How to debug a diagram

The task of pinpointing what systems are breaking your diagram may be off-putting. Here are a few tricks you can employ to isolate and fix any issues.

While building your diagram you’ll probably find yourself hitting Play time and again, to make sure the flow works. If at any point during Play Nodes/systems that should be active aren’t, open the Runtime log (the bar at the bottom left of the canvas, or press L): it lists those Nodes and Connections and says why each one is disabled. Click a line to select the component it is about.

Let’s say you’ve finished all or a big part of what you want to design. You hit Play, but something’s not right. However, you’re not sure where the diagram breaks: all Nodes and Connections seem to activate properly. Use the Step button in the play bar (the triangle with a bar, next to the unit menu) to go through the system one Step at a time, and evaluate which Nodes/Connections don’t act as intended.

You can also change the speed of a Play with the speed menu next to Step (0.25×, 0.5×, 1×, 2× or 4×): slow it down to be able to follow the Resource tokens flowing through the diagram.

If you went over the steps above, but when you press Play or Forecast something is still off, add an End Condition and end the Play after the first cycle of your diagram. Evaluate if everything is normal, then change the End Condition to trigger after the first 2 cycles, and re-evaluate. This way, you’ll be able to isolate what breaks the progression.

For huge diagrams, or maybe for diagrams that were built by a colleague, take each system (e.g. a power-up) and disconnect them from the whole, one by one. After each disconnect, Play the diagram. If at some point the diagram starts acting as intended, you have the culprit. See what’s wrong with the isolated system, by going through the debugging steps above, fix the problem, and reconnect it.