The game started easy and it was quick to progress to the next levels, but as you go higher, the requirements to unlock the next level increases exponentially while the rewards only increases marginally, making it difficult to progress. It's even worse in the arena. As your arena rating increases, the app always match you with opponents with higher flock power, making it impossible to win even if you spend gems (which needs money to buy). I spent too much money trying to win impossible matches.