The 4th Call

A browser game about late-game football play-calling. You get the score, the clock, the timeouts and 22 players on the field; you call the plays (27 of them), manage the clock and call the defense. Every decision is graded by playing the rest of the game out thousands of times for every option you had.

• Daily: three spots a day, the same for everyone (by UTC date), resumable after a refresh, shareable result.
• Survivor: random spots back to back; one loss ends the run.
• Practice: build any spot; optional Coach mode shows each option's win chance before you call it.

Rosters, jersey numbers and season statistics come from nflverse (CC-BY 4.0; see scripts/build-rosters.mjs, which also documents how the 0-100 game ratings are computed from those statistics). Game situations are made up. Results come from a simplified simulation written for this game; grades are its estimates, not official evaluations or real-world probabilities.

Run it

npm install
npm run dev        # http://localhost:5173
npm test           # engine tests (Vitest)
npm run build      # type-check + production build into dist/
npm run preview    # serve dist/ at http://localhost:4173

Requires Node 18 or newer.

Configure before deploying

Copy .env.example to .env.production (or set the same variables in your host's build settings):

Variable	Required	What it does
VITE_SITE_URL	Required for search	Your public address, e.g. https://your-domain.com (no trailing slash). Makes the social-preview image, canonical link and structured data absolute, and adds sitemap.xml plus its line in robots.txt. Without it, search engines get no sitemap and no canonical URL.
VITE_GA_ID	Optional	Google Analytics 4 measurement ID. The site tag is built in (in src/game/analytics.ts); set this to use another, or off to load no analytics (for local builds).
VITE_FEEDBACK_URL, VITE_SUPPORT_URL	Optional	The footer's Feedback and Support the developer links (https:// or mailto:). Not shown when empty.
VITE_ADS, VITE_ADSENSE_CLIENT, VITE_ADSENSE_SLOT	Optional	Display ads, off by default. See MONETIZATION.md before setting them.

Analytics events (when enabled): game_start, call_made, spot_complete (game complete), play_again, daily_complete, survivor_end, share (the full list is in src/game/analytics.ts). No personal data is sent. If you enable analytics for visitors in the EU/UK, you may need a consent banner.

Deploy

The build is a static site in dist/ with relative asset paths and hash-based navigation (#survivor, #practice), so it needs no server rewrites. Any static host works:

• Netlify / Vercel / Cloudflare Pages: connect the repository, build command npm run build, output directory dist, Node 18+. Add VITE_SITE_URL (and optionally VITE_GA_ID) as build environment variables. Point your domain at the project in the host's dashboard.
• Any other static host / S3 / GitHub Pages: run npm run build locally with .env.production in place and upload the contents of dist/.

public/404.html is the not-found page (Netlify, Cloudflare Pages and GitHub Pages use it automatically).

Search (SEO)

The title, description and crawlable text (the pre-render fallback in index.html and the footer blurb in src/App.tsx) describe the game in generic terms: a free football strategy and play-calling game built around the two-minute drill. They deliberately don't lead with "NFL": the game is an independent fan game, and "NFL" is the league's trademark (and "NFL 2 Minute Drill" is also the name of Sega's arcade game). Keep the no-affiliation disclaimer (footer, About, fallback text) in place.

vite.config.ts adds JSON-LD (WebSite + VideoGame), robots.txt and sitemap.xml at build time from VITE_SITE_URL. The sitemap lists only the indexable pages: / and /how-to-play/. The Worker's /leaderboard/ and /stats/ pages are noindex, follow while they are thin; to index them later, flip INDEXABLE in server/site/worker.js and add them back to PAGES in vite.config.ts. After deploying:

1. In Google Search Console, submit https://your-domain.com/sitemap.xml and use URL Inspection → Request indexing on the home page.
2. Do the same in Bing Webmaster Tools (it can import from Search Console), and run npm run indexnow after a deploy.
3. Get linked from places where players are (see marketing/). A new site with no inbound links ranks for very little, whatever its tags say.

The launch checklist is marketing/LAUNCH_CHECKLIST.md. Open search tasks are in TODO.md.

Project layout

• src/engine/: the football engine (pure TypeScript). sim.ts resolves plays and runs the clock, evaluate.ts values decisions by simulation, scenario.ts builds the daily/survivor spots, worker.ts runs evaluations off the main thread. Tests in sim.test.ts.
• src/game/: session (deterministic replay of saved picks), grading, storage, sharing, analytics.
• src/ui/: React screens and the SVG field renderer (field.ts).

Rosters and player ratings

The game uses real teams and players. src/data/nfl-rosters.json is generated, never hand-edited:

node scripts/build-rosters.mjs 2025     # downloads nflverse data into data-cache/ (git-ignored) and rebuilds the JSON

• Source: nflverse rosters (names, jersey numbers, positions) and regular-season player statistics, licensed CC-BY 4.0. The season is recorded in the JSON and shown in the game.
• Ratings: every 0–100 rating is computed by scripts/build-rosters.mjs from that season's statistics, by the formulas documented at the top of that script (rank among the league's starters at the position, mapped to 52–98). Linemen, kickers and low-snap players have no usable individual stats and are marked estimated. These are this game's own ratings, not official measurements and not any other game's ratings.
• Starters: the most-used player at each position on each team that season.
• Checks: validateRoster() (src/engine/roster.ts) runs on every team in the test suite: missing players, duplicate or position-illegal jersey numbers, missing or out-of-range ratings, stat-derived ratings with no season.

Rights: read before a public launch

• The data license (CC-BY 4.0) requires attribution to nflverse, which the About page and this file give.
• Team names and nicknames are NFL trademarks and players' names and identities are the players' own. Using them to identify real teams and players in an unaffiliated fan game, with no logos, no marks and a clear no-affiliation disclaimer, is how this build is set up, but public availability of the data does not by itself grant every commercial use. Using many current players' identities in a commercial product normally involves the NFL Players Association's group licensing. Have this reviewed by a lawyer before a commercial launch; the fictional roster generator (engine/scenario.ts makeTeam) is still there as a fallback if you need to switch back.

The daily and the leaderboard

The Daily is one game a day, the same for everyone (by UTC date). Its situation type rotates through a weekly shuffle of seven kinds (two-minute drill, dig out of the hole, win it on this drive, close it out, goal-line stand, four downs to win, fourth-down call), and the two teams are never the same as the day before.

The end-of-day screen shows the score, a percentile against simulated play-callers (src/data/percentiles.json, regenerate with npm run percentiles after balance changes), the coach profile, a share card and, when connected, Everyone today: your rank, a histogram and today's best.

"Everyone today" is served by the site's own Worker (server/site/worker.js, configured in wrangler.jsonc): the static game from dist/, and the leaderboard API under /v1/. Scores are kept in Durable Objects (one per day, plus one for the all-days summary), which the migration in wrangler.jsonc creates on deploy, so there is nothing to set up by hand. The worker stores a nickname, the score and the grade string per browser token per day; nothing identifying. Names are cleaned and obvious abuse is replaced with "Coach". Scores are self-reported by the browser, so treat the board as friendly competition, not a contest with prizes.

Run the site and the leaderboard locally with npm run build && npx wrangler dev. VITE_LEADERBOARD_URL points the game at a different server, or off turns the board off; the Vite dev server has no Worker, so the board is off there.