Dynamic Friction

Type
Friction

Intent
A drain automatically consumes resources produced by the player, the consumption rate is affected by the state of other elements in the game.

Motivation
Dynamic friction counteracts production but adapts to the performance of the player. Dynamic friction is a classic application of negative feedback in a game.

Applicability
Use dynamic friction when:
 * You want to balance games in which resources are produced too fast.
 * You want to create a mechanism that counters production and automatically scales with players’ progress or power.
 * You want to reduce the effectiveness of long-term strategies created by a dynamic engine in favor of short-term strategies.

Structure


Participants

 * A resource: energy
 * A dynamic drain that consumes energy
 * A production mechanism that produces energy
 * Other actions that consume energy

Collaborations
The production mechanism produces energy that players need to perform actions. The dynamic drain consumes energy outside players’ direct control but is affected by the state of at least one other element in the game system.

Consequences
Dynamic friction is a good way to counter positive feedback created by engine patterns. Dynamic friction adds a negative feedback loop to the game system.

Implementation
There are several ways of implementing dynamic feedback. An important consideration is the choice of the element that causes the consumption rate to change. In general, this can be either the amount of available energy itself, the number of upgrades to a dynamic engine or a converter engine, or the player’s progress toward a goal. When the amount of available energy changes the friction, the negative feedback tends to be fast. When progress or production power is the cause, the feedback is more indirect and probably slower.

When dynamic friction is used to counter a positive feedback loop, it is important to consider the difference in characteristics of the positive feedback loop and the negative feedback loop implemented through the dynamic friction. When the characteristics are similar (equally fast, equally durable, and so on), the effect is far more stable than when the differences are large. For example, when a slow and durable dynamic friction is acting against a fast but nondurable positive feedback that initially yields a good return, players will initially make a lot of progress but might suffer in the long run. Fast positive feedback and slow negative feedback seems to be the most frequently encountered combination.

Examples
The mechanics of tower defense games typically revolve around a dynamic drain on the player’s life points caused by enemies that the player must keep under control by building towers (see below). In this case, the goal of the game is to prevent dynamic friction from taking effect. In real tower defense games, placing the right types of towers involves a strategy that is omitted from this diagram.



Dynamic friction is used in the city production mechanism in Civilization (see below). In this game, the player builds cities to produce food, shields, and trade. As cities grow, they need more and more food for their own population. Players have some control over how much food is produced compared with other resources, but the players’ options are limited by the surrounding terrain. By choosing to produce a lot of food early, cities initially produce fewer other resources but grow faster because of great potential. Fast growth creates a problem, however, because the happiness rating of a city must stay equal to or higher than half the population, or else the production stops due to of civil unrest. Initially, a city has a happiness value of two. Players can create more happiness by building special buildings or by converting trade into culture. Both approaches cause more dynamic friction with different profiles on the production process. Constructing special buildings is slow and requires a high investment but is highly durable and has a relatively high rate of return. Converting trade to culture is fast but has a relatively low return for the investment required.



Related Patterns
and often is part of the multiple feedback pattern.
 * Dynamic friction is a good way to balance any pattern that causes positive feedback
 * Attrition elaborates dynamic friction that is the result of multiplayer interaction.
 * Dynamic friction is elaborated by a stopping mechanism.