1. Introduction.

1.1 The Field of Study.

"Interactive, multi-user computer games": despite containing three adjectives, the phrase is wide-ranging in its coverage. The first task in reviewing the area must therefore be to formulate a set of criteria that can be used to determine whether a system should, or should not, be the object of study.

The term 'games' refers to those pastimes which are undertaken primarily for the purpose of entertaining the user (or, in this context, player). Although games can be designed for business or educational use, rather than solely for leisure-time activity, nevertheless to qualify they must somehow be "fun". They also need a set of rules, and, if competitive, some means of gauging how close the player is to "winning" (ie. meeting a predefined overall objective). Additionally, most require some skill on the part of the players. In cases where modelling the real world is a significant aspect of a game, it may be referred to as a 'simulation' (although not all simulations are games).

'Computer games' are games which are played against, moderated by, or played using, a computer. In rare cases, they can be played between computers.

'Multi-player computer' games are computer-run games that several individuals can play simultaneously.

'Interactive, multi-player computer games' are those computer-run games where the individual players can issue commands which affect the way the game treats other players.

This specific-seeming definition nevertheless admits such activities as two friends playing a pinball down at the local pub. It's a game, there's a computer inside it controlling everything, it'll entertain up to four players taking turns, and one player's score affects the extent to which the other players will take risks (and, hence, is a means of interaction). Nevertheless, a pinball is not what is generally regarded as an interactive, multi-player computer game; indeed, if it were, then the range of other games that also fit the definition would reduce any overall analysis to a level of vague generalities.

1.2 Narrowing the Field of Study.

It is necessary to discard from consideration those games which lie outside the spirit of the definition. 'Computer games' in this context are those games which run solely on general-purpose computers. This excludes machines hard-wired to play one game (chess, Space Invaders, pinball), but still includes certain categories of games machine (Sega, Nintendo, modern video games).

If a game is to be 'multi-player', there are three alternatives: several people playing on the same machine in the same room; several people playing over a LAN; several people playing over a public network. In practice, only the latter is worth considering: games in the first category tend to be commercial flops unless the multi-player facility is merely a gimmicky extension to an essentially single-player game; games in the second category rarely sell, because most LANs are company-owned and are unavailable for leisure activities (although within the next few years they may be introduced into amusement arcades).

Thus, 'multi-player computer games' can be reduced to those which individuals contact over some public network, eg. that of the telephone. However, this further constrains the architecture of such games, in that unless users all have similar, tamper-proof machines, the bulk of processing must be centralised within a single computer (or a cluster). Otherwise, system security would be compromised. Although some processing can be done locally (graphics, sound effects, parsing etc.), nothing multi-user can be trusted to a user's home machine. Even in situations where all players are known to have identical hardware and software (as is the case with games consoles), unless one machine is in overall control there is a dangerous susceptibility to the sudden system failure of a component machine. Distributed games are not, for the moment at least, viable.

A special case is that of two-player games. With players who can trust one another not to cheat, modem-to-modem games can be played in distributed fashion. If finding a player is difficult, contact agencies can pair people up (CompuServe in the USA, for example, has a "Challenge Forum" for people wishing to find opponents for tandem games such as Falcon, Flight Simulator 3, Modem Wars, 'Vette and Omega). In this instance, the host machine is merely acting as a bulletin board or matchmaker. However, there do exist two-player games where major processing is done on the contact machine itself.

This leaves us with a set of games where the players have computers which they use as front-ends to access a (usually larger) computer, upon which the games themselves run. There are some games of the FIST variety where the user can dial telephone numbers to issue commands, but no such games have anything that is not subsumed by some aspect of play-by-modem games; not even the emerging voice-activated telephone games are much of an advance.

Finally, what is meant by the term 'interactive' when applied to multi-player computer games? Actually, the word is ambiguous: it can mean "allowing players to act upon one another", but also merely "on-line" (in a computer sense). Both these meanings are, to some extent, already implied. Although being multi-player indicates that there is some degree of awareness of other individuals playing at the same time (if you can't tell by playing that it's multi-player, it may as well not be), 'interactive' emphasises the requirement that players be able to do things with and to each other. This is exemplified by the ability to communicate freely. Limited forms of communication using standard protocols are possible in certain games (eg. bridge), but in general the players have to be able to send messages to one another in free-form natural language if they are to communicate effectively.

Inter-player communication not the end of it, however, because an ordinary chatline program can perform such a function; a chatline, though, is not a game. There may be conventions observed by participants, but there are no formal rules of play, and there is no way to "win" - or even advance in status - on a chatline. To be an interactive, multi-player game, communication between players is necessary, but not sufficient; players need to be able to do things to one another that, within the framework of the game, will have a tangible effect.

1.3 Acceptance Criteria.

To summarise, then, for the purposes of the remainder of this report, an interactive, multi-player computer game (IMPCG) is something which satisfies the following criteria:

• It is played by people primarily for fun.
• It has a set of rules, and an overall game-dependent objective.
• You need a general-purpose computer to play it.
• It runs primarily on a central computer, connected to the players' computers over a public network.
• More than one person can play it simultaneously.
• Players can communicate with one another in real time, using a natural language (eg. English).
• Players can issue commands independently which may affect the status of other players within the game.

1.4 Categories of IMPCGs.

Existing interactive, multi-player computer games satisfying the above criteria are, in the main, programs sharing a common heritage known variously as MUGs (Multi-User Games), MUDs (Multi-User Dungeons, Multi-User Dimensions) and MUAs (Multi-User Adventures). Although the terms are often used interchangeably, there are technical distinctions:

MUG

Used mainly by journalists and people who don't know any better. A UK-only term. Vague - soccer is a "multi-user game" - but employed in the present context the term refers to any on-line computer game, whether interactive or not. Scrabble^TM by modem is a MUG (and, on Minitel, a very popular one).

MUD

Ambiguous in that it can refer not only to a class of interactive, multi-player computer games, but also to a particular game (the first one of this genre). In the UK, normally the specific form is used, but elsewhere 'MUDs' is generic.

MUA

Perhaps the most accurate description. Multi-user adventures are, simply, adventure games for more than one player. "Adventure" is a term already used to refer to a popular form of single-player computer game, such as those produced by Infocom, Level 9 and Magnetic Scrolls. The very first adventure game (now called Colossal Cave) was originally entitled Adventure. MUA is used by purists, but rarely appears in non-technical magazine articles due to its being hard to incorporate into witty headlines.

MUAs are not the only IMPCGs, just the dominant form. There are other games which satisfy our adopted criteria, but they are one-off individuals, not classes of games. Examples are Island of Kesmai, You guessed it! and Sniper on CompuServe. All are characterised by communication and interaction, and they do not play the same as MUAs. They can, however, each be seen as a specialised form of MUA, and could, for example, readily be programmed in the better MUA definition languages.

This report will therefore concentrate on MUAs as best exemplifying IMPCGs, while making reference to other games that also qualify when appropriate.

1.5 Brief History (Industry).

Present day MUAs are all descendents of a single game known as MUD (Multi-User Dungeon; to avoid confusion with the generic term, the game will be referred to as MUD1 for the remainder of this report). Although there were early attempts to turn single-player adventures such as Colossal Cave and Zork into multi-player adventures, and there may have been attempts to write MUAs from scratch, these came to nothing or petered out. MUD1 was the first proper, workable multi-user adventure game.

MUD1 was written by Roy Trubshaw and Richard Bartle at Essex University on a DECsystem-10 mainframe. Trubshaw began in Autumn 1978, and Bartle took over in Summer 1980. Initially, the game was playable only by students at the university and guests using (what was then) EPSS. After a year or so, however, external players began to direct-dial from home using modems, and the game's popularity grew.

Many of MUD1's players found it difficult to get a slot in the game, since the number of dial-up ports on the university machine was limited, and because the game was only available late at night when there was spare processing capacity. Some of these players wrote their own MUAs, based on MUD1 and using similar commands. Among these were AMP, Gods and Shades.

After a flurry of articles in computer hobby magazines around 1984, MUD1's fame spread even wider. Bartle and Trubshaw formed MUSE Ltd to rewrite the game as MUD2, and run it on VAXes owned by a division of BT then known as NIS (Network Information Services). Due to an internal dispute between NIS and Prestel, Prestel declined to take MUD2 as "their" MUA, and chose the lookalike game Shades instead. MUD1 was, for two years, available on the CompuNet network in the UK, but it was removed when CompuNet discarded their DECsystem-10s. A version of MUD1 still runs on CompuServe in the USA, and, despite its venerable age, continues to be one of their most profitable leisure products.

After a time, people who had played games based on MUD1 wrote their own MUAs, and the process snowballed. Nowadays, there are some twenty or more MUAs in the UK of varying degrees of sophistication, six of which (MUD2, Shades, Gods/The Zone, Federation II, AberMUG and Bloodstone) are run on a commercial basis. The UK leads the world in this technology, despite the constraints of high communications charges (even using PSS, it costs over 5 times more per hour to call MUD2 than the game itself charges for playing).

This, then, is the state of the "industry" in the UK. However, there are two almost disjoint streams to the development of MUAs, the other one being based in academia.

1.6 Brief History (Academia).

With the publicity of the mid-1980's and the advent of JANet (Joint Academic Network - free inter-university networking), students at other universities continued to play MUD1 at Essex (along with other games written using the same shell, MIST being the main one). These students also wrote their own MUD1-like games. The first, AberMUD, was programmed at Aberystwyth, and made available to other sites over JANet and InterNet. This in turned spawned other MUAs based on it (TinyMUD, LPMUD), which were distributed freely to (mainly Unix) sites around the network. There are now some fifty sites running versions of these games, and the sources are available free to anyone who wants them. There is a thriving NewsNet section dedicated to these games (which are called "MUDs" by everyone), and new sites are coming on stream all the time. They're mainly in the USA, but can be found in many other countries as well. Only one game is run commercially, an incarnation of AberMUD called AberMUG, which was mentioned earlier; a version of TinyMUD has appeared alongside Gods, but as a test and without any publicity.

It can thus be seen that at present there are two almost completely disjoint MUA camps. Few people in one group are aware of people in the other. At present, the best games are the top-notch UK professional MUAs, but with the huge number of US academics presently engaged in MUA activity, it is only a matter of time before players over there start writing their own versions and marketing them commercially. Unless the UK can maintain the lead that history has given it, these American MUAs will doubtless come to dominate the scene over the coming years.