[Cogito]

To increase difficulty, I would try two things:

1. have the boom/recession cycle independent for each city

2. make the cycle more complex, potentially by adding multiple cycles of different periodicity together (wave addition)

These could be combined to, for example, have long period boom/recession cycles globally, and shorter term local cycles.

Was really fun overall :)

[kristianp]

Liquidity crises, not being able to refinance debt.

[xavils]

Love both ideas! Will definitely implement it and have global recessions with mini city-cycles. This way it will make more sense to buy one or the other.