Most Paralympic sports have an equivalent at Olympic level — but one sport that is unique to the Games is goalball.
What is goalball?
The game is played in an area the size of a volleyball court but has nets at either end.
The players are vision impaired and they wear eyeshades to ensure no-one has an advantage.
Once a game starts, players can only adjust their eyeshades by raising their arm in the air and getting permission from the referee.
And the players are not allowed to wear hearing aids or devices that assist them in making their way around the court.
The game is played three-a-side, with three more on the bench. The aim of the game is to roll or throw the ball, which has ball bearings inside to allow players to sense its location by hearing, along the floor of the court and into the opponents’ net.
In order to stop the ball going into the net, defenders must block the ball with their body by diving from a crouched position.
How does scoring work?
The goals run from side-to-side at either end of the court.
If the ball completely crosses the line into the net while it is in play, it’s a goal. And it doesn’t matter who throws it — if you accidentally throw it into your own net, it’s a goal to the opposition.
The team with the most goals at full time wins.
However, if a team leads at any point by 10 goals, the game ends immediately.
How long are matches?
Games of goalball are played in two halves of 12 minutes each.
Players are given an audible signal five minutes out from the start of the match, and another alert 90 seconds before the start of each half.
The referee asks everyone to turn off their phones and remain quiet during play. The official then throws the ball to the player closest to the centre of the court. They blow their whistle three times and call “play”, at which point the game clock starts.
When play stops for any reason, such as the ball going out of bounds or the ball being blocked out, the clock stops. The referee has to call out “play” before the clock can resume.
Because of the need for players to hear where the ball is, no sound can be made by the crowd or teams until a goal is scored. This can lead to huge bursts of cheering to break the silence, although the absence of fans in Tokyo may change the dynamic.
There are individual and team penalties.
Individual penalties include throwing a ball too long, too high or too short, delaying the game, unsportsmanlike conduct and making noise.
Team fouls include not throwing the ball back within 10 seconds, illegal coaching, delaying a game and making noise.
There are penalties for players who adjust their eyeshades without permission, and if they throw the ball before the referee has called “play”, it’s a loss of possession.
Also, if the ball hits a defender and rolls back over the centre line into the opposition’s half, it’s a loss of possession.
Who are the favourites for Tokyo?
In Rio in 2016, the men’s title was won by Lithuania, with United States taking silver and Brazil the bronze.,
The gold medal in the women’s event went to Turkey, with silver to China and bronze to the US.
Australia’s women’s team, the Belles, have qualified for Tokyo. The team’s best result to date is fourth place in Atlanta. They came ninth in Rio five years ago.