[farmergiles]

While some factors are growth factors others are limiting factors.

Just as a crude example compare the no. of factories manufacturing goods (used among other things to expand economies thereby furthering the markets for the above goods as well as producing materials to build more factories) to the profitability of obtaining finite fossil fuels and raw materials (used in those factories as well as for other things). The first will increase exponentially until the logarithmic decay of the second limits it. Nature as well as economics is a series of checks and balances.

Computer games tend to be unrealistic and fail to be open ended.