What this actually is

RACK is one HTML file. No framework, no bundle, no fonts, no images, no requests — it names no URL at all. The seed arrives as a single constant, the modules are derived from it, and the puzzle is constructed so that a solution always exists in the pool you are given. It is 22,336 bytes, held under a 24,576-byte budget by a test rather than by intention.

That size is not a flourish. It is roughly what a contract can return from tokenURI without heroics, and building to it from the first commit is the only way to know it fits. Written as components inside this site, RACK could never be returned that way, and we would find out at the worst possible moment.

Nothing here is minted. There is no contract, no token, no wallet connection, no chain read and no chain write. This page serves a static file from /public, and your streak is kept in your own browser and sent nowhere. Whether RACK is ever minted is a separate decision, and it has not been made.

Why we built it this way

Robinhood Chain has NFTs described as on-chain instruments whose bytes live anywhere but the chain. NFTzWORLD TONE is the clearest example. Measured against chain 4663 on 2026-09-21, from the contract and the live payloads:

• the contract is 6,799 bytes of runtime bytecode and knows nothing about the synthesizer;
• tokenURI(1) returns a hardcoded HTTPS URL at a Pinata gateway — a web address, not an ipfs:// reference;
• that metadata's image and animation_url both point at catbox.moe, a free file host;
• tokens 1, 2, 42 and 420 each point at a different pre-built HTML file with its traits baked in. The HTML never reads a token id — its one query parameter is a debug flag.

Here is the encouraging half, and it is why RACK exists rather than merely a story about TONE: the synthesizer itself is good. It is 20,455 bytes, one <script>, Web Audio and SVG, no src, no href, no fetch — the only two URLs in it sit in comments. A thing that self-contained is small enough to live on the chain it is named after. What it needs is one renderer parameterised by the token id instead of 420 uploads, which is the shape RACK is built in.

We are not claiming TONE's files will vanish, and we have no position in it. We are pointing at where the bytes are: if catbox purges them, 420 instruments go quiet and the chain still says everything it ever said.

How the puzzle is made

Backwards, on purpose. The day's seed draws a hidden chain first; its feature vector — fundamental note, brightness, rhythm, timbre — becomes the target you hear, and each pool is that hidden module plus decoys. Solvability is therefore a property of the construction, not something we hope holds. The alternative — roll a target and trust the pool to reach it — fails silently, and a player finds it instead of us. A test walks a full year of daily seeds and requires every one to be solvable from its own pool.

Scoring compares what the rack sounds like, not which cards you picked, so two different filters that land on the same brightness are both right. The source is in this repository at arcade/rack/src/; the file this page embeds is built from it by scripts/build-rack.mjs, committed, and checked against a fresh build by a test so the two can never drift apart unnoticed.