Click on towers to upgrade them. The amount of money needed to upgrade increases every upgrade. press D to make dart monkeys point to mouse pointer, S for supermonkey. You can drag in player now.
@Roll_TheDice Upgrades: Dart monkey: Upgrade 1 is 20, 2 is 40, 3 is 60 and so on Super monkey: Upgrade 1 is 550, 2 is 1,100, 3 is 1,650 and so on
