Goalball is a team sport designed specifically for blind athletes. Participants compete in teams of three, and try to throw a ball that has bells embedded in it into the opponents' goal. Teams alternate throwing or rolling the ball from one end of the playing area to the other, and players remain in the area of their own goal in both defense and attack. Players must use the sound of the bell to judge the position and movement of the ball. Games consist of two 12-minute halves, and eyeshades allow partially sighted players to compete on an equal footing with totally blind players.