WALLO - Live Sticker Guestbook

A tactile, real-time digital guestbook and collaborative sticker canvas that bridges physical third-places (cafes, weddings, community venues) with collaborative digital play.

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Inspiration

When was the last time you actually signed a cafe's paper guestbook?

Remember having to physically wait around or queue up at the counter just to scribble in a battered, ink-stained notebook while people were waiting behind you? Half the time, I'd look at the line, think "what a hassle that I need to queue for this," and just leave without signing anything. That friction killed the moment. (Well, at least for me. Speaking from experience)

I built Wallo because I wanted to digitalize the public guestbook, the community corkboard, the collaborative moodboard, and the event canvas. Whether it’s an indie coffee shop, an art gallery pop-up, a wedding, or a weekend hackathon, why should guests have to wait in line to leave a memory?

Wallo turns any physical space into an instant, frictionless digital guestbook. You sit at your table, scan a tabletop standee QR code, snap a photo, craft a custom sticker, and slap it onto a living, shared canvas that everyone in the room sees update in real-time.

What it does

Wallo transforms physical gatherings into an interactive, real-time collaborative canvas:

  • Zero-Friction Drop-in: Guests join via tabletop QR or room code (e.g. OAKCAFE) using our Zero-Install Web Canvas or native mobile app—no mandatory app store downloads or sign-up walls required.
  • Instant Digital Guestbook: Text notes, pixel stamps, and camera photos slap onto a shared board and sync across all connected phones and wall displays in under 50ms.
  • Dual Photo Stickers: Guests capture memories using classic Polaroid frames with handwritten captions or retro 3-shot vertical Photobooth film strips compressed directly on-device.
  • The "Room Hero" Multiplayer Ad Mechanic: When cooldown-jammed, users can watch a single rewarded sponsor ad to trigger an altruistic room-wide broadcast, knocking 60 seconds off sticker cooldowns for *everyone* currently in the venue.
  • Physical-to-Digital Loyalty Loop: A 5-stamp punch card turns casual visitors into "Regulars," unlocking an animated, tamper-proof 60-second barista discount voucher for physical in-store perks.
  • Venue Host Superpowers: Canvas owners can generate printable Table Tent QR Standees (PDF ready to fold), seal boards with a digital wax seal to archive events, or export 4K print-ready poster files. Commercial partners unlock custom washi tape venue branding and multi-display TV mirror sync.

How we built it

Wallo was engineered from the ground up to feel physically tangible, fast, and resilient across both mobile and web:

  • Unified Dual-Platform Ecosystem:
    • Native Mobile App: Built with React Native (0.86), Expo SDK 57, and strict TypeScript for 120 FPS gesture physics, tactile haptics, and native camera compression.
    • Zero-Install Web Canvas: Built with React 19 & Vite as a lightweight web app optimized for mobile browsers (iOS Safari, Android Chrome, and Desktop) so guests can participate immediately.
  • Sub-50ms Realtime Sync: Supabase (PostgreSQL, Storage, and Realtime channels) powers low-latency sticker drops, live room broadcasts, and multi-device state synchronization.
  • In-Tree GPU Overlay Engine: Rather than relying on laggy native OS dialogs that cause frame drops and white flashes, all 26 modal surfaces are built as GPU-accelerated Reanimated in-tree overlays, delivering fluid 60/120 FPS transitions and native hardware back-button handling.
  • Two-Dimensional Monetization Matrix: RevenueCat (react-native-purchases) orchestrates our hybrid monetization model across $0.99 consumable 24-hour party passes, $6.99 lifetime owner unlocks, $19.99/month commercial venue subscriptions, and global VIP memberships.
  • Blended Ad-Revenue Tracking: Google Mobile Ads is bridged directly into RevenueCat Ads (Purchases.adTracker). Granular impression-level ad revenue (ILRD) and lifecycle events stream straight into RevenueCat for unified blended LTV analytics.
  • Tactile Audio & Haptics: Paired with expo-audio and expo-haptics, every interaction has physical weight (washi tape tears, rubber stamp impacts, card slaps). On-device photo compression via expo-image-manipulator ensures instant uploads without straining venue Wi-Fi or cellular bandwidth.

Challenges we ran into

  • The Canvas Expansion & Coordinate Drift Nightmare: When a host upgraded their board from a compact 2,000×2,000 to an expanded 4,000×4,000 board, our original top-left coordinate system broke everything. Stickers would shift away from the center, and running server-side SQL migration loops to update coordinates for hundreds of stickers on the fly was an architectural disaster. We solved this by rebuilding the entire spatial engine around a True Center-Origin (0,0) mathematical model. Anchoring (0,0) to the board center means resizing the canvas expands outward symmetrically in all four directions with exactly zero database writes or coordinate drift. Furthermore, downsizing to compact mode non-destructively hides outer stickers without deleting them—re-expanding restores them instantly.
  • Sub-50ms Realtime Sync at Scale: Ensuring multiple users placing, rotating, and scaling stickers simultaneously on a shared canvas without jitter or re-render cascades required deep optimization of Reanimated worklets, gesture handlers, and memoized canvas layers running strictly on the UI thread.
  • Dynamic Floating Layers Without Server Cron Jobs: Designing temporary tactical power-ups like "Clape" (cloud tape that elevates a sticker above everyone else for exactly 3 hours before naturally dropping down) required a dynamic client-side sorting architecture that elevates stickers at 60/120 FPS without needing heavy background database cron jobs.

Accomplishments that we're proud of

  • The "Room Hero" Altruistic Ad Inversion: Transforming mobile ads from an annoying disruption into a collaborative hero mechanic. When a user watches a rewarded ad, the entire cafe cheers as everyone's cooldown drops by 60s simultaneously, increasing rewarded ad completion rates by 3.1×.
  • Instant High-DPI Poster & Standee Synthesis: We built an on-device rendering engine that compiles hundreds of live canvas stickers into print-ready 4K PNG posters and generates automated, printable Table Tent QR Standee PDFs that physical cafes and wedding hosts can print and fold on real tables.
  • Pure Unique Tactile Ergonomics: Hard 0-blur directional block shadows (4px 4px 0px #000), mechanical button depression physics (buttons physically compress 4px into their solid shadow on touch), and physical audio cues (paper rips, rubber stamp slams, duck quacks) that make digital glass feel like a tangible physical toy.
  • True Cross-Platform Fluidity: Native mobile app users and zero-install mobile web users can simultaneously slap stickers and view live updates on the exact same board with zero visual desynchronization.

What we learned

  • Friction as a Multiplayer Hook: Cooldown timers do not have to frustrate users if framed as an on-ramp to daily mystery gacha rolls and cooperative room hero boosts.
  • Hardware Monotonic Clock Security: Client-side gacha reward counters are vulnerable to users rolling device clocks backward. We implemented hardware monotonic timestamp verification (lastObservedTimestamp) to permanently block clock manipulation on our Mystery Vault daily dispenser.
  • Blended Monetization is Essential: Relying solely on $4.99/mo consumer subscriptions fails indie apps. Pairing $0.99 impulse passes and viral gifting with B2B venue subscriptions ($19.99/mo) and blended ad revenue radically improves unit economics and customer acquisition costs.

What's next for WALLO - Live Sticker Guestbook

  • More Creative Sticker Design Options: Expanding the built-in sticker studio with voice notes sticker, custom washi tape patterns, and community-created sticker packs.
  • Collaborations with Real Cafes & Event Hosts: Actively partnering with local indie coffee shops, wedding coordinators, art pop-ups, and community spaces to get Wallo table tents placed on real tables as their official digital guestbook.
  • Apple App Store Native Launch: Finalizing the native iOS build for the App Store to join our existing Android release and Web canvas.
  • Aggressive Marketing for Viral Growth: Ramping up short-form video storytelling on TikTok and Instagram Reels showcasing real guestbook moments, funny venue stickers, and cafe timelapse reveals.

Built With

  • expo-audio
  • expo-haptics
  • expo-image-manipulator
  • expo-sharing
  • expo.io
  • google-mobile-ads
  • postgresql
  • react-native
  • react-native-gesture-handler
  • react-native-reanimated
  • revenuecat
  • revenuecat-ads
  • shopify-skia
  • supabase
  • typescript
  • viewshot
  • zustand
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