-Point with your MOUSE to aim the towers. Once a wave starts, the towers will automatically start firing. -Press SPACE to place a marker for your towers to shoot at. -You can UPGRADE your towers by clicking on them, and then clicking the box, if you have enough cash to do so. (You can click outside the box to close it after it opens) -You can also SELL a tower from the upgrade menu. (It will only return the amount of money you spent to buy the tower) -Each wave gets progressively harder, along with different Zombies that will start spawning after a certain number of rounds.
