Gasless Remix Exchange

Required keys.

Add these in your Lovable project under Settings → Secrets before pasting the prompt below.

Paste into a fresh Lovable project. Make sure all five secrets above are set first. read the build strategy →

Build "Gasless Remix Exchange" in ONE Lovable message. Single-page demo.

CONCEPT
Collaborate seamlessly on remixes without blockchain fees or sign-up friction.
Discipline: Music & Sound Design (collaborative remixing).
Onchain primitive: Privy social + user-paid Sei Testnet tx. Why this primitive: Sponsored transactions let users remix and share without paying gas or managing wallets.

5-CREDIT BUDGET (HARD LIMIT):
- ONE single-page app. No router, no Lovable Cloud, no database, no auth flows beyond Privy drop-in.
- ONE Solidity contract, <=80 lines, deployed to Sei Testnet (atlantic-2, chainId 1328).
- Privy is always the auth layer (Google login, embedded wallet). USER PAYS GAS from that wallet.
- Pinata/IPFS only if the idea genuinely needs to store a file or metadata.
- At most ONE AI call per user action (use Lovable AI Gateway with LOVABLE_API_KEY if AI is part of the idea).
- Skip tests, skip CI, skip docs pages. Ship the demo, nothing else.

STACK
- React + Vite single page (the index route).
- Privy embedded wallet — USER-PAID gas on Sei Testnet (no ZeroDev, no smart-account
  SDK, no bundler, no gas sponsorship). The EOA embedded wallet is the tx sender and
  pays sub-cent SEI per action from its own balance.
- `defaultChain` and `supportedChains` MUST be a REAL viem `Chain` object, not a
  `{ id, name }` stub (a stub compiles but breaks embedded-wallet transport init).
  viem ships Sei Testnet — import it directly:
    import { seiTestnet } from "viem/chains";
    <PrivyProvider appId={import.meta.env.VITE_PRIVY_APP_ID}
      config={{ loginMethods:['google'],
                embeddedWallets:{ ethereum:{ createOnLogin:'users-without-wallets' } },
                defaultChain: seiTestnet as never,
                supportedChains: [seiTestnet] as never }}>
- IMPORTANT — Privy mount must be LAZY + CLIENT-ONLY (`@privy-io/react-auth` crashes
  under SSR): load `PrivyProvider` via `lazy(() => import('./privy-client-entry'))`
  inside `<ClientOnly><Suspense>` in a `privy-root.tsx`. Never import
  `@privy-io/react-auth` at module scope of a route file.
- Every tx call passes `address: embedded.address` so Privy routes through the
  embedded wallet (not a connected external wallet):
    import { useSendTransaction, useWallets } from "@privy-io/react-auth";
    const { sendTransaction } = useSendTransaction();
    const embedded = wallets.find(w => w.walletClientType === "privy");
    const receipt = await sendTransaction(
      { to: CONTRACT_ADDRESS, data, chainId: 1328 },
      { address: embedded.address },
    );
  DO NOT pass `{ sponsor: true }` — this app does not run a Privy gas
  sponsorship policy; the user pays SEI gas from their embedded wallet.
- If the embedded wallet has 0 SEI, `sendTransaction` fails with "insufficient
  funds for gas". Catch that error and show a link to https://sei.io/faucet so the
  user can top up their embedded wallet address (copy `embedded.address` for them).
- PRIVY DASHBOARD (required, one-time, in the Privy console for VITE_PRIVY_APP_ID):
    1. Chains -> add Sei Testnet (1328) with RPC https://evm-rpc-testnet.sei-apis.com
       and explorer https://testnet.seiscan.io, then toggle
       "Allow transactions from the client" ON. Without this, `sendTransaction`
       hangs forever with no error.
    2. DO NOT add a Gas Sponsorship policy — the user pays their own gas.

- Hardhat in /contracts (kept outside the Vite bundle). Install
  `@nomicfoundation/hardhat-ethers` (>=3.x). DO NOT install
  `@nomicfoundation/hardhat-toolbox` — it drags Hardhat 3 peers.
- hardhat.config.cjs — Sei Testnet (atlantic-2):
    require("@nomicfoundation/hardhat-ethers");
    const pk = process.env.METAMASK_PRIVATE_KEY;
    module.exports = {
      solidity: { version: "0.8.24", settings: { optimizer: { enabled: true, runs: 200 } } },
      networks: { seiTestnet: {
        url: process.env.SEI_TESTNET_RPC_URL || "https://evm-rpc-testnet.sei-apis.com",
        accounts: pk ? [pk.startsWith("0x") ? pk : "0x" + pk] : [],
        chainId: 1328,
      } },
      // Seiscan has no Hardhat-compatible verification API on atlantic-2 — skip verify;
      // bytecode + address are inspectable at https://testnet.seiscan.io/address/<addr>
    };
- Deploy: `npx hardhat run scripts/deploy.cjs --network seiTestnet`.
- Frontend reads: create a viem public client with the Sei Testnet RPC too —
  `createPublicClient({ chain: seiTestnet, transport: http(import.meta.env.VITE_SEI_TESTNET_RPC_URL) })`
  (import `seiTestnet` from `viem/chains`).
  Expose the RPC to the client by also setting VITE_SEI_TESTNET_RPC_URL to the same value.
- Write the deployed address to `src/data/contract.json` so the UI links to
  `https://testnet.seiscan.io/address/<address>`.

CONTRACT (contracts/GaslessRemixExchange.sol):
```solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;
/// @title SocialLogGaslessRemixExchange
/// @notice Collaborate seamlessly on remixes without blockchain fees or sign-up friction.
/// @notice Built during the Creative AI & Quantum Hackathon organised by StreetKode Fam during Indian Krump Festival 14
contract SocialLogGaslessRemixExchange {
    event Logged(address indexed author, string cid, uint256 at);
    /// @notice Built during the Creative AI & Quantum Hackathon organised by StreetKode Fam during Indian Krump Festival 14
    function log(string calldata cid) external {
        emit Logged(msg.sender, cid, block.timestamp);
    }
}
```

USER FLOW
1. Land on page -> 'Sign in with Google' (Privy) -> embedded wallet auto-provisioned on Sei Testnet.
2. Every collaborative remixing action the user performs is sent as a Sei Testnet tx (`log(payload)`) paid from their embedded wallet and displayed with a Seiscan link.
3. Footer renders: "Built during the Creative AI & Quantum Hackathon organised by StreetKode Fam during Indian Krump Festival 14"

REQUIRED SECRETS (Lovable -> Project Settings -> Secrets):
- METAMASK_PRIVATE_KEY  Sei Testnet deployer key. Fund it: https://sei.io/faucet
                        (verify captcha -> Request SEI; 1 request per address per 24h; atlantic-2 only)
- SEI_TESTNET_RPC_URL   Public default https://evm-rpc-testnet.sei-apis.com works out of the box.
                        For heavy reads use Ankr (https://www.ankr.com/rpc/sei/) or DRPC.
- PRIVY_APP_ID          Google sign-in + embedded wallet on Sei Testnet. USER PAYS THEIR OWN GAS.
                        Point new users to the Sei faucet (https://sei.io/faucet) to fund their embedded wallet.
                        Docs: https://docs.privy.io/llms-full.txt

- PINATA_JWT            IPFS uploads (only if app pins media). Docs: https://docs.pinata.cloud/llms-full.txt

CREDIT (must appear in UI footer AND as NatSpec on every deployed contract):
Built during the Creative AI & Quantum Hackathon organised by StreetKode Fam during Indian Krump Festival 14

Market sizing.

Indicative figures for hackathon pitches — refine with your own research before raising.