The best place to play this game is outdoors on a grass playing field. On a windy day, it is better to move the game indoors, in a gymnasium. Asteroid is designed for two to 30 players, from age 6 to adults. In addition to a 4- to 6-foot diameter earth ball, a minimum of six playground balls are needed. The object is for a team to knock the earth ball out of its orbit--over the orbit line on the other team's half. The playground balls are the "asteroids" used to achieve this.
The playing area is a rectangle, 100 feet long. The width should be large enough to accommodate the number of players, allowing each player enough room to throw without crowding others. The area is divided with a center line and two "orbit" lines, 20 feet on each side of the center line.
The game starts with the earth ball positioned on the center line. Teams line up along their own end line and must be behind the end lines when throwing the "asteroids" at the earth ball. Players can only retrieve balls on their side of the field. Players should be warned not to stand too close to the earth ball when the playground balls are being thrown. The playground balls can rebound off the earth ball quickly, causing injury to players. The earth ball starts at the center line after every point.
For safety reasons, balls between the earth ball and the opposing team must stop moving before being retrieved, otherwise a point is awarded to the opponent. Players can retrieve moving balls that are between the earth ball and their own end line without penalty. If a team is successful in knocking the earth ball over the opposing team's orbit line, they score a point. Games can be played either with a time limit or until one team has reached a certain number of points.