Loopy is a free online simulation tool designed for modeling systems using causal loop diagrams. Users lay out the components of the system and link them with positive or negative connections. (In a positive connection, an increase in the first component leads to an increase in the second. In a negative connection, an increase in the first component leads to a decrease in the second and vice versa.) To run the simulation, the user triggers an increase or decrease in one component; they can then watch that increase propagate and see how their change affects the levels of other components throughout the system.
Loopy allows the user to explore the time dependence of a system, and to visualize dynamic relationships, and it can be particularly useful for understanding positive and negative feedback loops. System “components” are necessarily limited to those where an “increase” or “decrease” is meaningful, but that still allows modeling of a wide range of systems; examples given on the Loopy website include ecology, economics, mental health, and more.
