GeoGacha

Problem Statement

GeoGacha is a Web3-powered exploration app that turns the real world into a loot map. Users walk to GPS-based locations, check in, and trigger onchain randomized rewards secured by onchain randomness on Flow . Designed for outdoor adventurers, brand activations, and gamified tourism, GeoGacha blends physical movement with provably fair digital rewards.

Solution

How GeoGacha Was BuiltCore Stack:Frontend: Next.js 15 + TypeScript + Tailwind CSS for a mobile-first PWA experienceWeb3: Ethers.js connecting to Flow EVM Testnet (Chain ID: 545)Smart Contract: Solidity contract using Flow's Cadence Random Consumer for true on-chain randomnessUI: Shadcn/UI components with custom animations and responsive designArchitecture Flow:GPS Simulation → Mock location data triggers proximity detectionWallet Connection → Auto-detects MetaMask, switches to Flow EVM, handles network additionContract Calls → Two-step randomness:getRandomNumber()for rarity,selectRandomItem()for specific rewardsFallback System → Graceful degradation when contract calls failPartner Tech Benefits:Flow EVM: Ethereum compatibility with Flow's performance and native randomnessCadence Random Consumer: Eliminates need for external oracles like Chainlink VRFNotable Hacks:Dual Randomness Strategy: Contract-first with local fallback ensures 100% uptimeNetwork Auto-Switching: Automatically adds Flow EVM Testnet to MetaMask if missingGPS Proximity Simulation: Uses percentage-based positioning for demo without requiring actual GPSWeighted Rarity System: Single contract call determines rarity (5% legendary, 20% rare, 75% common) then selects from appropriate poolClever Implementation: The app calls your deployed randomness contract for authentic blockchain-based rewards while maintaining smooth UX through optimistic UI updates and error handling.