Spotter: prototype

A shared iPad station for single-arm bicep curls. You tap in, the camera counts your reps and sets on the device and shows only an abstract figure, you enter weight once, you tap out, and you see your history on your phone.

Run it

The station is a static app in public/ (plain HTML, CSS and ES modules), served at / by a Next.js shell. That way the beta can add API routes and a real database in the same Vercel project.

npm install
npm run dev

Open http://localhost:3000 in Chrome or Safari. The camera works on localhost without HTTPS.

On an iPad: open the Vercel deployment URL (it's HTTPS, which iPad Safari needs before it allows the camera), then use Share → Add to Home Screen so it runs full screen. Mount the iPad about 2 m away at chest height, with the curling arm toward it.

The flow

1. Check in. Tap a member card (simulated NFC), or add a new member.
2. Consent (first visit only). Choose camera + figure, camera with count only, or no camera (tap +1 yourself).
3. Weight + arm. Entered once. It pre-fills from last time.
4. Track. Reps are counted from the elbow angle. A set ends after 8 s with no reps, and the rest timer starts. Use −/+ to correct the current set or past sets.
5. Check out. You get a summary, a comparison with last time, and a QR code for the phone view. The station goes back to idle after 30 s. If nobody does anything for 3 min, it checks out automatically and the camera turns off.
6. Phone history (#/history/<member-id>). Shows a trend chart and sessions, and lets you delete a session or export a CSV.

Real vs simulated

Piece	Status	What the beta needs
Pose tracking (MediaPipe Pose Landmarker, on-device, numPoses: 1)	Real	Tune thresholds with real users (speeds, positions, body sizes)
Rep counting, sets ending on their own, corrections	Real	Validate accuracy against hand counts
Silhouette-only display (camera frames never drawn)	Real	—
NFC check-in/out	Simulated (member picker). Real Web NFC is used on Android Chrome if present	iPad can't read NFC from the web: use NFC tags/stickers that open a check-in URL on the member's phone, or a USB NFC reader
Cloud sync to phone	Simulated (browser localStorage)	Swap js/store.js for Supabase/Firebase keyed by tag ID, plus auth
Simulated camera	Demo aid	Turn it on from the Prototype badge when there's no camera

Files

• next.config.ts: rewrites / to public/index.html

• public/js/app.js: screens and session logic

• public/js/reps.js: elbow-angle curl counter (thresholds at the top)

• public/js/pose.js: camera + MediaPipe source, simulated source, silhouette renderer

• public/js/store.js: data layer (swap this for a real backend)