Every replay on the newest game, and a basketball simulation that knows what a travel is

basketball.casa is a basketball league where every game is simulated. Nobody scripts the plays: each one comes out of who the players are at that moment, how tall, fast and tired they are, what they see and what they decide. Every game can be watched back exactly as it happened, because it is stored as a seed, a starting number from which the same game plays out the same way every time. This update is about keeping those replays right, and about one of the oldest rules in basketball.

Players no longer vanish from replays

Some of you watched a replay and saw players disappear. Here is what happened. The game is built in versions: each time the simulation changes how players move or decide, its version number goes up. A day of games played on an older version was still on the site, and its replays carried a description of the players' bodies from before the newest change, the one that lets a tired player bend over. The new drawing code looked for a value the old replay did not have, and could not draw those players at all.

Two things changed. The replay now draws every body from its own code, never from what a stored game says, so a change to how players look can never break a game again. And the site now shows only games played on the newest version. We used to keep every finished day for good; now a day played on an older version leaves the site when the game moves on. It is a trade we chose: a smaller archive, in exchange for every replay you open being the game as it plays today.

The game now knows what a travel is

A travel is a violation for taking too many steps with the ball without dribbling. Once a player stops dribbling and gathers the ball, they get a couple of steps to shoot, pass or stop. Take more and the referee blows the whistle, and the ball goes to the other team.

In this league nobody counts steps by hand. Whether a player travels comes from their own body: how fast they were moving when they gathered the ball, and how long they then take to let it go. A player flying in at full speed who takes a long time to release a shot has more steps to fit in, and so more chances to take one too many. That only became possible recently, when every shot started to leave the hands at its own pace instead of all at one speed.

The honest part: in the games played since, nobody has travelled yet. Real players are called for it a little under once every hundred times their team comes down the floor, so the players here are, for now, cleaner with their feet than real ones. That gap is measured and on the list.

Update, 13 October 2026: travels now happen

The sentence above has stopped being true. Over 60 league games on the current version of the game, 10,876 times a team came down the floor, and the referees called 19 travels: about 0.2 for every hundred possessions, or one in roughly 570. Real players are called a little under once in a hundred, so the players here still keep their feet cleaner than real ones do, but the rule now fires, and it fires because of how fast a player was moving when they gathered the ball and how long they took to let it go. The gap to real players is still measured and still on the list.