This app is made for one business purposes.
You need gems or coins to upgrade your weapons and you need them a lot. But at the last you need a lot of gems and coins but that time it will be very hard to get gems and coins and that time it will become impossible to win any dingy. So it will force you to buy gems. May be the price will be more for somebody and less for somebody but it’s taking money just to give gems in that game. No use.
Another thing that it say free gems just to see some video. Actual thing is that those are advertisement by some company and as much as we watch the advertisement they will get money for that.
So it means in both the cases they will get paid.
But it is good as a game.