All challenges gets harder and harder, Win 600B coins in 50 spins, win 1.6T coins in big wins etc... Are some example of challenges. No hope to get it. Don't buy prime pass, cos U won't get money's worth, app keep force you to bet higher so you loose quicker. Odds are so against players, Random is totally BS. Force player to spent Real money. U will loose all coins trying to get 1 challenge, it just won't pay up. It's worst app I ever tried. If U use real money, its not worth it!