How to make a demo version?

Question

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Previously, I wanted to put the game just for sale, but as I understand it, there will be problems with advertising and promotion of the purchased game ...
Therefore, I decided to make the game free but with a demo version, that is, you go through 10 levels and then it says "pay to continue to continue", well and of course, right at the start of the game, it is to indicate that they say this is a demo, but at some point you will need to buy ...

How to arrange it correctly?
Is this a free game with paid content, or are there other options?
It’s just that I don’t see any other variations, tell me how it’s right in this option ...

Answer 1

there is a great service, try https://tinypng.com

Answer 2

if the game itself is not supposed to make a purchase, then just as a free game... you can put the word Demo or Trial in the title, and indicate in the description how many levels are available for this version...