Fourth Up

Find pickleball and tennis players near you, at your level. Go available, post a game at your court, and watch it fill live.

Stack: Next.js 15 (App Router) · Supabase (Postgres + PostGIS, Auth, Realtime) · Web Push · MapLibre + OpenFreeMap (OpenStreetMap data, free, no API key) · Vercel

How it works

• Availability: a player goes available for 1–4 hours within a 2–20 mi radius. Their location is saved when they toggle on.
• Hosting: the host picks a court, format, start time and rating range. The app shows a fill-chance estimate: a Poisson model over the available and nearby players at that court and level (lib/util.ts).
• Pings: on posting, /api/notify sends a web push to players who are available, in range, and at the right level (push_targets in SQL).
• Joining: join_game locks the game row, so two people can't take the last spot.
• Trust: after a game, the host logs no-shows, which builds each player's show-up rate.
• Sports: pickleball and tennis. Every game has a sport, and matching uses your level in that sport.
• Ratings that learn: after a game, one player logs the score and everyone's level updates with a two-team TrueSkill model (submit_result). Players also rate each other's level and say whether they'd play together again. See docs/DATA_MODEL.md.
• Stats: fill rate, median time to fill, show-up rate, and fills by start hour (app_stats).

Setup

1. Create a Supabase project. In the SQL Editor, run every file in supabase/migrations/ in filename order (or connect the repo with Supabase's GitHub integration, which applies them automatically).
2. Supabase → Authentication → URL Configuration: set Site URL to your production URL and add https://*.vercel.app/** to Redirect URLs.
3. Set these env vars (see .env.example):
   • NEXT_PUBLIC_SUPABASE_URL, NEXT_PUBLIC_SUPABASE_ANON_KEY
   • NEXT_PUBLIC_VAPID_PUBLIC_KEY, VAPID_PRIVATE_KEY, VAPID_SUBJECT (generate keys with npx web-push generate-vapid-keys)
4. npm install && npm run dev
5. npm run test:db tests the ratings SQL in an in-process Postgres.

Key metric

Fill rate. Under ~50% means not enough players per court. Grow one court cluster at a time.