Trade

Intent
Allow trade between players to introduce multiplayer dynamics and negative, constructive feedback.

Motivation
Players are allowed to trade important resources. Usually this means that leading players will face tougher negotiations, while trailing players can help each other to catch up. Trade works especially well when the flow of resources is unstable and/or not equally distributed among players.

Applicability
Use trade when:


 * You want to introduce multiplayer dynamics to the game.
 * You want to introduce negative, constructive feedback.
 * You want to introduce a social mechanic that encourages players to interact with one another via commerce (as opposed to combat).

Structure


Participants

 * A trading mechanism that allows resources to be traded among players
 * Multiple tradable resources that can be exchanged or used in various ways
 * Actions that require using tradable resources

Collaborations
The tradable resources can be exchanged by the players using the trading mechanism.

Consequences
Trade introduces negative feedback that does not really slow down the game but usually helps trailing players catch up (because it is not destructive).

Trade favors players with good social and bartering skills.

Implementation
In board games, trade is very easy to implement. The game simply needs to specify how and when players can trade resources. In a multiplayer computer game, trade is also easy. However, creating a trading mechanism that involves computer-controlled characters is far from trivial.

To implement a successful trading mechanism, multiple tradable resources are required, and the production rates of these resources must fluctuate or at least be different among players. Trading works only when there is an imbalance in the distribution of resources among the trading parties. It also helps to include many actions that consume the tradable resources and to create actions that consume resources of multiple types at once, because this further exaggerates the imbalance when players choose different courses of action.

Examples
In The Settlers of Catan, players build up an uncertain dynamic engine: villages and cities that produce the resources used to build more villages and cities. The randomness of these engines is partly countered by allowing all players to trade resources with the player who is currently taking her turn. The exchange rate is set by mutual agreement and usually determined by the availability of the resource and the position of the player. Players who are in the lead can afford to pay more for their resources. When close to winning, players might find it impossible to make a deal.

In Civilization III, players can exchange strategic resources, money, and knowledge. This mutually benefits both parties and allows weaker civilizations to catch up fairly quickly.

Related Patterns
Attrition can be an alternative source of multiplayer feedback that is not constructive but destructive in nature.