Follow a team in a simulated basketball league: every game kept, every replay a click away

basketball.casa is a basketball league where every game is simulated. No one scripts the plays: each one comes out of who the players are at that moment, how tall and fast and tired they are, what they can see and what they decide, and you can watch any of it back as it happened. A tournament is played every day. Until now, though, a day vanished from the site as soon as the next one began, so a team you liked was hard to find again. That changes today.

Every finished day, kept

The new archive lists every finished tournament day, newest first, each one laid out round by round from the first round to the final, with every score. Type part of a team's name into the filter and the list narrows to the games of every team whose name contains it. The site keeps a week of replays, so any game from the last seven days opens straight from its row; older days stay listed with their scores.

A replay here is not a video. It is drawn from the numbers the simulation recorded for that game: where every player was and what each decided, moment by moment. And every game starts from a seed, a starting number, so the same seed under the same version of the simulation plays out exactly the same way every time it is run. That is what lets a game from last Tuesday play again, shot for shot.

A team to call your own

Every team that has played now has a page: its games day by day, each with the round, the opponent, the score and whether it won, a replay for the days still kept, and then its players. Take the American Samoa Barons: their page shows a 103 to 80 first-round win on Saturday 3 October, and the quarterfinal they lost later that day.

A team's page has a Follow button, and so does the page of any player whose team has played. Press it and the Following page gathers, in one place, the games of every team you follow and of the teams your players play for. The list lives only in your own browser, and nothing about it is sent anywhere, so there is no account to make and nothing to sign up for.

A camera that holds still

In basketball, the player with the ball dribbles it, bouncing it on the floor as they move. The replay's camera follows the ball, and it used to rise and fall with every one of those bounces, so the whole picture shook every time someone brought the ball up the floor. Now the camera's height eases toward the ball on a slower clock of its own, so it keeps the ball in view without bouncing along with it. In a test clip, the picture's swing over half a bounce went from between 72 and 151 pixels to between 6 and 23.

Moving without the ball

Only one of the five players on a team has the ball. What the other four do decides a lot: a player who moves to an open spot is easy to pass to, and a player who stands still lets their defender relax. Until now, the players without the ball stood on their spots and waited.

Now, each time a pass is completed, every one of them weighs staying where they are against moving a few steps to a better place, using their own judgement and their own legs, and the ones who choose to move run there. Nobody tells them to; it is each player's own decision, which is how everything in this league is meant to work. The inspiration was a number from tracking cameras in real games: about three in ten of the players away from the ball are running at the speed of a cut in the two seconds after a pass. Here it was about one in twenty. In the tests that led to this change it rose to about three in ten, so the floor moves the way a real one does.