I read the 1 star reviews and mostly people kept saying that the cards are too hard to level up and they are stuck at lessons and I agree to them. Also, when getting more materials to rank up card is so HARD because we only have small energy. Improve these more than improving and making events because we will never win them if our cards are weak and our energy is small. It's only fun and easy in the beginning but when you reach a higher level it becomes extremely difficult and boring. o(≧口≦)o