It's a great game, but devs are money hungry and there are many bugs. The current bug is within the ads. Sometimes they open & sometimes it force closes. The last event I used lots of gems I brought to get energy for an arch and completed the arch with a few more gems. Probably 250 gems/2500 energy in total well an ad popped up and it force closed my game. My gems/energy were gone & arch was incomplete again. I contacted support & they said they'll see and after review they credited 14 gems.