Not just Pay to win, but Pay to Play! Once you reach the 4th zone the games difficulty jumps up so high you have 0 hope if even passing the missions without paying $$$. On the 5 zone I went from green gear to blue, went up about 25% in power, but suddenly the enemies started hiring HARDER!!! YUP! That's right, the enemies power level is BASED ON YOURS! So if you go up in power, so do they. Went from getting the boss to 10% HP to not even able to get past 50% AFTER upgrading all my heros!!!