Tips & gotchas

Iterate small

Add one rule, click Step a few times, and see what changes. With the change log and Undo, you can experiment without fear.

Use Setup early and often

Setup always gives the same starting state. If something looks odd, Setup brings the model back to it.

Use the seed when reproducing bugs

If a run looks wrong, note its seed before you report it or ask the AI. On a wide screen the seed is in the bar above the workspace. On every screen it is under World settings (the cog on the World panel). The same seed gives the same run.

Patches before agents, sometimes

Does the landscape change, as with regrowing grass, fire or pollution? Add the patch property first. Then add the agent rules that read it. That way the setup is easier to follow.

When something doesn't behave

Did the world start over when you edited a rule? A change to a rule, property, agent type or the world's settings sets the model up again. The next Go runs the model as it now stands. Changing a slider or another global leaves the run as it is.
Is the rule enabled? The toggle is right there in the rule editor.
Is the agent type initial_count non-zero (or do you create them yourself in a setup rule)?