Default criteria for what to build

The machine's default criteria for suggesting what to build are often
very stupid.  For instance, they suggest building a temple even when
the city has no unhappy population (and won't have any soon).

When a city has a high pollution level, it should suggest building
mass transit or a recycling center.

When you finish building an airport, it should suggest building
a bomber.


Events that are more likely to be reasons to turn your attention to a
city could be marked in the Messages window with a star.  These
include completion of building settlers or engineers, and civil
disorder.