It would have been a much better game if it worked in the background when you quit the app. But it doesn't, so you must abandon everything else while you play, and lose progress when you log out. Secondly, money accrues too slowly. It will take like 100 years to get a decent daily earning even if you spend all your time and resources developing income. It's a frustrating pay-to-play game. Devs fix these 2 issues for 4 stars.