Sadly, the game is fun, but a HUGE money pit. If you want to progress in the game without buying anything, you will never finish the game before retirement. Each world gets more expensive to upgrade trains, and the rewards you get from completed missions doesn't go very far. I would not recommend this game to anyone looking to pass some time. It has you checking back every hour to check on returning trains. The missions take too long, and the rewards suck. I give up. I am going to try one of those games that you pay once to get rid of ads, and never pay again, and again, and again...