Every player now reacts at their own speed

basketball.casa is a league where every game is simulated from its players' bodies up: how tall, fast and tired they are, what they see and what they decide. This update is about a small number with a large reach: how long it takes a player to start moving after something happens.

One reaction for everybody was one too few

Until now every player in the league answered a move in the same time. A defender waited about a third of a second before starting to run, and a defender guarding a drive took the same half second as everyone else to decide where to stand. That was a placeholder, and a placeholder is the opposite of what this league is for: nobody here is an average, and how quickly a body answers is part of who they are.

What we built, and what we left out

Each player now has two reaction times of their own. The first is how long they take to start a run after they see what they must run to: their simple reaction, about 0.3 seconds for the league's most ordinary player. The second is how long they take to answer a choice, such as where to stand against a player driving to the rim: about 0.55 seconds for that same ordinary player. Both come from the same trait, how aware the player is of what is around them, the one that already decides how fast they make their choices. A more aware player answers sooner, a less aware one later, and the player in the middle of the league answers exactly as the league always did.

The honest part: the research we could find says that how fast people react at the reflex level barely separates trained players from untrained ones, so the spread between players here is small, a tenth to a quarter of the average, and no more. What does separate good defenders is reading the play early, anticipation, and no study we found measured how much that is worth between players, so we did not invent a number for it. It is on the list, waiting for a measurement.

What you will see

Open any player's card and the reaction time is there, listed as built from their body instead of marked as a stand-in. Watch a replay slowed down with the pauses switched on and each defender's standing still before a run is their own length. And where a defender stands against the player they guard is now set by that defender's own answer: a quicker, more aware defender stands closer to the player they guard, which is the direction the research points. The effect on any single play is small; across a season it is another way the players differ because of who they are, not because a number was handed to them.

What it cost

Different reactions make players' paths meet at more moments than one shared reaction did, so the simulation has more to work out: about a quarter more arithmetic. That is the price of detail, and we paid it on purpose.