Drop-In/Drop-Out
Designed support to handle players entering and leaving ongoing game sessions.
Players cannot always participate in whole game sessions, having to stop prematurely to do something else. This causes problems for the game design in how it should keep the game balanced and interesting for the remaining gamers, but another type of problem can occur if the gamers that left wants to come back again to the same game session. For this problem the game design needs have mechanisms for re-introducing players without disrupting game balances nor making the effort of the already present players unrewarded in comparison with the returning players.
Examples
Many casino games, e.g. Roulette or Blackjack, consist of many quite quick game instances. This allow players entry points often into the meta game of winning money and the players are also free to leave at the end of each game instance.
The multiplayer arcade game Gauntlet partly supported players leaving and entering the game during a game session. Players whose character had died could start playing again simply by inserting coins and new players could do the same. There was however no graceful way for a player to leave the game when one had a healthy character since that character would keep the others to that area until the abandoned character died (this meant that leaving was worse the more health the character had).
The Lego Star Wars series (except the GBA version) supports a second player to at any point join the game with a character, and then leave whenever by simply choosing this option in the game. Given that the gameplay never requires both players and that players can replay levels infinitely the gameplay does not degrade when a player drops out.
All massively multiplayer games need to support Drop-In/Drop-Out since it is impossible to synchronize hundreds or thousands of players spread over the world. This is simplification though, since the game structure may imply dedication to participate (e.g. instances in World of Warcraft) or that emergent gameplay may have entered a critical phase and all players in a local part of the Game World need each other (Eve Online is an example of a game where this can occur). The latter can also easily occur in other genres where Drop-In/Drop-Out is supported, e.g. team-based first person shooters such as Counter-Strike, Enemy Territory: Quake Wars, and the Team Fortress series as well as in real-time tactics games such as World in Conflict.
All game sessions in the Left 4 Dead series begin with four human characters but only one of them needs to controlled by human gamers. Those not played by humans are computer-controlled but can be replaced by gamers joining the games session. Likewise, if a gamer leaves the game (or loses network connection) the computer takes control over the character without disruption to the other gamers' gameplay. People can even "pause" the game to take their own short breaks while the other gamers continue with a temporary computer substitute.
Using the pattern
The use of Drop-In/Drop-Out it typically discussed for Multiplayer Games, and when it is used in Single-Player Games to allow additional players this issues become the same as for Multiplayer Games. It is however rather uncomplicated to have in Single-Player Games - one can simply use Game Pauses.
For Multiplayer Games, the basic mechanics of supporting Drop-In/Drop-Out are typically not the main challenge with using the pattern (but Dedicated Game Facilitators such as Game Masters can avoid Excise), rather it is to maintain Challenging Gameplay, Value of Effort, and Team Balance for games with Teams. How this can be done typically depends on if the game is based on Cooperation between the players or not. When games revolve around Competition or Conflict rather than Cooperation leaving them can be seen as accepting defeat (indeed, many of them use Player Elimination, e.g. Counter-Strike) and does not need to unbalance gameplay for other players (but see diegetic aspects). Entering the game, i.e. supporting Late Arriving Players, can be more problematic. New or returning players may not need Player Balance in relation to the old players, but at least need Empowerment or Exaggerated Perception of Influence. The former can be achieved by giving them Temporary Abilities or having Balancing Effects but this risks that existing players feel that their Value of Effort is lost. This can be avoided by instead having games built around Tournaments but this centers the entry and exit points to the beginning and end of specific game sessions. The use of Private Game Spaces can for games based upon Competition but not Conflict address issues of Challenging Gameplay but less readily Value of Effort.
For games built on Cooperation, e.g. those using Parties, the issue of Player Balance may also be dealt with through Balancing Effects. However, the risk of old players feeling a loss of Value of Effort is lessened since the players typically have Mutual Goals. An alternative is to not actually reduce the number of players, either through replacing them with existing or newly-created AI Players (as for e.g. in the Left 4 Dead series), Game Masters (appropriate for Roleplaying games with Player Characters), or other players taking on extra roles (Theoretically, any type of Agent could be introduced but have a stable source of new humans willing to take over for leaving players can be difficult to achieve in a design - use of Spectators seems to be a possible starting point). The latter is easy to do in Self-Facilitated Games (e.g. in roleplaying systems such as Dungeons & Dragons or GURPS) but require additional account handling in computer-mediated games. The reason these solutions cannot be used for non-cooperative games is than the competition usual is against the other human players and not the other characters so replacing the human with another human or an Agent changes the conflict. The use of Invites (present in FarmVille to add new players and in the Left 4 Dead series to replace AI Players) gives people some control over the flow of players in the game.
Massively Multiplayer Online Games and others Persistent Game Worlds need the support of Drop-In/Drop-Out to handle that it difficult to coordinate large groups of players to begin and stop playing at the same time in Multiplayer Games. For making players want to return to games supporting Drop-In/Drop-Out, there are various way to have Encouraged Return Visits including Investments, Collecting, and Altruistic Actions.
Negotiable Game Instance Duration is an alternative to Drop-In/Drop-Out which lets players control how low game sessions will be but with the limitation that it must be done in agreement with other players.
Diegetic Aspects
If players are represented in a game through Avatars it is easy to show the entering or exiting of the game session by simply adding or removing the Avatars in Game Worlds. The removal can be done without causes discrepancies between the theme and the events (i.e. without introducing Non-Diegetic Features) in the Game World if the Avatars represent expendable units that are easy to kill, since players may time their leaving to when they died and abandoned Avatars will probably be killed soon anyway. Introducing new Avatars can be trickier but Spawn Points in close proximity to Inaccessible Areas can provide a diegetic explanation.
For other types of games, the use of Agents can let the deigetic presentation continue undisturbed when players leave.
Interface Aspects
The are typically several reasons for other players to wish to know when another player leaves or joins a game session, e.g. if this will change gameplay, Agents act differently from human players, or if they wish to engage in Social Interaction. This can be done through Game State Indicators or Non-Diegetic Features.
Consequences
Drop-In/Drop-Out allows players of Multiplayer Games to have Negotiable Play Sessions and Negotiable Game Sessions in that they do not need to adjust their own play sessions to other players sessions. Besides being able to choose how long time they wish to play, Drop-In/Drop-Out gives the game Interruptibility since players can use the functionality to define the breaks in the game session rather than define play sessions, but may cause breaks in a game's Diegetic Consistency. For games with Pervasive Gameplay, this can let players smoothly handle transitions between playing and not playing to avoid problematic social encounters.
When the addition or removal of players requires game elements to likewise be added or removed, this makes Drop-In/Drop-Out require Game Element Insertion and Game Element Removal respectively. In games with Altruistic Actions, Delayed Effects, Development Time, or Delayed Reciprocity, Drop-In/Drop-Out may provide Encouraged Return Visits.
Exaggerated Perception of Influence may be difficult to maintain with games that support Drop-In/Drop-Out. This since, quite naturally, the players that enter and leave the game cannot have had a strong effect on the overall development of the game as a whole. However, this does allow for a level of Ubiquitous Gameplay in Multiplayer Games.
For games that are supposed to have Split-Screen Views, the presence of Drop-In/Drop-Out gameplay requires designers to consider how these views should change - if at all - when the number of players change.
Relations
Can Instantiate
Game Element Insertion, Game Element Removal, Interruptibility, Negotiable Game Sessions, Negotiable Play Sessions, Ubiquitous Gameplay
with Multiplayer Games
Massively Multiplayer Online Games
with Altruistic Actions, Delayed Effects, Development Time, or Delayed Reciprocity
with Single-Player Games
Can Modulate
Agents, Multiplayer Games, Parties, Persistent Game Worlds, Pervasive Gameplay, Single-Player Games, Split-Screen Views, Teams
Can Be Instantiated By
AI Players, Dedicated Game Facilitators, Game Masters, Late Arriving Players, Self-Facilitated Games, Tournaments
Single-Player Games together with Game Pauses
Can Be Modulated By
Balancing Effects, Encouraged Return Visits, Game State Indicators, Invites, Non-Diegetic Features, Private Game Spaces, Temporary Abilities
Possible Closure Effects
-
Potentially Conflicting With
Challenging Gameplay, Empowerment, Exaggerated Perception of Influence, Team Balance, Value of Effort
Diegetic Consistency in Multiplayer Games
History
New pattern created in this wiki.
References
Online article describing a Microsoft patent for one type of Drop-In/Drop-Out
