Slitherlink is a popular puzzle game for Android devices.
It includes a tutorial with explanation of game rules, tips and
tricks; a demo and a full version are available. Android
Slitherlink supports most devices, from small screens to tablets (with
tablets making gameplay especially pleasant).
Ever wonder what postal code or county boundaries you are in? What
the phone numbers look like around you? The "Where Am I?" app for
Android answers these questions and provides other useful
information as well. Free app, supported by voluntary donations.