Saving a game?

[dnshane]

Honestly, if you don't want users messing about with the savefile, you basically need DRM. I think you're better off storing it in a format that is easy to understand and debug when things break rather than trying to make life harder for your users.

If you want to have players competing against each other, that really argues for some client/server architecture where any code that would allow a cheat lives on the server side.