Cash is one of the game's top priorities as you need it to do almost anything in the game.
Cash is measured in two meters: p/m, the money you make "per-minute", and the actual amount of money you have, displayed in green. At the start of every round, each player gets 300 cash.
Cash is used to buy anything in the game. To earn cash, you need to have any of the following buildings: Power Plant, Nuclear Plant, Fusion Plant, Oil Rig. Cash is also obtained by selling troops/buildings that you own. (Recommended when using explosive tanks etc.)