How to save the game?

Hi guys,I want that my game is autosaved each 30 seconds & when the player close it,can I do this? 

Also,where the save information are stored?
Also,what is saved?The status of the global attributes? There is even the smaller risk to lose a save? 

1. you can save. 2. it creates a cookie for your computer. 3. attributes, and which scene your on.

To clarify #3, not every attribute gets saved. Only global or "game" attributes can be saved

there is a risk that some program that keep clean the pc delete this coockie & force you to start over?   

Yes, there is. For example, CCleaner can wipe out all your cookies if don't tell it otherwise.