Buying vs having enough resources for purchase
It would be good if the buttons for buying things differed depending if you've got enough resources, or whether you'll need to use cash to buy some of them:
green: can upgrade/purchase with existing resources
blue: can upgrade/purchase but need to buy some resources from the market
You can mouseover to see this but often you forget, see the button unghosted and spend all your cash inadvertently ![]()