It's hard to say. I have problems with ads and sales. One way is only available for me to save the game is to make donates for some products inside the game.
You can let some trains need money to buy,(real money) or you can buy the point I the games like 1 point$0.1
如果这个游戏都要氪金，那还有什么可玩的呢
那他实在没钱去做研发了，再说肯定有破解版，那就让傻的去充钱就ok了
有道理
