In-Game Purchase - Level Download?

Question

Game development

Good day!
There is a game on a mobile platform, the game has an internal currency (coins). By playing the game, the user earns coins. It seems like a simple question, but I'm still a young Padawan in this business :)
Task: to present paid content to the user in the form of buying additional levels.
Question: please advise what to do if I decide to sell levels for coins...
It turns out that I don’t need to place my levels as Products in Windows stores, Google ..., but I need to implement their storage (localization, etc.) on my server and when I click Buy, just write off coins? What if I place them in the store, but at a price = 0 (but then it is necessary to indicate somehow that coins in such and such an amount will be written off)? Surely the user, even at a price of 0, will be shown information about withdrawing 0 money from the card? If you place the levels as products in the store for real money, then coins seem to be not needed, the meaning of the in-game currency is lost...
The advantage of implementing the storage of information on your server is that you do not have to start the same products in their stores for different platforms. It seems to me that it is enough to sell the in-game currency for real money, as I understand it, it must already be issued in the appropriate stores as a product. Please tell me which direction should I go? Can you recommend some smart articles on this topic ?! Thank you.

Answer 1

You have a slight confusion in terminology.
In-game purchase, in-app is only about purchases for money.
1. If you sell levels for coins, and coins are earned in the game itself, this has nothing to do with In-App . Your game is completely free from the point of view of the store, and what you do inside, how you unlock levels, whether you sell something or not, it doesn’t matter to them.
2. But if you start selling the coins themselves for real money - the coins can now be called "premium currency" and you will show the windows "buy 100 coins for 1 dollar?". But again, after buying a premium currency, the store is completely indifferent to what exactly the user will spend them on. You will need to count everything on your server - the user profile, the user's wallet, what has already been purchased by the user.
3. But if you sell levels for real money - in this case it makes sense to use non-consumable in-app - one-time purchases that the user can buy exactly once. Then the store to the question "did the user buy such and such a level?" will answer - "yes, I bought it." But it's a little more complicated from the game side, and besides, you still need your own server.

• The store takes 30% (usually, sometimes a little less or more) from all in-game purchases, which is why they are only interested in purchases for real money
  
• it is impossible to put a price of 0 money, from the point of view of the store it makes no sense
  
• some stores have a distinction between one-time (non-consumable) and multiple (consumable) purchases, some do not. I recommend using reusable ones, they are easier to understand. Disposable ones are easier to control and take into account, but it’s better not to get into it yet, in the case of a cross-platform you will get confused at all.
  

Answer 2

In the store of the target platform, you sell coins in different portions, you open levels for coins in the user's save, you download levels from the server. Much attention should be paid to the process of buying coins so that they are not lost along the way if there is no Internet or the application crashes.