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Hi, I'm developing an app that involves the user solving problems. I want my app to have a free trial, but I'd like that trial to expire after the user has solved a certain number of problems, as opposed to after some pre-specified time period. When the trial expires, they'll need to either purchase a non-renewing subscription, else some functionality limitations will be imposed. Given the above, I have two questions: I know that a time-based free trial is permitted by Apple, but is a usage-based free trial - as described above - allowed? If a usage-based free trial is allowed, are there any specific details relating to how this trial (and/or the subscription) should be communicated to the user?