Node Modifiers
Node Modifiers connect two Nodes and allow you to change the state of one Node (its origin) to modify the number of Resources in another Node (the target Node) according to the Node Modifier’s Formula (M).
When the origin Node changes, it influences the target Node in the next time step. More than one origin Node can modify a target Node. The formula for this is nearly identical to the formula used for Formula Modifiers:
Nt + 1 = Nt + ∑ ( M × S )
Example – Settlers of Catan
In the below example from Settlers of Catan, players gain 1 Victory Point for each settlement and 2 Victory Points for each city. The number of settlements is one Origin Node, the number of cities is a second Origin Node, and both modify the Target Node, which is the player’s total number of victory points.
Please press the Play button to start the diagram and click on the interactive Sources for Settlement or City to change the Player’s Victory Points.
Node Modifiers can have Formulas that are fractions, for example, +1/3 or -2/4.
In this case, the change on the origin is multiplied by the fraction: every Resource the origin gains or loses changes the target by the fraction’s value, and the result keeps its decimals.
This way, when the number of Resources on an origin Node changes from 7 to 8, the target is lowered by 0.5 if the modifier is -2/4, and raised by 0.33 if the modifier is +1/3. When the origin grows from 0 to 80, the same modifiers lower the target by 40 and raise it by 26.67.
See the example diagram below.
For a more in-depth explanation of how Formulas work, read Labels, Formulas, Intervals
If at the start of a Play the Origin Node already has an input to transmit to its Target, then this change takes effect at the beginning of the 1st Step of the execution. After this, the Node will only affect its Target if its state changes. See the example below.
Think of it in terms of programming, as initializing a variable.