Defense + Action = Innovative Action-Defense Game !!
You can get energy by killing monsters by hitting the last-hit as a hero. When the energy obtained from the last-hit is charged, you can build a tower. Without towers, you can't stop the growing wave of monsters.
However, the dilemma is that it becomes difficult to hit the last-hit when there are more towers! The only solution to this is strategically building towers and focusing on the last-hit.