Watch the math move, one step at a time
Each explainer runs a real simulation in the page. The numbers in the side panel are computed as the steps play, and every one comes with a short video of the full run.
How an Elo rating moves after one game
Expected score, K-factor and the margin multiplier, one step at a time.
How a Markov chain ranks 32 teams
A voter wanders from loser to winner until the league settles into a ranking.
How k-means sorts running backs into tiers
Centroids move, players switch groups, and the tiers stop changing.
How win probability moves through one drive
Every snap changes the clock, the field and the down; the model prices each one.
How a point spread becomes a win probability
From a margin to a normal curve to a moneyline, and where the margin in two prices sits.
Why simulations instead of diagrams
A diagram of a rating system shows what the method is supposed to do. A simulation shows what it actually does with real games. Each explainer here runs the model in the page from named data: one real NFL game for the Elo update, the first weeks of the 2026 season for the Markov chain, the top running backs of 2025 for k-means, one real two-minute drive for win probability and 7,017 games for the point spread. The side panel names the formula behind every number, and one step in each explainer either breaks the method on purpose or checks it against the published ratings.
The videos are recordings of the same pages, narrated. The pages come first: every step is written out as text under the scene, so the explanation reads just as well without the animation. Each explainer links the long-form article on the same method and the calculator that runs it on new inputs. A good order for a first visit: start with the Elo update, which needs only arithmetic, then the point spread, then win probability through a drive, and finish with the two that need a little linear algebra, the Markov chain and k-means.
Frequently asked questions
What is a stepped explainer?
A page that walks through one idea in short steps, each with a one-line caption over a scene. The scene is a simulation running in the page, so every number on screen is computed from real data rather than typed in, and a side panel shows how each number is made.
Where does the data in the explainers come from?
From the open nflverse releases: real game results, real play-by-play snaps and real player statistics, under a CC-BY 4.0 license. Each explainer lists its sources and the exact games or seasons it uses.
Can the explainers be read without the animation?
Yes. Every step is also written out as ordinary text under the scene, and each page has a transcript of the narration and a short video of the full run.
Do the explainers match the site’s ratings and calculators?
They use the same formulas and constants. Each explainer checks its own result against the numbers the site publishes, and shows that check as its last step.