How to read a Gist.

Every exhibit on this site shows one thing you can change beside one thing that stays fixed. In the pitch exhibits the fixed thing is a ball under gravity alone, drawn dashed. The pitch you control is drawn solid, in red. The gap between them at the plate is the whole lesson.

Each number carries a label that says where it came from.

Observed

Measured by MLB’s tracking: speed, spin, where the ball crossed the plate, the score.

Aggregate

A season average across many pitches, such as a pitcher’s mean fastball speed.

Derived

Calculated from observed data: a pitch’s flight drawn from its tracked position and speed, or a win probability from MLB’s model.

Simulated

A teaching model you can adjust. It shows a relationship, not a real pitch.

AI-generated

Made with an image tool. Only the footer illustration and the logo character.

Start with induced vertical break, the number behind the fastball that seems to rise. Make a prediction before the reveal. The answer means more when you have a read to check it against.