Sticks is a free app that lets you control gravity as you turn your phone and tumble the sticks. Touch the screen and you change gravity as the Sticks fall toward the black hole your finger is now the center of!

Sidenote: At the time of posting this program has been marked as beeing freely available without any costs. As this program is hosted with the AppStore the status might change. Authors like to publish their programs for free and / or for promotion purpose and then start charging.