In this model, the effect of crowding is shown. New groups can only be made if there is open space. This is the result of a new condition in the behavior of the group. Can you find the new condition and understand how it works?

Try different shapes and sizes of background. Select the hand tool and click on a green square. Then select the background and the gray rectangle tool to create new shapes. Try several rectangles connected by narrow strips. This might simulate continents that the groups colonize.

Run the model for a long time. Does the population seem to level out? What do you predict for the final population? Stop the program and count the number of filled and empty cells. Does this agree with your prediction?

The population tends to drift upward because the new groups are always made above an old one. Can you fix this by sometimes making new groups below the old one?