claims 53 to 60 comprising communicating directly and wirelessly with another mobile client device using the communications interface.

62. The method of any of Claims 53 to 60 comprising communicating with another mobile client device via a remote server using the communications interface.

63. A method for implementing a real-world interactive game, the method comprising: determining a real-world position of a mobile device; determining a distance associated with the real-world position of the device and a target position; and outputting an indication of the determined distance.

64. The method of Claim 63 comprising displaying a graphical representation of a real-world geographical area in the vicinity of the mobile device on a display of the mobile device and indicating on the graphical representation the real-world position of the mobile device.

65. The method of Claim 63 or Claim 64 comprising transmitting data describing the real world position of the device using a communications interface of the device.

66. The method of Claim 65 when dependent on Claim 64 comprising receiving data describing the real world position of another mobile device via and indicating on the graphical representation the real-world position of the other mobile device.

67. The device of any of Claims 63 to 66, wherein the distance associated with the real-world position of the device and a target position is determined by: r determining a distance between the real-world position of the device and the real-world target position; deducting a predetermined minimum distance from the distance between the real-world position of the client device and the real world target position.

68. The method of Claim 67 comprising responding to an event comprising the determined distance having a negative value by outputting an indication of the event.

69. A method for implementing a real-world interactive game played between users of a plurality of mobile client devices, the method comprising: a server storing data associated with each mobile client device, the data including: an identifier for each mobile client device, and data describing conditions for the triggering of at least one game event for each mobile client device, wherein each game event is associated with a real-world position of the mobile client device, and transmitting and receiving data describing game events to and from the mobile client devices via a communications interface of the server.

70. The method of Claim 69, comprising receiving data describing the real- world position of a mobile client device via the communications interface.

71. The method of Claim 70, comprising transmitting data describing the real world position of a mobile client device to other mobile client devices via the communications interface.

72. The method of Claim 69 or Claim 70, comprising using the data describing the real-world position of a mobile client device and the data describing the conditions for the triggering of game events for that mobile client device to determine whether a game event has been triggered, and where a game event 1 1 has been triggered, to transmitting data describing the determined game event to the mobile client devices via the communications interface.

73. The method of Claim 72, wherein the game event is a target event triggered by the real-world position of a mobile client device coming within a predetermined minimum distance from a target position allocated to that mobile client device.

74. The method of Claim 72, wherein the game event is an opponent target event triggered by the real-world position of a mobile client device coming within a predetermined minimum distance from a target position allocated to another mobile client device.

75. A computer program product comprising program instructions executable to implement the method of any of Claims 43 to 74.

76. The computer program product of Claim 75 on a carrier medium.

77. A mobile client device substantially as herein before described with reference to the accompanying drawings.

78. A server substantially as herein before described with reference to the accompanying drawings.

79. A system substantially as herein before described with reference to the accompanying drawings.

80. A method substantially as herein before described with reference to the accompanying drawings.

81. A computer program product substantially as herein before described with reference to the accompanying drawings.