GIWA Tap — Instant On-Chain Tips & Micro-Payments

MVP for the GASOK application (Mass Adoption track). A single QR code or link lets anyone send an instant, low-fee on-chain tip/payment on GIWA Sepolia (Ethereum L2) — no account, no signup, no custody. Built for cafes, street vendors, creators, and event organizers who want "tap to pay" simplicity with the transparency of on-chain settlement.

What's in this folder

File	Purpose
GiwaTap.sol	The on-chain contract. One function (tap) forwards ETH instantly to a recipient and logs sender, amount, optional message, and timestamp. Non-custodial — the contract never holds a balance between calls.
GiwaTap.abi.json	Compiled ABI (generated locally with solc 0.8.24, optimizer on, 200 runs). Compiles clean with zero errors/warnings.
index.html	The entire app frontend — one file, no build step. Generates a QR code / shareable link for any address, connects MetaMask, auto-adds/switches to GIWA Sepolia, sends tips, and shows a live history feed.

1. Deploy the contract (2 minutes, no CLI needed)

1. Go to Remix IDE.
2. Create a new file GiwaTap.sol and paste in the contents of GiwaTap.sol from this folder.
3. Compile tab → select compiler 0.8.24 (or any 0.8.x) → Compile.
4. Deploy & Run tab → Environment: Injected Provider - MetaMask.
5. In MetaMask, make sure you're on GIWA Sepolia:
   • Chain ID: 91342
   • RPC URL: https://sepolia-rpc.giwa.io/
   • Currency symbol: ETH
   • Block explorer: https://sepolia-explorer.giwa.io
   • (Fund your wallet first from the GIWA Sepolia faucet — linked from the docs/explorer site — since you need testnet ETH to deploy and to send tips.)
6. Click Deploy, confirm in MetaMask. Copy the deployed contract address from Remix.

2. Point the frontend at your deployed contract

Open index.html, find this line near the top of the <script> block:

const CONTRACT_ADDRESS = "0x0000000000000000000000000000000000dEaD"; // <-- REPLACE after deploy

Replace it with your deployed address. That's it — no build step, no dependencies to install.

Until you do this, the app still works end-to-end in a fallback mode: it sends a plain ETH transfer instead of calling the contract, so you can demo the QR/link/send flow immediately and wire in the contract (for on-chain messages + history) right after.

3. Run it

Any static file host works — GitHub Pages, Vercel, Netlify, or just open index.html locally. For local testing:

python3 -m http.server 8080
# open http://localhost:8080/index.html

How the demo flow works

1. Receive tab — a cafe/creator connects their wallet (or pastes an address), gets an instant QR code + shareable link (?to=0xADDRESS).
2. Send tab — whoever scans the QR lands with the recipient pre-filled, connects MetaMask (auto-prompted to add/switch to GIWA Sepolia if needed), enters an amount and optional message, and taps Gönder. Funds land in the recipient's wallet in the same transaction.
3. Every tip is logged on-chain (Tipped event) and shown in a live feed on both tabs — provable, permanent, and shareable payment history with zero backend/server required.

Why this fits GASOK's Mass Adoption track

• Real-world use case, zero learning curve: scan → send → done. No wallet jargon exposed beyond the one MetaMask popup users already know from any dApp.
• GIWA Wallet-compatible by design: the app only depends on the standard window.ethereum / EIP-1193 provider interface, so it works with MetaMask today and the GIWA Wallet the moment it ships, without code changes.
• Non-custodial & auditable: the contract never custodies funds; every tip is a public event on GIWA Sepolia, viewable on the explorer.
• Cheap to run at scale: GIWA's L2 fees make micro-tips (a few cents) economically viable, which isn't true on L1 Ethereum.

Roadmap (post-MVP, if selected)

• Phase 2 (MVP → testnet users): add ENS-style memorable handles instead of raw addresses, static QR stickers for physical venues (cafes, markets), basic analytics dashboard for recipients (total received, top supporters).
• Phase 3 (productize): GIWA Wallet in-app placement, batched/recurring tips (subscriptions), fiat on-ramp for first-time senders, merchant dashboard with CSV export for accounting.
• Growth: partner with a handful of Korea Blockchain Week vendors / creators for a live on-site pilot at demo day.

Technical notes

• Contract compiled locally with solc@0.8.24: 0 errors, 0 warnings, optimizer enabled (200 runs). Bytecode verified reproducible from GiwaTap.sol as committed here.
• Frontend tested headlessly (Playwright/Chromium) against the real ethers@6.13.4 and qrcodejs@1.0.0 packages: QR generation, shareable-link construction, and ?to= deep-link pre-fill all verified working with zero console errors.
• No backend, no database, no API keys required to run the MVP — everything reads/writes directly against GIWA Sepolia.