Before a battle starts you can select which units you are going to use and see which opponents you will face. 

Energy is required to start a battle. If you run out, it gets replenished over time or it can come back in the form of energy bottles, found as rewards, or by using premium currency. 

The overall gameplay works like classic turn-based games. Each of the units attack one at a time, taking turns.

You select which enemy to attack by tapping on them.

You can use the normal attack, or a special ability once it's charged up and unlocked.

Each unit has a health number, and once it's depleted it dies.

Enemies will appear in waves, until the final wave is defeated. Only 3 enemies per wave are encountered.

You can also use mana or health potions to your advantage. These are obtained as rewards, or purchased.