The group forms a circle, standing with their legs a little more than shoulder width apart. Their feet must touch the feet of the person next to them. The window is between each player's legs. A ball is rolled underarm across the circle. Each player must prevent their window from being broken by protecting it with their hands.
If the ball breaks a persons window, the thrower gets one point. If a person stops it from breaking their window, they get the next throw.
Introduce more than one ball to make it more interesting. All players can have their eyes closed (or be blindfolded) and use a ball with a bell inside to make it more difficult.