You pick East and West locations that define the goals and North and South locations that define the walls. A ball travels over the map of your city kinda slowly and you have to drive your phone within a certain distance, like 10 yards to make it bounce back towards your opponent. Could cause some reckless driving, but would be a hella fun party game with teams of people in two cars trying to decided where to intercept the ball and how to get there quickly. In theory, you could play across the globe by adjusting the horizonal and vertical speed of the ball.