Healthy choices, real cashback. SNAPback turns every grocery receipt into personalized, culturally-aware nutrition guidance — and rewards SNAP / WIC families with real cashback when they sustain healthier shopping habits.
Built for George Hacks × United Nations — Reboot the Earth Hackathon 2026 Track: FAO — AI for equitable and personalized nutrition in diverse U.S. communities
The U.S. is living through a dual crisis of malnutrition. Diet-related diseases — obesity, diabetes, heart disease — disproportionately hit low-income and marginalized households, while ultra-processed food is the cheapest, most available option on the shelf. In ethnically diverse cities like New York, families on SNAP and WIC rarely get nutrition guidance that respects their budget and their culture. Generic "eat more vegetables" advice doesn't help a Caribbean grandmother shopping for callaloo, or a South Asian family buying atta and dal on a $480/month budget.
SNAPback is a Flutter mobile app that closes the loop between what families actually buy and how their government benefits could reward better choices.
- Snap a photo of any grocery receipt.
- Gemini 2.5 Flash reads it multimodally — every line item, quantity, and price.
- Each edible item is scored 0–5 against a USDA-derived healthy-foods rubric (per the resources provided in the FAO problem statement) and tagged for cultural relevance to the user's declared cuisines.
- The app awards per-item cashback (5% for 5★ items, 3% for 4★, 1% for 3★, +1pp cultural bonus) — but the cashback is only redeemable when the household's monthly average health score stays at or above 4 / 5.
- We also generate nutritious recipe suggestions from what they just bought, in their preferred cuisines.
The redemption gate is the heart of the design: families are nudged toward sustained healthy patterns, not one-off "healthy hauls."
- Personalized to budget and culture — our cultural bonus rewards Caribbean, South Asian, West African, Latin American, East Asian, and 19 other cuisines, not a one-size-fits-all "Mediterranean" recommendation.
- Behavior-gated cashback — most cashback apps reward any purchase. We only release cashback when the monthly health average crosses 4/5. That's the policy lever that turns nutrition science into action.
- Closed loop with Gemini multimodal — no separate OCR step. One model reads the receipt, classifies items, scores them against USDA criteria, and powers the recipe suggestions.
- Designed for the people who actually use SNAP — large fonts, bouncing scroll, light/dark themes, household-level case ID, and a redemption summary that makes "what I'd actually get" plain.
Receipt photo
↓ (Flutter — image_picker + crop)
Firebase Storage → Cloud Function: processReceipt
↓ (Gemini 2.5 Flash, structured JSON, USDA rubric)
Firestore: items + per-item health score
↓ trigger
Cloud Function: scoreTrip
↓ tiered cashback + monthly cap + redemption gate + recipes
Firestore: trip result + monthly stats
↓ live stream
Flutter UI ← Dashboard / History / Trip Result auto-update in real time
| Layer | Choice |
|---|---|
| Mobile | Flutter (Dart) — iOS + Android |
| State | Provider (MVVM) |
| Navigation | go_router + IndexedStack for persistent tabs |
| Auth | Firebase Auth (email / password) |
| Database | Cloud Firestore (real-time streams) |
| Storage | Firebase Storage |
| Server logic | Firebase Cloud Functions (Node 20, 2nd gen) |
| AI | Gemini 2.5 Flash via @google/genai (structured JSON output) |
| Charts | fl_chart |
| Health rubric | USDA-derived healthy-foods criteria (per FAO problem statement resources) |
lib/
core/ constants, router, theme, utils
models/ UserProfile, TripResult, TripItem, RecipeSuggestion, UserStats
services/ Firebase wrappers (auth, profile, trips, receipt, preferences)
viewmodels/ one per screen — pure Provider, no Firebase imports in UI
views/
screens/ onboarding, home, scan, trip_result, history, profile
shared/ widgets (ScoreRing, GlassCard, SnapbackLoader, ItemHealthBar, …)
shells/ main_shell with persistent bottom nav
functions/
index.js processReceipt + scoreTrip (Gemini integration, scoring, recipes)
firestore.rules
storage.rules
- Flutter SDK 3.22+
- Node.js 20 (for Cloud Functions)
- Firebase CLI (
npm i -g firebase-tools) - A Firebase project with Auth (Email/Password), Firestore, Storage, and Functions enabled
- A
GEMINI_API_KEYfrom Google AI Studio
git clone https://github.com/<your-org>/SNAPback.git
cd SNAPback
# 1. Configure Firebase for your account
flutterfire configure
# 2. Set the Gemini secret
firebase functions:secrets:set GEMINI_API_KEY
# 3. Deploy backend
firebase deploy --only firestore:rules,storage,functions
# 4. Run the app
flutter pub get
flutter run- Sign up with email + password.
- Complete onboarding (3 steps: name + language → SNAP amount + family size → cultural preferences).
- Tap Scan → snap a grocery receipt.
- Within a few seconds the Trip Result screen shows item-by-item scoring, cashback earned, redemption status, and recipe suggestions.
Per item:
- 5★ item → 5% cashback on its line total
- 4★ → 3%
- 3★ → 1%
- ≤2★ → 0%
- Cultural-match item → +1pp bonus
Monthly cap: min(10% × monthly SNAP amount, $25 × family size)
Redemption gate: the accumulated cashback for the month is only released when the household's item-weighted average health score ≥ 4 / 5 for that calendar month. Below the gate, cashback keeps accruing but stays locked — the UI shows exactly how far away the family is from unlocking.
- Screen-reader labels on the score ring, redemption badge, scan button, and trip rows
- Light + dark themes that meet WCAG AA contrast on primary surfaces
- Bouncing scroll physics + persistent bottom nav for predictable navigation
- Large, bold typography on key numerics
- Tap targets ≥ 44 pt across primary actions
- Real localization (Spanish + Mandarin ARB files) — language picker is currently English-only
- FCM push: "Cashback unlocked" on the 1st of each month + monthly progress nudges
- WIC-specific item recognition (formula, eligible categories)
- Direct EBT credit integration via state pilots
- Open API for community-vetted cultural food databases
Prithvi Saran · Roshini · Anaswara · Hidhayath
MIT — built for open collaboration with public health programs.
- USDA — healthy-foods criteria used to score items (per FAO problem statement resources)
- Google Gemini — multimodal receipt understanding
- Firebase — auth, storage, Firestore, functions, hosting
- George Hacks × UN Reboot the Earth 2026 — for the prompt and the platform
