Common Mechanisms - Game Mechanics: Advanced Game Design - page 118

Multiple Feedback loops
In the section “Categorizing Emergence” in Chapter 3, we discussed Jochen Fromm's
typology of emergent systems. According to Fromm, systems with multiple feedback
loops display more emergent behavior than systems with only one feedback loop.
This is also true for games. Most games need more than one feedback loop to pro-
vide interesting emergent behavior. The board game Risk is an excellent example of
this. In Risk, no fewer than four feedback loops interact.

T IP Like Monopoly,
Risk is a classic board
game that illustrates
certain principles of
mechanics design well.
if you are not famil-
iar with Risk, you can
download a copy of the
rules at www.hasbro.
com/common/instruct/
risk.pdf. The Wikipedia
entry for Risk also
includes an extensive
analysis.

the ideal number oF Feedback loops

it is clear that games with multiple feedback loops exhibit more emergence than games
with only one or even no feedback loop at all. however, the ideal number of feedback
loops is much harder to determine. We have found that somewhere between two and
four major feedback loops seems to be sufficient for most types of games. depending on
how complex you want the game to be, you can try more feedback loops, but you have
to be careful not to create a game that is too hard to understand. remember that as a
designer you have a good grasp over the feedback loops that operate within your game,
but your players do not.

another important distinction here is the difference between major and minor feedback
loops. sometimes a feedback loop acts only locally and has little effect on any other
mechanism—a minor feedback loop. in contrast, a major feedback loop involves multiple
important mechanisms of your game and has a much greater impact on the gameplay.
You might have more than four minor feedback loops without complicating the rules too
much, but including more than four major feedback loops will make your game difficult
to master.

The core feedback loop in Risk involves the resources armies and territories : The more
territories a player holds, the more armies he can build. Figure 6.24 depicts this core
feedback loop. The player expends armies to gain territories by clicking the interac-
tive Attack gate. The armies that succeed pass to the converter, which turns them
into territories. The label +1/3 of the label modifier that sets the output flow rate of
the interactive source Build indicates that the output of the source goes up by one
for every three territories the player has.

FIGURe 6.24
The core feedback loop
involving armies and
territories in Risk