Basketball

Invented deliberately, in one afternoon, for a specific problem.

Basketball is unusual among major sports in having a documented inventor and origin date. James Naismith devised it in December 1891 in Springfield, Massachusetts, asked to create an indoor game that would keep students active through a New England winter without the injury rate of football.

The original design constraints

Naismith wanted to remove the running tackle, so he required the ball be passed rather than carried. He placed the goal horizontally and above head height so scoring needed accuracy rather than force. The first goals were peach baskets, and the bottoms were not removed — someone retrieved the ball after every score.

Rules in brief

Two teams of five score by shooting through the opponent's hoop. A field goal is two points, or three from beyond the arc; a free throw is one. The ball must be dribbled while moving — taking steps without dribbling is travelling, and resuming a dribble after stopping is a double dribble. Contact fouls send the fouled player to the free-throw line depending on the situation and the team foul count.

Positions

These are conventions rather than rules, and modern play has eroded them considerably as three-point shooting spread to every position.