Sometimes the ads are two frequent (they sometimes fire for every new tile). There are only 3 planets. Sometimes the app freezes and has to be hard restarted. All that said, this is great, unique game. There's constantly things to do, and it's not plagued by time gates the way other games are (like energy which refills over time). You're not bombarded with options to pay for things either. Look forward to more levels being added.