Just updated the app a few weeks back and now it's only worthwhile if you are willing to buy the caravan tickets. They lowered the amount of experience ya use to get for clearing a level BIG TIME! I used to clear levels that would cost literally one to two million of energy likely more. And before that upgrade I would've gotten at least several hundred thousand bonus experience for completely clearing the level. I got 65,000 is all. Really pathetic. It took days to clear. Total downer!