I think this game is a bit of a con to be honest, it gets progressively more frustrating and drawn out so that you feel more tempted to be swindled out of your hard-earned cash to buy expensive boosters (which I don't buy!), and some levels you just simply cannot win in any reasonable timescale without a serious booster! The game writers must be making a mint from this, dripping you only measly boosters now and again in the form of a "reward".

People will just give up with game if they make it too hard and then they'll make no money on it at all.