How do I close the game?

You can exit Jackpot Planet the same way you close other apps on your phone, and your progress will be saved.

Tap the button to show your recent applications, usually this is on the bottom left corner of your phone.
Scroll through the list until you see the thumbnail of your Jackpot Planet app.
Using your fingers, tap and hold on the app and swipe it off the screen, or tap the X.