You can progress without buying the upgrades.. or you can pay to get them immediately... I prefer to work playing the game to get them. Very well put together.. some ads are annoying but they pay for the game. I enjoy this game... Anyone who rates ANY game "5 Stars" is an imbecile. 5 stars is false advertising and makes for bad development of worse games. 4 stars MAX. This game is work but you can get ahead without paying real money