Boccia sounds remarkably simple. Throw one or more of six coloured balls closer to a white target ball, or jack, than your opponent.
Simple? Think again. This sport is a combination of chess, snooker and bowls where strategy, precision, steely nerves -- and a little luck -- all come into play.
One of two Paralympic Sports at Tokyo 2020 that has no Olympic equivalent, it shares similarities with the French game of boules or the Italian equivalent, bocce.
The game traces its roots back to Ancient Greece and Egypt and is thought to be one of the oldest sports played by humans.
But this is no game played by old men on dusty Italian or French town squares, this is gripping -- and addictive to watch.
Designed so athletes with cerebral palsy, muscular dystrophy or any kind of neurological impairment that impacts motor function can take part, boccia has been part of the Paralympics since 1984.
Players in wheelchairs use throws from hands, feet or helped by assistive devices such as ramps and pointers, to deliver the leather balls which are filled with plastic granules so they do not bounce and are easy to grip.
- 'Incredibly impressive' -
Whichever method is employed, angles, trajectory, speed and a calculating brain are crucial to prevail on an indoor playing field roughly the size of a badminton court.
But leading Canadian player Julian Ciobanu, who has muscular dystrophy, compares it to another sport.
"It's like archery," he told AFP on Sunday after winning his second consecutive pool match in the BC4 class at the Ariake Gymnasium in Tokyo.
"But you are shooting with your hand or foot."
Some boccia players have severe physical impairments, and Ciobanu, who competes in the unassisted category and throws conventionally from his hand, is in awe of some of his fellow boccia athletes and the accuracy with which they can deliver each shot.
"It's incredibly impressive when you see these people with their physical limits," he said. "It's a precise sport.
"It's a sport that involves a lot of passion, a lot of concentration and a lot of strategy, like a game of chess. You need to play with a lot of confidence and always think two or three bowls ahead."
One of the flamboyant stars of the sport is Britain's David Smith, who is aiming for a second straight BC1 Paralympic gold.
Unmistakable with his striking blue and red mohawk-like hairstyle, Smith identified one other attribute you need in boccia, and it's one you can't control.
"I had to dig in a bit and get a little bit of luck," said Smith after squeezing past Argentina's Mauricio Ibarbure 4-3 in a titanic pool tussle.
"Sometimes it's all about the run of the ball on this floor," added Smith who won the silver at London 2012 and is chasing a third straight Paralympics Games medal.
"Games can be won and lost by little details, so yeah I'll take all the luck I can get, to be honest," said Smith who holds a "triple crown" of major tournament titles -- 2016 Paralympics, 2018 World Championships and 2019 European Championships.
Individual medals in the four classes of competition, which are all open for men and women, will be decided in finals on Wednesday, followed by pairs and team competitions which conclude on Saturday.