The Keeper of 4 Elements

The Keeper of 4 Elements invites to a fight in 15 levels. We begin with an easy level. Place the towers on the given places with one of the 4 elements water, earth, air, fire. In the ongoing levels we can build more upgrades and expand them, also the maps will be more difficult. To collect as many stars as possible we have to beat all the stages in the medium and hardmode.