Wow, so recently the devs has lowered the rewards, very few to start with, nothing for free in this game! The challenges provide no incentive due to very little in return, greed at its best... Or worse!... Levels are difficult, but with a few days of play it can be completed, however, loads of pop ups to encourage you to pay, I'm not sure why people play this game, including me! or support the devs, which I don't. Give it a miss. Curious as to how it's rated 4.6 when all reviews are negative!