Click on the tower type you want to build on the right side of the screen, then once its selected, place the tower in the maze. Press escape to deselect or cancel your current action. You can sell towers for extra money for 80% of what you paid for them. Larger colored bloons have smaller bloons inside them, so watch out! Created by Ninja Kiwi. Have a look at Bloons Tower Defense 3 as well, or the first version.