A free program for Android, by Playfox.

A Monster Ball is a kind of mobile Augmented Reality (AR) app, which allows you to see and interact with objects in the environment. The way that it works is by taking your current location, or what you consider to be your current location, and then throwing a ball into the world. As it comes to the rest, it will go to the nearest obstacle, which will then get in the way of the ball and stop it. This way, you can go through the obstacles and reach the goal.

As you can see, it is really easy to play and very simple to understand.