Instructions and controls: You must prevent balloons from coming through. Place different cannons that you can afford at the side of the road. Earn money so you can buy more cannons. There will be a new unit available every time so save your money. Just click on the cannon that you can avail at the side of the screen then place it wherever you want. You can sell some cannons by clicking on them the selecting the SELL button. You can also select the target priority of each cannon by clicking on them.