Build Run Cards, a one-page website on Ethereum Sepolia (chain ID 11155111) for an NFT game that is already deployed. Do not write or deploy any contract: the site only reads and calls the existing RunCards contract below. Unofficial fan build for Squeekchain: a real hamster, Squeektoshi, runs on a wheel, and his work is settled on-chain in 10-minute rounds.

THE GAME (show it in plain words on the page)

• A run is one session of Squeektoshi on the wheel, read from Squeekchain's settled rounds. It ends once 4 hours (24 rounds) pass with no work.
• Join while he is running: lock 30,000 $CARDIO in the contract. You need to approve RunCards for exactly 30,000 $CARDIO first (each join uses it up).
• Leave any time before delivery: your 30,000 $CARDIO comes back at once, and you get no card.
• When the run has ended, anyone presses Deliver: every runner gets one on-chain pixel-hamster card (ERC-721, art fully on-chain), and every runner gets their 30,000 $CARDIO back, in one transaction.
• Cards show "not revealed yet" until his next run settles; then rarity shows (Common, Rare, Epic, Legendary). Longer runs give better odds.
• Up to 100 runners per run. Joining closes once a settled round with no work follows his last one. No fees, no owner, test coins only.

CONTRACTS ON SEPOLIA (you work offline: use these exactly)

• RunCards: 0x79224b71fec04bbd1c34d0922e04a11da56d56cf (ERC-721 "Run Cards"), deployed in Sepolia block 12074980. Run 1 is a run that was already under way at deployment (startedEarly): nobody can join it; the first joinable run is the next one.
• $CARDIO: 0x1CCcE5C1D320F931B9e409C480F532Ca95C0A26B, a plain 18-decimal ERC-20 (balanceOf, allowance, approve).
• SqueekCore: 0xfd6c166d4b8e2962e65746a13e5a0797cd4de0c4, read state() for the settled round and block height: struct CoreState { uint64 settledThroughRound; uint64 cumulativeWork; uint96 cumulativeBlockUnits; uint64 blockHeight; uint96 blockProgress; uint32 workPerThousandBlocks; uint256 authorizationNonce; bool paused; } function state() view returns (CoreState).

RUNCARDS ABI (human-readable, exactly as deployed)

function join()

function leave(uint256 runNumber)

function deliver(uint256 runNumber) returns (uint256 minted)

function reveal(uint256 runNumber)

function sync() returns (bool caughtUp)

function running() view returns (bool)

function openRun() view returns (uint256)

function runCount() view returns (uint256)

function runInfo(uint256 runNumber) view returns (tuple(uint64 startRound, uint64 lastActiveRound, uint32 activeRounds, uint64 work, uint64 topWork, uint96 unitsBefore, uint96 unitsAfter, bytes32 dataHash, bool closed, bool startedEarly, uint32 minted, uint64 revealAfter, bool revealed, uint64 firstToken, uint64 revealRound, bytes32 revealHash) run, uint256 joiners)

function joined(uint256 runNumber, address who) view returns (bool)

function placeOf(uint256 runNumber, address who) view returns (uint256)

function revealOf(uint256 runNumber) view returns (uint64 round, bytes32 hash)

function ownerOf(uint256 tokenId) view returns (address)

function tokenURI(uint256 tokenId) view returns (string)

event Joined(uint256 runNumber, address runner)

event Left(uint256 runNumber, address runner)

event Delivered(uint256 runNumber, address runner, uint256 tokenId)

event RunStarted(uint256 runNumber, uint64 startRound)

event RunEnded(uint256 runNumber, uint64 lastActiveRound, uint64 work)

event Revealed(uint256 runNumber, uint64 revealRound)

error NotApproved() error NotEnoughCardio() error NotRunning() error NoOpenRun() error AlreadyJoined() error RunFull() error NotJoined() error RunNotEnded() error AlreadyDelivered() error NothingToDeliver() error NothingToReveal() error RevealRoundNotSettled() error NoSuchRun() error NotCaughtUp()

Show each error as a plain sentence (for example NotRunning: "He is resting: joining opens again when he runs").

THE PAGE

1. Header: Run Cards, one line on the game, "Unofficial, on Sepolia testnet. Test coins only."
2. Live wheel: is he running now? Read GET https://api.squeekchain.com/v1/status (field measurement.coreStatus is RUNNING or IDLE; measurement.speedMmPerSecond) every 30 seconds, and SqueekCore.state() for the settled round. Show Running or Resting and km/h.
3. This run: from openRun(), runInfo() and running(): run number, started round, rounds with work, work so far, runners of 100, and whether joining is open. If runCount() is 0 or openRun() is 0, say no run has started since the contract was deployed.
4. Wallet: Connect button using EIP-6963 wallet discovery (fall back to window.ethereum), then switch the wallet to Sepolia (add it if missing). Show the $CARDIO balance and whether it has 30,000.
5. Buttons, each enabled only when a free eth_call simulation of the same call from the connected wallet succeeds (or, for Join, fails only with NotApproved): Approve 30,000 $CARDIO (when the allowance is below 30,000), Join, Leave (for a run the wallet joined and that is not delivered), Deliver (for an ended, closed run that is not delivered; if deliver says RunNotEnded, send sync() first), Reveal (when revealOf gives a settled round and the run is not revealed). Join: if it reverts NotCaughtUp, send sync() until it returns true, then join. Use fixed gas limits so wallets need not estimate: join 1,500,000, leave 400,000, sync 4,000,000, reveal 400,000, deliver 40,000,000.
6. My cards: the wallet's cards, found from Delivered events (from the deploy block on) whose runner is the wallet and still owned (ownerOf). For each, call tokenURI, which returns data:application/json;base64 with an image field that is a data:image/svg+xml SVG: decode and show the picture, name and attributes. Unrevealed cards say so.
7. Past runs: a short table of the last runs: number, work, runners, delivered or not, revealed or not.
8. How it works and FAQ, in plain words, from THE GAME above. Links: the RunCards contract and $CARDIO on sepolia.etherscan.io, $CARDIO on Wheelpad https://wheelpad.fun/coin/0x1CCcE5C1D320F931B9e409C480F532Ca95C0A26B, Squeekchain https://squeekchain.com.

RULES

• Static site: no backend, analytics or keys; bundle one pinned copy of ethers v6.
• Public Sepolia RPCs, in order, next one on any error or 15 s timeout: https://sepolia.gateway.tenderly.co, https://ethereum-sepolia-rpc.publicnode.com, https://1rpc.io/sepolia. Query logs in windows of at most 10,000 blocks.
• Poll only while the tab is visible; back off to 5 minutes after errors.
• Never ask for or handle a private key or seed phrase; the wallet signs.
• Look: dark background, warm orange accent, rounded cards, pixel-art hamster feel, readable on a phone (no sideways scrolling at 375 px).
• Wording: plain, short English. Never promise value: say test coins and cards have no value.