iPhone Game pause and resume, is it worth implementing?

Allow me to describe my situation:

I want to develop a game, that is round-base, and pay-to-play. That means you pay one coin, for one round of game, like Pinball etc.

The problem is, when there is interruption, ideally the game should pause, and resume whenever the user desires. Implementing that seems to be a challenge. S开发者_如何学编程ay my game was put into background, I would save the game state in ApplicationDidEnterBackground. However the game may or may not get terminated while in the background. So the next launch could be a "fresh start" , or, a "resume from last saved state".

If the app is left in the background long enough, say 1 week, its almost certain that other apps fighting for memory will cause the game to be terminated at some point. When the user starts my app again, they would be playing from a new round, meaning that the previously unfinished game, is gone.

From a customer point of view, this is unfair.

What I can think of is, to implement it so that whenever my app is brought to the foreground, I would go check if there was a saved game. If there was, I shall resume it instead. This poses a security issue:

Saved game, either in most primitive plist format or other formats, are persisted, and poses security problems. (What if players edit the game state and score 10 million points as top score... etc)

Are there any recommended ways to tackle these problems?

I see some Apps simply give up on saving the game, and a new round will be started on resume. Those are not paid to play games, otherwise I can imagine users getting very angry.

I have seen some Apps that saves the game state for a while, but when it got terminated, when next launched, it will start a fresh round. Which seems just as unacceptable in the case where players actually paid money for the round.

And when taken into account the possibility of crashes, I cannot come up with a good solution that ensure paying customer will get to play a full round of game. It would really help me if someone with relevant experience could share their thoughts, and how they make their decisions.

Why not tie the round finishing to the payment? If the round doesn't finish, no payment is taken. If the user's credits are insufficient at the time the round finishes, you could give them the option to purchase more credits immediately (via in-app purchase) to finish the current round.

That simplifies your task as a developer, and also provides a way to prompt the user for additional payment in a non-obnoxious way.

Here's a great tutorial on using NSCoding to save game states. It won't have any problem with the player going in a editing the file, as it is done in NSCoding. If a user REALLY wants to figure out how to un-encode the file and change the contents, which is crazy, you could do some kind of encryption on the data BEFORE you write it to file, so there would be no way the user could change it. Hope that helps!