it's a classic pay to play freemium game.
But i gave it 4 stars because unlike all the other garbage, this game actually has ways of bypassing the paywall without paying. Contests, missions, quests and a total of 3K free premium currency all of which will get you half way through the game with ease. The only thing holding you back is the energy system which is a test of patience. Of course you can bypass that too if you are good at math. time your fights properly so that you get the most of levelup refills.