I wonder how idle games, games where players only make a few clicks to get a game progress, work. These games appear to be running in the background, even when the app is closed. Therefore these games may be implemented on the server side and run on it accordingly. I'm interested in the kind of implementation.
Is there a program running on the server that creates a separate instance for each player and performs the actions accordingly?
Or is this realised via a database?
Furthermore I ask myself where the data is stored, on the client (susceptible to manipulation) or on the server (high memory requirements).
Maybe one of you has experience in this area and can give me more information, insights or explain how it works. I am also happy about further reading or links.