How can I force the game shut?

For Android:

1. Go to Settings>Apps>Manage Apps.
2. Select the app and tap on "Shut down".
3. Go back to the home page and restart the game's app.

For iOS:

1. Press on the Home button fast twice.
2. All the open apps will appear on the screen; slide right or left to find the app.
3. Slide the preview image of the app up.
4. Go back to the home page and restart the game's app.