Pause game play and tap the "I" button to check what kinds of waves will be coming, especially before building towers. Make sure you always have the advantage based on your tower and the types of enemies that will approach in a particular round. Most of the time, waves come in combinations of three troop types. However there are some levels where you need to focus on a specific type. For example in levels that feature aerial units, it is useless to build land-based Cannon Towers; instead, focus on maximizing your Arrow Towers. Build Mage Towers for mini-bosses. This is the only tower that you must have all the time. Mage Towers are specifically designed for strong solo enemies. Besides the Mage Tower that is perfect for eliminating single enemy, there are two different types of towers you will start with. The Cannon Tower is effective against hordes of enemies that will attack in waves. It has the ability to do splash damage and can instantly eliminate several enemies at once. The Arrow Tower is best used against flying enemies.