Common Mechanisms - Game Mechanics: Advanced Game Design - page 109

You can use random flow rates with inter vals. A production rate of D6/3 will pro-
duce between one and six resources every three steps. Intervals can be random as
well. A production rate of 1/(D4+2) indicates that one resource is produced every
three to six steps. Random intervals can be a good way to keep the player's attention
on the game (see the “Random Intervals in Games” sidebar). You can even use a pro-
duction rate of D6/D6, which indicates between one and six resources are produced
every one to six steps.
random interVals in Games
in his article “Behavioral Game design,” John hopson (2001) reports that experiments in
behavioral psychology suggest that player behavior is affected by chance and the interval
at which the player is rewarded for actions. When a player has a chance to be rewarded
at regular intervals, the player's attention and activity will spike at those intervals. When
those intervals have random lengths, players will be active most of the time because they
never quite know when their next action might lead to a new reward. Use this powerful
knowledge with caution.
Intervals can also be modified dynamically. Label modifiers that have an i as a unit
of their modification (for example, +1i or -3i) will change their target's interval. For
example, in Figure 6.4, the interval of the output of the source A is increased as
more resources arrive in pool B.
FIGURe 6.4
dynamic intervals
Multipliers
When working with random flow rates, it is often useful to combine multiple
chances into one value. For example, a source might have two chances to produce
a resource during every time step. You can represent this with two outputs with a
probable flow rate for each ( Figure 6.5, left side), but as long as the probabilities are
equal for each chance, using a multiplier is more convenient. A multiplier is created
by adding n * before the flow rate, for example 3*50%, 2*10%, or 3*D3 ( Figure 6.5,
right side). The two constructions are equivalent, but the one on the right is less
cluttered. If you need to use different probabilities, however, you will have to create
a construction like the one on the left.
FIGURe 6.5
multiplying a flow rate