Whether you are modeling a game economy, a viral outbreak, or a SaaS business, complex systems are just collections of accumulation, flows, and feedback loops.

Before diving into the specific simulations, here is how to read the visual canvas.

The Visual Metaphor ​

Every system is built using three core building blocks.

See It in Action ​

Below is a simple Balancing Feedback Loop. Water flows into the tank, but as the tank fills up, the pressure triggers a drain pipe to open, eventually stabilizing the system.

Try this: Drag the Target Level slider up and down. Watch how the pipes automatically adjust their flow rates to hunt for the new balance.

The Two Types of Loops ​

When you start combining tanks and pipes, you create loops. There are only two types you need to know:

1. Reinforcing Loops (Snowballs): Action produces a result, which produces more of the action. (e.g., Money earns interest, which earns more interest. A virus infects people, who infect more people.)
2. Balancing Loops (Thermostats): Action produces a result, which triggers a counter-action to slow things down. (e.g., A predator population grows too large, they eat all the prey, and then starve.)

Ready to build? ​

Now that you know how the plumbing works, let's look at how these loops dictate the real world.