Filo

The map your friends would draw.

Filo is a social discovery app for cities. Instead of searching Yelp or scrolling TikTok, you open Filo and see a map of everywhere your friends have actually been — their pins, their impressions, their ranked favorites. Discovery through people you trust, not algorithms you don't.

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What Filo Is

Filo is built around a single idea: the best way to find a place is through someone you know. The name comes from the Italian/Greek word for thread — the red thread of fate (運命の赤い糸) — which connects people to the places and people they are meant to find. Every pin is a thread. Every friend's map is a web of threads you can follow.

The product launches at Columbia University, invite-only, with email verification (@columbia.edu / @barnard.edu) required. The constraint is the moat: every user is a real verified student, every place is somewhere a real person has been, and the graph is small enough to feel personal.

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Core Features

The City Map

The central screen. A live map of New York City showing pins from you and your friends. Toggle between your own map and your friends' combined map. Tap any pin to see who saved it, what they thought, and how they ranked it. Filter by category, friend, or neighborhood.

Pins

A pin is a place you've visited or want to go. Each pin has a category, a status (visited / want to go), an optional photo, and an optional short impression. No star ratings. No 0–10 scores. Just signal.

Rankings

For places you've visited, you can rank them within a category — a living, drag-reorderable list. Rankings are the core of the taste graph. They power the Twins feature and fuel the discovery engine over time.

Boards

Named collections of pins. "Morningside Essentials." "Late Night Eats." "Ideal Date Spots." Shareable via link (filo.app/b/<token>) — from a dating profile, in a text, in a social bio. The cover is a collage of the first four pin photos.

Discover

Six named discovery lenses:

1. Trending near you — what's being pinned most this week
2. New to your network — places pinned by friends you haven't saved yet
3. Friends disagree on — places where your friends' rankings diverge most
4. Hidden gems — high-ranked by friends, rarely pinned by others
5. Most pinned in [category] — the consensus favorites
6. Saved by people like you — taste-match recommendations

Taste Twins

You are someone's twin in a category if your ranked overlap is ≥3 places and your Spearman correlation on those overlapping ranks is ≥0.6. The Twins screen shows your top match per category — who you are most aligned with and where you diverge.

Feed

A chronological activity feed of what your network is pinning and saving. No infinite scroll — it stops.

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Design System

Filo uses a tight, opinionated design system built around three core ideas:

The thread. Red (#d8423a) is the only accent color. It appears on the FAB, active rankings, save confirmations, and brand display text — and nowhere else. One accent, used with precision.

Sticker shadow. Every card has a hard offset shadow (2px Y, 0 blur, ink at 100%). No soft drop shadows, no elevation blur. Cards look like they're physically stuck to the surface.

Italic accent word. Display titles use Fraunces serif with one italicized word in red: "different tastes, same map." This is the brand voice signature — it appears on every major screen.

Type stack:

• Fraunces — display titles, place names
• Inter — UI, body, buttons
• DM Mono — labels, counts, addresses, ranks

Palettes: Paper (default), Concrete, Midnight, Sky. All four are supported; Paper ships.

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Architecture

The mobile app is React Native + Expo (Expo Router, file-based), iOS-first, on Supabase (Postgres + RLS + Storage + RPCs) with Mapbox for maps. State is fetched per-screen through feature hooks; the taste-graph math is pure and unit-tested.

Stack: React Native · Expo (Router, SDK 54) · Supabase · Mapbox (@rnmapbox/maps) · expo-image · PostHog · Jest.

Layout:

Path	Role
app/	Screens + routing (auth/, onboarding/, (app)/, pin/, board-modal/)
app/_layout.tsx	Session/onboarding auth gate
hooks/	usePins, useBoards, useFollow, useCurrentUserId
lib/	supabase, secureStore (encrypted session), places, params, and the tested algorithm modules tasteMatch / rankInsert / streak
contexts/	UploadContext (background photo queue), onboarding
constants/theme.ts	The design system (palettes, type, sticker shadows)
supabase/migrations/	Schema deltas — apply in order
schema.sql	Original v1.0 baseline (superseded by migrations)

Core data model (schema.sql + migrations):

• users — profiles, handles, is_private, campus
• places — deduped venues (Google Places–backed), category, geo
• pins — the atomic unit; (user, place), status, photo, impression
• rankings — ordered lists per (user, category); re-ranked atomically via the rerank_place RPC
• boards / board_pins — named, shareable, drag-reorderable collections
• follows — the social graph (active / pending for private accounts)
• auth_allowed_domains — the campus-email allowlist

Server-side logic (RPCs): get_friends_feed (bounded friend feed), get_discover_counts (all six discovery lenses in one round trip), rerank_place (atomic ranking insertion), notify_new_follow (push). All identity-bound to auth.uid().

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Getting Started

npm install
cp .env.example .env.local     # then fill in the values (see below)
npm start                      # Expo dev server

Environment — copy .env.example to .env.local and set:

• EXPO_PUBLIC_SUPABASE_URL, EXPO_PUBLIC_SUPABASE_ANON_KEY — public, RLS-protected
• EXPO_PUBLIC_MAPBOX_TOKEN — Mapbox public (pk.) token
• EXPO_PUBLIC_GOOGLE_PLACES_KEY — must be restricted to the app bundle id + Places API in Google Cloud
• RNMAPBOX_MAPS_DOWNLOAD_TOKEN — Mapbox sk. build secret (injected via app.config.js; an EAS secret in CI)
• SUPABASE_SERVICE_ROLE_KEY — server/seed scripts only, never shipped

.env.local is gitignored — never commit real values.

Database — apply the SQL migrations to your Supabase project in filename order:

supabase db push          # or run supabase/migrations/*.sql in order

Scripts:

Command	What
npm start	Expo dev server
npm run ios / android	Native builds
npm run typecheck	tsc --noEmit (RN app only)
npm run lint	ESLint (react-hooks rules enforced)
npm test	Jest — algorithm unit tests

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Security

The invite-only model is enforced server-side, not just in the UI:

• Campus gate — signup is restricted to domains in the auth_allowed_domains table (seeded columbia.edu / barnard.edu) by a trigger on users. Add a domain with one INSERT to allow demo accounts.
• Row-Level Security on every table. is_private actually hides pins; private-account follows land as pending (status is forced by a trigger, never trusted from the client); board pins can only reference your own or public pins.
• Identity-bound RPCs — every SECURITY DEFINER function checks auth.uid() and pins its search_path.
• Encrypted session — auth tokens are persisted with an AES key in the device Keychain/Keystore (lib/secureStore.ts), not plain AsyncStorage.
• Secrets — no secrets in tracked source; the Mapbox sk. token is injected from the environment via app.config.js.

⚠️ A Mapbox sk. download token was previously committed to app.json and remains in git history — rotate it in the Mapbox account.

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Target Categories

Filo is for businesses where word-of-mouth is already the primary growth engine:

Category	Examples
Food & Drink	Restaurants, cafes, coffee shops, bakeries
Bars & Nightlife	Bars, cocktail lounges, rooftops, clubs
Beauty & Grooming	Hair salons, nail studios, barbershops, lash bars
Experiences	Yoga studios, climbing gyms, pottery classes
Taste Retail	Vintage stores, bookshops, boutiques, record stores

Not included: doctor, vet, lawyer, pharmacy, dry cleaner. Nobody pins these.

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Anti-Patterns

Things Filo will never do:

• ❌ Public star ratings or 0–10 scores
• ❌ Sponsored or algorithmic content in the feed
• ❌ Infinite scroll
• ❌ Emoji in core UI (allowed in user-generated content only)
• ❌ Gradient backgrounds
• ❌ Beige/cream backgrounds (we tried; rejected)
• ❌ More than 4 cards visible without scroll

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Status

Current: Consumer MVP, prototype complete, React Native mobile build in progress. Next: Columbia campus launch, invite-only, targeting 200 active users + 500 pins in 30 days.

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Filo — the thread connects everything: your people, your places, your city. The more you use it, the harder it is to leave.